Organometallic Chemistry, Volume 29

Organometallic Chemistry

Volume 29

SPECIALIST PERIODICAL REPORTS Systematic and detailedreview coverage in major areas of chemical research. A unique service for the active research chemist with annual or biennial,in-depth accounts of progress in particularfields of chemistry,in print and online.

NOW AVAILABLE ELECTRONICALLY - chapters from volumes published 1998 onwards are now available online,My searchableby key word, on a pay-to-viewbasis. Contents pages can be viewed free of charge.

Or visic our web pages today:

www.rsc.org/spr k

RSeC ROYAL SOCIETY OF CHEMISTRY

Orders 6 further derails Sales L Customer Care Dept Royal Society o f Chemistry - Thomas Graham House Science Park' Milton Road. Cambridge C B O~ W F ' UK T t 4 4 ( 0 ) n z j 432360 F +44(0)1zz3413429 E [email protected] Or visit our website: www.rsr.org Part of the chemistry societies' network: www.chemsoc.org

A Specialist Periodical Report

Organometallic Chemistry Volume 29 A Review of the Literature Published during 1999 Senior Reporter M. Green, University of Bristol, UK Re po rters M.J. Almond, University of Reading, UK J.G. Brennan, State University of New Jersey, Rutgers, Piscataway, New Jersey, USA I.R. Butler, University College of North Wales, Bangor, UK M.P. Cifuentes, Australian National University, Canberra, Australia K.R. Flower, UMlST, Manchester, UK C.G.Frost, University of Bath, UK M.G. Humphrey, Australian National University, Canberra, Australia C. Jones, University of Wales, Cardiff, UK R.A. Layfield, University of Cambridge, UK D.J. Linton, University of Cambridge, UK J.M. Lynam, University of Bristol, UK F?C. McGowan, University of Leeds, UK S. Macgregor, Heriot- Watt University, Edinburgh, UK E.M. Page, University of Reading, UK A. Sella, University College, London, UK J.A. Timney, Central Newcastle High School, Newcastle upon Tyne, UK A.S. Weller, University of Bath, UK A.E.H. Wheatley, University of Cambridge, UK M.K. Whittlesey, University of Bath, UK M.C. Willis, University of Bath, UK D.S. Wright, University of Cambridge, UK

RSaC ROYAL SOCIETY OF CHEMISTRY

ISBN 0-85404-328-4 ISSN 0301-0074 Copyright 0The Royal Society of Chemistry 2001 All rights reserved Apart from any fair dealing for the purposes of research or private study, or criticism or review as permitted under the terms of the UK Copyright, Designs and Patents Act, 1988, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the address printed on this page.

Published by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 OWF, UK Registered Charity Number 207890 For further information see our web site at www.rsc.org Typeset by Computape (Pickering) Ltd, Pickering, North Yorkshire, UK Printed by Athenaeum Press Ltd, Gateshead, Tyne and Wear, UK

This volume has the same layout as was used last year. Organometallic chemistry continues to flourish and it is a pleasure to thank all of this year’s contributors. To further illustrate the increasing importance of metal complexes in organic synthesis Richard Schrock’s chiral alkene metathesis catalyst is illustrated on the front cover. Michael Green

Contents

Chapter

Chapter

1

Theoretical Organometallic Chemistry By Stuart A. Macgregor

1

1

Introduction

1

2

s-Block Metals 2.1 Structural and Spectroscopic Studies 2.2 Mechanistic Studies

1 1 3

3

p-Block Metals 3.1 Structural and Spectroscopic Studies 3.2 Mechanistic Studies

5 5 8

4

d- and f-Block Metals 4.1 Structural and Spectroscopic Studies 4.2 Mechanistic Studies

9 9 22

References

29

2

Group 1: The Alkali and Coinage Metals By David J. Linton and Andrew E. H. Wheatley

42

1

Alkali Metals 1.1 Introduction 1.2 Alkyl Derivatives 1.3 Alkenyl, Allyl, Vinyl, Alkynyl and Related Derivatives 1.4 Aryl Derivatives 1.5 Cyclopentadienyl and Related Derivatives

42 42 42 48 51 54

2

Copper, Silver and Gold 2.1 Introduction 2.2 Copper Compounds 2.3 Silver Compounds 2.4 Gold Compounds

55

55 55 58 59

61

References

Organometallic Chemistry, Volume 29

0The Royal Society of Chemistry, 2001 vii

Contents

Vlll

Chapter

3

I 2 3

Group 2 (Be-Ba) and Group 12 (Zn-Hg) By Richard A. Lay$eld and Dominic S. Wright Scope and Organisation of the Review Group2 Group 12 References

Chapter

Chapter

69

69 69 75 82

4

Scandium, Yttrium and the Lanthanides By John G. Brennan and Andrea Sella

85

1

Introduction

85

2

New Compounds - Structure and Reactivity 2.1 Cp Compounds 2.2 Substituted Cp Ancillaries 2.3 Cp* Chemistry 2.4 Donor Cp Chemistry 2.5 Indene Chemistry 2.6 Linked Cp Chemistry 2.7 Naphthalide Complexes 2.8 COT Chemistry 2.9 Miscellaneous Ancillary Ligands

85 85 87 89 91 92 92 94 94 95

3

Polymerization Catalysis

101

4

Applications to Organic Synthesis

104

5

Theoretical and Spectroscopic Studies 5.1 Computational Studies 5.2 Spectroscopic Studies 5.3 Gas Phase Chemistry

106 106 108 108

References

109

5

Carboranes, Including Their Metal Complexes By Andrew S. Weller

115

1

Introduction

115

2

Theoretical Chemistry

116

3

Carboranes 3.1 {CBg} and {CBI,} 3.2 {C2B2}and {C~BS} and {C2B8} 3.3 {C3B,} and {C4B8} 3.4 {C6&j>and {C5B7} 3.5 { c 2 B 9 > 3-6 { C A o }

116 116 117 117 117 117 118

ix

Contents 4

Metallacarbaboranes 4.1 (MC2B4) 4.2 (MC3Bs) 4.3 (MC2B9) 4.4 (exo-MC2Bg) 4.5 (MCBlo} 4.6 WCZB101 4.7 (exo-MC2Blo)

119 119 120 120 121 121 122 122

5

Complexes with Sn and Si

123

References

Chapter

6

Group 13: Boron, Aluminium, Gallium, Indium and Thallium By Matthew J. Almond

127

1

Boron 1.1 General 1.2 Compounds Incorporating the B(C6F5)3 Moiety 1.3 Compounds Containing Nitrogen or Phosphorus Atoms 1.4 Compounds Containing Oxygen Atoms 1.5 Compounds Containing Metal Atoms

127 127 127

2

Aluminium 2.1 General 2.2 Compounds Containing Group 15 Atoms 2.3 Compounds Containing Group 16 Atoms 2.4 Compounds Containing Another Metal Atom

134 134 135 140 142

3

Gallium 3.1 General 3.2 Compounds Containing Group 15 or 16 Atoms 3.3 Compounds Containing Another Metal Atom

143 143 144 146

4

Indium

147

References

Chapter

124

129 130 131

149

7

Group 15: Phosphorus, Arsenic, Antimony and Bismuth By Cameron Jones

153

1

Phosphorus

153

2

Arsenic, Antimony and Bismuth

160

References

165

Contents

X

Chapter

Chapter

8

Organic Aspects of Organometallic Chemistry By Christopher G. Frost and Michael C. Willis

170

1

Introduction

170

2

Coupling Reactions 2.1 Cross-coupling Reactions 2.2 Allylic Substitution

170 170 175

3

Carbonylation Reactions 3.1 Pauson-Khand and Related Reactions

178 179

4

Organometallic Methods of C-C Bond Formation 4.1 Metathesis Reactions 4.2 Diazo-carbenoid Chemistry 4.3 1,2- and 1,4-Addition Reactions 4.4 C-H and C-C Bond Activation 4.5 Multi-component Cyclisations

180 180 185 187 190 191

5

Oxidative and Reductive Processes 5.1 Oxidation Reactions 5.2 Reduction Reactions

192 192 194

6

Lewis Acid Mediated Processes

196

7

Emerging Areas 7.1 High-throughput Catalyst ldentification 7.2 Non-traditional Solvents in Organometallic Transformations

200 200 200

References

203

9

Metal Carbonyls By John A. Timneji

207

1

Introduction

207

2

Reviews

208

3

Theoretical, Spectroscopic and General Studies 3.1 Theoretical Studies 3.2 Spectroscopic Studies 3.3 General Studies

208 208 209 21 1

4

Chemistry of the Metal Carbonyls 4.1 Titanium, Zirconium and Hafnium 4.2 Vanadium, Niobium and Tantalum 4.3 Chromium, Molybdenum and Tungsten 4.4 Manganese, Technetium and Rhenium

212 21 2 212 212 214

xi

Contents

4.5 4.6 4.7 4.8 4.9

Iron, Ruthenium and Osmium Cobalt, Rhodium and Iridium Nickel, Palladium and Platinum Copper, Silver and Gold Carbonyl Complexes Containing Two or More Different Metal Atoms

References

Chapter

Chapter

216 218 219 220 220 22 1

10 Complexes Containing Metal-Carbon o-Bonds of the Groups Titanium to Manganese, Including Carbenes and Carbynes By Patrick C. McGowan, Elizabeth M. Page, Michael K. Whittlesey and Jason M. Lynam

Part I: Group 4, By Patrick C.McGowan

227

References

253

Part 11: Group 5, By Elizabeth M. Page

256

1

Reviews

256

2

Alkyl Compexes

256

3

Alkylidene Complexes

257

4

Alkyne Complexes

260

5

Butadiene and Similar Complexes

263

6

Imido Complexes

264

7

Other Complexes

266

References

268

Part 111: Group 6, By Michael K. Whittlesey

269

References

275

Part IV: Group 7, By Jason M. Lynam

278

References

287

11 Organo-Transition Metal Cluster Compounds By Mark G. Humphrey and Marie P. Cifuentes

289

1

289

Introduction

xii

Contents 2

General Reviews

289

3

Spectroscopic Studies 3.1 IR 3.2 NMR 3.3 MS 3.4 Theory

289 289 290 290 290

4

Structural Studies

29 1

5

Large Clusters

29 1

6

Group 4

295

7

Group 5

295

8

Group 6 8.1 Chromium 8.2 Molybdenum and Tungsten

295 295 295

9

Group 7 9.1 Manganese 9.2 Rhenium

296 296 296

10 Group 8

General Iron Ruthenium Osmium Mixed-metal Clusters Containing Only Group 8 Metals

297 297 298 300 3 10 315

11 Group 9 11.1 Cobalt 11.2 Rhodium and Iridium 11.3 Mixed-metal Clusters Containing Only Group 9 Metals

316 316 318 318

12 Group 10 12.1 Nickel 12.2 Palladium 12.3 Platinum

319 319 319 320

13 Group 11 13.1 Copper 13.2 Silver 13.3 Gold 13.4 Mixed-metal Clusters Containing Only Group 11 Metals

320 320 32 1 322 323

14 Group 12

323

15 Mixed-metal Clusters

323

10.1 10.2 10.3 10.4 10.5

...

Contents

Xlll

15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8

Chapter

Chapter

Group 4 Group 5 Group 6 Group 7 Group 8 Group 9 Group 10 Compounds Containing Three Different Metals

324 324 324 328 329 335 336 336

References

338

12 Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalts and Nickel, Including Carbenes and Carbynes By Michael K. Whittlesey

350

1

Reviews and Articles of General Interest

350

2

Metal-Carbon o-Bonds Involving Group 8,9 and 10 Metals 2.1 The Iron Triad 2.2 The Cobalt Triad 2.3 The Nickel Triad

350 350 359 365

3

Carbene and Carbyne Complexes of Groups 8 , 9 and 10

37 1

References

375

13 Hydrocarbon Transition Metal m-Compexes other than r)-C5H5 and q-Arene Complexes By Kevin R. Flower

384

1

Introduction

384

2

Reviews

384

3

Complexes Containing Allyls or Monoalkenes 3.1 Cr, Mo, W 3.2 Fe, Ru, 0s 3.3 Co, Rh, Ir 3.4 Ni, Pd, Pt 3.5 Other Metals

385 385 387 390 392 396

4

Complexes Containing Unconjugated Alkenes

399

5

Complexes Containing Cyclic Conjugated Alkenes 5.1 Cr, Mo, W 5.2 Fe, Ru, 0 s 5.3 Other Metals

403 404 405 406

Contents

xiv

Chapter

6

Complexes Containing Acyclic Alkenes

408

7

Complexes Containing Alkynes

41 1

8

Polymetallic Complexes 8.1 Bimetallic Complexes 8.2 Multimetallic Complexes 8.3 Ferrocenyl Containing Complexes

41 3 413

419 423

References

424

14 Transition Metal Complexes of Cyclopentadienyl Ligands By Ian R. Butler

442

1

General Introduction

442

2

Main Group, Lanthanides and Actinides

443

3

Titanium, Zirconium and Hafnium

445

4

Vanadium, Niobium and Tantalum

449

5

Chromium, Molybdenum and Tungsten

450

6

Manganese and Rhenium

452

7

Iron, Ruthenium and Osmium 7.1 Ferrocenylphosphine Ligand Chemistry 7.2 Ferrocenophanes 7.3 Materials

453 457 458 458

8

Cobalt, Rhodium and Iridium

465

9

Nickel, Palladium and Platinum

467

References Author Index

468 479

Abbreviations

Ac acac acacen Ad AIBN amPY Ar Ar* Ar‘f arphos ATP Azb 9-BBN BHT Biim BINAP biPY Bis bma BNCT BP bpcd bPk Bpz4 Butbpy t -bupy Bz Bzac cbd 1,5,9-~dt chd chpt CIDNP

P I (CO) cod coe cot CP/MAS CP CPR

acetate acetylacetonate NN-ethylenebis(acety1acetoneiminate) adamantyl azoisobutyronitrile 2-amino-6-methylpyridine Aryl 2,4,6-tri(t-butyl)phenyl 3,5-bis(trifluoromethyl)phenyl 1-(diphenylphosphino)-2-(diphenylarsino)ethane adenosine triphosphate azobenzene 9-borabicyclo[3.3.llnonane

2,6-dibutyl-4-methylphenyl biimidazole 2,2’-bis(dipheny1phosphino)-1,1‘-binaphthyl 2,2’-bipyridyl bis(trimethylsily1)methyl 2,3-bis(diphenylphosphino)maleic anhydride boron neutron capture therapy biphenyl 4,5-bis(diphenylphosphino)-cyclopent-4-en1,3-dione benzophenone ketyl (diphenylketyl) tetra( 1-pyrazolyl)borate

4,4-di-tert-butyl-2,2’-bipyridine t-butylpyridine benzyl benzoylacetona te cyclobutadiene cyclododeca-1,5,9-triene cyclohexadiene cycloheptatriene Chemically Induced Dynamic Nuclear Polarisation cobalamin cobalozime [C~(dmg)~derivative] cyclo-octa-l,5-diene cyclo-octene cyclo -oct atr iene Cross Polarization/Magnetic Angle Spinning q’-cyclopentadienyl q 5-alkylcyclopentadienyl xv

Abbreviations

XVl

CP" CP' Cp" cv CVD CY Cyclam CYm CYttP dab dabco dba dbpe DBU DCA depe depm DFT diars diarsop dien diop DlPAMP diphos DiPP dipyam DMAD

DMAP DmbPY DME DMF dmg dmgH dmgH2 DMP dmpe dmpm dmpz DMSO dpae dpam dPPa dPPb dPPbZ dPPe dPPf dPPm dPPP

q 5-pentamethylcyclopentadienyl trimet hylsilylcyclopentadienyl tetramethylethylcyclopentadienyl cyclic voltammetry(ogram) chemical vapour deposition cyclohexyl 1,4,8,11-tetraazacyclotetradecane p-cymene PhP( C H ~ C H ~ C H ~ P C Y ~ ) ~ I74-diazabutadiene 1,4-diazabicyclo[2.2.2]octane dibenzylideneacetone 1,2-bis(dibutylphosphino)ethane 1,8-diazabicyclo[5.4.O]undec7-ene 9,lO-dicyanoanthracene 1,2-bis(diethylphosphino)ethane 1,2-bis(diethylphosphino)methane density functional theory o-phenylenebis(dimethy1)arsine {[(2,2-dimethyl-1,3-dioxolan-4,5-diyl)bis(methylene)]bis [diphenylarsine]] diethylenetriamine { [(2,2-dimethyl-173-dio~olan-4~5-diyl)bis(methyiene)]bis-1-[diphenylphosphine] ] 1,2-bis(phenyl-o-anisoylphosphino)ethane 1,2-bis(diphenylphosphino)ethane 2,6-di-isopropylphenyl di-(2-pyridy1)amine dimethyl acetylenedicarboxylate 2-dimethylaminopyridine dimethylbipyridine 1,2-dimethoxyethane NN-dimethylformamide dimethylglyoximate monoanion of dimethylglyoxime dimethylgly oxime dimethylpiperazine

1,2-bis(dimethylphosphino)ethane bis(dimethy1phosphino)methane 1,3-dimethylpyrazolyl dimethyl suifoxide 1,2-bis(diphenyiarsin0)ethane bis(dipheny1arsino)methane 1,2-bis(diphenylphosphino)ethyne

1,4-bis(diphenylphosphino)butane 1,2-bis(diphenylphosphino)benzene 1,2-bis(diphenylphosphino)ethane 1,1 '-bis(dipheny1phosphino)ferrocene bis(dipheny1phosphino)methane 1,3-bis(diphenylphosphino)propane

Abbreviations

XVll

diamond-square-diamond ethane- 1,2-dithiolate ethylenediaminetetraacetate enantiomeric excess electron energy loss spectroscopy extended Huckel molecular orbital electron localisation function ethylene-1,2-diamine electrospray mass spectrometry extended X-ray absorption fine structure hexafluoroacetylacetonate ferrocenyl Fe(C0)2Cp* Fe(W2Cp Fe(C0)2(q5-C~H4Me) Fourier Transform Infra-red flash vacuum pyrolysis ethyleneglycol dimethyl ether generalized valence bond tris(pyazoly1)borate tris(3,5-dimethylpyrazolyl)borate tetraaza-l,4,7,1O-cyclododecane N-hydroxyethylethylenediaminetetraacetate hexafluoroacetone hexafluoroacetylacetonato hexafluorobut yne hexamethyl phosphoric triamide high nuclearity carbonyl cluster highest occupied molecular orbital individual gauge for localized orbitals imidazole 2,4,6-tri-isopropylphenyl inner shell electron energy loss spectroscopy potassium hydrotris( 1-pyrazolyl)borate lithium diisopropylamide lithium di-t -butylbiphenyl low nuclearity carbonyl cluster methyl alumoxane 5,7,7,12,14,14-hexamethyl1,4,8,11-tetra-azacyclotetradeca-4,11-diene 5,5,7,12,12,14-hexamethyl1,4,8,11-tetra-azacyclotetra-decane Me6[141N4 4,7-dimethyl-l , 10-phenanthroline 4,7-Me2phen 3,4,7,8-Me4phen 3,4,7,8,-tetramethyl-1,lO-phenanthroline mesityl Mes 2,4,6-tributylphenyl Mes* methyltetrahydro furan MeTHF metachloroperbenzoic acid mcpba Metal-Ligand Charge Transfer MLCT methylrhenium trioxide MTO 1-naphthyl nap

DSD edt EDTA ee EELS EH MO ELF en ES MS EXAFS F6acac Fc Fe* FP FP’ FTIR FVP glyme GVB HBpz3 HBpz*3 H4cyclen HEDTA hfa hfacac hfb HMPA HNCC HOMO IGLO im Is* ISEELS KTP LDA LiDBB LNCC MA0 Me6[14]dieneN4

Abbreviations

xviii nb nbd NBS NCS NCT Neo NP np3 nta OEP OTf Pc PES PMDT Pd phen pic Pin pmedta PP3 [PPN]+ PY PYdZ PZ R-PROPHOS R,R-SKEWPHOS RDF ROMP sal salen saloph SCF TCNE TCNQ terPY tetraphos TFA tfbb tfacac tfo THF thsa tht TMBD TMEDA (tmena) tmP TMS to1 TP TP"

norbornene norbornadiene N- bromosuccinimide N-chlorosuccinimide neutron capture theory neopentyl 1-naphthyl N(CH2CH2PPh213 nitrilotriacetate octaethylporphyrin trifluoromethanesolfonate (triflate) phthalocyanin photoelectron spectroscopy pen tamethylenediethylenetetramine pentane-2,4-dionate 1,lO-phenanthroline pyridine-2-carboxylic acid (+)-pinany1 pentamethyldiethylenetriamine P(CH2CH2PPh& [(Ph3P)2NI+ pyridine pyridazine py razolyl (R)-( +)-1,2-bis(diphenylphosphino)propane

(2R,4R)-bis(diphenylphosphino)pentane radial distribution function ring opening metathesis polymerisation salicylaldehyde NN'-bis( salicyla1dehydo)ethylenediamine NN-bisalicylidene-o-pheny lenediamine self consistent field tetracyanoethylene

7,7,8,8-tetracyanoquinodimethane 2,2',2"- terpyridyl 1,I ,4,7,10,1O-hexaphenyl-l,4,7,10-tetraphosphadecane trifluoroacetic acid tetrafiuorobenzobarrelene trifluoroacetylacetonato triflate, trifluoromethylsulfonate tetrahydrofur an thiosalicylate (2-thiobenzoate) tetrahydrothiophen NNN'N"-tetramethyl-2-butene- 1,4-diarnine tetramethylet hylenediamine 2,2,6-6-tetramethylpiperidino tet ramet hylsilane tolyl hydro tris( 1-pyrazolyl)borate hydro tris(2,5-dimethylpyrazolyl)borate

xix

Abbreviations

TPP Trip Triph triphos TRIR Tsi TTF vi WGSR XPS XYl

meso-tetraphenylporphyrin 2,4,6-triisopropylphenyl 2,4,6-(tripheny1)phenyl 1,1,l -tris(diphenylphosphinomethyl)ethane Time resolved infrared (spectroscopy) tris(trimethy1silyl)methyl(Me3Si)& tetrathiafulvalene vinyl water gas shift reaction X-ray photoelectron spectroscopy XYlYl

1 Theoretical Organometallic Chemistry BY STUART A. MACGREGOR

1

Introduction

This chapter aims to cover theoretical studies on systems containing at least one metal-carbon bond. Studies on ‘carbon-analogue’ ligands (e.g. silane complexes) are included but work on cyanide complexes is excluded, as are studies of extended systems and organic species on models for metal surfaces. Sections 2 and 3 deal with the s- and p-block metals respectively with the dand f-block metals treated together in Section 4. Subsections treat structural andlor spectroscopic studies and mechanistic studies in turn, the latter generally including the determination of transition states. Only a brief mention of the methodology employed can be given and the highest level of theory is indicated, using standard abbreviations. Work based on density functional theory is designated DF (employing ‘pure’ density functionals: BP86, BLYP, etc.) or HDF (‘hybrid’ density functionals: B3LYP, B3PW91, etc.). Where different, model systems used in calculations are given, rather than the original experimental species. 2

s-Block Metals

2.1 Structural and Spectroscopic Studies. - 2. I . 1 Interactions with Carbon and Carbanions. Potential energy curves and spectroscopic properties for LiC (4E-),LiC+ (31T) and LiC- (’E-) have been studied with MRSDCI calculations.* Including core-valence effects shortens Re and increases We and De. HDF calculations on [MeLiI2and MeLi. - -LiNMe2highlight the importance of monomer distortions in maximising intermolecular electrostatic interactiom2 For MeLi...S systems (S = Me20, C6H6, MeC-CMe) monomer distortion is less significant. The stability of ketenimines, RHC=C=NH, is greatest for electropositive ~ubstituents.~ When R = Li or MgH, HF-computed geometries suggest an ynamine resonance form is significant. With R = Na a n-complex is located. HDF calculations on diaminocarbenes, C(NR2)2 (R = H, Me), show that lithiation causes an increase in the rotation barrier around the C-N bonds and an upfield shift in 13Cresonance, although these effects are only about half those of protonation? The interaction between phosphavinylidene, [MeP=C(Cl)]-, and [Li(DME)2]+is primarily ionic in nature and has little Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001 1

2

Organometallic Chemistry

effect on the structure of the anion (HDF calculation^).^ Alternative chelating structures for dilithiosulfoximes and lithiated phosphoric triamides have been studied. The former favour a 1,3-dilithiosulfoxime (CBS-Q//MP2)6 while a C,O chelate is preferred in the latter (MP2//RHF).7 Mg-C distances in MgR2 (R = Me, Et) at the RHF level agree well with observed data (R = n-pentyl).' 2.1.2 Interactions with Small Molecules. Gas-phase Na+ affinities for (in order of increasing interaction) CH4, c02, C2H2, C2H4, C6H6 and C ~ H S O Hhave been calculated at the MP2 level.' The interactions of Na' with C2H6, CH4 and C 0 2 within a model aluminosilicate cage have been studied with DF calculations. l o MP2//DF calculations show an increased interaction between [Li(OMe2)3]+and the fluorobenzene C-F bond compared with benzene C-H bonds, consistent with enhanced cation binding exhibited by fluorinated cryptands." Li atoms are computed at the QCISD level to form fourmembered ring structures with HNCX (X = 0, s)species.12 QCISD(T) and HDF calculations on [M-C0I2' (M = Mg, Ca) and [MCO]+ (M = Li, Na, K, Mg, Ca, Al) reveal a preference for the carbonyl over the isocarbonyl form.l3 Dissociation to M2+ + CO is hardest for [Mg-C0l2+. Geometries and vibrational frequencies for Group 2 M(OH)2(CO) species have been computed at the RHF 1 e ~ e l .D l ~F calculations predict a doubly-bridged silonyl structure for Li2Si0 and a 40% red-shift in vsio upon c~mplexation.'~ A phosgene-like structure is computed for the Ag analogue. An 0-bound geometry was found for Naf-C02 using methods up to the CCSD(T) levelI6 while Mg forms a metastable q2-0,0-bound c0mp1ex.l~In addition, a weakly bound van der Waals complex was computed for Mg(C2H4) but Mg(C2H4)2 and Mg(C2H4)(C02) both form stable five-membered metallacyclic structures (MP2 level).

2.1.3 Interactions with n-Ligunds. Several studies on the interaction of Group 1 cations with benzene have been published.' Inclusion of electron correlation and BSSE effects is important, although MP2 and CCSD(T) results are similar. * Cation-n-complex interactions decrease going down the group but are competitive with complexation by amines, ethers or alcohols. Topological analysis of the RHF-calculated electron density in M-n-complexes (M = Li+, Na+, Mg2+) helps establish a bond order-bond length relationship for arene ligands.19 [M(naphthalene)],+ complexes (M = Li, Na, K; n = 1, 2) have been studied with HDF methods.20 [M(naphthalene)]+ exhibits a C, minimum with the cation placed centrally over one c6 ring. Binding energies again decrease down the group. C2h minima are most stable for [M(naphthalene)12+species with the second naphthalene molecule binding more strongly than the first. Interactions of s-block cations with heteroaromatics have also been studied." Anisole is computed to be an ambidentate ligand, the q6-site being preferred to an 0-bound form with Li+, although this is reversed for the heavier cations (Na+-Cs+, MP2 calculations).2' Analogous structures with phenol are close in energy (Na+, MP2 calculations;' Na+, K+, Mg2+, HDF calculations22). Although B3LYP calculations overestimate binding energies,

I : Theoretical Organometallic Chemistry

3

trends are reasonable with higher values computed for phenol and indole than benzene. HDF calculations on LiCp, Li2C4BH5,Li3C3B2H5and Li3C3B2H3Ph2.Me20 (1-4) show the short Li-heterocycle distances in an analogue of the last mentioned to arise from (i) the large negative charge on the ring (ii) the lack of external ligands on the ring-capping Li cations and (iii) the ligation of the q2Li by the ether and phenyl ring moieties.23A linear structure for cesocene, [Cp3Cs2]-, is computed in the gas-phase (HDF calculations) but force-field calculations indicate a bent structure in the solid state.24RHF calculations on the chiral amide, [PhC(H)MeI2NLi, show the most stable rotamer benefits from Li-- .Ph ring n;-interactions which result in significant rotation barriers.25 x-interactions are also important in the selective extraction of Cs+ by 2benzylphenol/2-benzylphenolateassemblies and have been studied using MM and a6 initio methods.26MP2 calculations show the lowest energy conformation of the l-aminoallyl complexes, Me2NCHCHCH2M(M = Li, K) is an q4endo-in structure, 5.27 For M = Li, dimerisation is favourable and specific solvation induces a 3-lithioenamine structure. In contrast, dimerisation is disfavoured for M = K and solvation has little effect on the monomer structure. D F calculations on an A1(8-hydroxyquinoline)3 complex doped with Li and K atoms28 and EHMO calculations on the electronic structure of a 2]29 have been lithium molybdate complex [LiMo(NAr)2(o-C6H4(CH2NMe2)} published. Both systems feature stablising M -..C interactions.

1

2

3

4

5

2.1.4 Fullerenes and Carbon Nanotubes. D F calculations show that the photoionisation cross sections and asymmetry parameters of M@C60 species (M = Li, Na, K) are unaffected by the nature of the metal, although ionisation potentials are shifted relative to c60, consistent with electron transfer from M to C ~ O .INDO-calculated ~' geometries of C60M 12 species show regular structures for M = Li and Na with metal atoms lying above the C60 pentagonal faces.31For M = Be a Jahn-Teller distortion is calculated. Barriers for insertion of Na or K atoms into carbon nanotubes have been simulated with D F molecular dynamics calculations and show upper limits of 40 and 90 eV respectively.32

2.2 Mechanistic Studies. - 2.2.1 Alkyl-lithium and -magnesium Reagents. The stereoselectivity of silyl group migration in a-metallated silyl ethers, MCH(R)OSiH3 (the Reverse Brook reaction, M = Li, Na) has been studied with MP2 calculation^.^^ Rearrangement to a stable intermediate featuring a five-coordinate Si centre occurs through C-0 bond rotation (with retention of

4

Organometallic Chemistry

configuration at C) or through SN2-like attack of SiH3 at C (with inversion). For R = H both pathways are similar in energy; when R = Me retention is favoured while for R = vinyl inversion is preferred, consistent with experimental trends. Retention of configuration at Si occurs in all cases. A similar five-coordinate pathway is computed for the related Wright-West rearrangement of LiCH20GeH3 although here no intermediate was located.34 An alternative dissociative pathway is much higher in energy (CCSD(T) calculations). PM3, MP2 and HDF calculations all indicate that the steric bulk of the diamino auxiliary is most important in producing high enantioselectivity in the depot onation of alkyl carbama tes with alkyllithium reagents.35 Similarly, the diamino auxiliary controls the alkylation of lithio-indenyl car barn ate^.^^ With C 1 ( -)-sparteine PM3 calculations highlight possible stereoisomerism between two diastereomers. With C2 symmetric ( -)-a-isosparteine one diastereomer is favoured and higher selectivity is predicted and indeed observed. PM3 calculations also account for the reactivities of 2-butenoic acids with ~ - B u L ~ . ~ ~ Computed activation energies suggest that conjugate addition is favoured over metallation for 2-butenoic acid, but that E-y-metallation is slightly more favoured for 2-methylbut-2-enoic acid. With 3-methylbut-2-enoic acid Z - y metallation is preferred. HDF calculations show a significantly reduced barrier for the Li-ene cyclisation of lithiated dienes (6) compared with an alternative carbanion induced-ene cyclisation (7). The former is 11-12 kcal/mol endergonic, however, and so must be followed by an irreversible rea~tion.~'

6

7

DF studies on Mg, and MeMg, clusters (n = 1-8) suggest the latter are stable enough to act as intermediates in Grignard reagent formation.39 The organometallic species are also more reducing and feature stronger Mg-Mg bonding. Further calculations on MeMg2 and MeMg4 show structures with terminally bound Me groups are most stable, with significant barriers for ligand movement around the cluster.40A novel mechanism involving MeMgCl bound to the metallic surface was modelled with calculations on a MeMg5C1 cluster, which, upon optimisation led directly to the Grignard species. 2.2.2 Other Reactions lnvolving Lithium and Sodium Reagents. HDF calculations show a key intermediate in the diastereoselective methylation of cyclohexenone with (Me2CuLi)2 is a copper-olefin complex from which rate-determining methyl migration occurs.41A Li-carbonyl complex is kinetically unimportant. MNDO calculations on the reaction of [PhLiI2 with E-cinnamaldehyde shows Li attack at the P-carbon facilitates a [1,2]-H shift, yielding dihydrochalcone product p r e c ~ r s o r s .Inclusion ~~ of solvation effects (THF via a COSMO approach) significantly reduces the activation barrier. MP2//RHF energy profiles for the addition of H-, LiH and Li+H- to MeC = CH show that the Li

1: Theoretical Organometallic Chemistry

5

species decrease activation energies and increase the preference for Markovnikov products.43Li reduction of hexaphenylbenzene yields a distorted dianion in which the central ring interacts with Li+ (DFIMNDO calculations).44This structure brings two ortho-hydrogens close together facilitating dehydrogenation and C-C bond formation. An MP2IIRHF study shows the reaction of CH3+ with q2-C,0 CH2=C(Na)OH to involve isomerisation to an O-bound form followed by CH3+ attack, displacing Na+.45An alternative carbenoid mechanism is much higher in energy. With CH3- metal-assisted ionisation occurs with a subsequent 1,2-migrationresulting in OH- displacement.

3

p-Block Metals

3.1 Structural and Spectroscopic Studies. - 3.1.1 Species Combining Aluminium and Carbon. A1C2 adopts a C2, 2A1structure with a C,, alternative lying 8.7 [CCSD(T)46] or 11.4 kcalImo1 (QCISD47) higher in energy. A 4BI structure is favoured for AlC3 while AlC2N features a C2N triangle with an exocyclic Al.46Boldyrev and co-workers also show that AlC2- exhibits a cyclic structure while AlCSi- and AlCSi are q ~ a s i - l i n e a rCCSD(T) .~~ calculations on A1,C- species (n = 3,48 449 and 5”) indicate effectively planar structures, supported by computed ionisation potentials. Al. - .A1 interactions make A14C- the smallest species with a planar, tetracoordinate C atom. 3.1.2 Group 13 Metal Alkyls. HDF-computed structures and vibrational frequencies for M-CH3 species (M = Ga, In) support the first experimental characterisation of these species in Ar matrices.51In+ affinities for CH3 and C2H3 (as well as CH4and C6H6)are in excess of 20 kcal/mol (HDF calculations), but lower than those for Al+.52 The experimental characterisation of Me2A10CH3 is supported by good agreement between observed and HDFcalculated vibrational energies.53 Bond energies and heats of formation have been computed at the CCSD(T) level for InMe, species (AH298= 40.3, 50.2 and Intramolecular transfer of Br to 20.1 kcallmol for n = 1 , 2 and 3 re~pectively).~~ In in Br21nCH2Bris calculated to cost 87 kJImo1, with decomposition to InBr3 and C2H4 being exothermic by 31 kJImol (PM3 calculation^).^^ A bonding analysis of an AlC2 heterocycle with an exocyclic A1R2 substituent reveals nonclassical 3c-2e- bonding consistent with the observed short C-Ale,, and long Al-C,,d, bonds (RHF and HDF calculations, QS6

8

9

3.1.3 Group 13 Metal n-Complexes. A review of CpAl(II1) chemistry includes theoretical progress in this area.57 A novel contrabinding rotation has been

6

Organometallic Chemistry

identified in Al+-L systems (L = benzene, furan, cyclopentadiene and pyrrole) in which the n-ligand rotates towards the metal ~ e n t r e . ’Transition ~ states, e.g. for benzene, 9, lie below dissociation limits (DF, HDF and up to QCISD(T) methods). Complexes of AlX3 (X = H, F, C1) with benzene exhibit C, structures while with C2H4 symmetrical complexes, dominated by electrostatic interactions, are found (MP2 le~el).’~The computed structure of the Alf(C2H4)(02) cluster6’ suggests that the dioxygen moiety barely perturbs the Al+(C2H4) unit.61The interaction of Al+ with phenol and indoles has also been studied.22 RHF//DF-computed 69Ga, 31P and 13C chemical shifts for (C4H2t-Bu2P)Ga support experimental evidence for an q ’-structure, the first main group metal complex featuring a polyhapto phospholyl ligand.62MP2 calculations on [MCpln complexes (M = T1, In; n = 1, 2) yield good agreement with experimental structures (n = 1) and dimerisation energies (- 12.4 and - 15.8 kcal/mol for In and T1 re~pectively).~~ Linear geometries are computed for [Cp2M]- and [Cp2MIf and C3”structures for MCp,. HDF calculations locate a bent gas-phase structure for [Cp3T12]-.24 3.1.4 Systems with Metal-Metal Bonds. Reviews of systems featuring Group 13 metals bound to transition metals64 and of those containing multiply bonded Group 13 metals6’ have been published. Analysis of the M-Fe interaction in RMFe(C0)4 species [R = Me, Cp, N(SiH&; M = Al, Ga, In] shows it to be dominated by o-donation from the lone pair of the singlet RM fragment with little evidence of Fe+M n-back bonding.66 MeM binds more strongly than CpM and interaction energies decrease going down Group 13. D F calculations on CpAlCr(C0)’ reproduce experimental structures reasonably with the short A1-C distance and low vco interpreted in terms of strong Al+Cr donation.67 In contrast, Frenking and co-workers present evidence for enhanced Fe--+Ga n-back bonding in PhGaFe(C0)4 (D,(GaFe) = 54.9 kcal/mol) compared with CpGaFe(C0)4 (D,(GaFe) = 32.9 kcal/mol).@‘These workers question viewing these systems in terms of single or triple metal-metal bonds and advocate Dewar-Chatt-Duncanson bonding schemes, quantified via CDA schemes. HDF calculations imply strong bonding and significant Ni+E n-back donation in Ni(EMe)4 species (Do= 53.2 (E = Al) > 40.7 (Ga) = 43.4 (In) > 27.0 (Tl) CJ 20.0 kcal/mol calculated for Ni(C0)4).69 Ligand substituent effects on Co-Ga bond lengths in [(L’(C0)3Co)GaX2L] ( L = CO, PH,; L = NH3; X = H, Cl) have also been analysed with HDF c a l c ~ l a t i o n sHDF . ~ ~ calculations on Me2Ga2(02CH)2 favour a bridged form and support sp-hybridised Ga

centre^.^' 3.1.5 Others Studies with Group 13 Metals. MP2 calculations on L-EX3

adducts (X = C1, F, E = A1-In) show donor strengths generally follow the trend L = C(NH2)2 > NH3 > C0.72The interaction of CO with Al(OH)3 has been computed at the RHF level14 and complexes formed between A1 and Ga atoms with CO2, CS2 and COS have been studied at the HDF and QCISD(T)// MP2 levels.73 The tendency for A1 to form pentacoordinate structures in bicyclic pentalene-like structures is intermediate between that of B and Si

I : Theoretical Organometallic Chemistry

7

(MP2 Of six possible isomers considered for the interaction of an A1 atom with acetylene a C-H insertion species is most stable, with a vinylidene structure lying to slightly higher energy (DF and HDF calculation^).^^ CCSD(T) calculations show linear [T1(CO)2]3' to be a local minimum structure, but a low barrier for decomposition to TI+ + 2CO+ suggests this species may be difficult to observe.76 3.1.6 Group 14 Organometallic Species. HDF calculations on the [Ge,H,C]"+ systems show linear 'E and 211 Ge-C-H structures are most stable for the cationic and neutral systems respectively, while bent3 A ' [H-Ge-C]+ may be observable e~perimentally.~~ An HDF study has compared the stability of diand tetra-valency in the Ge, Sn and Pd congeners of formic acid and hydroper~xycarbene.~'The tetravalent form is always preferred, but the divalent species do become more accessible down the group. MP2 calculations show the Ge-C bond in RGeH3 (R = CH3, C2H5, C2H3 and C2H) weakens and lengthens upon d e p r ~ t o n a t i o nThe . ~ ~various structures of GeC2Hx(with an intact C-C bond, x = 4-7) and their formation from GeHx-4 and C2H4 have been considered with QCISD(T) calculations." Calculations and electron diffraction data have defined gas phase structures for Me2GeC4&," Me3MONMe2 (M = Ge,82 Sn,83 all MP2) and HC(GeBr3)' (RHFg4). The photoelectron spectra of two germaimines have been assigned with the aid of HDF calculations85~86 and computational studies on p-anisylgermane (MP287), arylgermatranes (MNDO") and Group 14 metalloles (AM 1") have been reported. MNDO heats of formation for Cp-type Group 14 metal derivatives of C20H15 and C60H5 indicate such complexes are most accessible for M = Ge.90 MM-based MD simulations of 9R,12S-[t-Bu2Sn]2O-derivatised erythromycin-A produce a well-defined conformation consistent with 17 3J ('H-'H) and 21 J (13C-'H) experimental coupling constant^.^' PM3 calculations have identified possible complexes formed between Me2SnIv and a dinucleoside triphosphate duplex.92Two feature tetrahedral Sn bound to base heteroatoms while two exhibit octahedral Sn (consistent with Mossbauer data) bound to phosphate backbone oxygens and two water molecules. AM 1 calculations locate distorted tetrahedral structures for various R3Sn(carboxylate) species and highlight a link between geometry and Lewis a~idity.~'GIAO-DFT calculations of 207Pbchemical shifts for Me3PbX species (X = x-donors) using either the ZORA or Pauli spin-orbit formalisms both give good qualitative agreement with experiment, although the former gives better absolute agreement.94PM3-optimised structures for Mes3PbBr and Mes2PbBr2are in reasonable agreement with experimental structure^.^^ Three reviews of the chemistry of doubly bonded Group 14 species summarise theoretical progress in this MP4//RHF calculations indicate that the s-trans conformer, 10, of tetragermabutadiene is most stable with both Ge=Ge bonds exhibiting a trans-bent arrangement.99Although two cyclic isomers, 11 and 12, are more stable, their formation would depend on the steric demands of any bulky groups used experimentally. Computed

8

Organometallic Chemistry

geometries for tria- and penta-fulvene species with exocyclic Ge and Sn derivatives suggest low aromatic character, albeit larger than in C and Si analogues.'" A DF calculation on (H3P)2NiGeR2 (R = 2,4,6(CF3)&H2) reproduces the short observed Ni-Ge distance, indicating the presence of Ni -+Ge .n-back bonding. lo' H Ge-Gk

I \

Ge-Ge,,,H Hi\' 4 b H H

H 10

11

H Ge.H:Ge

I

Ge-Ge,,,H H\\' 4 H

\

H

12

3.1. 7 Organobismuth Species. PM3 calculations on a series of mononuclear and binuclear organobismuthines show that the former are all pyramidal with inversion barriers ranging from 33.7 to 68.7 kcal/mol.lo2 Computed bond orders suggest a degree of Bi-Bi bonding in the binuclear species. Reaction energies for the addition of hydroxy anions and methyl cations help establish trends in stability.

3.2 Mechanistic Studies. - 3.2.1 Group 13 Species. D F calculations on polymethylaluminoxane (MAO) indicate a cage structure with four-coordinate aluminium and three-coordinate oxygen is favoured. lo3 Formation of Lewis acid sites requires interaction with A12Me6 and a novel structure for the ionpair intermediate, [MAO-Me]- [Cp2ZrMe]+, featuring an occluded methyl group is proposed. A barrier of approximately 25 kcal/mol is computed for the insertion of C2H4 into the A-Me bond of [AlMe{MeC(NMe)2)]' with both D F and Carr-Parrinello MD methods. lo4 Insertion into the terminal AlMe bond of a related dimer is significantly harder. An MP2 study shows the carboalumination of alkenes and alkynes with X,Al-R species (R = Me, Et; X = H, C1, R) proceeds via a n-complex followed by nucleophilic attack of the alkyl anion.8 Substituent effects are small. RHF calculations show the formation of Me2A1(Me2N)2Li.pyrfrom [ { Me2A1NMe2l2] and [{ Me2NLi.pyr}2] dimers is exothermic by 18.4 kcaVmol and driven by the alleviation of steric strain in the Li dimer.'05 The mixed-metal benzyl analogue gains extra stability from Li-C(H)benzylinteractions. DF- and MP2-energetics for the uni- and bimolecular decomposition of Me2AlH are similar and suggest these are unlikely processes in low temperature CVD regimes.lo6 Dimer or trimer formation is much more favourable. 3.2.2 Group 14 Species. The oxidative addition of (H0)2-XH3 to M(PH3)2 (M = Pd, Pt)lo7 and C-X bond forming reductive elimination from Pd(XH3>(q3C3H5)(PH3)(X = C, Si, Ge, Sn)lo8have been studied. Su and Chu have studied the reactions of germylenes with small molecules. HDF calculations show trends for the insertion reactions of germylenes, GeXY (X = H, Y = H, Li, CH3, halides; X = Y = Li, CH3, halides), and Ge=CH2with CH4 are related to

1: Theoretical Organometallic Chemistry

9

the germylene singlet-triplet energy gap. '09,' lo This is lowest for x-acceptor, bulky or electropositive substituents and results in low activation energies and more exothermic reactions. A study of the same reaction with the germylene Arduengo-type carbene analogue revealed less favourable energetics compared to the C and Si analogues."' The insertion of Ge(CH3)2into X-H bonds (X = CH3, NH2, OH, F, SiH3, PH2, SH, C1) was easiest for HCl, the reaction becoming harder moving up and to the left along the periodic table.'I2 Trends are again related to reactant singlet-triplet energy gaps and steric effects. Finally, the cycloaddition of ethene with various germylenes including Ge(CH3)2 and Ge=CH2 involves an initial x-complex and is favoured with electropositive substituents.' l 3 Fragmentation energies for [Me3Sn-R]+.radical cations at the MNDO level follow the trend R = i-Pr > Me > allyl > benzyl > Ph and reflect Sn-R bond strengths. l4 The observed greater alkylating ability of the allyl and benzyl species arises from the lower ionisation energies of the neutral precursors. HDF-computed 13C chemical shifts are consistent with an endo structure for cyclononatetraenyl(trimethyl)tin, C9H9SnMe3.l1 A computed activation energy for a [1,9]-SnMe3 sigmatropic shift (26.4 kJ/mol) is in excellent agreement with the experimental value and this process is clearly favoured over [1 4 - and [ 1,7]- alternatives. The preferred pathway for 1,3 migration of H3XCH2C(0)H species (X = Si, Ge, Sn) features intramolecular nucleophilic attack with retention of configuration at X (HDF calculations).' l 6 Activation energies decrease down the group, reflecting the greater accessibility of pentacoordinate geometries. A QM/MM (HDF) study of transition states for the reactions of 1-alkoxy- and 1-alkyl-1-alk-2-enylstannanes with aldehydes shows that the cis product is favoured by both bulky groups and electronwithdrawing C1 ligands on Sn.' l7 The 1-alkoxy substituent allows hexacoordination of Sn in the transition state, lowering activation barriers.

'

4

d- and f-Block Metals

4.1 Structural and Spectroscopic Studies. - 4.1.I Species Combining a Transition Metal and Carbon. MRCI calculations on the 'Z+ ground state of NiC yield re = 1.621 we = 874 cm-' and Do = 2.70 eV.l18 HDF calculations indicate that quintet Ti2C2 has a rhombic structure with a transannular C-C bond.'" DF calculations show the structures of Ti,C2, species build into cyclic clusters with Tic2 subunits'20 while Ti6C13and Ti7C13resemble more closely TigC12.121For FeC2 a CzVquintet lies only 20 kcal/mol below a linear species; the accessibility of the latter may lie behind the difficulty in forming iron MetCar species.122 HDF calculations show [PtC,]+ species (n = 3-9) prefer linear geometries while larger structures favour open- and closed-ring forms (n = 1016).123 and La2@C79Nsuggest that non-IPR HDF//HF calculations on structures and those featuring heptagonal rings may be stabilised by encapsulated metals.124 Calculations indicate that the bonding in the endohedral

A,

Organometallic Chemistry

10

fullerenes sc2@c82 (HF12') and Sc3@Cg2 (DF'26) is highly ionic. The latter also exhibits a non-IPR structure. Geometries of metal-coated fullerenes C60M62 (M = Ti, V) have been computed with D F calculation^'^^ and HDFcomputed structures are reported for Nb+@C40, Nb+@C40H4 and NbfC39. 128 4.1.2 Cyclopentadienyl Derivatives. The MP2 calculated Zr-I bond energy in Cp2Zr12 is in reasonable agreement with that of an experimental analogue (64.0 vs. 58.0 kcaymol). 129 The photoelectron spectrum of C P ~ Z ~ ( B H has ~)~ also been assigned with MP2 c a l c ~ l a t i o n s . 'A ~ ~new force field for ansazirconocene complexes has been developed. 31 Comparison of [ZrCp3]+with B(C6F5)3shows the former to be a stronger Lewis acid as no rehybridisation is required upon adduct formation (DF calculations). 32 CASSCF calculations on (CpM)(CpM')(p-COT) systems (13) suggest the two mononuclear subunits are unchanged from the parent metallocenes. M-M' bonding occurs when both centres have unpaired electron density.133 The electronic structures of [Cp2Ta(q2-butadiene)(CNMe)]and [Cp2Ta(CNMe)2]+show the bonding of the isonitrile ligand to be dominated by electrostatic effects.134

'

M = M' = V, Cr, Fe, Co

13

14

CO dissociation from ansa-bridged Cp2MCO species (M = Cr < Mo < W, D F calculations) is disfavoured as the favoured parallel ring geometry of the triplet metallocene cannot be accessed.135 Poli and co-workers have studied CpCrX2(PH3), species with HDF calculations. For X = CN a doublet 17ecomplex (n = 2) is readily accessible.'36 For X = C1 a quartet 15e- species is located while the quartet 17e- species corresponds to a PH3-exchange transition state. 137 A further study showed (pyramidal) singlet and (planar) triplet forms of CpW(N0)L (L = PH3, CO, =CH2, C2H2 and C2H4) are close in energy. 138 Two-state singlet-triplet-singlet processes were proposed for inversion of the singlet species (L = CO) and rotation of the alkylidene ligand. D F calculations reproduce the unusual structures exhibited by [CpWH3(dppe)]O/+ species and the strengthening of the W-H bond upon 0 ~ i d a t i o n . The l ~ ~ nature of the spin-carrying orbitals in bis-isodicyclopentadienyl derivatives (M = VNi)l4O and decamethylbimetallocenes (M = Co, Ni)141 have been studied by EHMO calculations. D F calculations on [CPM~(PH~)~=C=C(R)C(R)=C=Mn(PH3)2Cp]o'1+'2+ systems suggest an electronic preference for a trans C=C-C=C unit (R = H) although steric effects (R = Ph) may force a twisted ~ t r u c t u r e . 'HDF ~ ~ calculations find the Cr-Cr bond in the fulvalene complex, 14, is 1.7 kcal/mol stronger than in the conventional Cp dimer.'43 ML homolytic bond strengths have been computed with D F methods for TiLC13

I : Theoretical Organornetallic Chemistry

11

(L = Cp > NPH3) and Re03L complexes (L = NPH3 > C P ) . ' ~Re-0 homolytic bond strengths in LRe03 species (L = Me, Ph, Cp, Cp*) suggest that HDF methods provide the best comparison with experimental data.'45 HF calculations on c60H~FeCpsuggest the interaction of FeCp with the fullerene ligand may be greater than that with Cp itself. 146 HDF calculations on Cp*Ru(q5-C3H3N2)highlight similarities between the q 5-pyrazolato and Cp ligands, suggesting a range of such complexes should be ac~essib1e.l~~ A new structural force field for Group 8 metallocenes has been developed and tested on Cp2M derivatives.148 MM calculations have also probed the conformations of CpFe(CO)2-CH2C(0)NEt2.'49 A joint NMR and HDF study of [Cp2FeH]+suggests the proton is delocalised between the Fe and all ten C atoms. The electronic structure of (C5H4L)2Fe[L = C E C-Pt(PH3),H] has been studied with EHMO calculation^.'^' DF studies on 16e- CpFeL2 species suggest that triplet, pseudo C2v geometries are stabilised by large HOMOLUMO gaps (L = n-donor) or poor HOMO-LUMO overlap (L = H). Strong z-acceptors induce good HOMO-LUMO overlap and singlet pyramidal geometries.152 The chemical inertness of planar [Cp*Ru(NN)]+systems (NN = chelating diamine ligands) also derives from a large HOMO-LUMO gap that develops upon distortion to a pyramidal geometry.lS3The NLO activity of derivatised (arene)FeCp* species has been assessed with INDO calculations'54 and the site of nucleophilic attack at a Cp*Ru-complexed biaryl lactone rationalised via the DF-calculated Fukui function. 55 HDF calculation. favour triplet forms of CpCoL (L = PH3 or C2H4) and the accessibility of the triplet means that dissociative PR3 exchange on C ~ C O ( P Rshould ~ ) ~ be facile. EHMO calculations have been used to interpret the ESR spectra of CpCo(pentafulvene) complexes. 57

'

4.1.3 Other Metal-Polyene Complexes. HDF calculations on M+- C6H6 systems (M+ = Ti+ to Cu) locate c 6 v geometries, except where Jahn-Teller effects lead to C2vboat structures (M = V+, 6Fef, 4Fe+ and Ni+).'58HDF and MRSDCI calculations show Nb-.-C& also has a c 6 v geometry while Nbf..-C6H6 is c2v. In Nb2+--.C6H6the Nb2 unit lies over the ring while Nb2+--.C6H4 features one n- and one cr-bound metal.159Cr+ exhibits an inplane bridging mode with C6H6--nFn species when adjacent fluorines are present, otherwise an q6-mode is favoured. HDF binding energies increase by around 5 kcal/mol for each additional fluorine.16' The bonding of Cr+ and Fe+ to phenol and indole is significantly stronger than that to benzene.22For Cr+/ phenol n- and 0-bound forms are close in energy while the former is preferred with Fe+. MP2 calculations on Group 11 M+---C& species find q q2- and q6-forms are close in energy for Cu+ and Ag+ while the q6-structure is disfavoured for Au+. DF calculations find q2-binding modes are preferred for benzene, toluene and p-xylene with [FeT"TPP]+and interaction energies increase with the degree of methylation.'62 HF, MP2 and HDF calculations on Hg;+ (n = 2 or 3) with benzene or chloride ions in the axial primary coordination sites suggest that benzene prefers an q '/quasi-q3 binding mode and that aromatic species may be able to stabilise such subvalent clusters.163

'-,

12

Organometallic Chemistry

Two studies show the Cr(C0)3 unit can significantly stabilise benzyl cations and anions. The benzyl radical, however, exhibits an undistorted q6 geometry and little change in hydrogen atom affinity upon complexation. 164 Further calculations highlight the greater conformational stability of the charged species.'65 A new force field for (q6-arene)Cr(C0)3 species has been developed'66 and force field'679i68 and EHM0'69 calculations have been applied to derivitised analogues. EHMO calculations confirm delocalisation of the unpaired electron density onto the alkyne in the [(~-arene)Cr(CO)~HC = CHI+ ~ati0n.I~' The site of protonation in (q-arene)Mo(P3) species can be related to the sterically accessible electron density, as visualised from PM3 calculations. 71 HDF calculations on ( ~ l ~ - x ) M n ( Cand 0 ) ~[(q3-X)Mn(C0),l2- species (X = cyclic n-ligands) show X-Mn bonding weakens as the n-system becomes more extensive.172 Exocyclic q3-binding is preferred with rigid C5 ligands while more flexible ligands can accommodate folded endocyclic q "geometries. The fluorenyl ligand in (q3-indenyl)Mo(q3-fluorenyI)(C0)2exhibits an exocyclic q3binding mode.173 Calhorda and Veiros have reviewed their work in this area.174q6,q6 haptotropic rearrangements in substituted naphthalene chromium tricarbonyls involve a trimethylenemethane transition state structure with DF activation energies of 26-30 kJlrn01.'~~EHMO calculations on (H0)3V-C6H6-V(OH)3 suggest that p:q3,q3 and p:q2,q2 benzene binding modes are similar in energy and preferred over a p:q6,q6 Calculations on ( T ~ - C ~ H ~ ) F ~stress ( C O )the ~ need to treat electron correlation to produce an adequate description of this m01ecule.l~~ HDF calculations on the three isomers of (q-C4H5Me)Fe(C0)3 have related geometries and configurational stabilities of the corresponding cationic, anionic and radical systems to the synthetic utility of these species.17' Computed thermodynamic preferences for rotameric forms of C4-substituted (q-C4HsR)Fe(C0)3 derivatives (R = vinyl, acyl) are consistent with the observed selectivities of nucleophilic attack. 179 D F calculations on (q5-C7H7)Fe(CO), show a slightly higher hydride affinity compared to the free tropylium cation, although reactivity with nucleophiles may be slowed due to a destabilisation of the polyene LUMO and a lower degree of C-based character, 'O EHMO calculations indicate that a cis geometry is preferred for the 1-azadiene ligand when bound to the Fe(C0)3 unit. 18' Diphosphacyclobutadiene complexes of CpCo and (C0T)Ti have been studied with HDF calculations. For CpCo direct formation of the ligand from bis-phosphaalkyne precursors is likely while metallacycle intermediates are more accessible with (C0T)Ti.lS2 The electronic structure of [(q3-CH2C= CPh)Pt(PH&]' has been studied with Fenske-Hall calculations. 183 D F calculations reproduce the experimental structure satisfactorily once the Ph substituent is included. Nucleophilic attack occurs at the central carbon and a possible metallacyclobutene intermediate is proposed. The bonding of MeM to the C12Ti(C=CH)2 'tweezer' ligand (M = Cu, Ag, Au) is dominated by charge donation from MeM to the acetylide, the Lewis acidity of which is enhanced by the TiC12 unit.'84 CASSCF, MRCI and CCSD(T)//MP2 calculations on bis-arene lanthanide

1: Theoretical Organometallic Chemistry

13

and bis-arene Th and U species indicate all are stable with respect to loss of both arene ligands.185 Metal-ring interactions are stronger for the actinides (Th > Ce; U > Nd), due in part to relativistic effects which enhance back donation. D F calculations on (1, ~ , ~ - R & G H ~species ) ~ A C(Ac = Th-Am) prefer a bent C2" structure for the earlier metals when R = H or Me.'86 However, steric repulsion (R = t-Bu ) forces a linear structure. A further DF study on (C6H6)2Ln species (Ln = La, Ce, Eu, Gd and Lu) correctly reproduces experimental trends in bond dissociation energies, although absolute values are ~nderestimated."~Metal 5d to arene n-back donation in these systems arises from 6s 5d electron promotion. D F calculations on bis-pentalene complexes of Th and U indicate a preference for D2d or D2 structures over a D 2 h form.'88 Computed ionisation energies agree well with PES data and an MO analysis indicates metal-ligand covalent bonding is more significant with the 6d rather than the 5f metal orbitals. DF calculations have also been carried out on (C0T)Sm systems and suggest that intramolecular coordination is possible when COT ligands bear chelate arms.189 -+

4.1.4 Metal Carbonyls. Zhou and Andrews have used DF-computed vibra-

tional data and isotopic labelling studies to identify the products formed from laser ablated transition metal atoms (SC,'~'Ti and V,191 Nb,'92 Fe, Ru and os,'937'94 Co, Rh and Ir,195,196and C U ' ~ and ~ ) CO. The BP86 functional produces closer agreement with observed data than the B3LYP approach. The ground and excited states of [FeCO]+ have also been computed with MCQDPT2 and CCSD(T) methods'98 and studies of MCO (M = Fe, Ni)'99 and Ni(C0)2 have been published.200The homoleptic carbonyls of Group 11 and 12 metal cations [M(C0)1-6]+'2+have been surveyed.201 CCSD(T)//MP2 bond dissociation energies agree well with experimental data but these are overestimated with D F methods, especially for monocarbonyls. NBO/CDA analyses show coulombic interactions dominate bonding, especially for the Group 12 species. D F calculations show thiophene forms weak adducts with Cu(CO)1-3 species and does not displace C0.202UCO and U(C0)2, formed from the reaction of U atoms with CO, have also been studied. Photolysis produces CUO, OCCUO and ultimately (q2-C2)U02. A very short U-C distance of 1.764 is computed for CU0.203 Increasingly sophisticated methods are being applied to the electronic spectroscopy and photochemistry of transition metal carbonyls. Baerends and co-workers have published the first time-dependent DFT calculations of the electronic spectra of transition metal complexes.204 For Ni(C0)4 and Mn2(CO)lo results are competitive with CASPT2 and SAC-CI methods, although results are sensitive to the geometry used and assignments vary with the functional employed. For Mn2(CO)lo the weak, lowest energy band is assigned to a dn-+ o* transition with a stronger o+o* band to higher energy. Calculations on Group 6 M(CO)6 species confirm the orbitally-forbidden CT nature of the lowest band which is responsible for CO diss~ciation.~'~ Earlier ASCF results are similar to TDDFT calculations in the absence of significant configuration mixing. A CASSCF/MR-CCI study of the electronic spectrum

A

14

Organometallic Chemistry

of Fe(CO)5 locates three allowed transitions in the UVIvis region.206A d-d band at 27,000 cm- is responsible for the low energy photochemistry of this system while higher energy CT bands can lead to the loss of up to three CO ligands. CASSCFIIHDF calculations on Cr(C0)4(bpy) show an MLCT transition has a similar effect to one-electron reduction, resulting in population of a bpy x* orbital with some delocalisation onto the axial carbonyls via d x * mixing.207Spin-orbit coupling CI calculations on Mn(H)(C0)3(H-DAB) (HDAB = 1,4-diaza-1,3-butadiene) indicate a small splitting of the triplet GM-HLCT excited state which rises to 1000 cm-l for the Re analogue.208Coupling to a singlet MLCT band is inefficient and wave packet dynamics based on CASSCFIMR-CCI potentials suggest that direct CO dissociation is the only reaction arising from excitation in the visible region.209 The products of photolysis of CpV(CO)4 in triethylsilane have been characterised with CASSCF-PT2//HDF calculations.210Singlet CpV(CO)3 is more stable than the triplet form and solvation via an Si-H bond is favoured over a C-H Ginteraction. The electronic spectrum of Co2(C0)6C2RR' species has been analysed with ZINDO calculations.21 Computation of 95M0 chemical shifts in organometallic and inorganic species found pure density functionals performed better than hybrid methods.212GIAO-DFT methods have also been applied to the computation of 183Wchemical shifts.94Use of the ZORA approach in geometry optimisation of W(CO)6, Os(CO)5 and Pt(CO), has allowed basis set convergence studies for all-electron basis sets, results comparing favourably with CCSD(T)//MP2 calculations.213Treatment of relativistic effects in DFT,214the use of DFT to compute chemical shifts215and its application to organometallic structure and reactivity216have been reviewed. A further CIAO-DFT study of 57Fechemical shifts for ferrocene and Fe(CO)5 has highlighted the role of d-d couplings, with pure density functionals providing consistent results while hybrid functionals cause dramatic variation due to the incorporation of H F exchange.21 Fe-CO dissociation energies for Fe(CO)5 have been computed with hybrid and pure density functionals and compared with CCSD(T) calculations.218The incorrect description of atomic multiplets by pure DF methods affords poor results for FeCO and Fe(C0)3. SCF, MP2 and D F calculations on the geometries of M2(CO)9 and M3(C0)12(M = Fe, Ru, 0 s ) show D F methods perform best, especially for iron219The structures and CO dissociation energies of Cr(C0)6, Fe(CO)5 and Ni(C0)4 have been used to test the new PBE functional, with promising results.220 Symmetry force fields for transition metal carbonyl complexes have been produced on the basis of D F calculations.221Trends in force constants for isoelectronic [M(CO)6]" species are related to reduced x-back donation and significant electrostatic effects as the positive charge increases. A normal coordinate analysis of [Fe(Co)6]2' allows the assignment of force constants for all 13 fundamentals of this species.222LDA calculations including solvation effects (COSMO model) produce the best agreement with experimental IR data for Mn(CO)5Br and Mn2(CO)lo. PM3 and D F calculations on

1: Theoretical Organometallic Chemistry

15

Mn2(C0)6(PH2CH2PH2)2provide conflicting results.223The latter favour the all terminal-CO isomer with a barrier of 15-19 kcaVmol for CO exchange via a bridged form. Experimental and computational data suggest a C, geometry for MnCo(CO)9 and equatorial substitution in MnCo(CO)9-.(CNR), species (n = 1, 2).224D F calculations favour a C, form for HMn(C0)4 but suggest a C4" alternative may be observed in matrix isolation studies with a computed 140 cm- shift in V M ~ - Hof potential diagnostic use.225The vibrational spectrum of Re(CO)(H)2(NO)(PMe3)2provides a good test of the reliability of D F calculations as implemented in GAUSSIAN and ADF.226The ordering of VCO, VNO and V R ~ - His generally well reproduced; however, the intensities of two Re-H stretches are only reproduced with extended basis sets and accurate numerical integration. HDF calculations on Fe(C0)4(C2H4)aid in the assignment of the microwave spectrum of this species.227 n-Effects promote CO dissociation from Group 6 [M(CO)5X]- species through stabilisation of the 16e- species produced as well as destabilisation of the 18e- species.228Both effects decrease along the series X = NH2 > OH > F > C1 > Br > I > CH3 > H (DF calculations). mstabilisation in the 16eintermediate formed via CO loss from [W(C0)5(2-thiouracilate)]- is augmented by interaction of the chelate with a cis CO ligand, although the overall reaction is slightly endothermic (DF calculation^).^^^ An FMO analysis indicates that n-stabilisation is important in the [Mn(CO)3(S,S-C6H4)]complex. Ligand exchange with NH,S-C6H4 is endothermic (MP2 level) by 12 kcaYmol, in line with experimental CASSPTYIHDF calculations on phosphinidene complexes, Cr(CO)S(PR) (R = H, CH3, SiH3, NH2, PH2, OH, SH), show Cr-P bonding arises primarily from P+Cr o-donation, although n-back donation is significant when R is H, CH3 or SiH3.231A singlet electronic state is preferred with n-donor substituents. Cr-P bond energies vary from 216 (R = NH2) to 127 kJ/mol (R = SiH3). Steric effects in Cr(CO)5L complexes (L = organic substituents) have been assessed by ligand repulsion energies derived from MM calculations.232Good correlations with cone angles and solid angles are seen, although poorer agreement with A-values derived experimentally suggest electronic factors are also important. Other Group 6 M(CO)5L systems studied theoretically are for L = 1,2,4-selena- and tellura-diphospholes (HF and HDF calculations233), H3B-PH3 (Fenske-Hall calculation^^^^), E- 1,2-di-4-pyridylethane (HF and HDF calculations235),=C(H)O(BH2)2(MP2 and PCCP.237In the last case metal complexation represents a possible method to isolate the kinetically unstable ligand. Changes in the N-Re-N angle of the [Re(N0)2(PH3)2]' unit upon ligation depend on the nature of the added ligand, L, increasing for strong o-donorslzacceptors (L = CO, CNR) and decreasing with n - d ~ n o r s .Isoelectronic ~~~ R u ( C O ) ~ ( H ~ P C H ~ C H ~isP H computed ~) to have a distorted square-planar structure with inequivalent phosphorus atoms (HDF calculation^).^^^ However, a minimal barrier for CO exchange is found, consistent with NMR studies which indicate only one 31Presonance. The phosphirane and phospholene species (15 and 16 respectively) formed upon reaction of the iron-

Orgunometallic Chemistry

16

phosphinimidato complex, Fe(C0)4(PNH2), with tetramethyldiallene have been studied with D F calculations.240A CDA//HDF analysis of the carbodiphosphorane complexes, Ni(CO),(PH3P=C=PPh3), (n = 2, 3) indicates that the Ni-carbodiphosphorane interaction is dominated by o - d ~ n a t i o n . ~ ~ ~

15

16

Papers of relevance here to bioinorganic chemistry have focussed on metalloporphyrin systems. HDF calculations of XO adducts of Fel'(porphyrin) and Fe"(porphyrin)(imidazole) reproduce observed geometries and IR data well for C0.242However, the six-coordinate adducts of NO and O2 are poorly described. HDF calculations on M(OEP)CO(l-MeIm) (M = Fe, Ru, 0s; 1-MeIm = 1-methylimidazole) reproduce solid state MASNMR 13C, 15N and 1 7 0 NMR data.243The related Fe(TPP)(CN'Pr)( 1-MeIm) species features a carbene-like isocyanide ligand with a bent geometry at N. An analysis of vco and vFe-CO in myoglobins suggests that the former may provide a useful empirical measure of distal pocket polarity and the stability of 0 2 a d d ~ c t s . ~ ~ ~ 4.1.5 Metal Dimers and Clusters. Cp4M4E4species (M = Cr, Mo; E = 0, S)

have been investigated with broken-symmetry D F calculations.245The metalsulfide clusters exhibit strong M-M bonding with a delocalised Td core. However for Cp4Cr404 spin polarisation dominates leading to electron localisation and a distorted rhombic structure. For both Cr species the alternative M4 bonding extreme is close in energy and major structural rearrangements may be energetically proximate. Analysis of the metal-metal species suggests a stronger interbonding in (HO)3W(p-PH2)(p-PHR)Pt(PH3) action when R = W(CO), compared to R = H.246Fenske-Hall calculations on the clusters CP*~(J-L-H)W~BXH~ (n-4 SEPs), (Cp*W)2B7H9and (Cp*Re)2B7H7 (12-2 SEPs) rationalise the collapse of the boron cage to a more condensed framework upon substitution of organometallic fragments.247The stability and diamagnetism of 50e- late transition metal triangular clusters have been rationalised viu EHMO calculations.24xCalculations have also been used to probe structural preferences in diimido bridged tungsten d i m e r ~triangular ,~~~ clusters of iron,250 r ~ t h e n i u m ~ ~and ' > ~osmium253 ,~ as well as cobalt clusters.254*255 BP86 structures and vibrational data have been computed for Rh2(p-RiSS)(CO), and Rh2(p-XySS)(C0)4 featuring chiral dithiol bridging ligands derived from carbohydrate^.^^^ With the XySS ligand a conformer with a Rh-..O interaction derived from the furanose ring is favoured. EHMO calculations on (Cp2Ti)(Cp2Ru)(p3-S)4 place 12 cluster electrons in largely Rulocalised orbitals, although some delocalisation onto the Ti centres implies a degree of Ru-+Ti dative bonding.257 A topological analysis of the electron

1: Theoretical Organometallic Chemistry

17

density of (PH3)2(H)(CO)Ru(p-OMe)(p-H)Ir(cod) indicates that a Ru-Ir bond is not present.258 D F calculations on the series of raft-like clusters, [Pt3Fe3(CO),s]o'-'2- correctly reproduce the lengthening of the Pt-Pt distances upon reduction.259 Two overviews of structure and M-M bonding in d8-d8 dimers featuring bridging n-donor ligands have been HF, D F and HDF calculations on the Pt(1) dimer (C0)Pt { P - P ( C H ~ ) ~ ) ~ P ~ ( P all H Moveresti~~) mate the Pt-Pt distance.262Protonation is favoured at the phosphine-ligated metal centre. Two electron oxidation of Pt2(p-PH2)2(C6F5)4produces a Ptl"Pt'" dimer with a Pt-Pt single bond.263D F and HDF calculations correctly replicate the shortening of the Pt-Pt distance, although the SVWN functional provides the best agreement with experiment. EHMO calculations on [Pd4(CNMe)10]2+ and [Pd4(CNMe)8(PH3)2]2+indicate the frontier orbitals are derived from combinations of do* orbitals.264 4.1.6 Metal-Hydrides, Dihydrogen and Silane Complexes. D F calculations

show the binding of Lewis acids to Cp2NbH3favours a dihydrogen form and reduces barriers for H2 reductive elimination.265CH2 and SiH2 ansa-bridged ligands promote hydrogen exchange in [CP~W(H)~]+ species, in contrast to trends in methane reductive elimination from [CP~W(H)~CH~]+ analogues (DF calculations).266Small inter-ring angles weaken the central W-H bond and stabilise an acceptor orbital in the q2-H2 transition state. The three sites of protonation in the C ~ R U ( H ) ( P Hderivative ~)~ 17 are computed to lie close in energy with HDF calculations.267Protonation at the in good amine yields a dihydrogen bond with an H.-.H distance of 1.545 agreement with experimental data. The proposed mechanism for hydrogen exchange involves cleavage of the H - - . Hbond and rotation of the Cp ligand, delivering the proton to the metal. The Cp ligand then rotates back to remove the original hydride. HDF-calculated deprotonation energies for [LM(dmpe)2(q2-H2>ln+ species (M = Ru, 0s) correlate well with experimental pK, values.268Higher acidity is promoted when anionic L is a weaker o-donor or when neutral L is a strong z-acceptor. Dihydrogenldihydride preferences have been explored in O S C I L ~ ( P ~ P ~ ~complexes ) ~ ( H ~ ) using HDF calculations (L2 = oxime: dihydride; L2 = imine: d i h y d r ~ g e n )The . ~ ~need ~ for appropriate modelling of phosphine ligands is emphasised in a study of the equilibrium 18.270Experimentally, more electron withdrawing phosphines favour dihydrogen cleavage and this is reproduced in a series of D F calculations using

A,

18

Organometallic Chemistry

PH,F3-, ligands. The discrete variable representation of [CpRu(q2-H2)(PH2CH2PH2)]+,which features a highly anharmonic, elongated dihydrogen ligand, produces both accurate vibrational levels and wave functions when compared with orbital-based methods.271 The study suggests previous assignments to vH-H and vRu-H in fact exhibit significant mixing of these two modes. D F calculations on bis(halosily1)-substituted niobocene hydrides give evidence for non-classical interligand hypervalent interactions arising via electron transfer from the metal-hydride bond to the Si-X G * - M O . The ~ ~ ~structural manifestations of these interactions - a shorter M-Si bond, longer Si-X bond and Si...H contact - can not be explained by a normal 3c-2e- o-complex. Two HDF studies of the chelating disilane complex Ru(H)2 { (q2-HSiR2)2X}(PR'3)2 reproduce the trans-C2, structure deduced from experiment. Chelate size affects the extent of Si-H activation and therefore the interaction with Ru,273 although the same basic structure is retained for the bis q2-HSiH3species.274 TpRu(H)(q2-HSiH3)(PH3) exhibits a transition state for hydride exchange only 0.5 kcal/mol higher than the silane complex.275 4.1.7 Metal Alkyls, Aryls, Alkenyls and Related Species. HDF calculations on methyltitanium complexes suggest that TiMe4 may be observed in non-donor alkane solvents.276 Trigonal bipyramidal and square pyramidal forms of [TiMe5]- are close in energy, An analysis of the structures of MX2Y2 species, including several metal alkyls, indicate that the application of Bent's Rule may be more limited than for main group analogues.277MP2I1RHF calculations show metallacycle formation from titanaethene, C12Ti=CH2, or titanaallene, C12Ti=C=CH2,with unsaturated species X=Y (X = CH2, CH, 0, S, N, P; Y = CH2, CH, C=O, CCH2, NCH3) is more favoured with the latter where an exocyclic methylene group is present .278 The titanacycloalkenes H2TiC2H2, HTiC3H3, H2TiC4H4 all exhibit planar geometries, while for HTiC5H5 a C2, boat structure is located (MP2, D F and HDF calculation^).^^^ H F calculations favour an ql-0-bound ion-pair enolate between [TiF3]+and [XC(0)CH2]- (X = NH2, PH2, Ph and PhS(0)CH2)280while with [Cu(PH3)]' the ql-C form is more accessible and is preferred when X = NH2.281 D F calculations on WX6_.Me, (X = F, Cl; n = 1-3) species show that the trigonal prismatic geometry becomes more accessible with increasing n and is favoured for WC13Me3 and WF5Me.282In addition, W&Me2 and WX2Me4 are predicted to be thermodynamically stable relative to WMe6 + w x 6 . Agostic bonding in Mo{ C(0)CH3)(S2CNH2)(CO)(PH3)2involves activation of both the Cp-H and C,-Cp bonds, estimated to contribute 2.9 and 9.8 kcal/mol respectively to the overall interaction (MP2 calculation^).^^^ HDF calculations on (C5R5)Fe(C0)2Si2X5species (R = H, Me; X = H, Cl) show the metal weakens the a-Si-X bond, consistent with the greater reactivity at this site.284 A molecular mechanics force field has been developed for alkylcobaltoximes, models for vitamin BI2 coenzyme.285H F calculations on [MMe3{(H2C=N-NH)3CH>If and MMe3{(H2C=N-NH)3BH} (M = Pd, Pt) reproduce trends in M-C distances (Pd z Pt) and M-N distances (Pd > Pt)

I : Theoretical Organometallic Chemistry

19

observed experimentally in tris(indazo1-1-yl)borate analogues.286EPR hyperfine coupling constants have been computed for the Cd-CH3 radical via MRSDCI calculations287and the vibrational spectra of [M-CH3Io'+ (M = Cd, Zn) have been computed and compared with the results of ZEKE spectrocopy.^^^ 199Hgchemical shifts for Hg(CH3)2 and MeHgX species (X = CN, C1, Br, I), computed using the ZORA approximation, fall within 3% of experimental data.289Formation enthalpies for Group 12 dialkyls have been estimated based on electronegativity equilibration, in which C-C bond enthalpies are related to charges at carbon.290This approach, supported by MP2 calculations, has been extended to RHgX species and main group alkyls. HF calculations on ScPh3 and S C P ~ ~ ( T H show F ) ~ that the axial THF molecules force a planar geometry in the ScPh3 unit.291The HDF-computed structure of trans-[RhCl2(Ph){ PH2(CH=CH2)2] agrees well with that of trans[RhC12(Ph)(PPh&]with the exception of the Rh. --ortho-Hdistance, indicating that intramolecular steric repulsion can force the interaction of PPh3 phenyl rings with metal centres.292Anion binding by cyclic, trimeric perfluoro-ophenylenemercury has been investigated with AM 1 calculations and structures have been proposed for [ ( o - C ~ F ~ H ~ ) ~ (-B, H[ (~o) ]- C ~ F ~ H ~ ) ~ ( B H and ~)~]~[{(o'C6F4Hg)3 12(BH4)]- *293 RHF and HDF calculations on the metal-alkenyl species, Cp2ZrCl(CH=CHSiH3), CpIr(PH3)(C2H3)(H) and [Pt(PH3),(CH=CHMe)]', suggest the short C=C bond distances determined experimentally arise from disorder in the crystal structure via fractional population of two conformers arising from rotation around the M-C* bond.294The preference for q2-alkenyl ligands to eclipse other metal-ligand bonds in complexes with the ReC1(PH3)4 and C ~ M O ( P Hfragments ~)~ is related to d/p hybridisation induced at the metal centre which enhances n-back donation (HDF calculation^).^^^ The MP2 geometry of Hg(CF=CF2)2 exhibits a C2 minimum with a low barrier for rotation, consistent with experimental data.296The short Hg-C distance arises from the sp2 hybridised carbon rather than any H g - K n-back donation. 4.1.8 Metal Alkylidenes and Alkylidynes. Ti& (X = F, Cl) and BF3 display

similar Lewis acidities towards diaminocarbenes, although the titanium species can bind two carbene ligands with equal strength.72 D F calculations on trans,C ~ S - L ~ R U C ~ ~ ( = C H ~ )where ( C ~ HL~ = ) , N-heterocyclic carbenes or PH3 ligands, show the former are more strongly bound and labilise the trans ligand L more effectively, promoting the role of these species in alkene metathesis.297 The cis isomer of R u ( P H ~ ) ~ C ~ ~ ( =isC7-10 H ~ ) kcal/mol less stable than the trans form (HDF calculation^).^^^ Computation of Rh(PHzCH2PH2)C12(=CH2)shows dissociation of one chelate arm to cost around 9 kcal/mol. The LUMO of these cis-phosphine systems is primarily alkylidene-based and nucleophilic attack at this site may be relevant in alkene metathesis reactions. HDF calculations on the reaction of (PH3)2Ru(H)Lwith vinyl ether show an alkene adduct and (PH3)2Ru(H)L'{=C(Me)(OMe)} alkylidene species are of similar stability for L' = CO or C1, but that an alkyl insertion product is favoured for L = CO, especially as extra stabilisation via Ru-0 binding is

Orgunometullic Chemistry

20

possible in this case.299MP2 calculations on OSX(=CH,)C~(CO)(PH~)~ (X = H, C1) reproduce the larger distortion of the trans-P-0s-P angle in the hydride species, a result of greater Os-+CH2 n-back donation in this case.3ooThe isomeric methyl species is 26 kcallmol more stable than the hydrido-alkylidene, but appears kinetically inaccessible. An EHMO analysis of the electronic structure of (tmtaa)Ru(=CRR’) species (R = R’ = H, Ph; R = Ph, R’ = H, C02Me) suggests that carbene migration to the ring may be induced by addition of a trans ligand. Carbene loss follows a radical pathway and is aided by small HOMO-LUMO gaps.3o1 Factors enhancing the stability of Rusilylene complexes, [CpL2Ru=SiX2]’ (L = CO, PH3, PMe3; X = H, SH, Me), have been probed via B3PW91 calculations.302 Tactics include the use of donating ligands, L, avoiding electron withdrawing groups, X, as well as excessive steric bulk which distorts the Ru=SiX2 moiety. HDF calculations on isomeric alkylidyne and bis-alkylidene complexes, (CH&M( E CH)X and (CH3)M(=CH2)2X, for do (M = Mo, W) and d2 (M = Os, Ru) metal centres (X = Cl, CH3, CF3, SiH3, SiF3) show that the do bisalkylidene form is stabilised by increasing n-acceptor ability of X and is favoured for X = SiF3.303For the d2 species the bis-alkylidene form is always favoured and two geometries are possible due to a Jahn-Teller instability. The electronic structures of [(calix)W(= CMe)]- and (calix)W(=CHMe) (calix = pt-B~-calix[4]-(0)~) have been computed via EHMO methods.3o4D F calculations on CpW(CO)(q ‘-HCCO)(q2-NCH) confirm the electronic preference for the q ‘-ketenyl/q2-nitrile structure seen in experimental analogues.3o5Calculations on alternative alkylidyne and metallacyclopropene isomers formed from the reaction of OS(PH~)~(H)~(OAC)(H~O) with alkynes, HC = CR, show the former is preferred for R = H or Me, while hyperconjugation stabilises the metallacyclopropene form when R = Ph.306High level CAS calculations have been performed on linear Fe(CH)2 and indicate the singlet spin-state is most stable.3o7 4. I . 9 Metul Alkene and Alkyne Complexes. GIAO-HDF-computed Io3Rh chemical shifts for Rh(cod)L2 systems (L2 = neutral N-donors, 2C1 and acac) show a mean absolute deviation of 44 ppm compared with experimental data. The Rh-N distance, and not the N-Rh-N angle, is important in determining 6 103~h.308 The most stable conformer of [(nbd)Rh(H2PCH2CHOHCHOHCH2PH2)]+ exhibits a Rh. - -0interaction and calculations reproduce the large downfield shift in 6 Io3Rh for this five-coordinate species and its cod a n a l ~ g u e . ”MM ~ and HDF calculations on [ ( C O ~ ) R ~ ( H , P ( C H ~ ) ~indiPH~)] cate that a chair-like conformation is preferred at low temperature, but that a boat shape dominates above 200 0C.310 D F calculations on Group 10 M(PH3)2(C2X4)species (X = H, F, CN) show that metal-alkene n-back donation is more significant than alkene o-donat i ~ n . ~Discrepancies ’ between calculated and experimental M-alkene bond dissociation energies can be traced to significant M(PR& reorganisation energies, assumed to be negligible in the experimental study. M-alkene bonding energies are 60-120 kJ/mol higher for X = F and CN. CCSD(T)//

’

1: Theoretical Organometallic Chemistry

21

HDF bonding energies for Pt(PH3), complexes of tricyclic alkene complexes (19) increase with alkene strain and are related to increased n-back donation.'12 DF calculations on [PdC13(C,X,)]- (X = H, D) in conjunction with normal coordinate analysis provide an assignment of the vibrational spectra of these species.313The interactions of ethene with Pt314 and Au315 atoms have also been studied. The bonding of norbornadiene to the Cu'(8-oxoquinolato) photosensitiser has been analysed via CISllHDF calculations.316The bound system is predicted to absorb in the visible region due to stabilisation of the alkene n* orbital via n-back donation. An EHMO analysis of Mo(q2C60)(C0)2(phen)(C2H4)rationalises the observed three-fold reduction and subsequent fragmentation upon addition of a fourth electron.317The geometries and electronic structures of q2-C60Pt(PH3), (n = 1, 2) species have been studied with D F calculations. I

7C

/ \

N\-C, / H-C-C-H \

19

20

H

/

21

Evidence for Ni-Ni bonding in homoleptic Ni,(RC = CR),+I complexes (20, 21) is obtained from DF calculations. However, the extent of this effect is reduced by M-alkyne n-back donation and so an extra driving force for the formation of such species may be required.319Computation of the alkyne n-complex [Me2Cu(C2H2)]- requires a treatment of electron correlation (MP2 or HDF methods).320 A similar structure is computed for [Me2Au(C2H2)]-, but the zinc analogue gives only a weak interaction. The availability of the Cu 3d orbitals is the key to the reactivity of these species as alkylating species.320b 4.1.10 Miscellaneous Studies. The products of the reaction of transition metal

atoms with C02 have been identified via DF calculations and isotopic substitution studies. For M = Ti, V321and Cr-Ni322 the insertion product OMCO is formed. In contrast, a separate study suggests that insertion is favoured only with early transition metal atoms (M = Ti-Cr) and is barrierless for titanium.323M(C02) adducts are preferred for late first row transition metal atoms (M = Fe-Cu) and structures for Ni(C02) and Ni(C02>(N2), ( n = 1, 2) are discussed. MP2, DF and HDF calculations show that a linear M+...OCO geometry is preferred for all M (M = S C + - Z ~ + )Products . ~ ~ ~ of the photochemically-induced reaction of Cr02C12 with R C r C R (R = H, Me) and H2C=C=CH2 (vinylidene and cyclopropanone complexes respectively) have been characterised with HDF calculations.325

22

Organometallic Chemistry

Mechanistic Studies. - 4.2.I Reactions Involving Highly Unsaturated Metal Species. The initiation step for the gas-phase polymerisation of isobutylene by Ti+ has been studied with CCSD(T)//HDF calculations.326 The reaction, on the quartet surface, proceeds via a novel hydrido-ally1 intermediate with subsequent concerted elimination of H2 producing a titanacyclobutene active species. The interaction of first row transition metal cations with CH4 results in a significantly reduced inversion barrier and may present a new mechanism for the loss of stereochemistry at carbon.327In a further study, two CH4 molecules are found to bind to Ti+ with similar energies (HDF calculations). A third CH4 molecule binds weakly and dehydrogenation to [(CH4)Ti(CH3)2]+becomes f a ~ o u r a b l e . ~The ~ ' oxidative addition of HX species (X = C-F; Si-C1) to Ti+ has also been studied.329HDF calculations show that the reaction of ethane with singlet V 0 2 + produces triplet V(OH)Z+ and ethene via successive C-H activation steps.330 Oxidation of ethene proceeds viu an asymmetric carbocation with a coupled 0-transferlH migration step yielding ethanal and triplet VO+. The reaction of sextet FeO' with CH4 involves a spin-state change to the quartet surface which reduces the activation barrier for C-H cleavage. The system reverts back to the sextet surface during MeOH product release.331A HDF similar sequence is computed for the oxidation of benzene to calculations locate a 5A" alkenyl as the most stable species for the [Fe,C2,H3]+ system.333The barrier for conversion to a hydrido-acetylene complex is lower on the triplet surface, although the computed value on the quintet surface agrees well with experimental data. HDF calculations show that the most favoured reaction of 5D5/2Ni+ with n-butane leads to C2H6.334 Both this, and another process yielding H2, involve insertion into the central C-C bond followed by 0-H migration via multicentre transition states. Insertion into the terminal C-C bond or C-H bonds is disfavoured. Comparison with statistical rate theory suggests the multicentre barriers may be overestimated by 2-7 kcal/mol. A reinvestigation of the dehydrogenation of CH4 with Pt+ using HDF calculations shows CHJCD4 exchange occurs through Pt+(CH4)(CD4) intermediates without H/D scrambling, as Pt+ can not activate more than one C-H bond at a time.'35 HDF calculations find the reactions of Pt=CH2+ with NH3 to form either Pt-H and CH2NH2+ or [Pt=C(H)NH2]+ to be exothermic. Dehydrogenation of the latter to [PtC 5NH]+ is kinetically d i ~ f a v o u r e d . ~ ~ ~ The reactions of 3P Group 12 metal atoms with XH4 (X = C, Si) to form 'Al HMXH3 species are computed with HDF functionals to proceed via a 3A1 HMXH3 intermediate.337Dissociation to M-H and XH3 may be possible in the gas phase, especially for X = C. A further study employing MCSCF and CIPSI calculations suggests the reactions of 3P Cd and Hg atoms with SiH4 lead spontaneously to M-H and XH3 via, for M = Cd, a shallow 3A1HMXH3 minimum."' The 'S atoms are inert to reaction and require excitation to the 'P state to give 'A1 HMXH3. C-F bond activation by Ce+ and Ho+ for both CH3F and C6H5F involves 'harpoon' processes with fluorine abstraction occurring via either linear or bent C-F...Ln transition states (HDF calcula-

4.2

1: Theoretical Organometallic Chemistry

23

tions). The latter is significantly favoured for C6H5F, explaining its greater reactivity. 4.2.2 Alkene Polymerisation. A volume dedicated to recent theoretical progress in this area is available.339D F calculations, including solvation effects, on methyl group abstraction from CpMMe3, (CpSiH2NH)MMe2 and Cp2MMe2 species (M = Ti, Zr) by B(C6F5)3 indicate that contact ion-pair formation is always exothermic and favoured by electron-releasing l i g a n d ~ . ~Subsequent ~' ion-pair separation by ethene is endothermic, but is exothermic with a toluene solvent molecule for CpMMe3 and (CpSiH2NH)ZrMe2. For Cp2MMe2catalysts ethene approach is preferred over toluene and these species are predicted to have the highest activity, especially with bulky ligands. A structure for the [MAO-Me]- [Cp2ZrMe]+ intermediate featuring an occluded methyl has been proposed. *03 Ziegler and co-workers have studied chain termination pathways with do metal Ziegler-Natta polymerisation catalysts using D F cal~ulations.~~' With high alkene concentrations P-H transfer should be the dominant process. Group 3 metals exhibit a high intrinsic aptitude for chain propagation and, although less favoured with Group 4 cations, this can be enhanced by increased steric bulk. Morokuma et al. have considered a range of Ti-chelating ~ ~ ~ HDF calculations the bridged catalysts, 22, for p o l y m e r i ~ a t i o n .Using lowest insertion barriers were found with more electron-releasing X and when R is both conjugated and has electron-donating substituents. A novel polymerisation mechanism in which Cp ligands act as the active site has been proposed on the basis of semi-empirical calculations.343 Stereoerrors in propene polymerisation with zirconocene catalysts, in which the reaction of 1-D-propene leads to label incorporation into the Me side groups, have been investigated with DF calculation^.^^ After insertion a series of P-H transfedalkene reinsertion steps account for the observed results, with direct y-H transfer being ruled out. A sec-propyl chain-end group formed via propene insertion with [ua~-H~C(3-t-Bu-l-indenyl)~ZrH]+ exhibits stabilising P-H agostic interactions which slow chain propagation (DF QMlMM calculat i o n ~ )D . ~F ~QM/MM ~ calculations also show that C2-symmetric Group 4 metallocene catalysts favour insertion of 2-2-butene while insertion of the Eform is preferred with C,-symmetric species.346 R

Me

+ -Y-R

22 X = Y = 0 , S, Se, Te; R = Cd4, C2H.2, C2H4

\

R' 23 R = Me, R' = diisopropylphenyl, R" = H 24 R = fipropyl, R' = diisopropylphenyl, R" = Me

R

25 R = diisopropylphenyl, R' = H, Me, ANAP (AN AP =

~)

24

Organometallic Chemistry

A number of studies on late transition metal diimine-based alkene polymerisation catalysts have been published. Alkene binding to 23 and the energy change for insertion into the Fe-Me bond is similar to that for the related Ni" a-diimine catalysts but a much reduced insertion barrier is computed (2.5 kcal/ mol, HDF calculations) .347 D F QMlMM calculations on the related n-propyl analogue, 24, suggest an Fe'I-alkyl resting state, in contrast to Ni/Pd systems where this is the alkyllalkene complex.348 Chain propagation is very exothermic and termination occurs via P-H transfer to monomer. The rate determining step for both processes is alkene capture and bulky groups heighten the barrier along the termination pathway. The Co" analogues have also been studied using similar methods. 349 While including bulky groups leads to high barriers for ethene uptake, isomerisation processes and chain termination, the insertion barrier is lowered. The role of backbone substituents on the chain branching ratio with Ni"-diimine catalysts, 25, has been studied, again using D F QM/MM methods.350Use of various partitioning schemes highlights both steric and electronic influences. DF calculations on the insertion of propene with [(HN=CHCH=NH)Pd-R]+species (R = primary, secondary or tertiary alkyls) show a reduced n-complex stability and increased insertion barriers as the bulk of the alkyl group increases."' A 2,l insertion regioselectivity is preferred with subsequent chain straightening being disfavoured. Stereoregulation of the cis-1,4-p0lymerisation of butadiene has been studied with DF calculation^.'^^ Using a [Ni(C7H 1)(C4H6)]+precatalyst, rate determining insertion proceeds from the more stable anti -q3-butenyl n-complex isomer with a free activation energy of +12 kcal/mol. A similar free activation energy is found for insertion via a related syn isomer which leads to a trans polymer; however, a large barrier for anti-syn isomerisation (1 9 kcal/mol) renders this species inaccessible (26). Butenyl group isomerisation via a n-o conversion followed by rotation around the C&3 bond has also been studied in detail (27).353The transition state is stabilised by electron-donating ligands, L, but destabilised when R = Me.

I

A@ = +12 kcal/mol

cis-l,4-polymer

26

/A@ = +12 kcal/mol

27

trans-l,4-polyrner

4.2.3 Other Reactions of Alkenes and Related Species. QM/MM calculations have been applied to the asymmetric dihydroxylation of styrene using the bis(dihydroquinoline)-3,6-piradazine-O~0~ catalytic system.354The two lowest energy pathways for alkene approach both correspond to R product formation. The lowest S pathway is l l . l kJ/mol higher in energy, equating to a 99.4% e.e. (cf. > 96% experimentally). Stability is governed by alkenelcatalyst stacking interactions, especially face-to-face interactions of the substrate with

I : Theoretical Organometallic Chemistry

25

one of the quinoline rings. An alternative and potentially efficient approach to model this dihydroxylation reaction is the use of force field calculations parameterised via QM transition states.355Alkene dihydroxylation by Mn04has been studied using HDF calculations and proceeds via a [3+2] mechanism, similar to that seen with 0 ~ 0 4With . ~ trans-2,4-pentadienoic ~ ~ acid an unsymmetrical transition state is located, consistent with relative secondary kinetic isotope effects at the a- and P-hydrogens. Calculations on the addition of ethene to LRe03 species (L = 0, Cl, Cp) and Os04 via [2+2] and [3+2] processes indicate that the former is relatively more favoured with the Re species but that the [3+2] process is more accessible.357HDF calculations on ethene epoxidation with L,Ti(q2-02) and L,Ti(OOR) species favour reaction with the hydro- or alkyl-peroxo species.358A study of this reaction with MeRe(O2)20-Lspecies found that Lewis bases, L, increase barriers by reducing the electrophilicityof the peroxo ligand.359DF calculations of ethene oxidation by chromyl chloride favour [3+2] additions, either to two Cr=O bonds or one Cr=O and one Cr-Cl bond leading to epoxide or chlorohydrin precursor species re~pectively.~~’ Product release may need the participation of a water molecule. The role of titanacyclobutanes in alkene metathesis and ROMP reactions has been studied with DF calculations.361Alkene exchange energies compare well with experimental data but no evidence for an alkylidene-alkene intermediate is found. With cyclopentene and norborndiene alkene elimination is favoured over ROMP unless the polymer chain is present. GIAO-DFT calculations highlight a trend between 6 51Vand computed ethene insertion barriers with Me3V=NR (R = H, t-Bu, C(CF3)3, Ph).362 0-H transfer in CpFe(CO),Et has been studied with D F and MP2 calculations.363Ethene hydrosilylation with HSiC13 at TiX2 (X = H, C1, Cp) proceeds via C2H4 binding followed by barrierless Si-H activation to give C13SiCzH4TiX2H species (MP2 c a l c ~ l a t i o n s )Ethene . ~ ~ hydrosilylation with Pt(H)(SiH3)(PH3)2 incorporating cis-trans isomerisation has been studied with MP4(SDQ) and CCD calculations.365PH3-promoted isomerisation entails a higher barrier than subsequent alkene insertion into the Pt-H bond and is competitive with insertion into the Pt-Si bond. With C2H4 as the fifth ligand isomerisation becomes more favoured and may occur prior to insertion. Sakaki and coworkers have summarised their work in this area.366Hydroboration of ethene with (H0)ZBH using a Cp2SmH catalyst involves facile insertion of ethene into the Sm-H bond.367 Formation of the borane adduct, 28, is promoted by the ionic character of the intermediate Sm-C bond. Product dissociation from 28 is very endothermic, due to Sm oxophilicity. The performance of C2-symmetric bidentate phosphine ligands in the asymmetric hydroformylation of styrene with HRh(C0)2(P-P) species has been analysed using D F QM/MM ~alculations’~~ and a molecular mechanics study of some chelating ligands used for hydroformylation has also been reported.369 The Wacker oxidation of ethene by P ~ ( O A Cdimers )~ has been modelled using DF calculations, including solvent effects via a continuum method. An outersphere mechanism is preferred with coordinated acetate facilitating the various

26

Orgunometullic Chemistry

H-transfer steps, one of which, leading to acetaldehyde ligand formation, is rate determining.370 A similar mechanism is proposed for the Pd(OAc)2/ HOAc-catalysed formation of vinyl acetate from ethene.371Barriers for the insertion of propene with [Pt(PR3)2H]’ species (R = H, F, Me) range from 2 to 16 kJ/mol (HDF and MP2 calculations).372Linear alkyls are preferred while for secondary alkyls an isopropyl rock mechanism for P-H exchange is favoured in non-coordinating solvents.

Mechanisms for the hydrogenation of aromatic ketones by ( C ~ H ~ ) R U ( H ~ N C H ~ C H ~have O H )been C ~ considered by HDF calculations.373 The favoured process involves concerted transfer of a metal-hydride and an amino proton to the ketone (29). Of four possible pathways for the hydrogenation of the Rhmeamide species only one (30) exhibits both facile dihydrogen complex formation and subsequent migratory insertion (HDF calculations).374 No low energy pathway for isomerisation of the dihydride intermediate could be found. D F calculations on imine metathesis with M o ( N H ) ~ Xspecies ~ (X = F, Cl, Br, OCH3, OCF3) find diazametallacycles are viable intermediates with higher formationldecomposition barriers than the equivalent metallacyclobutanes of alkene metathesis212The preferred pathway has an imido ligand trans to the forming M-N bond, so variation in X has little effect on activation energies. The insertion of imines into different Pd-C bonds has been studied with [L2Pd-R]+ model systems (L2 = bidentate phosphine or a-diimine ligands; R = Me, C(0)Me).375Insertion into the Pd-acyl is kinetically favoured and driven by the formation of a strong amide linkage. Reaction with the Pd-alkyl bond entails a much higher barrier, consistent with the experimental observation of a a-imine complex. 4.2.4 Reactions of Alkynes. Torrent and co-workers have confirmed that a chromahexatriene species formed via alkyne insertion with (OC)&r=C(OH)C2H3is a viable alternative to other proposed intermediates for the Dotz benzannulation reaction (DF calculation^).^^^ While an q4-vinylketene species is close in energy, chromacycloheptadienone intermediates should be rejected. Alkyne trimerisation on CpCo(PH& involves, after phosphine displacement, oxidative coupling to yield a cobaltacyclopentadiene species (HDF calculat i o n ~ ) Further . ~ ~ ~ reaction with alkyne gives an q4-benzene complex with no cycloheptatriene intermediate being located. Vinylidene to alkyne isomerisation on [(~l’-indenyl)Ru(PH~)~]+ proceeds via a metal-mediated 1,2 H shift.378 The alkyne form is less stable but should still be accessible at elevated temperatures (HDF calculations). MP2 calculations on this same process on

1: Theoretical Organometallic Chemistry

27

[(PP3)M]' species (M = Co, Rh) show the hydrido-acetylide isomer is a key intermediate for M = Co with the vinylidene being 8 kcal/mol more stable.379 For M = Rh the alkyne species is most stable and two significant activation barriers block the path to the vinylidene. MP4(SDQ) calculations find acetylene insertion into the Pt-H bond of Pt(PH3)H(SiH3)is more facile than that into the Pt-Si bond, although the latter reaction is more exothermic.380The ease of insertion is related to the extent of distortion of the Pt-H/SiH3 moieties in the transition states. 4.2.5 Palladium-assisted Allylic Alkylations. Calculated transition states for NH3 attack at [(q-C3H5)Pd(PH3)2]' show a low gas-phase barrier (9 kJ/mol) rises to 33-47 kJ/mol in solution (dichloromethane and water, PCM and SM2 continuum models).381 With anionic nucleophiles (F-, CN-) the very exothermic addition is barrierless in the gas-phase, but solvation produces large barriers with reaction being more favourable for CN-. New MM3* parameters have been developed for both Pd-alkene382 and Pd-ally1 species.383?384 Other studies have computed conformational minima for Pdalkene and -ally1 species bearing bulky chelating ~ o l i g a n d s and ~~~ have ,~~~ assessed the role of phosphine and amine coligands in determining regioselect i ~ i t i e s HDF . ~ ~ ~ calculations on cationic 1,3-disubstituted allyl-Pd species successfully reproduce geometries and 3C NMR data. In unsymmetrical species nucleophilic attack is favoured at the carbon bearing the more electron-donating ~ u b s t i t u e n t .HDF ~ ~ ~ calculations on P-silyl-substituted allyl-Pd species show hyperconjugation between the C-Si bond and the allylPd unit enhances a 1,4-regioselectivity for nucleophilic attack.390Differences in the mechanism of ethoxide attack at [(q-2-Cl-allyl)M(PH3)2]+complexes (M = Pd, Pt) have been addressed with MP2 calculations.391For Pd, attack at the terminal carbon leads to an alkene species, while with Pt attack at C(2) yields a metallacyclobutane intermediate from which the Cl- ion is readily displaced. 4.2.6 C-H Bond Activation, Oxidative Addition and Reductive Elimination Processes. HDF calculations including solvation effects have been applied to the oxidation of CH4 by Pt(NH3)2C12 species in sulfuric acid.392[Pt(NH&(OS03H)(H$04)]+, 31, is the most likely catalytically-active species and C-H bond activation, via electrophilic attack by CH4 with expulsion of H+, is mildly endothermic at 473°C. Oxidative addition to a Pt" species is much less favourable, although catalysis by Pt'V(NH3)2C12(0S03H)2is thermodynamically feasible. The mechanism of methane oxidation by methane monooxygenase has also been the subject of two papers, Using slightly different models (32393and 33394below) HDF calculations identified H atom abstraction from CH4 at a bridging oxygen ligand as a key event, with strongly exothermic formation of a p-MeOH product. Model 32 produces an earlier transition state but with model 33 an intermediate with a weakly-bound methyl radical was also located. The use of DFT to model biological systems has been reviewed.395

Organometallic Chemistry

28 H

H I

0

31

32 X = irnidazole, Y = HCQ 33 X = NH2, Y = H20

The thermolysis of MMe4 and M(n-Pr)Me3 (M =Ti, Zr, Hf) has been studied with MP2//RHF calculations. Bimolecular CH4 elimination from MMe4 is favoured over a unimolecular process with activation energies following the trend M = Zr < Hf < Ti.396With M(n-Pr)Me3 y-H abstraction is preferred over a-H abstraction for M = Zr and Hf. CH4 activation at [Cp2ZrR]+(R = H, CH3) via a facile o-bond metathesis has been studied with D F calculations.397 HDF calculations show that the oxidative addition of arenes to OS(CO)(PH~)~ is a highly favourable process and that no low energy pathway for H/D scrambling in OsD(Ph)(CO)(PH& exists. With fluorinated arenes reaction occurs at C-H bonds ortho to fluorine.398 Mechanisms for CX4 oxidative addition (X = halide) to trans-IrCl(PH3)2 have been studied with HDF calculations.399For a concerted process the order of reactivity, both kinetically and thermodynamically, is X = I > Br > C1 >> F, a trend related to the smaller oc-x+ (~c-x*gap in the heavier tetrahalides. Radical pathways become competitive for X = Br and I, where C-X bonds are weaker. SN2 pathways are strongly disfavoured. The oxidative addition of propane and cyclopropane to CpM(PH3) fragments (M = Rh, Ir) suggests the ease of C-H activation follows the trend secondary (cyclopropane) > primary (propane) > secondary (pr~pane).~"Reactions with M = Ir are favoured but those with M = Rh are more discriminating. The oxidative addition of CH4 to CpML species (M = Rh, Ir; L = CH2, CO, SH2, PH3) has also been studied (HDF calc~lations).~~' The ability of tridentate ligands, L, to promote the oxidative addition of CH4 to d8 MLCl species varies considerably (MP2 and HDF c a l ~ u l a t i o n s ) .Stable ~ ~ ~ d6 products, MMe(L)(H)Cl, are predicted for L = cyclohexane-l,3,5-triamineor 1,4,7-triazacyclonona-2,5,8-triene and M = Pd, Pt and Ir. D F calculations on various dinuclear species formed from the oxidative addition of H2 to RhX(CO)(PH3)2 with subsequent trapping by RhX(CO)(PH& (X = C1, Br, I) show the bis-halide bridged species are most stable.403 Ethane dehydrogenation with both (PCP')Ir(H)2 and [CpIr(PH3)(H)]+(PCP' = q 3-C6H3(CH2PH2)2) proceeds via oxidative addition, H2 reductive elimination and b-H elimination.404(PCP')Ir(H)2 species enable a catalytic process as the reaction endothermicity is achieved gradually over all three steps, whereas the Ir-alkene intermediate is too stable with the Cp system. The ease of ethane dehydrogenation by [CpM]+ species (M = Co, Ni) has been correlated to the enhanced 4s character in the LUMO of these species (EHMO c a l c ~ l a t i o n s ) An . ~ ~EHMO ~ analysis of [M(9S3)2]"2' species (M =

I: Theoretical Organometallic Chemistry

29

Mo-Pd) suggests the C-S bonds are activated compared with the free ligand, especially when M = T c . ~ ' ~ Reaction of CH4 with [PtL2(CH3)]' (L2 = en, tmeda) proceeds via a concerted oxidative addition pathway rather than a o-bond metathesis process.407Inclusion of an NF2H solvent molecule stabilises the PtIV product (DF calculations). CCSD(T) calculations on the oxidation addition of (H0)2B-XH3 species (X = C-Sn) to M(PH3)2 (M = Pd, Pt) show the reaction is favoured for M = Pt and the heavier Group 14 congeners.lo7Transition states are stabilised via M+B(p) donation and trends in reactivity can be related to X-B and M-X bond strengths. A very high trans influence for B(OH)2 was noted. A similar study of C-X bond forming reductive elimination from (qallyl)Pd(XH3)(PH3) found the reaction to be most exothermic for X = C, although this system also had the largest activation barrier due to the inability of C to exploit hypervalency. Reductive elimination from the ql-form becomes competitive when a second PH3 ligand is present."' 4.2.7 Reactions of CO. The mechanism of Fe(CO)5-catalysed water-gas shift reaction has been studied at the CCSD(T)//HDF The key steps are initial attack of OH- at bound CO and decarboxylation of [(OC)4Fe(COOH)]- via a concerted mechanism. Formation of Fe(C0)4H2 via Htransfer from H20 was found to be a bottleneck in this process and the displacement of H2 by CO via a novel SN2 mechanism was described, although this is higher in energy than simple H2 loss. The products formed from the C l ~[R~(bpy)(CO)~Cll~ with ethylene glycol have reaction of R ~ ( b p y ) ( C 0 ) ~ and been studied with HDF methods.409 4.2.8 Group I I and 22 Reagents. HDF calculations show that alkene dibromination with CuBr2/LiBr proceeds via a CuBr2-alkene complex and a solvated [CuBr2(CH2CH2Br)]- specie^.^" Electron loss and C-Br forming reductive elimination completes the reaction. The diastereoselective methylation of cyclohexanone with ( M e ~ c u L i has ) ~ been studied (see Section 2.2.2):' Various transition states for the enantioselective addition of Et2Zn to N-(diphenylphosphinoy1)benzyliminein the presence of 2-azanorbornyl-3-methanol have been computed at the H F level.41 Factors affecting selectivity were identified and exploited experimentally to produce high experimental enantiomeric excesses. HDF//RHF calculations have highlighted the factors at play in the transition states for the enantioselective methylation reaction of benzaldehyde with Me2Zn in the presence of a chiral p-amino alcohol auxiliary.412

References 1. 2.

F. B. C. Machado, R. Bravo, 0. Roberto-Neto, THEOCHEM, J. Mol. Struct., 1999,464,7. C. Fressignk, J. Maddaluno, C. Giessner-Prettre, J. Chem. Soc., Perkin Trans. 2, 1999,2197.

30 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32.

33. 34. 35. 36. 37.

Organometallic Chemistry

K. Sung, J. Chem. SOC.,Perkin Trans. 2, 1999, 1169. R. W. Alder, M. E. Blake, J. M. Oliva, J. Phys. Chem., A, 1999,103, 11200. E. Niecke, M. Nieger, 0. Schmidt, D. Gudat, W. W. Schoeller, J. Am. Chem. Soc., 1999,121, 519. J. F. K. Miiller, R. Batra, J. Organomet. Chem., 1999,584,27. J. F. K. Miiller, M. Zehnder, F. Barbosa, B. Spingler, Helv. Chim. Acta, 1999,82, 1486. J. W. Bundens, J. Yudenfreund, M. M. Francl, Organometallics, 18, 3913. S. Hoyau, K. Norman, T. B. McMahon, G. Ohanessian, J. Am. Chem. SOC., 1999,121,8864. A. Chatterjee, T. Iwasaki, J. Phys. Chem., A , 1999, 103,9857. H.-J. Buschmann, J. Hermann, M. Kaupp, H. Plenio, Chem. Eur. J., 1999, 5, 2566. T. Pasinszki, N. Kishimoto, K. Ohno, J. Phys. Chem., A , 1999,103,9195. S. Petrie, L. Radom, Int. J. Mass. Spec., 1999,192, 173. P. Li, Y. Xiang, V. H. Grassian, S. C. Larsen, J. Phys. Chem., B, 1999, 103, 5058. M. E. Alikhani, Int. J. Quant. Chem., 71,499. P. Soldan, E. P. F. Lee, S. D. Garnblin, T. G. Wright, Chem. Phys. Lett., 1999, 313, 379. V. N. Solov'ev, E. V. Polikarpov, A. V. Nemukhin, G. B. Sergeev, J. Phys. Chem., A, 1999,103,6721. J. B. Nicholas, B. P. Hay, D. A. Dixon, J. Phys. Chem., A, 1999,103,1394. E. Cubero, M. Orozco, F. J. Luque, J. Phys. Chem., A , 1999,103,315. S. Hashimoto, S. Ikuta, THEOCHEM, J. Mol. Struct., 1999,468, 85. J. B. Nicholas, B. P. Hay, J. Phys. Chem., A , 1999,103,9815. V. Ryzhov, R. C. Dunbar, J. Am. Chem. SOC.,1999,121,2259. D. Scheschkewitz, M. Menzel, M. Hofrnann, P. von R. Schleyer, G. Geiseler, W. Massa, K. Harms, A. Berndt, Angew. Chem., Int. Ed. Engl, 1999,38, 2936. L. E. Sansores, R. Salcedo, H. Flores, THEOCHEM, J. Mol. Struct., 1999,460,37. D. R. Armstrong, K. W. Henderson, A. R. Kennedy, W. J. Kerr, F. S. Mair, J. H. Moir, P. H. Moran, R. Snaith, J. Chem. SOC.,Dalton Trans., 1999,4063. J. C . Bryan, L. H. Delmau, B. P. Hay, J. B. Nicholas, L. M. Rogers, R. D. Rogers, B. A. Moyer, Struct. Chem., 1999,10, 187. J. Weston, H. Ahlbrecht, Tetrahedron, 1999,55,2289. N. Johansson, T. Osada, S. Stafstrom, W. R. Salaneck, V. Parente, D. A. dos Santos, X.Crispin, J. L. BrCdas, J. Chem. Phys., 1999,111, 2157. J. A. M. Brandts, P. van de Geijn, E. E van Faassen, J. Boersrna, G. van Koten, J. Organomet. Chem., 1999,584,246. M. Stener, G. Fronzoni, M. Venuti, P. Decleva, Chem. Phys. Lett., 1999,309, 129. A. C. Tang, Z. F. Shang, Q. W. Teng, Y. M. Pan, Z. S. Cai, X. H. Zhao, J. K. Feng, Int. J. Quant. Chem., 1999, 73, 505. A. A. Farajian, K. Ohno, K. Esfarjani, Y. Maruyama, Y. Kawazoe, J. Clzem. Ph-ys., 1999, 111,2164. Y. Wang, M. Dolg, Tetrahedron, 1999,55, 12751. P. Antoniotti, G. Tonachini, Organometallics, 1999,18,4538. E. U. Wiirthwein, K. Behrens, D. Hoppe, Chem. Eur. J., 1999,5, 3459. T. Heinl, S. Retzow, D. Hoppe, G. Fraenkel, A. Chow, Chem. Eur. J., 1999, 5, 3464. M. J. Aurell, L. R. Domingo, R. Mestres, E. Mufioz, R. J. Zaragoza, Tetrahedron, 1999,55, 815.

I : Theoretical Organometallic Chemistry 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55.

56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74.

31

D. Cheng, S. Zhu, X. Liu, S. H. Norton, T. Cohen, J. Am. Chem. Soc., 1999,121, 10241. E. Peralez, J.-C. Nkgrel, A. Goursot, M. Chanon, Main Group Met. Chem., 1999, 22, 185. E. Peralez, J.-C. Nigrel, A. Goursot, M. Chanon, Main Group Met. Chem., 1999, 22,201. S. Mori, E. Nakamura, Chem. Eur. J., 1999,5,1534. N. S. Nudelman, H. G. Schulz, J. Chem. Soc., Perkin Trans. 2, 1999,2761. N. M. Klimenko, K. V. Bozhenko, E. V. Strunina, E. A. Rykova, 0. N. Temkin, THEOCHEM, J. Mol. Struct., 1999,490,233. H. Bock, Z. Havlas, K. Gharagozloo-Hubmann, M. Sievert, Angew. Chem., Int. Ed. Engl, 1999,38,2240. Y.-G. Wang, M. Dolg, W. S. Bian, C. H. Deng, J. Phys. Chem., A, 1999,103,3472. X. Zheng, Z. Wang, A. Tang, J. Phys. Chem., A, 1999,103,9275. A. I. Boldyrev, J. Simons,X. Li, L.-S. Wang, J. Am. Chem. Soc., 1999,121,10193. A. I. Boldyrev, J. Simons, X. Li, W. Chen, L.-S. Wang, J. Chem. Phys., 1999, 110,8980. X. Li, L.-S. Wang, A. I. Boldyrev, J. Simons, J. Am. Chem. SOC.,1999,121,6033. A. I. Boldyrev, J. Simons, X. Li, L.-S. Wang, J. Chem. Phys., 1999,111,4993. H.-J. Himmel, A. J. Downs, T. M. Greene, L. Andrews, Chem. Commun., 1999, 2243. S. Arulmozhiraja, T. Fuji, H. Tokiwa, Chem. Phys., 1999,250, 237. B. S. Ault, J. L. Laboy, J. Mol. Struct., 1999, 475, 193 C. W. Bauschlicher, J. Phys. Chem., A, 1999,103,6429 A. B. de Carvalho, M. A. M. A. de Maurera, J. A. Nobrega, C. Peppe, M. A. Brown, D. G. Tuck, M. Z. Hernandes, E. Longo, F. R. Sensato, Organometallics, 1999,18,99. W. Uhl, T. Spies, R. Koch, W. Saak, Organometallics, 1999,18,4598. P. J. Shapiro, Coord. Chem. Rev., 1999,189, 1. D. Stockigt, Organometallics, 1999, 18, 1050. P. Tarakeshwar, K. S. Kim, J. Phys. Chem., A , 1999,103,9116. J. Chen, T.-H. Wong, P. D. Kleiber, Chem. Phys. Lett., 1999,307, 21. J. Chen, T.-H. Wong, P. D. Kleiber, K.-H. Yang, J. Chem. Phys., 1999, 110, 11798. A. Schnepf, G. Stosser, D. Carmichael, F. Mathey, H. Schnockel, Angew. Chem. Int. Ed. Engl., 1999,38, 1646. P. Pyykko, M. Straka, T. Tamm, Phys. Chem., Chem. Phys., 1999,1,3441. R. A. Fischer, J. Weiss, Angew. Chem. Int. Ed. Engl., 1999, 38, 2831. A. J. Downs, Coord. Chem. Rev., 1999,189,59. C. L. B. Macdonald, A. H. Cowley, J. Am. Chem. Soc., 1999,121,12113. Q. Yu, A. Purath, A. Donchev, H. Schnockel, J. Organomet. Chem., 1999,584,94. C. Boehme, G. Frenking, Chem. Eur. J., 1999,5,2184. W. Uhl, M. Benter, S. Melle, W. Saak, G . Frenking, J. Uddin, Organometallics, 1999,18,3778. R. A. Fischer, A. Miehr, H. Hoffmann, W. Rogge, C. Boehme, G. Frenking, E. Herdtweck, 2. Anorg. Allg. Chem., 1999,625, 1466. W. Uhl, T. Spies, R. Koch, J. Chem. SOC.,Dalton Trans., 1999,2385. A. Beste, 0. Kramer, A. Gerhard, G. Frenking, Eur. J. Inorg. Chem., 1999,2037. J. Panek, Z. Latajka, J. Phys. Chem., A , 1999,103,6845. R. M. Minyaev, A. G. Starikov, Russ. Chem. Bull., 1999,48, 1225.

32

Organometallic Chemistry

75. F. Mele, N. Russo, J. Rubio, M. Toscano, THEOCHEM, J. Mol. Struct., 1999, 466, 77. 76. V. Jonas, W. Thiel, J. Chem. Soc., Dalton Trans., 1999, 3783. 77. P. Jackson, M. Diefenbach, D. Schroder, H. Schwarz, Eur. J. Inorg. Chem., 1999, 1203. 78. N. A. Richardson, J. C. Rienstra-Kiracofe, H. F. Schaefer 111, J. Am. Chem. Soc., 1999,121, 10813 79. S. L. Boyd, R. J. Boyd, J. Phys. Chem., A, 1999,103,7087. 80. P. Antoniotti, P. Benzi, M. Castiglioni, P. Volpe, Eur. J. Inorg. Chem., 1999, 323. 81. K. Aarset, E. M. Page, D. A. Rice, J. Phys. Chem., A, 1999,103, 5574. 82. N. W. Mitzel, U. Losehand, A. D. Richardson, Inorg. Chem., 1999, 38, 5323. 83. N. W. Mitzel, U. Losehand, A. D. Richardson, Organometallics, 1999, 18, 2610. 84. A. Haaland, D. J. Shorokhov, H. V. Volden, J. McMurran, J. Kouvetakis, J. Mol. Struct., 1999,509,29. 85. S. Foucat, T. Pigot, G. Pfister-Guillouzo, S. Mazieres, H. Lavayssiere, Eur. J. Inorg. Chem., 1999, 1 151. 86. S. Foucat, T. Pigot, G. Pfister-Guillouzo, H. Lavayssiere, S. Mazieres, Organometallics, 1999, 18, 5322. 87. F. Riedmiller, G. L. Wegner, A. Jockisch, H. Schmidbaur, Organometallics, 1999, 18,4317. 88. E. Lukevics, L. Ignatovich, S. Belyakov, J. Organomet. Chem., 1999,588,222. 89. J. Ferman, J. P. Kakareka, W. T. Klooster, J. L. Mullin, J. Quattrucci, J. S. Ricci, H. J. Tracy, W. J. Vining, S. Wallace, Inorg. Chem., 1999,38, 2464. 90. A. L. Chistyakov, I. V. Stankevich, Rum. Chem. Bull., 1999,48, 1628. 91. J. C. Martins, R. Willem, F. A. G. Mercier, M. Gielen, M. Biesemans, J. Am. 1999,121,3284. Chem. SOC., 92. G. Barone, M. C. Ramusino, R. Barbieri, G. La Manna, THEOCHEM, J. Mol. Struct., 1999,469, 143. 93. J. K. Tsagatakis, N. A. Chaniotakis, K. Jurkschat, S. Damoun, P. Geerlings, A. Bouhdid, M. Gielen, I. Verbruggen, M. Biesemans, J. C. Martins, R. Willem, Helv. Chim. Acta, 1999,82, 53 1. 94. A. Rodriguez-Fortea, P. Alemany, T. Ziegler, J. Phys. Chem., A, 1999,103, 8288. 95. T. M. Klapotke, J. Knizek, H. Noth, B. Krumm, C. M. Rienacker, Polyhedron, 1999, 18, 839. 96. M. Weidenbruch, Eur. J. Inorg. Chem., 1999, 373. 97. J. Escudie, H. Ranaivonjatovo, Adv. Organomet. Chem., 1999,44, 113. 98. V. N. Khabashesku, S. E. Boganov, K. N. Kudin, J. L. Margrave, J. Michl, 0. M. Nefedov, Russ. Chem. Bull., 1999,48,2003. 99. G. Trinquier, C. Jouany, J. Phys. Chem., A , 1999,103,4723. 100. S. Saebar, S. Stroble, W. Collier, R.Ethridge, Z. Wilson, M. Tahai, C. U. Pittman Jr., J. Org. Chem., 1999,64, 1311. 101. J. E. Bender IV, A. J. Shusterman. M. M. B. Holl, J. W. Kampf, Organometallics, 1999,18, 1547. 102. R. Fossheim, Inorg. Chim. Acta, 1999,284, 167. 103. V. A. Zakharov, E. P. Talzi, I. I. Zakharov, D. E. Babushkin, N. V. Semikolenova, Kinet. Catal., 1999,40, 836. 104. M. Reinhold, J. E. McGrady, R. J. Meier, J. Chem. Soc., Dalton Trans., 1999, 487.

1: Theoretical Organometallic Chemistry

33

105. W. Clegg, S. T. Liddle, K. W. Henderson, F. E. Keenan, A. R. Kennedy, A. E. McKeown, R. E. Mulvey, J. Organomet. Chem., 1999,572,283, 106. T. Nakajima, K. Yamashita, THEOCHEM, J. Mol. Struct., 1999,490, 155. 107. S. Sakaki, S. Kai, M. Sugimoto, Organornetallics, 1999, 18,4825. 108. B. Biswas, M. Sugimoto, S. Sakaki, Organometallics, 1999, 18,4015. 109. M.-D. Su, S.-Y. Chu, J. Am. Chem. SOC.,1999,121,4229. 110. M.-D. Su, S.-Y. Chu, Tetrahedron Lett., 1999,40,4371. 111. M.-D. Su, S.-Y. Chu, Inorg. Chem., 1999,38,4819. 112. M.-D. Su, S.-Y. Chu, J. Phys. Chem. A, 1999,103, 11011. 113. M.-D. Su, S.-Y. Chu, J. Am. Chem. SOC.,1999,121,11478. 114. G. L. Borosky, A. B. Pierini, THEOCHEM, J. Mol. Struct., 1999,466, 165. 115. I. D. Gridnev, P. R. Schreiner, 0. L. Tok, Y. N. Bubnov, Chem. Eur. J., 1999, 5, 2828. 116. M. Takahashi, M. Kira, J. Am. Chem. SOC.,1999,121,8597. 117. M. A. Vincent, I. H. Hillier, R. J. Hall, E. J. Thomas, J. Org. Chem., 1999, 64, 4680. 118. I. Shim, K. A. Gingerich, Chem. Phys. Lett., 1999,303, 87. 119. R. Sumathi, M. Hendrickx, J. Phys. Chem., A, 1999,103,585. 120. M. F. Ge, J. K. Feng, C. Yang, Z. R. Li, C. C. Sun, Int. J. Quant. Chem., 1999, 71, 313. 121. J. Muiioz, M. M. Rohmer, M. Benard, C . Bo, J.-M. Poblet, J. Phys. Chem., A, 1999,103,4762. 122. A. V. Arbuznikov, M. Hendrickx, L. G. Vanquickenborne, Chem. Phys. Lett., 1999,310,515. 123. T. F. Miller 111, M. B. Hall, J. Am. Chem. SOC.,1999, 121, 7389. 124. S. Nagase, K. Kobayashi, T. Akasaka, THEOCHEM, J. Mol. Struct. , 1999,462, 97. 125. C.-R. Wang, M. Inakuma, H. Shinohara, Chem. Phys. Lett., 1999,300,379. 126. K. Kobayashi, S. Nagase, Chem. Phys. Lett., 1999,313,45. 127. M. R. Pederson, D. V. Porezag, D. C. Patton, E. Kaxiras, Chem. Phys. Lett., 1999,303,373. 128. M Cui, H. Zhang, M. Ge, J. Feng, W. Tian, C. Sun, Chem. Phys. Lett., 1999, 309,344. 129. W. A. King, S. Di Bella, A. Gulino, G. Lanza, I. L. Fragali, C. L. Stern, T. J. Marks, J. Am. Chem. Soc., 1999,121,355. 130. B. Sztaray, E. Rosta, Z. Bocskey, L. Szepes, J. Organomet. Chem., 1999,582,267. 131. H.-H. Brintzinger, M.-H. Prosenc, F. Schaper, A. Weeber, U. Wieser, J. Mol. Struct., 1999,486,409. 132. H. Jacobsen, H. Berke, S. Doring, G. Kehr, G. Erker, R. Frohlich, 0. Meyer, Organometallics, 1999,18, 1724. 133. U. Richter, J. Heck, J. Reinhold, Inorg. Chem., 1999,38,77. 134. H. C. Strauch, B. Wibbeling, R. Frohlich, G. Erker, H. Jacobsen, H. Berke, Organometallics, 1999, 18,3802. 135. J. C. Green, C. N. Jardine, J. Chem. SOC.,Dalton Trans., 1999, 3767. 136. R. Poli, K. M. Smith, Eur. J. Inorg. Chem., 1999,12,2343. 137. E. Collange, D. Duret, R. Poli, J. Chem. SOC.,Dalton Trans., 1999,875. 138. K. M. Smith, R. Poli, P. Legzdins, Chem. Eur. J., 1999,5, 1598. 139. B. Pleune, D. Morales, R. Meunier-Prest, P. Richard, E. Collange, J. C. Fettinger, R. Poli, J. Am. Chem. SOC.,1999, 121, 2209. 140. I. Gattinger, M. A. Herker, W. Hiller, F. H. Kohler, Inorg. Chem., 1999,38,2359.

34

Organometallic Chemistry

141. P. Hudeczek, F. H. Kohler, P. Bergerat, 0. Kahn, Chem. Eur. J., 1999,5,70. 142. D. Unseld, V. V. Krivykh, K. Heinze, F. Wild, G. Artus, H. Schmalle, H. Berke, Organometallics, 1999, 18, 1525. 143. K. P. C. Vollhardt, J. K. Cammack, A. J. Matzger, A. Bauer, K. B. Capps, C. D. Hoff, Inorg. Chein., 1999,38,2624. 144. A. Diefenbach, F. M. Bickelhaupt, Z. Anorg. Allg. Chem., 1999,625, 892. 145. P. Gisdakis, S. Antonczak, N. Rosch, Organometallics, 1999,18, 5044. 146. A. L. Chistyakov, I. V. Stankevich, Rum. Chem. Bull., 1999, 48, 1636. 147. J. R. Perera, M. J. Heeg, H. B. Schlegel, C. H. Winter, J. Am. Chem. Soe., 1999, 121,4536. 148. P. Comba, T. Gyr, Eur. J. Inorg. Chenz., 1999, 1787. 149. D. C. MacLaren, S. C. Mackie, J. Organomet. Chem., 1999,590,253. 150. A. Karlsson, A. Broo, P. Ahlberg, Can. J. Chem., 1999,77,628. 151. N. J. Long, A. J. Martin, R. Vilar, A. J. P. White, D. J. Williams, M. Younus, Organometallics, 1999, 18,4261. 152. K. Costuas, J.-Y. Saillard, Organometallics, 1999, 18, 2505. 153. C. Gemel, V. N. Sapunov, K. Mereiter, M. Ferencic, R. Schmid, K, Kirchner, Inorg. Chim. Acta, 1999,286, 114. 154. C. Lambert, W. Gaschler, M. Zabel, R. Matschiner, R. Wortmann, J. Organomet. Chem., 1999,592, 109. 155. G. Bringmann, A. Wuzik, R. Stowasser, C. Rummey, L. Gobel, D. Stalke, M. Pfeiffer, W. A. Schenk, Organometallics, 1999, 18, 5017. 156. R. Poli, K. M. Smith, Eur. J. Inorg. Chem., 1999, 877. 157. H. Wadepohl, F.-J. Paffen, H. Pritzkow, J. Organomet. Chem., 1999,579, 391. 158. C.-N. Yang, S. J. Klippenstein, J. Phys. Chem., A , 1999,103, 1094. 159. S. Roszak, D. Majumdara, K. Balasubramaniana, J. Phys. Chem., A, 1999, 103, 5801. 160. V. Ryzhov, C.-N. Yang, S. J. Klippenstein, R. C. Dunbar, Int. J. Mass Spect., 1999,187. 161. T. K. Dargel, R. H. Hertwig, W. Koch, Mot. Phys., 1999,96, 583. 162. D. R. Evans, N. L. R. Fackler, Z. Xie, C. E. F. Rickard, P. D. W. Boyd, C. A. Reed, J. Am. Chem. Soc., 1999,121, 8466. 163. S. Ulvenlund, J. Rosdahl, A. Fischer, P. Schwerdtfeger, L. Kloo, Eur. J. Inorg. Chem., 1999,633. 164. C. A. Merlic, J. C. Walsh, D. J. Tantillo, K. N. Houk, J. Am. Chem. Soc., 1999, 121,3596. 165. A. Pfletschinger, T. K. Dargel, J. W. Bats, H.-G. Schmalz, W. Koch, Chem. Eur. J., 1999, 5, 537. 166. A. Elass, J. Mahieu, J. Brocard, G. Surpateanu, G. Vergoten, J. Mol. Struct., 1999,475,279. 167. S. J. Hughes, J. R. Moss, K. J. Naidoo, J. F. Kelly, A. S. Batsanov, J. Organomet. Chem., 1999,588, 176. 168. K. J. Naidoo, S. J. Hughes, J. R. Moss, Macromol., 1999,32, 331. 169. A. Perjessy, D. Loos, E. Kolehmainen, P. Hrnciar, J. Organomet. Chem., 1999, 590, 261. 170. I. M. Bartlett, N. G. Connelly, A. J. Martin, A. G. Orpen, T. J. Paget, A. L. Rieger, P. H. Rieger, J. Chem. Soc., Dalton Trans., 1999, 691. 171. M. T. Ashby, V. S. Asirvatham, A. S. Kowalski, M. A. Khan, Organometallics, 1999,18,5004. 172. L. F. Veiros, J. Organomet. Chem., 1999,587,221.

I : Theoretical Organometallic Chemistry

35

173. M. J. Calhorda, I. S. Gonqalves, E. Herdtweck, C. C. Romiio, B. Royo, L. F. Veiros, Organometallics, 1999,18, 3956. 174. M. J. Calhorda, L. F. Veiros, Coord. Chem. Rev., 1999, 186, 37. 175. Y. F. Oprunenko, N. G. Akhmedov, D. N. Laikov, S. G. Malyugina, V. I. Mstislavsky, V. A. Roznyatovsky, Y. A. Ustynyuk, N. A. Ustynyuk, J. Organomet. Chem., 1999,583, 136. 176. A. S. Veige, T. S. Kleckley, R. M. Chamberlin, D. R. Neithamer, C. E. Lee, P. T. Wolczanski, E. B. Lobkovsky, W. V. Glassey, J. Urganomet. Chem., 1999, 591, 194. 177. M. Jaworska, Chem. Phys., 1999,242, 11. 178. A. Pfletschinger, H.-G. Schmalz, W. Koch, Eur. J. Inorg. Chem., 1999, 1869. 179. 0. Gonzalez-Blanco, V. Branchadell, R. Gree, Chem. Eur. J., 1999,5, 1722. 180. H. Mayr, K.-H. Muller, A. R. Ofial, M. Biihl, J. Am. Chem. SOC.,1999,121,2418. 181. W. Imhof, A. Gobel, D. Braga, P. De Leonardis, E. Tedesco, Organometallics, 1999, 18, 736. 182. S. Creve, M. T. Nguyen, L. G. Vanquickenborne, Eur. J. Inorg. Chem., 1999, 1281. 183. J. P. Graham, A. Wojcicki, B. E. Bursten, Organometallics, 1999,18, 837. 184. A. Kovacs, G . Frenking, Organometallics, 1999, 18, 887. 185. G. Hong, F. Schautz, M. Dolg, J. Am. Chem. SOC.,1999,121, 1502. 186. J. Li, B. E. Bursten, J. Anz. Chem. SOC.,1999,121, 10243. 187. H.-G. Lu, L.-M. Li, Theor. Chem. Acc., 1999,102, 121. 188. F. G. N. Cloke, J. C. Green, C. N. Jardine, Organometallics, 1999,18, 1080. 189. T. G. Wetzel, S. Dehnen, P. W. Roesky, Organometallics, 1999,18, 3835. 190. M. Zhou, L. Andrews, J. Phys. Chem. A, 1999,103,2964. 191. M. Zhou, L. Andrews, J. Phys. Chem. A, 1999,103,5259. 192. M. Zhou, L. Andrews, J. Phys. Chem. A, 1999,103,7785. 193. M. Zhou, L. Andrews, J. Chem. Phys., 1999, 110, 10370. 194. M. Zhou, L. Andrews, J. Phys. Chem. A, 1999,103,6956. 195. M. Zhou, L. Andrews, J. Am. Chem. SOC.,1999,121,9171. 196. M. Zhou, L. Andrews, J. Phys. Chem. A, 1999,103,7773. 197. M. Zhou, L. Andrews, J. Chem. Phys., 1999,111,4548. 198. K. R. Glaesemann, M. S. Gordon, H. Nakano, Phys. Chem., Chem. Phys., 1999, 1, 967. 199. X. Xu, X. Lu, N. Q. Wang, Q. N. Zhang, M. Ehara, H. Nakatsuji, Int. J. Quant. Chem., 1999,12,221. 200. L. Manceron, M. E. Alikhani, Chem. Phys., 1999,244,215. 201. A. J. Lupinetti, V. Jonas, W. Thiel, S. H. Strauss, G. Frenking, Chem. Eur. J . , 1999,5, 2573. 202. S. N. Cesaro, S. Dobos, A. Stirling, Vib. Spect., 1999, 20, 59. 203. M. Zhou, L. Andrews, J. Li, B. E. Bursten, J. Am. Chem. SOC.,1999,121,9712. 204. S. J. A. van Gisbergen, J. A. Groeneveld, A. Rosa, J. G. Snijders, E. J. Baerends, J. Phys. Chem., A, 1999,103,6835. 205. A. Rosa, E. J. Baerends, S. J. A. van Gisbergen, E. van Lenthe, J. A. Groeneveld, J. G. Snijders, J. Am. Chem. SOC.,1999,121, 10356. 206. 0.Rubner, V. Engel, M. R. Hachey, C. Daniel, Chem. Phys. Lett., 1999,302,489. 207. S. Zalis, C. Daniel, A. Vlcek, J. Chem. SOC.,Dalton Trans., 1999, 3081. 208. C. Daniel, D. Guillaumont, C. Ribbing, B. Minaev, J. Phys. Chem., A, 1999, 103, 5766. 209. D. Guillaumont, C. Daniel, J. Am. Chem. Soc., 1999, 121, 11733.

36

Organometallic Chemistry

210. P. T. Snee, H. Yang, K. T. Kotz, C. K. Payne, C. B. Harris, J. Phys. Chem., A , 1999,103, 10426. 211. A. P. Klyagina, V. Y. Kotov, S. I. Gorel’skii, S. P. Gubin, Russ. J. Coord. Chem., 1999,25, 576. 212. M. Biihl, Chem. Eur. J., 1999,5, 3514. 213. E. van Lenthe, A. Ehlers, E. J. Baerends, J. Chern. Phys., 1999,110, 8943. 214. C. van Wullen, J. Comput. Chem., 1999, 20, 51 215. M. Biihl, M. Kaupp, 0. L. Malkina, V. G. Malkin, J. Comput. Chem., 1999, 20, 91. 216. W. von Philipsborn, Chem. Soc. Rev., 1999, 28, 95. 217. G. Schreckenbach, J. Chem. Phys., 1999,110, 11936. 218. 0. Gonzalez-Blanco, V. Branchadell, J. Chem. Phys., 1999,110,778. 219. E. Hunstock, C. Mealli, M. J. Calhorda, J. Reinhold, Inorg. Chem., 1999, 38, 5053. 220. A. Matveev, M. Staufer, M. Mayer, N. Rosch, Int. J. Quant. Chem., 1999, 75, 863. 221. V. Jonas, W. Thiel, J. Phys. Chem. A . , 1999,103, 1381. 222. E. Bernhardt, B. Bley, R. Wartchow, H. Willner, E. Bill, P. Kuhn, I. H. T. Sham, M. Bodenbinder, R. Brochler, F. Aubke, J. Am. Chem. Soc., 1999,121,7188. 223. S. A. Decker, M. Klobukowski, Can. J. Chenz., 1999,77,65. 224. K. Beck, J. J. Alexander, J. A. K. Bauer, J. L. Nauss, Inorg. Chim. Acta, 1999, 288, 159. 225. D. Frigyes, G. Fogarasi, Organometallics, 1999,18, 5245. 226. H. Jacobsen, V. Jonas, D. Werner, A. Messmer, J. C. Panitz, H. Berke, W. Thiel, Helv. Chim. Acta, 1999,82, 297. 227. B. J. Drouin, S. G. Kukolich, J. Am. Chem. Soc., 1999,121,4023. 228. S. A. Macgregor, D. MacQueen, Inorg. Chem., 1999,38,4868. 229. D. J. Darensbourg, B. J. Frost, A. Derecskei-Kovacs, J. H. Reibenspies, Inorg. Chem., 1999, 38, 4715. 230. C.-M. Lee, G.-Y. Lin, C.-H. Hsieh, C.-H. Hu, G.-H. Lee, S.-M. Peng, W.-F. Liaw, J. Chem. Soc., Dalton Trans., 1999,2393. 231. S. Creve, K. Pierloot, M. T. Nguyen, L. G. Vanquickenborne, Eur. J. Inorg. Chem., 1999,107. 232. D. P. White, J. C. Anthony, A. 0. Oyefeso, J. Org. Chem., 1999,64,7707. 233. M. D. Francis, D. E. Hibbs, P. B. Hitchcock, M. B. Hursthouse, C. Jones, T. Mackewitz, J. F. Nixon, L. Nyulaszi, M. Regitz, N. Sakarya, J. Organomet. Chenz., 1999, 580, 156. 234. M. Shimoi, S. Nagai, M. lchikawa, Y. Kawano, K. Katoh, M. Uruichi, H. Ogino, J. Am. Chem. SOC.,1999, 121, 11704. 235. E. Peris, J. A. Mata, V. Moliner, J. Clzem. Soc., Dalton Trans., 1999, 3893. 236. J. Barluenga, F. Rodriguez, J. Vadecard, M. Bendix, F. J. Fafianas, F. LopezOrtiz, M. A. Rodriguez, J. Am. Chem. Soc., 1999, 121, 8776. 237. F. M. Bickelhaupt, F. Bickelhaupt, Clzem. Eur. J., 1999,5, 162. 238. H. Jacobsen, K. Heinze, A. Llamazares, H. W. Schmalle, G. Artus, H. Berke, J. Clzem. Soc., Dalton Trans., 1999, 1717. 239. T. Gottschalk-Gaudig, J. C. Huffman, K. G. Caulton, H. Gerard, 0. Eisenstein, J. Am. Chem. Soc., 1999,121,3242. 240. J. B. M. Wit, G. T. van Eijkel, F. J. J. de Kanter, M. Schakel, A. W. Ehlers, M. Lutz, A. L. Spek, K. Lammertsma, Angew. Chern. Int. Ed. Engl., 1999,38,2596. 241. W. Petz, F. Weller, J. Uddin, G. Frenking, Organometallics, 1999, 18. 619.

1: Theoretical Organornetallic Chemistry

37

242. K. M. Vogel, P. M. Kozlowski, M. Z. Zgierski, T. G. Spiro, J. Am. Chem. SOC., 1999,121,9915. 243. R. Salzmann, M. T. McMahon, N. Godbout, L. K. Sanders, M. Wojdelski, E. Oldfield, J. Am. Chem. SOC.,1999,121, 3818. 244. G. N. Phillips Jr., M. L. Teodoro, T. Li, B. Smith, J. S. Olson, J. Phys. Chem., B, 1999,103,8817. 245. J. E. McGrady, J. Chem. Soc., Dalton Trans., 1999, 1393. 246. P. Kramkowski, G. Baum, U. Radius, M. Kaupp, M. Scheer, Chem. Eur. J., 1999,5,2890 247. A. S. Weller, M. Shang, T. P. Fehlner, Organometullics, 1999, 18, 853. 248. M. T. Garland, K. Costuas, S. Kahlal, J.-Y. Saillard, New J. Chem., 1999,23,509. 249. G. Hogarth, D. G. Humphrey, N. Kaltsoyannis, W.-S. Kim, M. Y. Lee, T. Norman, S. P. Redmond, J. Chem. Soc., Dalton Trans., 1999,2705. 250, J. L. Perkinson, M.-H. Baik, G. E. Trullinger, C. K. Schauer, P. S. White, Inorg. Chim. Acta, 1999,294, 140. 251. G. Suss-Fink, I. Godefroy, V. Ferrand, A. Neels, H. Stoeckli-Evans, S. Kahlal, J.-Y. Saillard, M. T. Garland, J. Organomet. Chem., 1999,579,285. 252. M. I. Bruce, P. A. Humphrey, B. W. Skelton, A, H. White, K. Costuas, J.-F. Halet, J. Chem. Soc., Dalton Trans., 1999,479. 253. J. Nijhoff, F. Hartl, J. W. M. van Outersterp, D. J. Stufkens, M. J. Calhorda, L. F. Veiros, J. Organomet. Chern., 1999, 573, 12I. 254. P. J. Low, R. Rousseau, P. Lam, K. A. Udachin, G. D. Enright, J. S. Tse, D. D. M. Wayner, A. J. Carty, Organometallics, 1999,18,3885. 255. M. I. Bruce, J.-F. Halet, S. Kahlal, P. J. Low, B. W. Skelton, A. H. White, J. Organomet. Chem., 1999,578, 155. 256. 0.Pamies, G. Net, A. Ruiz, C. Bo, J. M. Poblet, C. Claver, J. Organomet. Chem., 1999,586,125. 257. S. Kabashima, S. Kuwata, M. Hidai, J. Am. Chem. SOC.,1999,121,7837. 258. M. L. Buil, M. A. Esteruelas, J. Modrego, E. Ofiate, New J. Chem., 1999,23,403. 259. M. Stener, K. Albert, N. Rosch, Inorg. Chim. Acta, 1999, 286, 30. 260. C. Mealli, A. Ienco, A. Galindo, E. P. Carreiio, Inorg. Chem., 1999,38,4620. 261. G. Aullon, G. Ujaque, A. Lledos, S. Alvarez, Chem. Euu. J., 1999,5, 1391. 262. P. Leoni, M. Pasquali, V. Cittadini, A. Fortunelli, M. Selmi, Inorg. Chem., 1999, 38, 5257. 263. E. Alonso, J. M. Casas, F. A. Cotton, X. Feng, J. ForniCs, C. Fortuiio, M. Tomas, Inorg. Chem., 1999,38, 5034. 264. T. Zhang, M. Drouin, P. D. Harvey, Inorg. Chem., 1999,38, 1305. 265. S. Camanyes, F. Maseras, N. Moreno, A. Lledos, J. M. Lluch, J. Bertran, Chem. Eur. J., 1999, 5, 1166. 266. J. C. Green, A. Scottow, New J. Chem., 1999,23,651. 267. J. A. Ayllon, S. F. Sayers, S. Sabo-Etienne, B. Donnadieu, B. Chaudret, E. Clot, Organometallics, 1999,18, 398 1. 268. Z. Xu, I. Bytheway, G. Jia, 2.Lin, Organometullics, 1999, 18, 1761. 269. R. Castarlenas, M. A. Esteruelas, E. Gutiesrez-Puebla, Y. Jean, A. Lledos, M. Martn, J. Tomas, Organometallics, 1999,18,4296. 270. D.-H. Lee, B. P. Patel, E. Clot, 0. Eisenstein, R. H. Crabtree, Chem. Commun., 1999,297 271. R. Gelabert, M. Moreno, J. M. Lluch, A. Lledos, Chem. Phys., 1999,241, 155. 272. G. I. Nikonov, L. G. Kuzmina, S. F. Vyboishchikov, D. A. Lemenovskii, J. A. K. Howard, Chem. Eur. J., 1999,5,2947.

38

Organometallic Chemistry

273. F. Delpech, S. Sabo-Etienne, J. C. Daran, B. Chaudret, K. Hussein, C. J. Marsden, J. C. Barthelat, J. Am. Chem. SOC., 1999, 121,6668. 274. M.-F. Fan, Z. Lin, Urganometallics, 1999,18,286. 275. S. M. Ng, C. P. Lau, M.-F. Fan, Z. Lin, Organometallics, 1999,18,2484. 276. S. Kleinhenz, K. Seppelt, Chem. Eur. J., 1999, 5, 3573. 277. M. Kaupp, Chem. Eur. J., 1999,5,3631. 278. U. Bohme, R. Beckhaus, J. Urganomet. Chem., 1999,585,179. 279. D. B. Lawson, R. L. DeKock, J. Phys. Chem., A , 1999,103, 1627. 280. M. Rosi, A. Sgamellotti, C. Floriani, THEOCHEM, J. Mol. Struct., 1999,459,47. 281. M. Rosi, A. Sgamellotti, C. Floriani, THEOCHEM, J. Mol. Struct., 1999,459,57. 282. M. Kaupp, Angew. Chem. Int. Ed. Engl., 1999,38,3034. 283. G. Ujaque, F. Maseras, A. Lledos, L. Contreras, A. Pizzano, D. Rodewald, L. Sanchez, E. Carmona, A. Monge, C. Ruiz, Organometallics, 1999,18, 3294. 284. W. Malisch, H. Jehle, S. Moller, G. Thum, J. Reising, A. Gbureck, V. Nagel, C. Fickert, W. Kiefer, M. Nieger, Eur. J. Inorg. Chem., 1999, 1597. 285. S. Geremia, M. Calligaris, L. Randaccio, Eur. J. Inorg. Chem., 1999,981. 286. A. J. Canty, A. Dedieu, H. Jin, A. Milet, B. W. Skelton, S. Trofimenko, A. H. White, Inorg. Chim. Acta, 1999,287, 27. 287. E. Karakyriakos, J. R. Davis, C. J. Wilson, S. A. Yates, A. J. McKinley, L. B. Knight, R. Babb, D. J. Tyler, J. Chem. Phys., 1999,110, 3398. 288. T. A. Barckholtz, D. E. Powers, T. A. Miller, B. E. Bursten, J. Am. Chem. SOC., 1999, 121, 2576. 289. S. K. Wolff, T. Ziegler, E. van Lenthe, E. J. Baerends, J. Chem. Phys., 1999, 110, 7689. 290. D. W. Smith, J. Urganomet. Chem., 1999,585, 150. 291. M. A. Putzer, G. P. Bartholomew, 2. Anorg. Allg. Chem., 1999,625, 1777 292. R. Cini, A. Cavaglioni, Inorg. Chern., 1999,38,3751. 293. L. N. Saitkulova, E. V. Bakhmutova, E. S. Shubina, I. A. Tikhonova, G. G. Furin, V. I. Bakhmutov, N. P. Gambaryan, A. L. Chistyakov, I. V. Stankevich, V. B. Shur, L. M. Epstein, J. Organornet. Chem., 1999,585,201. 294. M. B. Hall, S. Niu, J. H. Reibenspies, Polyhedron, 1999,18, 1717 295. S.-H. Choi, Z. Lin, Organometallics, 1999,18, 2473. 296. K. K. Banger. A. K. Brisdon, P. T. Brain, S. Parsons, D. W. H. Rankin, H. E. Robertson, B. A. Smart, M. Biihl, Inorg. Chem., 1999,38, 5894. 297. T. Weskamp, F. J. Kohl, W. Hieringer, D. Gleich, W. A. Herrmann, Angew. Chem. Int. Ed. Engl., 1999,38, 2416. 298. S. M. Hansen, F. Rominger, M. Metz, P. Hofmann, Chem. Eur. J., 1999,5, 557. 299. D. Huang, H. Gerard, E. Clot, V. Young Jr., W. E. Streib, 0. Eisenstein, K. G. Caulton, Organometallics, 1999, 18, 5441. 300. H. Gerard, E. Clot, 0. Eisenstein, New J. Chem., 1999,23,495. 301. A. Klose, E. Solari, J. Hesschenbrouck, C. Floriani, N. Re, S. Geremia, L. Randaccio, Organometallics,1999,18, 360. 302. F. P. Arnold Jr., Organometallics, 1999,18,4800. 303. S.-H. Choi, Z. Lin, Z. Xue, Urganometallics, 1999, 18, 5488. 304. L. Giannini, E. Solari, S. Dovesi, C. Floriani, N. Re, A. Chiesi-Villa, C. Rizzoli, J. Am. Chem. SOC.,1999,121,2784. 305. H. Wadepohl, U. Arnold, H. Pritzkow, M. J. Calhorda, L. F. Veiros, 3. Urganomet. Chem., 587, 233. 306. M. L. Buil, 0. Eisenstein, M. A. Esteruelas, C. Garcia-Yebra, E. Gutierrez-Puebla. M. Olivan, E. Oiiate, N. Ruiz, M. A. Tajada, Organometallics,1999,18,4949.

1: Theoretical Organometallic Chemistry

39

307. M. Jaworska, P. Lodowski, J. Math. Chem., 1999,25,7. 308. J. G. Donkervoort, M. Buhl, J. M. Ernsting, C. J. Elsevier, Eur. J. Inorg. Chem., 1999,27. 309. M. Buhl, W. Baumann, R. Kadyrov, A. Borner, Helv. Chim. Acta, 1999,82, 81 1. 310. R. Kadyrov, A. Borner, R. Selke, Eur. J. Inorg. Chem., 1999,705. 311. F. Nunzi, A. Sgamellotti, N. Re, C. Floriani, J. Chem. SOC.,Dalton Trans., 1999, 3487. 312. J. Uddin, S. Dapprich, G. Frenking, B. F. Yates, Organometallics, 1999,18,457. 313. E. Bencze, I. Papai, J. Mink, P. L. Goggin, J. Organomet. Chem., 1999,584, 118. 314. B. Minaev, H. Agren, Int. J. Quant. Chem., 1999,72, 581. 315. F. Mendizabal, Int. J. Quant. Chem., 1999,73,317. 316. M. Rosi, A. Sgamellotti,F. Franceschi, C. Floriani, Inorg. Chem., 1999,38, 1520. 317. P. Zanello, F. Laschi, R. Fontani, C . Mealli, A. Ienco, K. Tang, X. Jin, L. Li, J. Chem. SOC.,Dalton Trans., 1999,965. 318. J. M. Poblet, J. Muiioz, K. Winkler, M. Cancilla, A. Hayashi, C . B. Lebrilla, A. L. Balch, J. Chem. Soc,. Chem. Commun., 1999,493. 319. J. Koch, I. Hyla-Kryspin, R. Gleiter, T. Klettke, D. Walther, Organometallics, 1999,18,4942. 320. (a) S. Mori, E. Nakamura, THEOCHEM, J. Mol. Struct., 1999, 462, 167. (b) S. Mori, E. Nakamura, Tetrahedron Lett., 1999,40, 5319. 321. M. Zhou, L. Andrews, J. Phys. Chem., A, 1999,103,2066. 322. M. Zhou, B. Y. Liang, L. Andrews, J. Phys. Chem. A., 1999,103,2013. 323. J. Mascetti, F. Galan, I. Papai, Coord. Chem. Rev., 1999,192, 557. 324. H.-J. Fan, C.-W. Liu, Chem. Phys. Lett., 1999,300,351. 325. T. Wistuba, C. Limberg, Eur. J. Inorg. Chem., 1999,8, 1335. 326. A. Tachibana, K. Nakamura, THEOCHEM, J. Mol. Struct., 1999,462,269. 327. K. Yoshizawa, A. Suzuki, T. Yamabe, J. Am. Chem. SOC.,1999,121,5266. 328. P. A. M. van Koppen, J. K. Perry, P. R. Kemper, J. E. Bushnell, M. T. Bowers, Int. J. Mass. Spec., 1999,187,989. 329. C. J. Wang, S. Ye, Int. J. Quant. Chem., 1999,75,47. 330. J. N. Harvey, M. Diefenbach, D. Schroder, H. Schwarz, Int. J. Mass. Spec., 1999, 183, 85. 331. K. Yoshizawa, Y. Shiota, T. Yamabe, J. Chem. Phys., 1999,111,538. 332. K. Yoshizawa, Y.Shiota, T. Yamabe, J. Am. Chem. SOC.,1999,121,147. 333. H. Chen, D. B. Jacobson, B. S. Freiser, Organometallics, 1999,18,5460. 334. M. Blomberg, S. S. Yi, R. J. Noll, J. C. Weisshaar, J. Phys. Chem., A, 1999, 103, 7254. 335. U. Achatz, M. Beyer, S. Joos, B. S . Fox, G. Niedner-Schatteburg, V. E. Bondybey, J. Phys. Chem., A, 1999,103,8200. 336. M. Diefenbach, M. Bronstrup, M. Aschi, D. Schroder, H. Schwarz, J. Am. Chem. SOC.,1999,121, 10614. 337. M. E. Alikhani, Chem. Phys. Lett., 1999,313,608. 338. H. Luna-Garcia, S. Castillo, A. Ramirez-Solis, J. Chem. Phys., 1999,110, 11315. 339. Top. Catal., 1999,7, Nos. 1-4. 340. M. S. W. Chan, K. Vanka, C. C. Pye, T. Ziegler, Organometallics,1999, 18,4624. 341. P. Margl, L. Deng, T. Ziegler, J. Am. Chem. SOC.,1999,121, 154. 342. R. D. J. Froese, D. G. Musaev, K. Morokuma, Organometallics, 1999,18, 373. 343. M. C. Chang, Bull. Kor. Chem. SOC.,1999,20, 1269. 344. J. C. W. Lohrenz, M. Buhl, M. Weber, W. Thiel, J. Organomet. Chem., 1999, 592, 11.

40

Organometallic Chemistry

345. G. Moscardi, F. Piemontesi, I,. Resconi, Organometallics, 1999,18, 5264. 346. G. Guerra, P. Longo, P. Corradini, L. Cavallo, J. Am. Chem. Soc., 1999,121,8651. 347. E. A. H. Griffiths, G. J. P. Britovsek, V. C. Gibson, I. R. Gould, Chem. Commun., 1999, 1333. 348. L. Deng, P. Margl, T. Ziegler, J. Am. Chem. Soc., 1999,121, 6479. 349. P. Margl, L. Deng, T. Ziegler, Organometallics, 1999,18, 5701. 350. T. K. Woo, T. Ziegler, J. Organomet. Chem., 1999,591,204. 351. A. Michalak, T. Ziegler, Organometallics, 1999, 18, 3998. 352. S. Tobisch, R. Taube, Organometallics, 1999,18, 5204. 353. S. Tobisch, R. Taube, Organometallics, 1999, 18, 3045. 354. G. Ujaque, F. Maseras, A. Lledos, J. Am. Chem. SOC.,1999,121, 1317. 355. P.-0. Norrby, T. Rasmussen, J. Haller, T. Strassner, K. N. Houk, J. Am. Chem. SOC., 1999, 121, 10186. 356. K. N. Houk, T. Strassner, J. Org. Chem., 1999,64, 800. 357. D. V. Deubel, G. Frenking, J. Am. Chem. SOC.,1999,121,2021. 358. I. V. Yudanov, P. Gisdakis, C. Di Valentin, N. Rosch, Eur. J. Inorg. Chem., 1999,2135. 359. F. E. Kiihn, A. M. Santos, P. W. Roesky, E. Herdtweck, W. Scherer, P. Gisdakis, I. V. Yudanov, C. Di Valentin, N. Rosch, Chem. Eur. J., 1999,5,3603. 360. M. Torrent, L. Deng, M. Duran, M. Sola, T. Ziegler, Can. J. Chem., 1999, 77, 1476. 361. F. U. Axe, J. W. Andzelm, J. Am. Chem. SOC., 1999,121,5396. 362. M. Buhl, Organometallics, 1999, 18,4894. 363. R. 0. Hill, C. F. Marais, J. R. Moss, K. J. Naidoo, J. Organomet. Chem., 1999, 587, 28. 364. B. M. Bode, M. S. Gordon, Theor. Chem. Acc., 1999,102,366. 365. S. Sakaki, N. Mizoe, Y. Musashi, M. Sugimoto, THEOCHEM, J. Mol. Struct., 1999,462,533. 366. S. Sakaki, N. Mizoe, M. Sugimoto, Y. Musashi, Coord. Chem. Rev.,1999, 192, 933. 367. S. A. Kulkarni, N. Koga, THEOCHEM, J. Mol. Struct., 1999,462,297. 368. D. Gleich, W. A. Herrmann, Organometallics, 1999,18,4354. 369. Z. Freixa, M. M. Pereira, A. A. C. C. Pais, J. C. Bayon, J. Chem. Soc., Dalton Trans., 1999,18, 3245. 370. D. D. Kragten, R. A. van Santen, J. J. Lerou, J. Phys. Chem., A, 1999,103,80. 371. D. D. Kragten, R. A. van Santen, M. Neurock, J. J. Lerou, J. Phys. Chern., A, 1999,103,2756. 372. S. Creve, H. Oevering, B. B. Coussens, Organometallics, 1999, 18, 1967. 373. D. A. Alonso, P. Brandt, S. J. M. Nordin, P. G. Anderson, J. Am. Chem. SOC., 1999,121,9580. 374. C. R. Landis, P. Hilfenhaus, S. Feldgus, J. Am. Chem. SOC.,1999,121, 8741. 375. L. Cavallo, J. Am. Chem. SOC.,1999,121,4238. 376. M. Torrent, M. Duran, M. Sola, J. Am. Chem. Soc., 1999,121, 1309. 377. J. H. Hardesty, J. B. Koerner, T. A. Albright, G.-Y. Lee, J. Am. Chem. SOC., 1999,121,6055. 378. V. Cadierno, M. P. Gamasa, J. Gimeno, E. Perez-Carrefio, S. Garcia-Granda, Organometallics, 1999, 18,2821. 379. E. Pkrez-Carrefio, P. Paoli, A. Ienco, C. Mealli, Eur. J. Inorg. Chem., 1999, 1315 380. M. Sugimoto, I. Yamasaki, N. Mizoe, M. Anzai, S. Sakaki, Theor. Chem. Acc., 1999,102,377.

1: Theoretical Organometallic Chemistry

41

381. H. Hagelin, B. Akermark, P.-0. Norrby, Chem. Eur. J., 1999,5,902. 382. H. Hagelin, M. Svensson, B. Akermark, P.-0. Norrby, Organometallics, 1999,18, 4574. 383. H. Hagelin, B. Akermark, P.-0. Norrby, Organometallics, 1999, 18,2884. 384. P. Dorizon, G. Su, G. Ludvig, L. Nikitina, R. Paugam, J. Ollivier, J. Salaiin, J. Org. Chem., 1999,64,4712. 385. R. J. van Haaren, H. Oevering, B. B. Coussens, G. P. F. van Strijdonck, J. N. H. Reek, P. C. J. Kamer, P. W. N. M. van Leeuwen, Eur. J. Inorg. Chem., 1999,1237. 386. M. Svensson, U. Bremberg, K. Hallman, I. Csoregh, C. Moberg, Organometallics, 1999, 18,4900. 387. C. Moberg, U. Bremberg, K. Hallman, M. Svensson, P.-0. Norrby, A. Hallberg, M. Larhed, I. Csoregh, Pure Appl. Chem., 1999,71, 1477. 388. H. Fujimoto, T. Suzuki, Int. J. Quant. Chem., 1999,74,735. 389. V. Branchadell, M. Moreno-Mafias, F. Pajuelo, R. Pleixats, Organometallics, 1999,18,4934. 390. I. Macsari, K. J. Szabo, Organometallics, 1999,18, 701. 391. T. Suzuki, H. Fujimoto, Inorg. Chem., 1999,38,370. 392. K. Mylvaganam, G. B. Bacskay, N. S. Hush, J. Am. Chem. Soc., 1999,121,4633. 393. P. E. M. Siegbahn, Inorg. Chem., 1999,38,2880. 394. H. Basch, K. Mogi, D. G. Musaev, K. Morokuma, J. Am. Chem. Soc., 1999,121, 7249. 395. P. E. M. Siegbahn, M. R. A. Blomberg, Ann. Rev. Phys. Chem., 1999,50,221. 396. Y.-D. Wu, Z.-H. Peng, K. W. K. Chan, X. Liu, A. A. Tuinman, Z. Xue, Organometallics, 1999,18,208 1. 397. L. Y. Ustynyuk, Y. A. Ustynyuk, D. N. Laikov, V. V. Lunin, Russ. Chem. Bull., 1999,48,2222. 398. K. B. Renkema, R. Bosque, W. E. Streib, F. Maseras, 0. Eisenstein, K. G. Caulton, J. Am. Chem. Soc., 1999,121, 10895. 399. M.-D. Su, S.-Y. Chu, J. Am. Chem. SOC.,1999,121,1045. 400. M.-D. Su, S.-Y. Chu, Chem. Eur. J., 1999,5, 198. 401. M.-D. Su, S.-Y. Chu, Int. J. Quant. Chem., 1999,72,405. 402. A. N. Vedernikov, G. A. Shamov, B. N. Solomonov, Russ. J. Gen. Chem., 1999, 69, 1102. 403. P. D. Morran, S. B. Duckett, P. R. Howe, J. E. McGrady, S. A. Colebrooke, R. Eisenberg, M. G. Partridge, J. A. B. Lohman, J. Chem. Soc., Dalton Trans., 1999, 3949 404. S. Niu, M. B. Hall, J. Am. Chem. Soc., 1999, 121, 3992. 405. D. Ekeberg, E. Uggerud, H.-Y. Lin, K. Sohlberg, H. Chen, D. P. Ridge, Organometallics, 1999,18,40 406. G. E. D. Mullen, T. F. Fassler, M. J. Went, K. Howland, B. Stein, P. J. Blower, J. Chem. SOC.,Dalton Trans., 1999, 3759. 407. H. Heiberg, 0. Swang, 0.B. Ryan, 0.Gropen, J. Phys. Chem., A, 1999,103,10004. 408. M. Torrent, M. Sola, G. Frenking, Organometallics, 1999,18,2801. 409. M. Haukka, P. Hirva, S. Luukkanen, M. Kallinen, M. Ahlgren, T. A. Pakkanen, Inorg. Chem., 1999,38, 3182. 410. R. Rodebaugh, J. S. Debenham, B. Fraser-Reid, J. P. Snyder, J. Org. Chem., 1999,64,1758. 41 1. P. Brandt, C. Hedberg, K. Lawonn, P. Pinho, P. G. Andersson, Chem. Eur. J., 1999,5, 1692. 412. M. Yamakawa, R. Noyori, Organometallics, 1999,18, 128.

2 Group 1: The Alkali and Coinage Metals BY DAVID J. LINTON AND ANDREW E. H. WHEATLEY

1

Alkali Metals

1.1 Introduction. - This review is categorised, as it has been for the last three years, primarily in terms of the organic anion component (R-) of the organometallic species R-M+ where M+ is an alkali metal. The review will concentrate on compounds containing at least one carbon-alkali metal interaction. Each section starts with an overview of the synthetic employment and mechanistic aspects of alkali metal-containing organometallic reagents. Thereafter, structural studies are presented. These are ordered according to the analytical technique employed and are dominated by solid-state investigations (for the most part by single-crystal X-ray diffraction but, where appropriate, by powder diffraction or solid-state NMR spectroscopy), solution NMR spectroscopy, and finally molecular orbital (MO) calculations. 1.2 Alkyl Derivatives. - Alkyllithium compounds have continued in 1999 to be a very useful synthetic tool. They have been employed in many transformations both in their own right and in order to afford new lithium reagents in situ. The role of alkyllithium species in the a-deprotonation of phosphane oxides - the lynchpin of Horner-Wittig chemistry - has lately formed part of a review of the SNP(V) reaction.' Also the subject of recent review have been the reactivity of acyl chlorides towards organometallic reagents2 and the employment of alkyllithium reagents in the syntheses of various thiols, selenols, sulfides, selenides, sulfoxides, selenoxides, sulfones and selenones.3 The reductive lithiation of 4-phenyl- 1,3-dioxanes has given dimetallated intermediates that incorporate both Li-0 and Li-C interactions. The trapping of these intermediates with electrophiles has afforded various 3-substituted and 3,3-disubstituted 3-phenylpropan- 1-01s.~The synthesis of new p-amino alcohols has lately been facilitated by the 1,3-asymmetric addition of 2[(trimethylsilyl)methyl]prop-2-enyllithium to imines and iminium ions.5 Further, the 1,4-addition of organolithium species to 2,6-bis(tert-butyl)-4methoxyphenyl naphthalenecarboxylate has afforded regioselectively substituted dihydronaphthalenecarboxylates which can be converted to 1,1,2- and 1,2,2-trisubstituted dihydronaphthalenylmethanols.6The propensity of p- or yhydroxy- or aminophenyl thioesters for sulfur-lithium exchange in the preOrganometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001 42

2: Group I : The Alkali and Coinage Metals

43

sence of either Bu"Li or else Li(0) and a catalytic quantity of 4,4'-di-tertbutylbiphenyl has been noted to enable the electrophilic trapping of various pand y-functionalised alkyllithium specie^.^ The functionalisation of other amine-containing species has been reported The substrate-directed for (9-and (R)-2-(N,N-diben~ylamino)carbamates.~ lithiation of these compounds, followed by their stereoselective addition to (92-(N,N-dibenzylamino)alkanals,has been studied with - in one case - controlled dioxygenation of the lithiated intermediate yielding the protected anti,syn,anti-a,6-diamino-P,y-diolthe core unit of anti-HIV 1 protease agents. The double reductive alkylation (Birch reduction) of highly substituted pyrroles, affording cis-3,4-disubstituted pyrrolidines, has been reported to be effected by elemental lithium in NH3/THF.9 Not only has MeLi been employed in the syntheses of aromatic sec-amides from esters via the dilithium amide," but its use in the dilithiation of an N'-aryl-N,N-dimethylurea has also been noted. However, in this case the second equivalent of lithium reagent performs lithium-halogen exchange at the 2-position of the aromatic ring, with subsequent carbonylation affording a convenient route to various isatins.l1 Unusual reactivity at the site of dilithiation has also been noted in the case of dimetallated chiral imidazolines, which undergo selective one-electron oxidation at this position in the presence of 2,2,6,6-tetramethylpiperidineN-oxide.l 2 The lithio derivatives of 1-(benzotriazol-1-yl)-1-phenoxyalkanes and (benzotriazol- 1-yl)ethoxyphenylmethane react with nitroarenes to afford a1kyl and aryl 4-nitroaryl ketones via initial OH a d d u c t ~ . Whereas '~ it is accepttd that ButLi deprotonates N-benzylbenzamides in the benzylic position with electrophilic work-up yielding the correspondingly substituted product, it has lately been reported that in the presence of excess HMPA, deprotonation is succeeded by dearomatising cyclisation of the lithiate to afford a mixture of cyclised isoindolinones.l4 Meanwhile, attempts to peri-lithiate 1-naphthamides have revealed that whereas blocking of the 2-position results in nucleophilic attack on the aromatic system, naphthalenes bearing 1-NMe2 or 1-CH2NMe2 groups will act as convenient precursors to 8-substituted 1-naphthamides.' ( - )-Sparteine-mediated deprotonation of the epoxide N-Boc hexahydroazonine oxide with various alkyllithium reagents has been noted to yield an indolizidinol ester, possibly via lithiation a to the epoxide 0-centre followed by transannular reaction to form an ammonium ylide which then undergoes the [1,2] migration of Boc.l6 Asymmetric lithiation-substitutions mediated by ( -)sparteine have also been noted in the field of intramolecular cyclisation, and in this way various enantioenriched 2-alkenyl- or aryl-substituted pyrrolidines and piperidines have been prepared.I7 Dibenzyl ether has been found to undergo an enantioselective [1,2] rearrangement when exposed to a pre-formed 1:1 Bu'Li/(S,S)-bis(dihydrooxazole) complex in OEt, to yield the corresponding (9-alcohol with 60% enantiomeric excess - the first observation of enantioselectivity in a Wittig rearrangement." Trisubstituted alkenes have been afforded from the [2,3] Wittig rearrangement of a,j3-disubstituted allylic ethers with insights being gained into the structural parameters which govern EIZ-selectivity in the rearrangement step.l9

44

Organometallic Chemistry

A simple, stereoselective route to trifluoromethylated penta-(22,4E)-dienenitriles has been established via the initial reaction of diethyl( 1-cyanoethyl)phosphonate with BunLi2* Also of interest, studies into the functionalisation of alkene-CO copolymers have led to the use of Bu"Li to incur a-substitution in, for example, poly( 1-methoxyiminotrimethylene).21 The regioselectivity with which Bu"Li adds to secondary cinnamyl amides has been studied and found to be 'contra-Michael' in the presence of (-)sparteine.22The syntheses of new atropisomeric 2-( 1-aminoalkyl)-1-naphtham i d e ~and ~ ~d i a m i d e ~have ~ ~ been reported via the tertiary amide-directed, stereoselective addition of sterically demanding organolithium reagents to imines. Moreover, the ability of tertiary amides to mediate ortho-lithiation has facilitated the metallation of ferrocene derivatives and the formation of ringsubstituted f ~ l v e n e sSimilarly, .~~ the ortho-directing capacity of the tert-butyl sulfoximine group has been monitored in the context of the metallation of S(trrt-butyl)-N-(trimethylsilyl)-S-phenylsulfoximineby Bu"Li.26 The enantioselective synthesis of thiepines has been enabled by the use of sulfur diimidazole in tandem with the double ortho-lithiation by Bu'Li of a diether.27 The addition of organolithium reagents to aliphatic sulfines has been found to afford a-sulfinyl carbanions which, in turn, generate dithioacetal oxides. The pronounced stereospecificities, surprising since sulfur-stabilised carbanions are generally rather configurationally unstable, have been rationalised in terms of a thermodynamic equilibrium between two diastereomeric forms of the carbanion. Hence, while retention of configuration is noted in the homometallic system, inversion is incurred by the addition of AlMe3 and the formation of an intermediate lithium aluminate.28 The use of alkyllithium reagents in conjunction with AlMe3 has also been reported in the asymmetric formation of apdibranched amines via alane-mediated 1,2-addition of the organolithium reagent to tert-butanesulfinyl k e t i m i n e ~Also . ~ ~ in the field of Li-A1 chemistry, the complex reaction of Bu'Li with dimethyl(2-pyridylani1ido)aluminium has afforded both [Ph(2-C5H4N)NI6(H)Li7 and ([Ph(2CSH4N)Nl6(H)Li8) +[(But2A1Me2)2Li]- molecular Main Group metal species which contain interstitial hydride in mono- and bicapped octahedral environments ,30 Lithiated methylthiomethyl 4-tolyl sulfone has been reported to undergo M(acac)3 (M = Ni, Fe) catalysed coupling reactions with lithiated alkyl sulfones to give methylthi~alkanes.~'It has also been reported that the treatment of active methane species which contain unactivated 4-pentynyl or 3,4-pentadienyl groups with a catalytic quantity of Bu"Li (or, for that matter, NaH) initiates a hydrocarbocyclisation reaction by a proton transfer mechanism to give methylenecyclopentane products.32 BunLi has been reacted with trimethylsilyldiazomethane to afford its metallated derivative. This has then been used to incur carbene formation with a view to employing 1,5-CH insertion as a key step in the synthesis of a,a-dialkyl-a-amino acids33and also in order to generate new methylenecyclopropanes.34Free carbenes incorporating redox-active ferrocenyl substituents have been investigated lately. The deprotonation of a N,N'-diferrocenylimidazoliniumsalt with MeLi, followed

2: Group I : The Alkali and Coinage Metals

45

by trapping of the resulting intermediate with sulfur, gave a thiourea which could be treated with K(0) to afford a 1,3-diferrocenylimidazolin-2-ylidene.35 Meanwhile the variable reactivity of MeLi towards iron cyclopentadienyls has been studied with respect to the electrophilic system (q5-Cp)Fe(C0)21/ P(OMe)3. Treatment of the 1:1 mixture with a stoichiometric amount of MeLi has been noted to yield (q4-exo-MeC5HS)Fe(C0)2P(OMe)3whereas catalytic addition of the alkyllithium species followed by sequential treatment of the intermediate with MeLi and Me1 gives [q5-C5H4P(0)(OMe)2]Fe(CO)[P(OMe)3]Me. In both cases MeLi initially acts as a reducing agent but thereafter it behaves as a nucleophile and as a base, re~pectively.~~ The transition metal hydride (q5-Cp*)Ir(PMe3)H2 has been deprotonated by ButLi to afford the strongly basic lithium iridate (q5-Cp*)Ir(PMe3)(H)Li - a novel species whose chemistry has been studied extensively of late.37 The use of EtLi/TMEDA to alkylate W(OMe)3C13has afforded (C2H4)4(H)W(Li.TMEDA)3;in the solid state this species reveals approximately trigonal bipyramidal geometry with the hydride ligand in an equatorial position while in solution it exhibits ethene interchange by Berry pseudorotation and ethene/hydride exchange which is rapid on the NMR time~cale.~’ The complex intermediate trialkylstannylmanganatolithium [‘RSn(Me)2MnLi’ R = Me, Bun] has been generated by the sequential treatment of MnC12 with MeLi (to yield ‘Me3MnLi’ in situ) and (R3Sn)2 and thence regio- and stereoselectively added to various propargylic alcohols.39 Higher Group 1 organometallic reagents have enjoyed much less synthetic use of late. n-Butylsodiurn has been employed in the synthesis of the sodium analogue of long-known lithium 2,2,6,6-tetramethylpiperidide. However, unlike the tetrameric lithiate, the sodium complex is a trimer in the solid state.40 Meanwhile, the syntheses of cyclopropanes have been affected by the treatment of 1-substituted 2,2-dimethyl-3-phenylpropanewith K O B U ~ . ~ ~ Several solid-state structures of Group 1 organometallic compounds were reported in 1999. The monolithiate Me2N(Me)2Si(Me3Si)2CYTHF)2has been structurally characterised and compared with the analogous Hg, Al, Ga and Sn species.42 In a similar vein to earlier work on the directing capacity of aromatic sulfoximines, the monolithiation of the benzylic sulfoximine Ph(O=)(MeN=)SCH2Ph in the presence of TMEDA has afforded a dimer incorporating both possible S-centre configurations with the metal centres bonding to N and 0, but not to S. Treatment of the racemic sulfoximine substrate with excess BunLi in the presence of trace H20 has yielded the unusual heterochiral, tetranuclear dilithiate Ph(O=)(MeN=)SCLi2PhLi20(THF)6, the core of which is characterised by an 0x0-centred Li6 ~ c t a h e d r o nFurthermore, .~~ an unusual methanide salt was synthesised by the treatment of (Me3SiN=PPh2)2CH2with RLi (R = Me, Ph). The product, (Me3SiN=PPh2)2CLi2,reveals a dimeric solid-state structure based on a Li4 square plane capped above and below by carbon centres.44The first geminally dilithiated phosphane oxide has been reported. Mixed-anion (Me0)2(0=)P(SiMe3)CLiiMe2NL(TMEDA)3 reveals a complex structure based on a central (0Li)2 ring to which six six-membered LiOLiCPO rings are fused and which

46

Orgunometullic Chemistry

can be viewed as a puckered ladder of a type noted previously in lithium siloxide chemistry.45 Recent studies into the substituted B2C33- heterocycle have resulted in the isolation and structural characterisation of trilithium salts in which the pentacycle is bicapped by two alkali metal cations. These ions, when otherwise only agostically stabilised, reveal short Li-ring plane distances [1.675(5), 1.702(5) A] as compared with when they are ether-solvated [whereupon the corresponding distance is extended to 1.778(5) A]. The third Li centre q2-coordinates to the BzB bond and also interacts with the ipso-C atoms of aromatic substituents on each boron centre and with a solvating ether molecule.46 Heterobimetallic complexes incorporating 2,3-C2B4-carborane ligands have also been studied lately. Half- and full-sandwich and mixedligand chlorohafnacarboranes have been synthesised by the reaction of mixedmetal Lima carboranes with a variety of hafnium reagents. Three fullsandwich mixed Li-Hf compounds were crystallographically characterised and found to exhibit bent-sandwich Hf(1V) structures in which the carborane ligands interacted with the alkali metal centre via their BH units.47 As part of an investigation into metallacyclic nickel compounds, the nucleophilic aminomethylation of (Me3P)ZNiClz by H2C[N(Me)CH2LiI2has been used to generate the dimer of Ni{[CH2N(Me)]2CH2}Li2. In the solid state this dinickelate has been found to be based on a Li4Ni2 cluster core.48 Intermetallic species containing two Main Group metals have also been noted. the complex reaction of various alkyllithium reagents with methylaluminium bis(2,6-di-tert-butyl-4-methylphenoxide)results in the isolation of a monomeric lithium aluminate which incorporates unusually strong agostic stabilisation of lithium.49 The synthesis of tris(triorganosily1)methyl salts has been noted not only for Li but also for K. Unlike the heterocyclic dimer [(MeOMe2Si)2(Me3Si)CLi]2, both (Me2NMe2Si)3CK and (Me2NMe&)(Me3Si)2CK are polymeric in the solid state with the cations being bonded to both N- and C-centres.” Isotope studies have enabled the investigation of transition state structures in aminative processes which involve the transfer of neutral or anionic nitrogen to a lithiated carbanion. In both cases results point to trigonal bipyramidal transition states caused by nucleophilic attack of the carbanion from the back side of the leaving group on N.51The effect of HMPA on the regioselectivity with which various monomeric organolithium reagents add to a,P-unsaturated ketones has recently been studied by 7Li NMR spectroscopy. It is claimed that whereas 1,4-addition results if HMPA prevents involvement of the alkali metal ion in reaction, mixtures of 1,2- and 1,4-addition product result from nucleophilic attack if the enone is allowed to 0-bond to Li+.52 Metallation (with ButLi) of the tertiary phosphine MeP[2-(Me2NCH2)C6H4]2 has yielded the dimeric benzyllithium species (MeP[2-(Me2NCH2)C6H4][2-(Me2NCHLi)C6H4])2,the solid-state structure of which has been presented. This compound exhibits interesting solution dynamics in toluene. The NMe2 groups coordinate to the metal and, at low temperature, bare diastereotopic methyl groups. Furthermore, ‘JPLicoupling observed in the 31P NMR spectrum points to a dynamic process which allows each Li to associate with either P and vice

2: Group I : The Alkali and Coinage Metals

47

versa.53Variable temperature 13Cand 6Li NMR spectroscopic data have been invoked as evidence for the existence of a cuboctahedral Prns(PrnO)4Li12 aggregate in cyclopentane solution. Results indicate that at low temperature the dodecameric aggregate resides in the slow fluxional exchange limit.54Intraand intermolecular kinetic effects in directed aromatic and benzylic lithiations by Bu’LUTMEDA have recently been analysed. Results point to these reactions proceeding by two step mechanisms wherein the initial step is the formation of a complex between substrate and organolithium reagent. Whereas complex formation is found to be irreversible for the benzylic metallation of N-benzyl-N,N-dimethyl urea it appears to be largely reversible for the ortho-metallation of both N,N-diisopropylbenzamide and Nisopr~pylbenzamide.~~ In an attempt to rationalise the design of synthetically useful lithium amides, extensive 6Li NMR spectroscopic investigations of etherate solutions of alkyllithium-polyfunctional lithium amide complexes have been ~ n d e r t a k e n The . ~ ~ product obtained when the mixture asymmetrically alkylates benzaldehyde reveals a significant enantiomeric excess if the dinuclear complex contains only one chiral centre. The ability of BunLi to generate (51-2-( 1-pyrrolidinylmethyl)pyrrolidide has allowed a dynamic NMR spectroscopic study of this frequently-employed lithium amide substrate. The lithium amide forms a 2:l complex which exhibits both exchange between free and complexed parent amine and also rapid intra-complex amine-amide interconversion. Semi-empirical and DFT calculations show good agreement with e ~ p e r i m e n tIntra-tetramer .~~ lithium and carbanion exchanges have also been monitored in this system with 6Li-6Li and 13C-13C EXSY being used to determine the rate constants for such processes. Evidently, exchange proceeds via reversible conversion of the tetramers into associated dimers in which the dimeric parts rotate.58 Reaction pathways have been subject to several theoretical investigations of late. Hence, the unusual stereospecifically retentive nature with which (R)- and (9-1-1ithioindan-1-yl N,N-diisopropylcarbamate (generated from the relevant chiral lithiocarbamate) undergoes substitution reactions has been probed. Semi-empirical methods suggest that the lithiated intermediate exhibits extreme pyramidalisation and a high energy barrier to planarisation - thus favouring frontal attack even by soft electrophile~.~~ The enantioselective deprotonation of alkyl carbamates has also been studied in the context of a theoretical analysis of the competing diastereomorphic transition states afforded by their treatment with Bu’Li in the presence of (R7R)-1,2-bis(N,Ndimet hy1amino)cyclohexane.6o Both semi-empirical and ab initio techniques have been used to study the propensity of diethenylnaphthalenes for anionic polymerisation.61 Following the mono- and dilithiation of the benzylic sulfoxime Ph(O=)(MeN=)SCH2Ph, ab initio techniques have been used to study various dilithio salts of (N-methyl)dimethylsulfoximines.62 Finally, ab initio methods have been used to compare the germyl Wright-West anion migration in (H2COGeH3)Li both with the corresponding free anion model and with Wittig rearrangement^.^^ Results suggest that the nondissociative rearrangement of the mixed Li-Ge species involves a one-step [1,2] Ge shift

48

Organometallic Chemistry

rather than a cyclic intermediate. Attempts to model the rearrangement via a dissociationheassociation pathway suggest that such a route is less favourable - conclusions which contrast sharply with calculations on the Wittig carbon rearrangement.

1.3 Alkenyl, Allyl, Vinyl, Alkynyl and Related Derivatives. - Alkenyllithium reagents have been employed to catalytically convert 1-alkenylbicyclo[3.2.0]hepten-7-ones into bicyclo[6.3.O]undecenediones by virtue of an intramolecular Michael addition process, and to thus afford a convenient route to angular t r i q ~ i n a n e s .Further, ~~ the perfluoroacyl olefination of nonenolisable aldehydes has been reported to be affected by P-lithio-P-thio-perfluoroalkyl enol ethers.65The stereochemistry with which vinyl sulfides undergo carbolithiation has recently been the subject of a review,66while the treatment of vinyl sulfones with Bu"Li has allowed alkylation a to the sulfone and afforded a new route to various heterocyclic 2 - a l k ~ l i d e n e s Perfluorovinyllithium .~~ has been used to generate perfluorovinylphosphines of the type PPh,(CF=CFZ), and P(CF=CF2),Cl,, (n + m = 3), with PPh(CF=CF2)2 having been crystallographically characterised.68The employment of excess Bu"Li has also been used in the functionalisation of dienol ethers, with the vinyllithiate only forming on the addition of e l e ~ t r o p h i l e .Phenyl ~~ vinyl thioether has been shown to undergo efficient lithiation at the substituted vinyl carbon centre to afford a convenient source of ethylene 1,l-diani~ns.~' The syntheses and reactivities of hexavinyllithium reagents have been investigated, these compounds having been generated from co-bromo polyeneacetal, o-bromo polyenol ether or cobromo non-conjugated aldehyde.71 Moreover, the generation of heterobimetallic vinyllithium species have been postulated in the novel synthesis of cyclopentenones via the carbonylation of zirconacylopentadienes in the presence of B u " L ~ .Mixed ~ ~ lithium-chalcogen species have also proved to be synthetically useful of late. Hence, the 1,5-dilithio substrate (E)-o-(2'-lithioviny1)benzyllithium has been generated by effecting the Te-Li exchange of 3tert-butyl-lH-isotellurochromene.73 Electrophilic work-up of the dilithio intermediate has afforded both styrene derivatives and also 1,2-dihydr0-2-metallanaphthalenes. Ketene thio(tel1uro) acetals (themselves synthesised by the treatment of lithiated thiomethyl phosphane oxides with aryl or alkyl tellurohalides) undergo Te-Li exchange on exposure to organolithium reagents, thus affording the 1-lithio vinyl sulfide - electrophilic work up of which has yielded, amongst other species, 2-a-phenyl thio-a, p-unsaturat ed aldehydes.74 The a-deprotonation of various silyl allene ethers has afforded an allenyllithium species capable of undergoing a Brook rearrangement to give, on treatment with aldehydes, a,p-unsaturated acyl ~ i l a n e s . ~ ~ An unusual intra-molecular process - the lithium-ene cyclisation - has received attention recently,76with results indicating that the process occurs via an allylic intermediate. Allylic and benzylic organolithium reagents have also recently been prepared from non-enolisable esters, amides, carbonates, carbamates and ~ r e a s with , ~ ~configurationally stable allylic and benzylic organo-

2: Group 1: The Alkali and Coinage Metals

49

lithium compounds having been used, in the presence of (-)-sparteine, to effect enantioselective carbonsarbon bond formation in acyclic doubly activated olefins and nitro-~lefins.~~ Treatment of 1-alkoxy-3-phenylseleno-1alkenes with LDA affords phenylseleno-substituted allyllithium intermediates which, on electrophilic work-up, give the corresponding a-addition products.79 Whereas lithiated N-allyl(bisdimethy1amino)-N-methylphosphoramides have been used to generate new precursors to 5-formyl-6-valerolactones,80 lithium aza-allyls have also been employed to good synthetic effect of late. Specifically, lithium 1,3-bis(trimethylsilyl)-1-aza-allyls have been used to generate various phosphorus enamines." Meanwhile, reaction of [(Me3Si)3Si]L(THF)3with 2,6Me2C6H3NC has afforded the 4-aryl(lithio)amino- 1-aza-2-silacyclobut-3-ene derivative. This species, a resonance hybrid of N- and C-anion forms, has been used to effect the thermal formation of an alkyne.82 Part of a recent review article on cyclyne chemistry concerns a discussion of the lithium-induced formation of ~ y c l y n e s .Terminal ~~ alkynyllithium compounds have been effectively generated from aldehydes by their reaction with a dihalomethyllithium synthon (a lithium amidedihalomethane mixture).84 Synthetic chemistry which utilises alkynyllithium reagents has recently been extended to the cleavage of heterosubstituted epoxides in the presence of catalytic quantities of MMe3 (M = Al,85Ga86).It is known that for aluminium the process is dependent on the oxophilicity of the Group 13 metal atom allowing chelation of the alane by the epoxide, rendering the metal centre pentacoordinate. Alkynyllithium species have also been utilised, in conjunction with a-amidoalkyl sulfones, to effect the formation of allylic and propargylic

corn pound^.^^ Several acetone-derived alkali metal dianionic salts have been reported to act as dinucleophiles towards chlorosilanes and carboxylic acid dichlorides, giving novel heterocycles, spirocycles and functionalised dienes.88Further, the employment of alkynyllithium compounds in conjunction with zirconacyclopentenes has lately afforded a convenient and highly selective route to carboncarbon bond formation and the syntheses of various 1,5-dienes and 1,5enyne~.~~ Sodium cyanide has found recent employment in the syntheses of new aromatic nitriles via its addition to a nitroarene-cationic cyclopentadienyliron adduct .90 Work on K+(aza222)M- (aza222 = fully methylated aza-analogue of cryptand[2.2.2]; M = Na, K)91has been followed by reports on the ability of Kf (15-cr0wn-5)~K-to cleave phenyl glycidyl ether and form KOC(H)(CH2)2 via KOPh y - e l i m i n a t i ~ n . ~ ~ The syntheses of 1,3-bis(silyl)allyllithium and of 1,3-bis(trirnethylsilyl)cyclohexenyllithium species have recently been achieved by reaction of the corresponding 1,3-bis(silyl)propene or 1,3-bis(trimethylsilyl)cyclohexene with Bu"Li. X-ray crystallography reveals that both species exist as monomeric, q3bonded TMEDA-solvates in the solid state.93The reaction of these complexes with ButCN has afforded the corresponding silyl-migration pr0ducts.9~While the reaction of 1,3,5-triazine with RH2CLi, R2HCLi or R3SiL(THF)3 (R = Me3Si) yields straightforward 1,4-adducts, its treatment with either

50

Orgunometallic Chemistry

[(R3C)2Li]-[L(THF)4]+ or R2NLi has, instead, been reported to afford 1,3,5re~pectively.~~ Selenium-lithium extri- or 1,3,5,7-tetraazaheptatrienyllithium, change has recently been utilised to generate a (cyclopropy1)allyllithium species in which the three-membered ring has a thioduryl substituent and is capable of undergoing rearrangement to give an a-duryl thio-substituted alkyllithium compound which exhibits controlled stereochemistry at the metallated carbon centre.96 The structural characterisation of lithiated organophosphorus enamines" has been lately enabled via their synthesis by the treatment of Ph2P(0)CH2Li with B u ~ C N While . ~ ~ the lithiated phosphane oxide substrate reveals an unusual TMEDA-hemisolvated structure, the enamide Ph2P(0)CH=C(Buf)N(H)Li has been characterised both as a tetramer and as a TMEDAhemisolvate in the solid state. Recently reported silylallyllithium complexes93have been converted to the corresponding potassiates by transmetallation with ButOK. One such species, dimethylsilyl-ansa-bis(cyc1ohexyl)potassium is a polymer in the solid state. The successive potassium centres reveal different coordination environments, with one being bonded to the ansa-bridged bis(cyclohexy1) unit and the other interacting with two such groups? Just as for the their lithium analogues, reaction of the potassiated species with ButCN has afforded a convenient route to the related silyl-migration pota~siates.'~ 6Li-31PHMQC NMR spectroscopy has been used to determine that recently synthesised and crystallographically characterised phosphoranylidene car benoids Mes*(E=)P=(X)CL(THF), [E = (Me3Si)2C,Mes*N; X = F, C1, Br] exist as THF-solvated monomers in solution, and to establish structural and kinetic stability differences between E- and Z - i s ~ m e r s . ~ ~ A group of 1-silaallylic lithium complexes have been found to be monomeric in etherate solvent, 13C NMR spectra revealing allylic shifts of roughly 6 40 and 75 - values which lie between those for model localised and delocalised species and thus suggest partially delocalised structures with detectable C-Li covalency (with concomitant spin coupling of -8 Hz). In one example, however, a rapidly interconverting equilibrium mixture of localised and delocalised forms has been observed.99 The dynamics which govern the transfer of TMEDA-coordinated lithium between two allylic faces have also been investigated by 13C NMR spectroscopy; AHJi and A S f have been calculated for inversion (Li transfer) and for the reorientation of TMEDA on one side of the allylic p1ane.l" A group of sec-benzylic lithium compounds have been studied, as both intra- and intermolecular complexes, by the same technique, with the temperature dependence of 6Li'3C coupling having been studied and with chemical shifts pointing to partially delocalised structures. lo' Finally, the solution structures and stereochemistries of alkyl- and silylsubstituted allenyl-propargyllithium compounds have been probed using 13C NMR spectroscopy, as have those of lithiated 2-butyne, 4-methylpentyne and 4,4-dimethylpentyne. It has been noted that the lithiation of triorganosilyl reagents afforded allenyllithium structures if silyl groups were at the allenyl position, whereas structures intermediate between allylic and propargylic were

2: Group 1: The Alkali and Coinage Metals

51

suggested if a silyl group resided at the propargylic position in the substrate. The observation of diastereotopic signals in certain lithiated derivatives allowed the calculation of barriers to configurational inversion for chiral allenyl moieties in Lewis base media.lo2 1.4 Aryl Derivatives. - Lithium naphthalenide has been reported to effect the synthesis of P-hydroxy ketones from a,P-epoxy ketones.lo3The lithiation of 2(chloropheny1)-1,3-dioxolanes has been found to proceed in the presence of catalytic quantities of naphthalene to afford formyl- and acetyl-analogues of phenyllithium.lo4 The naphthalenide radical anion has also been employed in abstraction of the benzotriazole protecting group from a variety of substituted pyrans and furans. lo5 The treatment of elemental lithium with either a catalytic amount of naphthalene- or of biphenyl-supported polymer has facilitated the metallation of a series of mono- and dichlorinated species.lo6 Attempts to derive synthons for syn- and anti- 1,3-diols have led to the use of lithium di-tertbutylphenylide to affect the reductive conversion of 4-(pheny1thio)-1,3-dioxanes into 4-lithio-1,3-dioxanes - species which have been successfully coupled by a variety of electrophiles with retention of configuration.lo7 Finally, lithium naphthalenide has also been employed in the formation of a-ferrocenyllithium derivatives which react, with retention of configuration, with various electrophiles to afford chiral ferrocenyl derivatives.lo8 Remaining with polymetallic systems, it has been reported that organolithium species will react with cyclorhenated and cyclomanganated (q6-arene)tricarbonylchromium complexes. Thus, for example, { 3-methyl-2-[(q6phenyl)tricarbonylchromium(O)]pyridine}rhenium(I) undergoes nucleophilic attack in the presence of PhLi to yield (exo-benzoyl)(tricarbonyl){ 3-methyl-2[(q6-phenyl)tricarbonylchrom~um(0)-~C2']pyr~d~ne-~N~ rhenate(1) - a new benzoylrhenate - by virtue of the addition of PhLi to a CO ligand on the rhenium centre.'" Just as novel cyclisation reactions have been noted previously,',76 unusual dearomatising anionic cyclisations have been reported for or tho-lithiated naphthamides bearing N-ally1 or N-prenyl groups, the assumption being that the ortho-lithiate undergoes an anion translocation prior to lithium enolate formation.' lo A new route to various heterocycles has been achieved by the carbonylation of dilithiated N-pivaloylanilines, 2-pivaloylamino- and 4-pivaloylaminopyridines. However, the dilithiated derivatives of N-pivaloyl-o-toluidines have been found to undergo direct intramolecular cyclisation (yielding 2tert-butylindoles) to the exclusion of CO. l1 Directing effects in indole metallation have been probed lately, with results suggesting that a bulky N-(2,2diethylbutanoyl) group incurs, unusually, lithiation at the 7-position.' l 2 While the 1,3-phenylene-19-crown-6 system has been found to undergo direct lithiation at the intraannular 2-position only slowly (and non-quantitatively), reaction of the 2-brominated analogue with Bu"Li has resulted in the facile formation of the intended 2-lithio-1,3-phenylene)-19-crown-6 molecule. Halogen-metal exchange has been employed to generate stilbenyllithium species, LC6H4C(H)=C(H)C6H4Li(L = Me2N, MeO), of a type which exhibit

52

Organomet a l k Chemistry

important C-C and C-X (X = heteroatom) bond forming properties, and have been employed in the syntheses of triarylmethane dyes. l4 The first examples of ortho-lithiated iodobenzenes have been reported lately, amongst the products afforded by metallating various 3,4-(alkylenedioxy)halobenzenes. The reactivities of substituted aromatic heterocycles have been studied. Thus, the regiospecificity with which 1-[(trifluorome thy l)phenyl]pyrroles undergo competitive mono- and dilithiation has been probed.' l 6 The sequential lithiation, formylation and reduction of 4-chloropyridine affords a one-pot route to 4chloro-3-(hydroxymethyl)pyridine - a species employed in the synthesis of new antibiotics"7 - while the ortho-lithiation of pyrazine-2,5-dicarboxylicacid derivatives has afforded a convenient precursor to pyrazine ladder polymers. I * Furthermore, lithiation of the C-2 position of a purine ring-system has been noted for the first time. This required the use of a complex purine derivative which, importantly, featured an 8-triisopropyl group (which resisted anion migration) and an electron withdrawing 6-chloro-substituent. Ammonolysis of the latter functionality effected concomitant desilylation, yielding a general route to 2-substituted adenosines.' l 9 Heterocyclic aromatic lithium species have themselves been used to perform metallation. Hence, both lithiothiazole and lithiobenzothiazole have been found to exhibit chemoselective nucleophilic addition towards the lactone carbonyl function in artemisinin trioxane lactone, affording a species with superior in vitro antimalarial properties.'20 The preparation and employment of difunctional organometallic species such as dilithiobenzene - has recently been reviewed.12' Phenoxy alcohols, PhO(CH2),0H ( n = 2-7), have been dilithiated, with the addition of electrophile and subsequent work-up affording ortho-disubstituted products,'22 while lithium-halogen exchange has been employed in such systems to incur metallation/electrophilic substitution at meta- and para-positions. 123 Ring-substituent effects on the dilithiation of various N'-aryl-N,N-dimethylureashave also been investigated; para-chloro-, para-fluoro- and para-trifluoromethylphenyl groups all incur ortho-lithiation, whereas para-methylphenyl and phenyl groups encourage deprotonation of the urea methyl groups. 124 Reversible ethylene fixation by a lanthanide metal complex has lately been observed for the first time with the isolation and structural characterisation of [CH2=C(H)OLi(Li .THF)2(Rs-calix-pyrrole)SmI2(p-CH2CH2) (R = alkyl), in which the Sm centres both bond directly to one N-atom and q5 to two pyrrole units with the alkali metal centres N-,q2- and q5-bonding to the pyrrole rings. 125 In DME elemental lithium has been noted to incur two-fold dehydrogenation of hexaphenylbenzene accompanied by CI.c bond formation to give the dilithium salt of the 9,lO-diphenyltetrabenzanthracenedianion. In the solid state partial solvent separation is observed with one lithium centre interacting with the carbon centres of the core benzoid ring and with the @so-centres of the 9,lO-phenyl substituents. In order to enable this coordination, the C6-core is significantly perturbed - with C-9 and C-10 each lying 43" out of the ringplane. 126 Lastly, the lithium molybdate(V1) species (4-MeC6H4)(ArN)2-

'

2: Group 1: The Alkali and Coinage Metals

53

Mo(Me)(2-Me2NCH2C6H4)LDMFreveals not only dimethylamino- but also q6-tolyl-stabilisation of the alkali metal centre. 127 In an extension to previously reported intermetallic antithetical 'crown ethers' it has lately been revealed that a twelve membered N6Na4Mg2 dicationic heterocycle is capable of encapsulating doubly deprotonated benzoid rings. 128 The solid-state structural chemistry of the porphyrin-bonded lanthanides Nd and Pr (= M) has been extended of late. The sodium reagent [(q5:q1:q5:q'-Et8N4)M]Na.(THF)2 has been reported to react with C2H4 or C2H2 to afford dimeric complexes in which the lanthanide metal centres are bridged by (C2H4)2- and (C2)2- ions, respectively.129 Mixed potassium-lanthanide systems have also been the subject of recent study. Reaction of Ln[q5-1,3-(Me3Si)2Cp]3 with elemental potassium in 18-crown-6) in which the benzene affords [$-I ,3-(Me3Si)2Cp]2Ln(q2-c6H6)K.( benzene ligand adopts a boat form and bonds to the alkali metal ion via the centroids of its 2,3- and 5,6-p0sitions.'~' The complexation of sodium and potassium cations by a receptor which The structure of the mimics the behaviour of tyrosine has been in~estigated.'~' complex between this species and a K+ ion reveals the first evidence for cationn: interactions involving the phenolic tyrosine side-chain. Potassium-arene bonds have also been reported in the polymeric salt [Ph2(S)PN(EtO)2POK], in which the alkali metal centres are stabilised both by q3-Ph and by (P=)OK and P(Et)OK i n t e r a ~ t i 0 n s . l ~ ~ A series of caesium arylphosphides have lately been crystallographically characterised. But2Mes(H)PCs.(18-crown-6) and Dmp(H)PCs.( 18-crown-6) Dmp = 2,6-dimesitylphenyl) both reveal (But2Mes = 2,4,6-tri-tert-butylphenyl, phosphorus, q6-aryl and crown ether stabilisation of the alkali metal ion, while the inclusion of benzene in Dmp(H)PCs.(q'-benzene).( 18-crown-6) reduces to q2 the hapticity with which the aromatic system in the Dmp ligand bonds to the caesium ion. Lastly, 18-crown-6 bridges two Cs+ ions in P- and q6-aryl bonded [Dmp(H)PCsI2.(18-crown-6).133 Several solution studies of metallated aromatics have been undertaken recently. The site of metallation and the stability of the chlorophenyl group in para-chloroanisole on exposure to Bu"Li has been studied in a variety of media, with benzyne formation being noted in polar solvents.'34 The benzene moieties of various quinazolinones, quinoxalines and phthalazines have been functionalised by treatment with Bu"Li. For derivatised quinoxalines, natural abundance 'H-"N GHMBC NMR spectroscopy has unambiguously elucidated the structures of the resulting aryllithium compounds.' 35 Radical anions of biphenyl, naphthalene, phenanthrene, anthracene and trans-stilbene were generated by reaction with 6/7Li(0).With the exception of lithium naphthalenide, the paramagnetic 6/7LiNMR shifts of the lithium species reveal a linear relationship with concentration in THF. 13' Lastly, ab initiu MO studies have been used to investigate the binding energies and ring centroid-metal ion distances for q 6-benzene.M+complexes for M = L ~ - C S . ' ~ ~

54

Organornetallic Chemistry

1.S Cyclopentadienyl and Related Derivatives. - The nucleophilic carbene 3borane- 1,4,5-trirnethylimidazol-2-ylidenyllithium has been noted to react with various electrophiles to yield 2-substituted imidazoles.' 38 Reaction of 6(dimethylamino)-6-methylfulvene with (Me3Si)2(H)CLi has afforded (1 -dimethylaminoethenyl)cyclopentadienyllithium, the treatment of which with MC14 (M = Zr, Hf) has resulted in the loss of LiCl and the formation of an allyl-bridged metallocene via an intramolecular HNMe2 elimination process.'39 The syntheses of poly(metal1ocenes) - reviewed recently14' - are facilitated by the use of organolithium reagents. Hence, for example, the dilithium salt of ferrocene is used in the formation of poly(ferroceny1enes). Similarly, poly(ferrocenyldimethylsi1ane) has been end-functionalised, by treatment of the end-reactive (Cp-lithiated) living homopolymer with ethylene sulfide, and deposited as electroactive layers on A u . ' ~ ' Dilithioferrocene has been employed in the syntheses of precursors to new silylene(germy1ene)ferroceiiylene polymers. 142 Lastly, sodium cyclopentadienyl has been used, in conjunction with Bu"Li, to effect the synthesis of [(C5H4)2B=N(SiMe3)2]Li2, the sequential treatment of which with TiCl;(THF)3 and PbC13 has yielded the first [ llboratitanocenophane. 143 Carbene-lithium interactions (see above) have recently been the subject of solid-state studies. Such complexes have been afforded by treating symmetrically N-substituted derivatives of imidazol-2-ylidene with 1,2,4-tris(trimethylsily1)cyclopentadienyllithium. For bis(tcrt-butyl) substitution, a carbenelithium bond of 2.154(4) A has been noted, with the alkali metal centre being supported by q5-interaction with the cyclopentadienyl ligand. 144 The dilithium salt of the silyl-substituted fulvene dianion has been found to be a monomeric contact ion pair in the solid state, with one lithium centre being q5-bonded to the 5-membered ring and the other q2-interacting with the em-cyclic carbon atom.'45 Both intramolecular dative NLi bonds and also intermolecular (NC4R2H2)Liq 5-interactions have been reported in the solidstate structure of a novel meso-substituted tetralithium porphyrinogen salt. 146 Recent advances in the use of X-ray powder diffraction have led to the characterisation of fluorenylsodium. The complex incorporates novel trigonal (NaF13)2ions (F1 = fluorenyl) with the benzoid rings in each fluorenyl ligand q6-coordinating to six further sodium cations, affording a complex polymeric s t r ~ c t u r e . 'The ~ ~ same study elucidated the solid-state structure of base-free indenyllithium. This complex reveals a stacked polymeric structure in which each alkali metal ion is q5,q5-sandwichedbetween the heterocyclic components of two indenyl anions.'47 Just as the stabilisation of potassium cations by the phenolic side-chain of tyrosine has been ~ t u d i e d , ' ~both ' solid-state and solution structural evidence been presented for the manner in which sodium or potassium ions are stabilised by the tryptophan side-chain, indole - the alkali metal ion preferring to bond with the pyrollo (rather than the benzo) subunit. 14' Indenyl, fluorenyl, cyclopentadienyl and pentamethylcyclopentadienyl potassiates have all been recently characterised by single crystal X-ray diffraction as 18-crown-6 solvates, with the octahedral alkali metal centres bonding to the

2: Group 1: The Alkali and Coinage Metals

55

crown ether and a single organic anion.'49 However, the phosphane salt [Ph2P(CH2)2C5H4]K
2

Copper, Silver and Gold

1.1. Introduction. - This section of the review is split into three parts, each of which considers a different coinage metal. As for Section 1 the review concerns itself almost exclusively with compounds that contain at least one carbonmetal interaction. Synthetic and mechanistic studies are discussed first in each part, after which solid-state, solution and theoretical structural studies are considered, in that order. 2.2 Copper Compounds. - Inorganic copper salts have catalysed the stereoand regiospecific reaction of silacyclopropanes with carbonyl species. Evidence has recently been presented for a transmetallation mechanism whereby the addition of CuX, (X = halide, n = 1, 2) to silacyclopropane results in the formation of Six and CuC bonds accompanied by ring opening, prior to carbonyl insertion. 55 The usefulness of the thermally stable organocopper substrate (Mes)Cu has been demonstrated in the selective and facile preparations of mono- and diarylated B, P and Sn halides.'56 Meanwhile, methoxya l l y l ~ o p p e r and ' ~ ~ its substituted analogues'58 have been shown to add to a,Punsaturated ketones in conjugate fashion. A collation of recent evidence (see last year's review) for the structures of both lower and higher order lithiocyanocuprates has lately been published.'59 Employment of these species in the addition and substitution chemistries of multiply unsaturated substrates has recently been the subject of review.I6' The reactivity profiles of iodo- and

Organometallic Chemistry

56

cyano-Gilman (higher order cyanocuprate) reagents have been investigated for the reactions of lithiocuprates with 2-cyclohexenone and iodocyclohexane the rates of reaction depending on the choice of organocuprate, lithium salt, solvent and amount of trimethylsilyl additive.16' The condensation of a higher order lithiocyanocuprate derived from 3-bromo-3-buten-2-01 with (R)-4-phenylbutylene oxide has afforded an intermediate species capable of being converted to an enantiopure tetrahydropyran. 162 Moreover, higher order lithiocyanocuprates have been diastereoselectively added to imino-derivatives 1-phenylethylamine.163 The synthetic utility of lithiocuprate species in of (9general has led to several studies in which they have been employed. Hence, the diastereoselective, conjugate addition of Grignard reagents to 2-oxoethylcyclohexenols may be effectively mediated by L i B r - c ~ B r . ' While ~~ trimethylsilylallyllithium can be used to open N-tolylaziridine rings to give convenient precursors to azetidines and pyrrolidines with reaction occurring either at the allyl a- or y-centre, the lithiocuprate analogue affords predominantly the yderivative. 165 Furthermore, the reaction of propargylic dithioacetals with lithioorganocuprates has led to the formation of allenyl thioethers (by protonolysis) and propargylic thioethers (by electrophilic work-up). Reaction of these with Grignard reagents in the presence of C12Ni(dppf) [dppf = 1,l'bis(diphenylphosphino)ferrocene] has afforded allenes. Lithiodialkylcuprates have recently been reacted with 1-(methylthio)- 1-alken-2-yl phenyl ketones to afford intermediate enolates which exhibit unusual reactivity towards oxygen and form cc-hydroperoxyketones.167 Higher order lithiocyanocuprates bearing transferable aromatic ligands have been employed in tandem with N-alkylhydroxylamines to yield the corresponding N-alkyl aromatic amines, while the use of mixed lithiocyanocuprate-lithium halide systems has allowed the regio- and stereospecific synthesis not only of aminoa l l e n e ~ ' but ~~~ also ' ~ of ~ vinylallenes via the 1,5-(&")-substitution of enyne acetates and ~ x i r a n e s . 'Further, ~~ the treatment of ArSeCH2ZnC1 (Ar = aryl) with CuCN/LiCl has afforded ArSeCH2Cu(CN)ZnC1 - a species which has been reacted with various aldehydes in the presence of BF;OEt2 to yield s e l e n ~ e t h a n o l s . The ' ~ ~ use of mixed Pd-Cu systems has been noted in the Pd2(dba)3-catalysed cyanation of various aryl and heteroaryl iodides using CuCN (dba = diben~ylideneacetone).'~~ Mixed Zr-Cu systems have been revealed to afford a straightforward route from arylacetylenes to arylcyclob ~ t e n e s .The ' ~ ~regio- and stereoselective stannylcupration of silylated alkynes and enynes has been achieved using water as the proton source in order to avoid desilylation of the alkyne function. 75 Finally, whereas the intermolecular transmetallation of cuprates with stannanes is recognised, it has recently been established that alkylarylcuprates which contain internally tethered stannane groups will undergo intracluster Cu(1)-Sn(1V) transmetallation to afford arylstannanes.' 76 Diaminocarbene ligands have recently been bonded to copper (and, for that matter, to silver). Thus, the facile reaction of [(MeCN)&u]BF4 with (CO)sM=C[N(R)CH2]2 (M = W, Mo, Cr; R = Et, allyl, benzyl, 4-pentenyl) yields the corresponding diaminocarbene via carbene ligand transfer, with the

'

2: Group 1: The Alkali and Coinuge Metals

57

Cu(1) [and the Ag(I)] complex undergoing efficient conversion to the imidazolidin-2-ylidinium salt as the result of acid-induced M=C cleavage.' 7 7 The recent review of cyclyne chemistry alluded to in Section 1.3 also extends to the employment of copper (and to some extent silver) reagents in metallacyclyne synthesis. Various NSz-macrocyclic ligands bearing a pendant naphthyl group have been used lately in the formation of new Cu(1) complexes. In the solid state, one of these systems has revealed q2-bonding of the pendant arene (using the C l q 2 bond) to the metal centre, with 'H NMR spectroscopy suggesting a AG' = 12-13 kcal barrier to the fluxional process of forming/ cleaving this interaction in CDC13.'78 A distorted tetrahedral Cu(1) complex using a tridentate N-donor ligand [N-(3-indolylmethyl)-N,N-bis(6-methyl-2pyridyl)amine] with a pendant indole has lately revealed a new q2-coordinative mode for the indole system C2 and C3 atoms towards the metal centre.'79 The interaction of Cu(1) with a single aromatic centre has been noted in the solidstate structure of the imidophosphorane complex { [Me3SiN=P(Ph)2C6H4]C~)2.180 The use of (Mes)Cu (see above)lS5 in conjunction with HN(S02CF& has afforded (OC)2CuN(S02CF3)2. This species - the first structurally Fharacterised example of a Cu(1) polycarbonyl - reveals long (mean 1.91 A) Cu-C bond lengths.18' Copper(1) cyanide in sodium thiosulfate has recently been employed in conjunction with diamines (da) to yield a variety of (crystallographically characterised) (CuCN);?da and C U ~ ( C N com)~~~ plexes. 82 The hydrothermal synthesis of the copper pseudo-halide organoamine species Cu3(CN)3(bipypy) [bipypy = bis-2,3-(2-pyridyl)pyrazine] has led to the observation of bipypy-chelation of each metal centre with intermolecular coordination of the (disordered) cyano-groups affording 28-membered rings, each of which include eight copper centres.'83 Remaining with pyrazine ligands, a threefold interpenetrating distorted-diamondoid framework has been noted in the crystal structure, obtained by X-ray powder diffraction, of C4H4N2.Me3SnCN.CuCN(C4H4N2= pyrazine).184 It has been demonstrated that the dirhenioethyne compound (OC)5ReC(CRe(CO)5will act as an q2ligand towards Cu(I), Ag(1) and Au(1) metal centres with the stability of the resultant complexes being poorest for Ag and greatest for Cu.lS5 As far as other heterobimetallic acetylide complexes are concerned, straightforward L-Pt(C=CR),.CuX [L = 2,2'-bipy, R = Ph, X = C1, Br;'86 L = 4,4'-Buf2(2,2'bipy), R = 4-MeC6H4, SiMe3, X = NCS'87] have been structurally characterised, as has Pt2C~4(C-CPh)3- a species which reveals a D4-symmetry trimer, with strong inter-monomer Pt-Pt bonds which give rise to novel nearIR photoluminescent properties. 188 Indeed, the photophysical and photochemical properties of polynuclear acetylides of Cu (and also of Ag and Au) have recently formed part of a review article on luminescent polynuclear metal acetylide complexes.189 The association of copper complexes has also lately been noted in systems where dppf is incorporated as a bridging ligand. Hence, (p-dppf)&-q '-CCR)2Cu2 (R = 2-MeC6H4)reveals two bridging dppf ligands and two bridging alkynyl groups.'90 As in previous years, the area of lithiocuprate structural chemistry has proved to be one of intense interest. The biological importance of Cu(1)-olefin

'

58

Organometallic Chemistry

complexes has led to the synthesis and solid-state characterisation of [Bu'P(NSiMe3)2-~2N]C~(q2-C2H4) and its norbornene analogue - the former complex revealing extreme stability in solution and even in the gas phase."' The solidstate structures of two organodicuprate species have recently been reported; hence, whereas the reaction of CuI with 1 eq. 2,6-Mes2C6H3Liafforded [2,6Mes2(CuI)2] [Li.(THF),]+, the analogous reaction with 2 eq. 2,6-Trip2C6H3Li yielded the Cu(y-1)Li-based species 2,6-Trip2C6H3CuIL.(OEt2)2 instead. 192 CuCN has been studied in the solid state by multinuclear magnetic (13C and "N) and quadrupole (63165Cu)resonance techniques. Results suggest the existence of linear, polymeric chains in which the cyanide groups exhibit headto-tail disorder. Dipolar coupling suggests CuC distances of approximately 1.88 A. lg3 63/65CuNMR spectroscopy on crystalline tripotassium tetracyanocuprate has revealed anisotropic chemical shielding of copper for the first time. lg4 Iodoalkynes have been shown to be precursors to alkynyl aryl sulfones, with kinetic data on the halogen exchange reaction between 4-C1C6H4C= CBr and CuI (which affords the iodoalkyne species) suggesting that the process is linearly dependent on the concentrations of both species.lg5 Of late, the aggregation states of various lithioorganocuprate species have been investigated by electrospray mass spectrometry in the first such study of anionic Cu(1) complexes containing copper-bonded carbon ligands.Ig6 DFT calculations have been used to investigate the stereoselectivity and rate-determining step in the conjugate addition of (Me2CuLi)2 to cyclohexenone, with a copper/olefin complex intermediate appearing to directly form the transition state (the conformation energy of which dictates the reaction stereoselctivity) and thence the product.lg7DFT studies have also been used to probe the bonding both in bis(q2-alkyne) complexes between H C = C H or X ( C Z C H ) ~(X = H2C, H2Si, C12Ti) and MMe (M = Cu, Ag, Au). Results point to the titanium halide moiety effectively orienting the actylide units for complexation and also enhancing their Lewis acidity. lg8

2.3 Silver Compounds. - N,N'-diferrocenylimidazolinium salt precursors to ferrocenyl-substituted carbenes have been reacted with Ag20 to afford a silver@)bis( 1,3-diferrocenylirnidazol-2-ylidene)cation which has been crystallographically ~ h a r a c t e r i s e dA. ~Ag-C ~ bond is observed in the crystal structure of the 'N-confused' (ie. one of the four pyrrole rings is inverted) tetraphenylporphyrin 5,10,15,20-tetraphenyl-2-aza-21 -carbaporphyrin argentate(II1). 199 Disilver complexes have been reported recently in which the two metal centres are bridged in a variety of modes by cyanide moieties, most strikingly (LAg)2(p-CN)' [L = 4,7-bis(2-cyanomethyl)-l -thia-4,7-diazacyclononane], which reveals the first example of JL~-KC:KC symmetric bridging by a twoelectron donor CN- .200 Direct reaction of XAg (X = N03, 02CMe) with 1,8diisocyano-para-menthane (= dmb) give rise to X2(dmb)?Ag2 complexes with the reaction of (NO3)2(dmb)ZAgz with (TCNQ)Li (TCNQ = tetracyanoquinodimethane) affording paramagnetic, tetranuclear TCNQ[(TCNQ)3(dmb)4Ag4].201 Various C2Ag2.xAgN03 double salts have

2: Group 1: The Alkali and Coinage Metals

59

been synthesised by the direct treatment of silver acetylide (for x = 1, 5.5, 6) or of the C2Ag21F3CC02Ag double salt (x = 5 ) with silver nitrate. These double salts are based on acetylide-encapsulating silver octahedra (x = l), monocapped trigonal prisms (x = 5 ) , monocapped octahedra (x = 5.5) or rhombohedra (x = 6).202The cationic tetrasilver complex of hexaphenylbenzene reveals the metal centres to be phenyl-bonded in both q1,q2- and q2,q2environments.203Treatment of AgBF4 with Ag(C = CBut) results in the isolation of the cationic alkynyl silver cluster polymer [(ButC= C)2Ag3+](,the solidstate structure of which reveals two types of metal centre: one o-bonds (endon) to a single alkynyl ligand while the other is n-bonded to two such moieties .204 The formation of two-dimensional polymeric networks has been investigated in the structures of complexes which incorporate silver(1) centres that are q2-bonded to the linear polycyclic hydrocarbons benzo[a]phenanthrene, dibenzo[a,h]anthracene, benz[a]anthracene and naphtha[2,3a l p ~ r e n e , ~and ' ~ also the non-linear arene benz~[e]acephenanthrylene.~~~ In a similar vein, ql-coordination of Ag(1) centres by the upper-rim carbon atoms in calixarene and resorcinarene complexes has afforded not only open dimers but also capped polymeric species.207 Recently, just as L.Pt(C(CR)2.CuX [L = 4,4'-But2(2,2'-bipy), R = 4MeC6H4, %Me3, X = NCS] has been structurally characterised, so too has the silver analogue - the thiocyanate ligand now acting as a S-donor. Similarly, mixed Ti-CdAg systems have been probed, with the sandwich complex (q5CSH4SiMe&Ti(C = CSiMe2C= CSiMe3)2AgBr revealing a bis(q2-TiC = CSi)bonded silver centre in the solid state but coordination of the coinage metal by all four acetylide units in solution.208

Gold Compounds. - Gold(1) complexes have recently been employed in a catalytic context to effect the dehydrogenative dimerisation of tributyl-, trioctyl- and triphenyl~tannanes.~~~ Au-C bond formation has been noted in the series of cyclometallated complexes ClLAu+ (where L is the tridentate N,N,C-donor ligand; deprotonated 6-benzyl-2,2'-bipyridine) by replacement of the chloride moiety with a phenylacetylide one.21o A reductive-elimination pathway has been used to subsequently afford PC-CL as the free ligand. Remaining with Au-C bond formation, the coordinative properties of the triarylphosphonium cyanomethylide/2-~yanoethylideylides have been probed with respect to gold species, with mono-, di- and trinuclear complexes being formed.21 Both anionic dimethylaurate(1) and tetramethylaurate(II1) complexes have recently been revealed to undergo one-electron oxidation by either ferrocenium or arenediazonium cations.212 While the gold(1) substrate is oxidised to a metastable dimethylgold(I1) intermediate (which can be trapped as the paramagnetic 9,lO-phenanthrenequinoneadduct), tetramethylaurate(111) affords highly unstable Me4Au(IV) which spontaneously emits a methyl radical by undergoing homolytic Au-C bond cleavage. Concomitantly formed Me3Au(III) has been trapped by the addition of PPh3. The activation of Au-C bonds has also been effected in 2-(alky1thio)pyridines { 2-[RC(O)CH2S]CSH4N 2.4

60

Organometallic Chemistry

(R = Ph, Me, OMe)); their treatment with Na(AuC14) affording a series of 2[RC(0)CH(AuC12)S]C5H4Ncomplexes.213 Just as studies into the copper and silver metal ion mediated cleavage of diaminocarbene ligands (see above) have been extended to gold, so too the synthesis, spectroscopic characteristics and solid-state structures of various gold(1) carbene complexes of the type L(R2bimy)Au (L = Cl, Br, I, bimy, thiophenolate, phenylacetylide; R = alkyl; bimy = benzimidazol-2-ylidene) have been reported.214 The spectroscopic and electronic properties of a variety of Cu and Au l-azaallylmetal(1) complexes have been investigated after their syntheses by the treatment of the aza-allyllithium compound [(Me3Si)2CC(Ph)NSiMe3]Liwith either ICu or C1(Me2S)Au. In the latter case the centro-symmetric dimer { [(Me3Si)2CC(Ph)NSiMe3]Au} The first isocyanide gold(1) nitrates have lately been prepared by the reaction of the corresponding chloride with AgN03. The resultant species, RNC(N03)Au, have been crystallographically characterised with Au- Au interactions being responsible for the formation of the associated tetramers noted for R = Et and the polymers noted for R = But, 2,6-Me2C6H3.216 Newly-characterised perfluorovinylphosphines (synthesised, as mentioned in Section 1.3, from perfluorovinyllithium)68 have been used to generate ([(CF2=CF)Ph2P]ClAu)2, the solid-state structure of which reveals short [2.217(2) A] AuP distances.68 The single-crystal structure of the first auracyclobutane complex has been reported with the species in question resulting from treatment of the gold(II1) complex (2-Me2NCH2)-5-MeOC6H3AuC12 with 1,1,3,3-tetracyanopropane in the presence of mediating silver(1) oxide.21 Various intermetallic gold-containing complexes were reported in 1999. While Fc2PhP (Fc = ferrocenyl) reacts with Cl(C6F5)2Au to afford C1(C6F5)2A~PPhF~2,21 the reaction of various gold(1) derivatives with the functionalised ferrocenyl substrate 3-ferrocenylpyridine (Fcpy) has afforded the complexes ( F ~ p y ) ( c ~ F ~ )and ~ A[u( F ~ p y ) ~ ( c ~ F ~ ) ~both A u ]of + ,which have been structurally ~haracterised.~'~ The complex 2-(Ph3PAuCH2)-6-RC5H3N (R = H, Me) has been investigated in the context of its reactivity towards HBF4, AgC104 and [(MeCN)4Cu][PF6]. The products are, respectively, [2(Ph3PAuCH2)-6-RC5H3N.AuPPh3]+ and the intermetallic species { [2(Ph3PAuCH2)-6-RC5H3NI2Mf+(M = Cu, Ag). For R = Me, M = Ag the solid-state structure has revealed short interactions between gold and silver centres.220The solid-state structure of BU~~S~(~-[(C~F~)AUP(P~)~]C~H~S has been presented in light of the displacement of tht (= tetrahydrothiophene) from (tht)(C6F5)Au by B u ' ~ S ~ [ ( ~ - P ~ ~ P ) S C ~ H ~ ] ~ . ~ ~ ~ Treatment of Ph3PAuC1 with methyl and benzyl isocyanide has afforded monomeric MeN=(O)CAuPPh3 and heterocyclic [MeN=(O)CAuPPh3I3, respectively.222 The controlled self-assembly of a series of organometallic catenanes has been followed by their isolation and structural characterisation. Hence, the reaction of a digold(1) diacetylide complex with the diphosphine species Ph2P(CH2),PPh2 has yielded not only the simple cyclic digold system

2: Group I : The Alkali and Coinage Metals

61

Me2C(4-[CH2(Ph)2PAuC= CCH20]C,H4} 2 but also several [2]catenanes based on heterocycles of this type.223 Lastly, calculations on the linear complexes [(NC)ZAu]- and [(OC)2Au]+ have been performed, the results being compared with those obtained for the Hg and T1 analogues, with vibrational frequencies, infra-red intensities, internal force fields and charge distributions all showing good agreement with experiment.224

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.

F. Eymery, B. Iorga and P. Savignac, Tetrahedron, 1999,55, 13109. R. K. Dieter, Tetrahedron, 1999,55,4177. D. J. Procter, J. Chem. Soc., Perkin Trans. 1, 1999,641. U. Azzena and L. Pilo, Synthesis, 1999,664. C. Agami, S. Comesse, C. Kadouri-Puchot and M. Lusinchi, Synlett, 1999, 1094. M. Shindo, K. Koga, Y. Asano and K. Tomioka, Tetrahedron Lett., 1999, 55, 4955. F. Foubelo, A. Gutiirrez and M. Yus, Synthesis, 1999, 503. B. Weber, S. Kolczewski, R. Frohlich and D. Hoppe, Synthesis, 1999, 1593. T. J. Donohoe, R. R. Harji and R. P. C. Cousins, Chem. Commun., 1999, 141. T. Ooi, E. Tayama, M. Yamada and K. Maruoka, Synlett, 1999,729. K. Smith, G. A. El-Hitiand A. C. Hawes, Synlett, 1999,945. P. I. Dalko, Tetrahedron Lett., 1999,40,4035. A. R. Katritzky, C. Chassaing, D. Toader and K. Gill, J. Chem. Res., 1999, 505. A. Ahmed, J. Clayden and S. A. Yasin, Chem. Commun., 1999,231. J. Clayden, C. S. Frampton, C . McCarthy and N. Westlund, Tetrahedron, 1999, 55,14161. D. M. Hodgson and L. A. Robinson, Chem. Commun., 1999,309. C. Serino, N. Stehle, Y. S. Park, S. Florio and P. Beak, J. Urg. Chem., 1999, 64, 1160. K. Tomooka, K. Yamamoto and T. Nakai, Angew. Chem. Int. Ed., 1999, 38, 3741. K. Tomooka, T. Igarashi, N. Kishi and T. Nakai, Tetrahedron Lett., 1999, 40, 6257. Y. Shen, J. Ni, P. Li and J. Sun, J. Chem. Soc., Perkin Trans. I , 1999, 509. P. Khansawai, R. M. Paton and D. Reed, Chem. Commun., 1999, 1297. N. Bremand, I. Marek and J. F. Normant, Tetrahedron Lett., 1999,40, 3379. J. Clayden, N. Westlund and F. X. Wilson, Tetrahedron Lett., 1999,40,3329. J. Clayden, N. Westlund and F. X. Wilson, Tetrahedron Lett., 1999,40,3331. B. Miao, M. Tinkl and V. Snieckus, Tetrahedron Lett., 1999,40,2449. V. Levacher, B. L. Eriksen, M. Begtrup, G. Dupas, G. Queguiner, J. Duflos and J. Bourguignon, Tetrahedron Lett., 1999,40, 1665. A. Hudson, A. G. Orpen, H. Phetmung and P. Wyatt, Tetrahedron Lett., 1999, 40, 813. F. Corbin, C. Alayrac and P. Metzner, Eur. J. Urg. Chem., 1999,2859. D. A. Cogan and J. A. Ellman, J. Am. Chem. Soc., 1999,121,268. D. R. Armstrong, W. Clegg, R. P. Davies, S. T. Liddle, D. J. Linton, P. R.

62

31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50.

51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61.

Organometallic Chemistry

Raithby, R. Snaith and A. E. H. Wheatley, Angew. Chem. Int. Ed., 1999, 38, 3367. I. Daub, A.-K. Habermann, A. Hobert and M. Julia, Eur. J. Org. Chem., 1999, 163. 0. Kitagawa, T. Suzuki, H. Fujiwara, M. Fujita and T. Taguchi, Tetrahedron Lett., 1999,40,4585. R. Gabaitsekgosi and C. J. Hayes, Tetrahedron Lett., 1999,40, 7713. A. Sakai, T. Aoyama and T. Shiori, Tetrahedron, 1999,55,3687. B. Bildstein, M. Malaun, H. Kopacka, K. Wurst, M. Mitterbock, K.-H. Ongania, G. Opromolla and P. Zanello, Organometallics, 1999,18,4325. L.-K. Liu, Y.-H. Liao and U. B. Eke, Organometallics, 1999,18, 1154. T. H. Peterson, J. T. Golden and R. G. Bergman, Organometallics, 1999, 18, 2005. Q. D. Shelby and G. S. Girolami, Organometallics, 1999, 18,2297. S. Usugi, J. Tang, H. Shinokubo and K. Oshima, Synlett, 1999, 1417. B. Gehrhus, P. H. Hitchcock, A. R. Kennedy, M. F. Lappert, R. E. Mulvey and P. J. A. Rodger, J. Organomet. Clzem., 1999,587, 88. J. E. Argiiello, A. B. Pefieiiory and R. A. Rossi, J. Org. Chem., 1999,64,6115. S. S. Al-Juaid, C. Eaborn, S. M. El-Hamruni, P. B. Hitchcock and J. D. Smith, Organometallics, 1999,18,45. J. F. K. Miiller, M. Neuburger and B. Spingler, Angew. Chem. Int. Ed., 1999, 38, 3549. A. Kasani, R. P. K. Babu, R. McDonald and R. G. Cavell, Angew. Chem. Int. Ed., 1999,38, 1483. J. F. K. Muller, M. Neuburger and B. Spingler, Angew. Chem. Int. Ed., 1999, 38, 92. D. Scheschkewitz, M. Menzel, M. Hofmann, P. von R. Schleyer, G. Geiseler, W. Massa, K. Harms and A. Berndt, Angew. Chem. Int. Ed., 1999,38,2936. N. S. Hosmane, H. Zhang, L. Jia, T. J. Colacot, J. A. Maguire, X. Wang, S. N. Hosmane and K. A. Brooks, Organometallics, 1999,18, 516. H. H. Karsch, K.-A. Schreiber and M. Reisky, Organometallics, 1999, 18, 3944. W. Clegg, E. Lamb, S. T. Liddle, R. Snaith and A. E. H. Wheatley, J. Organomet. Chem., 1999,573,305. S. S. Al-Juaid, C. Eaborn, S. El-Hamruni, A. Farook, P. B. Hitchcock, M. Hopman, J. D. Smith, W. Clegg and P. O’Shaughnessy, J. Chem. Sor., Dalton Trans., 1999, 3267. P. Beak, K. C. Basu and J. J. Li, J. Org. Chem., 1999,64, 5218. H. J. Reich and W. H. Sikorski, J. Org. Chem., 1999,64, 14. W. Clegg, K. Izod, W. McFarlane and P. O’Shaughnessy, Organometallics, 1999, 18, 3950. R. D. Thomas and H. Huang, J. Am. Chem. Sor., 1999,121, 11239. D. R. Anderson, N. C. Faibish and P. Beak, J. Am. Chem. Soc., 1999,121, 7553. P. I. Arvidsson, G. Hilmersson and 0.Davidsson, Chem. Eur. J., 1999,5,2348. P. I. Arvidsson, G. Hilmersson and P. Ahlberg, J. Am. Chem. SOC.,1999, 121, 1883. P. I. Arvidsson, P. Ahlberg and G. Hilmersson, Chern. Eur. J., 1999,5, 1348. C. Derwing, H. Frank and D. Hoppe, Eur. J. Org. Chem., 1999,3519. E.-U. Wiirthwein, K. Behrens and D. Hoppe, Chem. Eur. J., 1999,53459. A. Akin, S. S. Erdem, T. Nugay, V. Aviyente and H. Regat, J. Chem. Soc., Perkin Trans. 2, 1999, 5.

2: Group 1: The Alkali and Coinage Metals

62. 63. 64. 65. 66. 67. 68.

69. 70. 71. 72. 73. 74. 75. 76. 77.

78. 79. 80. 81. 82. 83. 84. 85.

86. 87. 88. 89. 90. 91. 92. 93. 94.

63

J. F. K. Muller and R. Batra, J. Organomet. Chem., 1999,584,27. P. Antoniotti and G. Tonachini, Organometallics, 1999,18,4538. J. M. MacDougall and H. W. Moore, J. Org. Chem., 1999,64,7445. M. Yoshimatsu, T. Sugimoto, N. Okada and S. Kinoshita, J. Org. Chem., 1999, 64, 5 162. R. W. Hoffmann, R. Koberstein and K. Harms, J. Chem. SOC.,Perkin Trans. 2, 1999,183. G. L. Edwards and D. J. Sinclair, Tetrahedron Lett., 1999,40, 3933. K. K. Banger, R. B. Banham, A. K. Brisdon, W. I. Cross, G. Damant, S. Parsons, R. G. Pritchard and A. Sousa-Pedrares, J. Chem. Soc., Dalton Trans., 1999,427. C. de GuignC, J.-E. Ancel and L. Duhamel, Tetrahedron Lett., 1999,40, 5523. F. Foubelo, A. Gutierrez and M. Yus, Tetrahedron Lett., 1999,40, 8173. P. Villiers, D. Soullez, Y. Ramondenc and G. Pit, Tetrahedron, 1999, 55, 14031. T. Takahashi, S. Huo, R. Hara, Y. Noguchi, K. Nakajima and W.-H. Sun, J. Am. Chem. SOC.,1999,121,1094. H. Sashida, Synthesis, 1999, 1866. C. C. Silveira, G. Perin, A. L. Braga, M. J. Dabdoub and R. G. Jacob, Tetrahedron, 1999,55,7421. I. A. Stergiades and M. A. Tius, J. Org. Chem., 1999,64, 7547. D. Cheng, S. Zhu, X. Liu, S. H. Norton and T. Cohen, J. Am. Chem. SOC.,1999, 121, 10241. E. Alonso, D. Guijarro, P. Martinez, D. J. Ram6n and M. Yus, Tetrahedron, 1999,55, 11027. M. D. Curtis and P. Beak, J. Org. Chem., 1999,64,2996. Y. Nishiyama, Y. Kishimoto, K. Itoh and N. Sonoda, Synlett, 1999,611. P. Coutrot, C. Grison and C. BGmont, J. Organomet. Chem., 1999,586,208. P. B. Hitchcock, M. F. Lappert and M. Layh, J. Organomet. Chem., 1999, 580, 386. P. B. Hitchcock, M. F. Lappert and M. Layh, Angew. Chem. Int. Ed., 1999, 38, 501. W. J. Youngs, C. A. Tessier and J. D. Bradshaw, Chem. Rev., 1999,99, 3153. Z . Wang, J. Yin, S. Campagna, J. A. Pesti and J. M. Fortunak, J. Org. Chem., 1999,64,6918. T. Ooi, N. Kagoshima, H. Ichikawa and K. Maruoka, J. Am. Chem. Soc., 1999, 121,3328. T. Ooi, J. Morikawa, H. Ichikawa and K. Maruoka, Tetrahedron Lett., 1999, 40, 5881. T. Mecozzi and M. Petrini, J. Org. Chem., 1999, 64, 8970. P. Langer, M. Doring and D. Seyferth, Synlett, 1999, 135. Y. Dumond and E. Negishi, J. Am. Chem. SOC.,1999,121,11223. A. S. Abd-El-Aziz, W. Boraie and N. T. Gavel, Organometallics, 1999,18, 1562. J. Kim, A. S. Ichimura, R. H. Huang, M. Redko, R. C. Phillips, J. E. Jackson and J. L. Dye, J. Am. Chem. SOC.,1999,121,10666. Z. Grobelny, A. Stolarzewicz, A. Maercker and W. Demuth, J. Organomet. Chem., 1999,590,153. P. B. Hitchcock, M. F. Lappert, W.-P. Leung, D.-S. Liu, T. C. W. Mak and Z.-X. Wang, J. Chem. SOC.,Dalton Trans., 1999, 1257. P. B. Hitchcock, M. F. Lappert, W.-P. Leung, D.-S. Liu, T. C. W. Mak and Z.-X. Wang, J. Chem. SOC.,Dalton Trans., 1999, 1263.

64

Organometallic Chemistry

95. W. M. Boesveld, P. B. Hitchcock and M. F. Lappert, J. Chem. SOC.,Dalton Trans., 1999,4041. 96. R. W. Hoffmann and R. Koberstein, Chem. Commun., 1999, 33. 97. W. Clegg, R. P. Davies, L. Dunbar, N. Feeder, S. T. Liddle, R. E. Mulvey, R. Snaith and A. E. H. Wheatley, Chern. Cornmun., 1999, 1401. 98. T. Baumgartner, D. Gudat, M. Nieger, E. Niecke and T. J. Schiffer, J. Am. Chem. SOC.,1999,121,5953. 99. G. Fraenkel, J. H. Duncan and J. Wang, J. Am. Chem. Soc., 1999,121,432. 100. G. Fraenkel, J. Cabral, C. Lanter and J. Wang, J. Org. Chem., 1999, 64, 1302. 101. G. Fraenkel, J. H. Duncan, K. Martin and J. Wang, J. Am. Chem. SOC.,1999, 121, 10538. 102. H. J. Reich, J. E. Holladay, T. G. Walker and J. L. Thompson, J. Am. Chem. Soc., 1999, 121,9769. 103. R. Jankowska, G. L. Mhehe and H.-J. Liu, Chem. Commun., 1999,1581. 104. F. F. Huerta, C. Gomez and M. Yus, Tetrahedron, 1999,55,4043. 105. Y. H. Kang and K. Kim, Tetrahedron, 1999,55,4271. 106. C. Gomez, S. Ruiz and M. Yus, Tetrahedron, 1999,55,7017. 107. S . D. Rychnovsky, A. J. Buckmelter, V. H. Dahanukar and D. J. Skalitzky, J. Org. Chem., 1999, 64,6849. 108. T. Ireland, J. J. A. Perea and P. Knochel, Angew. Chem. Int. Ed., 1999, 38, 1457. 109. J.-P. Djukic, A. Maisse, M. Pfeffer, K. H. Dotz and M. Nieger, Organometallics, 1999,18,2786. 110. A. Ahmed, J. Clayden and M. Rowley, ,Yynlett., 1999, 1954. 111. K. Smith, G. A. El-Hiti, G. J. Pritchard and A. Hamilton, J. Chem. SOC.,Perkin Trans. 1, 1999,2299. 112. T. Fukuda, R. Maeda and M. Iwao, Tetrahedron, 1999,55,9151. 113. I. D. Kostas, 0. S. Akkerman, F. Bickelhaupt, N. Veldman and A. L. Spek, J. Ovganomet. Chem., 1999,572,93. 114. C . Arbez-Gindre, C. G. Screttas, C. Fiorini, C. Schmidt and J.-M. Nunzi, Tetrahedron Lett ., 1999,40, 74 13. 115. R. J. Mattson, C. P. Sloan, C. C. Lockhart, J. D. Catt, Q. Gao and S. Huang, J. Org. Chem., 1999,64,8004. 116. F. Faigl, K. Fogassy, E. Sziics, K. Kovacs, G. M. Keserfi, V. Harmat, Z. Bocskei and L. Take, Tetrahedron, 1999,55,7881. 117. D. Albanese, M. Penso and M. Zenoni, Synthesis, 1999, 1294. 118. C . Y. Zhang and J. M. Tour, J. Am. Chem. SOC.,1999,121,8783. 119. H. Kumamoto, H. Tanaka, R. Tsukioka, Y. Ishida, A. Nakamura, S. Kimura, H. Hayakawa, K. Kato and T. Miyasaka, J. Org. Chem., 1999,64,7773. 120. H. O’Dowd, P. Ploypradith, S. Xie, T. A. Shapiro and G. H. Posner, Tetrahedron, 1999,55, 3625. 121. F. Bickelhaupt, Chenz. SOC.Rev., 1999, 28, 17. 122. C. S. Salteris, 1. D. Kostas, M. Micha-Screttas, G. A. Heropoulos and C . G. Screttas, J. Org. Chem., 1999,64, 5589. 123. C . S. Salteris, I. D. Kostas, M. Micha-Screttas, B. R. Steele, G. A. Heropoulos, C. G. Screttas and A. Terzis, J. Organonzet. Chem., 1999,590,63. 124. K. Smith, G. A. El-Hiti and A. P. Shukla, J. Chem. SOC.,Perkin Trans. 1, 1999, 2305. 125. T. Dube, S. Gambarotta and G. P. A. Yap, Angew. Chem. Int. Ed., 1999, 38, 1432.

2: Group 1: The Alkali and Coinage Metals

65

126. H. Bock, Z. Havlas, K. Gharagozloo-Hubmann and M. Sievert, Angew. Chem. Int. Ed., 1999,38,2240. 127. J. A. M. Brandts, M. van Leur, R. A. Gossage, J. Boersma, A. L. Spek and G. van Koten, Organometallics, 1999,18,2633. 128. D. R. Armstrong, A. R. Kennedy, R. E. Mulvey and R. B. Rowlings, Angew. Chem. Int. Ed., 1999,38, 131. 129. E. Campazzi, E. Solari, R. Scopelliti and C. Floriani, Chem. Cornmun., 1999, 1617. 130. M. C. Cassani, Y. K. Gun’ko, P. B. Hitchcock, M. F. Lappert and F. Laschi, Organometallics, 1999, 18, 5539. 131. S. L. De Wall, L. J. Barbour and G. W. Gokel, J. Am. Chem. Soc., 1999, 121, 8405. 132. G. Balazs, J. E. Drake, C. Silvestru and I. Haiduc, Inorg. Chim. Acta, 1999, 287, 61. 133. G. W. Rabe, L. M. Liable-Sands, C. D. Incarvito, K.-C. Lam and A. L. Rheingold, Inorg. Chem., 1999,38,4342. 134. D. W. Slocum and P. Dietzel, Tetrahedron Lett., 1999,40, 1823. 135. V. G. Chapouland, I. Salliot, N. Plk, A. Turck and G. QuCguiner, Tetrahedron, 1999,555389. Perkin 136. M. Micha-Screttas, G. A. Heropoulos and B. R. Steele, J. Chem. SOC., Trans. 2, 1999, 1443. 137. J. B. Nicholas, B. P. Hay and D. A. Dixon, J. Php. Chem., 1999,103, 1394. 138. A. Wacker, H. Pritzkow and W. Siebert, Eur. J. Inorg. Chem., 1999, 789. 139. S.-D. Bai, X.-H. Wei, J.-P. Guo, D.-S. Liu and Z.-Y. Zhou, Angew. Chem. Int. Ed., 1999, 38, 1926. 140. P. Nguyen, P. Gbmez-Elipe and I. Manners, Chem. Rev.,1999,99, 1515. 141. M. Peter, R. G. H. Lammertink, M. A. Hempenius, M. van Os, M. W. J. Beulen, D. N. Reinhoudt, W. Knoll and G. J. Vancso, Chem. Commun., 1999,359. 142. S. Sharma, N. Caballero, H. Li and K. H. Pannell, Organometallics, 1999, 18, 2855. 143. H. Braunschweig, C. von Koblinski and R. Wang, Eur. J. Inorg. Chem., 1999,69. 144. A. J. Arduengo 111, M. Tamm, J. C. Calabrese, F. Davidson and W. J. Marshall, Chem. Lett., 1999, 1021. 145. T. Malsuo, A. Sekiguchi and H. Sakurai, Bull. Chem. SOC.Jpn., 1999,72, 1115. 146. L. Bonomo, E. Solari, R. Scopelliti, M. Latronico and C. Floriani, Chem. Commun., 1999,2227. 147. R. E. Dinnebier, S. Neander, U. Behrens, F. Olbrich, Organometallics, 1999, 18, 2915. 148. S. L. De Wall, E. S. Meadows, L. J. Barbour and G. W. Gokel, J. Am. Chem. SOC.,1999,121, 5613. 149. S. Neander, R. Buschmann, U. Behrens and F. Olbrich, J. Organomet. Chem., 1999,582, 58. 150. H. H. Karsch, V. W. Graf and M. Reisky, Chem. Commun., 1999, 1695. 151. M. Veith, C. Mathur, S. Mathur and V. Huch, Inorg. Chem., 1999,38, 5461. 152. M. A. Beswick, H. Gornitzka, J. Karcher, M. E. G. Mosquera, J. S. Palmer, P. R. Raithby, C. A. Russell, D. Stalke, A. Steiner and D. S. Wright, Organometallics, 1999, 18, 1148. 153. J. S. Parry, F. G. N. Cloke, S. J. Coles and M. B. Hursthouse, J. Am. Chem. SOC., 1999,121,6867. 154. M. Kamaura and J. Inanaga, Tetrahedron Lett., 1999,40,7347.

66

Organometallic Chemistry

155. A. K. Franz and K. A. Woerpel, J. Am. Chem. Soc., 1999,121,949. 156. F. Jiikle and I. Manners, Organometallics, 1999, 18, 2628. 157. J.-F. Berrien, M.-N. Raymond, H. Moskowitz and J. Mayrargue, Tetrahedron Lett., 1999,40, 1313. 158. J.-F. Berrien, M.-N. Raymond, F. Zaari, H. Moskowitz and J. Mayrargue, Tetrahedron Lett., 1999,40, 3367. 159. N. Krause, Angew. Chem. Int. Ed., 1999,38, 79. 160. N. Krause and S. Thorand, Inorg. Chim. Acta, 1999,296, 1. 161. S. H. Bertz, A. Chopra, M. Eriksson, C. A. Ogle and P. Seagle, Chem. Eur. J., 1999,5. 2680. 162. M. J . Cloninger and L. E. Overman, J. Am. Chem. SOC.,1999,121, 1092. 163. M. Bandini, P. G. Cozzi, A. Umani-Ronchi and M. Villa, Tetrahedron, 1999, 55, 8103. 164. V. Dambrin, M. Villieras, H. Amri, J. Lebreton and J. Villitras, Synlett, 1999, 1057. 165. H.-J. Breternitz and E. Schaumann, J. Chem. SOC.,Perkin Trans. I , 1999, 1927. 166. H.-R. Tseng, C.-F. Lee, L.-M. Yang and T.-Y. Luh, J. Org. Chem., 1999, 64, 8582. 167. T. Arai, M. Akazome and K. Ogura, Chem. Lett., 1999, 107. 168. P. Bernardi, P. Dembech, G. Fabbri, A. Ricci and G. Seconi, J. Org. Chem., 1999, 64, 641. 169. H. Ohno, A. Toda, Y. Miwa, T. Taga, N. Fujii and T. Ibuka, Tetrahedron Lett., 1999,40, 349. 170. R. K. Dieter and L. E. Nice, Tetrahedron Lett., 1999,40,4293. 171. M. Purpura and N. Krause, Eur. J. Org. Chem., 1999,267. 172. D.-H. Duan and X. Huang, J. Chem. Res., 1999,26. 173 T. Sakamoto and K. Ohsawa, J. Chem. Soc., Perkin Trans. I , 1999,2323. 174. T. Takahashi, B. Shen, K. Nakajima and Z. Xi, J. Org. Chem., 1999,64,8706. 175. J.-F. Betzer and A. Pancrazi, Synthesis, 1999, 629. 176. C. Mateo, D. J . Cardenas, B. Martin-Matute and A. M. Echavarren, Chem. Commun., 1999,2205. 177. R.-Z. Ku, J.-C. Huang, J.-Y. Cho, F.-M. Kiang, K. R. Reddy, Y.-C. Chen, K.-J. Lee, J.-H. Lee, G.-H. Lee, S.-M. Peng and S.-T. Liu, Organometallics, 1999, 18, 2145. 178. R. R. Conry, W. S. Striejewske and A. A. Tipton, Inorg. Chem., 1999,38, 2833. 179. Y. Shimazaki, H. Yokoyama and 0. Yamauchi, Angew. Chem. Int. Ed., 1999,38, 240 1. 180. S. Wingerter, H. Gornitzka, G. Bertrand and D. Stalke, Eur. J. Znorg. C'hern., 1999, 173. 181. 0. G. Polyakov, S. M. Ivanova, C. M. Gaudinski, S. M. Miller, 0. P. Anderson and S. H. Strauss, Organometallics, 1999, 18, 3769. 182. F. B. Stocker, T. P. Staeva, C. M. Rienstra and D. Britton, Znorg. Chem., 1999, 38, 984. 183. D. J. Chesnut, A. Kusnetzow, R. R. Birge and J. Zubieta, Inorg. Chem., 1999,38, 2663. 184. E. Siebel, A. M. A. Ibrahim and R. D. Fischer, Inorg. Chem., 1999,38, 2530. 185. S. Mihan, K. Sunkel and W. Beck, Chem. Eur. J., 1999, 5, 745. 186. H. Lang, A. del Villar and G. Rheinwald, J. Organomet. Chem., 1999, 587, 284. 187. C. J. Adams and P. R. Raithby, J. Organomet. Chern., 1999,578, 178.

2: Group I : The Alkali and Coinage Metals

67

188. J. P. H. Charmant, J. Fornies, J. Gomez, E. Lalinde, R. I. Merino, M. T. Moreno and A. G. Orpen, Organometallics, 1999,18,3353. 189. V. W.-W. Yam, K. K.-W. Lo and K. M.-C. Wong, J. Organomet. Chem., 1999, 578, 3. 190. J. Diez, M. P. Gamasa, J. Gimeno, A. Aguirre, S. Garcia-Granda, J. Holubova and L. R. Falvello, Organometallics, 1999,18, 662. 191. B. F. Straub, F. Eisentrager and P. Hofmann, Chem. Commun., 1999,2507. 192. C.-S. Hwang and P. P. Power, Organometallics, 1999, 18, 697. 193 S. Kroeker, R. E. Wasylishen and J. V. Hanna, J. Am. Chem. Soc., 1999, 121, 1582. 194. S. Kroeker and R.E. Wasylishen, Can. J. Chem., 1999,77, 1962. 195. H. Abe and H. Suzuki, Bull. Chem. SOC. Jpn., 1999,72, 787. 196. B. H. Lipshutz, J. Keith and D. J. Buzard, Organometallics, 1999,18, 1571. 197. S. Mori and E. Nakamura, Chem. Eur. J., 1999,5, 1534. 198. A. Kovacs and G. Frenking, Organometallics, 1999, 18,887. 199. H. Furuta, T. Ogawa, Y. Uwatoko and K. Araki, Inorg. Chem., 1999,38,2676. 200. V. Lippolis, A. J. Blake, P. A. Cooke, F. Isaia, W.-S. Li and M. Schroder, G e m . Eur. J., 1999,5, 1987. 201. D. Fortin, M. Drouin, P. D. Harvey, F. G. Herring, D. A. Summers and R. C. Thompson, Inovg. Chem., 1999,38,1253. 202. G.-C. Guo, G.-D. Zhou and T. C. W. Mak, J. Am. Chem. SOC., 1999,121,3136. 203. G. L. Ning, M. Munakata, L. P. Wu, M. Maekawa, T. Kuroda-Sowa, Y. Suenaga and K. Sugimoto, Inorg. Chem., 1999,38,1376. 204. K. A. Al-Farnhan, M. H. Ja’far and 0. M. Abu-Salah, J. Organomet. Chem., 1999, 579, 59. 205. G. L. Ning, L. P. Wu, K. Sugimoto, M. Munakata, T. Kuroda-Sowa and M. Maekawa, J. Chem. SOC.,Dalton Trans., 1999,2529. 206. M. Munakata, G. L. Ning, Y. Suenaga, K. Sugimoto, T. Kuroda-Sowa and M. Maekawa, Chem. Commun., 1999,1545. 207. M. Munakata, L. P. Wu, T. Kuroda-Sowa, M. Maekawa, Y. Suenaga, K. Sugimoto and I. Ino, J. Chem. Soc., Dalton Trans., 1999, 373. 208. H. Lang, S. Weinmann, I. Y. Wu, T. Stein, A. Jacobi and G. Huttner, J. Organomet. Chem., 1999,575, 133. 209. H. Ito, T. Yajima, J. Tateiwa and A. Hosomi, Tetrahedron Lett., 1999,40, 7807. 210. M. A. Cinellu, G. Minghetti, M. V. Pinna, S. Stoccoro, A. Zucca and M. Manassero, J. Chem. SOC.,Dalton Trans., 1999, 2823. 211. J. Vicente, M.-T. Chicote and M.-C. Lagunas, Helv. Chim.Acta, 1999,82, 1202. 212. D. Zhu, S. V. Lindeman and J. K. Kochi, Organometallics, 1999, 18,2241. 213. J. Vicente, M. T. Chicote, M. I. Lozano and S. Huertas, Organometallics, 1999, 18, 753. 214. H. M. J. Wang, C. Y. L. Chen and I. J. B. Lin, Organometallics, 1999, 18, 1216. 215. P. B. Hitchcock, M. F. Lappert, M. Layh and A. Klein, J. Chem. SOC.,Dalton Trans., 1999, 1455. 216. T. J. Mathieson, A. G. Langdon, N. B. Milestone and B. K. Nicholson, J. Chem. SOC.,Dalton Trans., 1999, 201. 217. M. B. Dinger and W. Henderson, J. Organornet. Chem., 1999,577,219. 218. M. C. Gimeno, P. G. Jones, A. Laguna and C. Sarroca, J. Organomet. Chem., 1999,579,206. 219. E. M. Barranco, 0. Crespo, M. C. Grimeno, P. G. Jones, A. Laguna and M. D. Villacampa, J. Organomet. Chem., 1999, 592,258.

68

OrganornetallicChemistry

220. J. E. Casas, M. C. Gimeno, P. G. Jones, A. Laguna and M. Laguna, J. Chem. SOC.,Dalton Trans., 1999, 2819. 221. E. J. Fernandez, M. B. Hursthouse, M. Laguna and R. Terroba, J. Organornet. Chem., 1999,574,207. 222. A. L. Balch, M. M. Olmstead and J. C. Vickery, Inorg. Chem., 1999,38,3494. 223. C. P. McArdle, M. J. Irwin, M. C. Jennings and R. J. Puddephatt, Angew. Chem. Int. Ed., 1999,38, 3376. 224. V. Jonas and W. Thiel, J. Chem. Soc., Dalton Trans., 1999, 3783.

3 Group 2 (Be-Ba) and Group 12 (Zn-Hg) BY RICHARD A. LAYFIELD AND DOMINIC S. WRIGHT

1

Scope and Organisation of the Review

The year 1999 saw a number of significant discoveries, particularly in the areas of the structural inorganic chemistry of Group 2 and 12 organometallics and their applications to organic and organometallic synthesis. This review presents a perspective of the major achievements of the year which, although not intended to be fully comprehensive, is based on an extensive literature search. As with the reports of the previous few years, the strict definition of an organometallic compound as one containing at least one C-metal interaction or bond has been used in this survey. The review has been written as near as was possible as continuous text, aimed at highlighting the most important discoveries made and particularly the interrelation between them. This year, however, individual topic headings have been highlighted in bold script to allow more direct access to desired information.

2

Group2

Many of the most important recent studies of o-bonded Group 2 organometallics have focused on the structural chemistry and synthetic utility of the less well understood diorgano-alkaline earth metal complexes, with studies of 0bonded Grignard reagents (RMgX) in their own right continuing to decline in number. The recently reported simple bisazaallyl complex [Mg(N(SiMe3)C(‘Bu)C(H)SiMe3)2] 1 is nonetheless a relatively rare example of a o-diorganomagnesium compound to be structurally characterised. The adoption of the unusual, almost planar geometry for the Mg centre, which is reminiscent of that found in Mg porphyrins, stems from the steric demands of the bulky SiMe3 groups on the ligands (as revealed by DFT calculations). 1 and related complexes are useful in the synthesis of P-diketiminato Mg complexes [containing { N( SiMe3)-- C(R)) 2CH) - ligands] via C-centred nucleophilic addition of the 1-azaallyl ligands to R C z N , followed by C/N silyl migration. The structural characterisation of the Group 2 complexes [(Me3SiC E C)2M(18crown-6)] (M= Ca 2, Sr 3, Ba 4) has provided a unique opportunity to examine the ensuing structural effects brought about by changing the alkaline earth metal within a well-defined series; the Sr and Ba complexes (3 and 4,

’

Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001

69

70

Organometallic Chemistry

respectively) being the first examples of o-diorganometallics to be structurally characterised for these metals.2 One of the intriguing issues arising from this study is the observation of a reduction in the MC-C angle on descending Group 2 (from ca. 160" for 2 and 3, to 126.6(3)' and 141.3(3)' in 4). The latter may be explained by an increase in partial, side-on n-bonding of the C E C bond to the metals (as has been observed in Group 1 alkynyls). However, it is unclear at this stage whether n-bonding of this type is significant enough energetically to be responsible for the observed structural changes, or whether crystal packing effects are at work. New patterns of reactivity have been pinpointed in two important recent studies of o-bonded Group 2 complexes, concerning deprotonation of C-H bonds. In the first, the novel heterometallic complex [(Me3Si)2NCa(p-CH2SiMe3)2A1(CH2SiMe&]2 5 is isolated together with [(Me$WH2)2Al(NSiMe3)] from the reaction of [Ca(N(SiMe3)2>2]with [Al{CH2SiMe3)2)3]in nondonating toluene s01vent.~Complex 5 is assumed to result from an intermolecular acid/base reaction involving an intermediate donor-acceptor adduct. In the second study, the spectacular result of the reactions of "BuNa, ","Bu2Mg and C(Me2)(CH2)&(Me2)NH (= tmpH) (2:1:3 equivalents) in excess benzene 6 and or toluene are the complexes [(tmp)6Na4Mg2(c6&)] [(trnp)gNa4Mg2(C6H3CH3)] 7 (Figure l).4 These are host/guest complexes comprising the macrocyclic [(tmp)6Na4Mg2]2' cation which encapsulates doubly-deprotonated benzene (C6H42-) and toluene (C6H3CH32-) ligands within the cavity. The 'inverse-crown' behaviour of the [ ( t m ~ ) ~ N a ~ M g ~ ] ~ + cation in 6 and 7 can be likened to that of mercuracarborands reported by Hawthorne (e.g. 40 and 41 described latter).5 Strikingly, ab initio MO calculations show that the ortholmeta deprotonation of the toluene ligand observed in the structure of 7 is 14.0 kcal mol-' less stable than the most favoured a-/para doubly-deprotonated isomer. Thus, it appears that this unique site-selective metallation of arene ligands is in some way templated by the macrocyclic precursor (possibly the neutral macrocycle [(tmp)*Na4Mg2], the likely immediate precursor to 6 and 7). Further developments in this area may provide

7

Figure 1

3: Group 2 (Be-Ba) and Group 12 (Zn-Hg)

71

important breakthroughs in the regioselective functionalisation of organic ligands. Although interest in the solid-state structures of Grignards has waned in recent years, fundamental mechanistic investigations of Grignard reagents and their solution dynamics have continued to attract attention,&' as have novel and materials synthesis.' The influence of solvation applications in on the nature and activity of Grignard reagents has been stressed in a series of studies?' Among the various findings of this work, the discovery that Grigand reagents (RMgCl) with less sterically demanding organic groups (R= 'Pr, "Bu, 'Bu) can be prepared efficiently in toluene and in the presence of one or less equivalents of various organic bases (e.g. Et20, Et3N per RCl) has direct implications to large-scale ('cleaner') synthesis of these reagent^.^ In addition, a kinetic study of the reaction of ethyne with PhMgBr in the presence of various ratios of Et3N and MgBr2 has shown that the enhancement in the reactivity of the solvated species [PhMgBr.2Et3T\J1over the unsolvated Grignard (ca. 20,000 times faster) is accelarated still further by the addition of MgBr2, the results suggesting that the most active species is Et3N-solvated [(PhMgBr)2'MgBr2]8.7 Some of the most interesting discoveries involving Grignard reagents or magnesium metal itself have been made in the area of organic synthesis. Following the observation of a magnesium-mediated Barbier-Grignard reaction between allyl iodide or bromide (CH2=CHCH2X; X = C1, Br) and benzaldehyde in aqueous media in 1998, this facinating route has been extended to a range of allylation reactions involving a broad cross-section of substituted aryl aldehydes (ArCH=O).lo Using the optimum conditions (excess Mg/O. lmol dm-3 NH&l(aq)) overall conversions into mixtures of the coupled product [ArC(OH)CH2CH=CH2]9, the pinacol coupled product [ArCH(OH)CH(OH)Ar] 10, and the reduction product [ArCH20H]11 are in most cases in the range 27-58%. However, the distribution of these products is sensitive to the substituents and their effects on the reduction potential of the aldehyde, no reactions being observed in the presence a para-CH=O group or with aliphatic aldehydes. The latter supports the radical pathway initially proposed, involving quenching or coupling of radical anions of CH2=CHCH2X and RCH=O rather than intermediate allyl Grignards (as is thought to occur in nonaqueous conditions). This conclusion is further supported by mechansitic studies and by the use of the same aqueous conditions to promote highyielding pinacol coupling reactions with aldehydes alone. One of the significant features of this new reaction is its chemoselectivity: for example, only aryl aldehyde groups are susceptible to allylation or pinacol coupling in the presence of aliphatic aldehyde functionality. Chemoselectivity has also been observed in a study of the synthesis of functionalised alkenylmagnesium reagents via an iodine-magnesium exchange reaction. I la The reactions of the alkenyl iodides RR'C=CHI (R' = H or Ph) with 'PrMgBr or 'Pr2Mg at -70+25 "C give high yields (62-95%) of the products RR'C=CHE, after quenching of the organomagnesium intermediates with electrophiles (EX). Although fairly long reaction times are required (7-12h), these reactions occur with

72

Organornetallic Chemistry

complete retention of the 2 or E stereochemistry of the alkene and alkoxy, cyano, ester and carbamate functionality within their organic groups (R) is unaffected under these conditions. The same iodine-magnesium exchange reaction also provides a mild way of preparing resin-bound aryl and alkenyl Grignard reagents which are valuable in the synthesis of 2,5-dihydrofurans and 1,3-dihydroisobenzofurans.I b A related iodine-magnesium exchange reaction has also been employed in the regioselective functionalisation of 4iodopyrazole.12 In regard to materials synthesis, the preparation of high molecular weight polysilanes, polygermanes, silane-germane copolymers and polycarbosilanes using a electroreductive method is also worthy of mention. Monomers of the type RR'EC12 (R= Si, Ge) or 1,4-(ClSiRR')2(C6H4)are converted into the corresponding polymers using a single-compartment cell comprising a sacrificial Mg cathode and Mg anode in yields of up to 79% and with molecular weights as high as 31,000. Optimum conditions are found to be the use of an alternating current (set at 1 min intervals to avoid oxidation of products, 30mA cm-2), using LiC104 as the supporting electrolyte in THF solvent. Significantly, Mg is found to be the most effective electrode material, with A1 giving far lower yields of products and Cu and Ni being ineffective. The precise role of the Mg and the mechanism of the reaction is not understood at this stage, but it seems likely that Si-Mg and Ge-Mg bonded intermediates are involved in a Wurtz-type reaction and/or a radical mechanism is involved. Structural and synthetic studies of IT-complexesof Group 2 elements have continued to be an active area of research in 1999, particularly in regard to complexes containing ligands other than the archetypal cyclopentadienide family. One of the few simple cyclopentadienides to be structurally characterised was [(q5-Cp*)BeAs'Bu2] 12 (Cp* = C5Me5),the first beryllium diorganoarsenide and a rare example of a Be organometallic to be structu!ally elucid3ted in recent years.14 The rather short As-Be bond length (av. 2.18 A; cf. 2.47 A for the sum of the covalent radii of As and Be) does not appear to be due to any Be-a-As multiple bonding, as is indicated by the pyramidal (rather than planar) geometry of the As centre which is similar to that observed in the phosphorus analogue. The use of Ca-mediated reductive coupling of fulvenes has considerable applications in the synthesis and design of new ansa-ligand arrangements for transition metal catalysts. A recent study investigated the reductive coupling of the indenyl fulvene 1-E-benzylidene-4,7-dimethyl-indene 13, the hope being that the increased steric demands of the indenyl group over a substituted Cp ligand would confer greater conformational rigidity to the coupled ansa-metallocene product.15 Although the coupling reaction is stereoselective, generating a ca. 1:1 mixture of two out of the possible four isomers as a result of retention of the Egeometry about the fulvene C-C bond ([tran~-Ph~C~H~-rac-(q~-4,7-Me~ Ca(THF)2] 14 and [cis-Ph2C2H2-meso-(q5-4,7-Me2C9H4)2Ca(THF)2] 15}, the increased steric demands of the indenyl ligand are still not enough to avoid cis/ trans isomerisation at the C-C bridge. Transmetallation of a mixture of 14 and 15 with FeC12 occurs with some loss of stereochemistry; however, complete scrambling of the steteochemistry results with Zr.

3: Group 2 (Be-Ba) and Group 12 (Zn-Hg)

73

Complexes containing phospha- and arsacyclopentadienides have been almost unexplored for Group 2 elements. However, recent studies have provided unique access into alkaline earth metal complexes of this type. Following the discovery that [Mg(P(SiMe3)2}2] and [Ba{P(SiMe3)2}2]add to P h C r C C r C P h to give the novel compounds 16 and 17 (Figure 2), the Ph

\

SiMea

Ph

17

Figure 2

reaction mechanism has been further explored using [M { P(SiMe3)2}2-4THF] (M= Ca and Sr) as sources of the alkaline earth metals.16 The Group 2 metalP bonded phosphacyclopentadienides [M { P(2,5-Ph2-3,4-(SiMe3)2C4 )} 2-4THFI (M= Ca 18, Sr 19) are generated in high yields (Figure 3). The latter are

Figure 3

excellent sources of the phosphacyclopentadienide ligand, as shown by transmetallation with SnC12 giving the corresponding Sn(I1) bis-phosphacyclopentadienide also in high yield. The mechansim of these reactions appears to involve a series of addition and silyl migration steps, with the all-important cyclisation being achieved through a 1,3-silyl migration. The same authors have also shown that very simple access to phospha- and arsacyclopentadienide ligand frameworks is possible using the reactions of [Cp2Zr( 1,4-(Me3Si)2-2,3-Me2C4>]20 with PC13 and A~C13.l~ The novel complexes 21 and 22 (Figure 4),

Organometallic Chemistry

74

21

@ = SiMe3

22

Figure 4

which as a result of the lower extent of THF-solvation contain 7c-bonded phospha- and arsacyclopentadienide ligands (cf. 18 and 19 above), were stucturally characterised. Significant developments have been made also in the chemistry of azacyclopentadienide complexes of the alkaline earth metals. The first structurally authenticated examples [ ( M ( P ~ ~ * ) ~ . T H F ] Ca 23, Sr 24; pyr*H= 2,5-di-t(M= butylpyrrole) were prepared by the reactions of [Na(pyr*)] with MI2 in THF.18 NMR studies and the X-ray structures of both complexes confirm that the pyrrolyl ligands are q5-bonded to the metal centres, with the ring slippage biased towards the N atoms (suggesting a tendency towards q3-bonding involving the C...N-.-Cportion of the ligands). This new innovation has been taken a stage further in a study of the reaction of activated Ca metal in the presence of naphthalene with meso-octaalkylporphyrinogen 25 (Scheme I). l 9 The result is the unprecedented complex 26, in which all four of the pyrrolyl anions function together as n-bonding sites for the two Ca2+cations. Each of these ions is located at opposite sides of the N4 mean plane, being q3-bonded to two trans pyrrolyl ligands and ql-bonded to the other two ligands. This bonding pattern is modified in the heterometallic 27 (Scheme l), prepared by equilibriation of 26 with the tetralithiate of 25. The far lower steric congestion resulting from the presence of two Li' cations within the cavity gives a switch to an q5-bonding mode for the two trans pyrrolyl ligands which coordinate the sole Ca2+cation. This cation is also coordinated by the N centres of the other two pyrrolyl ligands.

3: Group 2 (Be-Ba) and Group 12 (Zn-Hg)

75

L = THF 25

26

Scheme 1

Finally, perhaps the most important fundamental breakthrough in this area has been the first structural characterisation of a bisallyl complex of the 28 heavier alkaline earth metals (Ca, Sr or Ba). [Ca( 1,3-SiMe3-C3H3}2.2THF] is obtained by the transmetallation reaction of the allyl-K salt [K( 1,3-SiMe3C3H3}] with Ca12 in THF at - 78 “C. Both of the allyl ligands bond in a symmetrical q3-mode to the Ca centre, the Ca-C bond lengths [av. 2.654(5) A] being remarkably similar to Ca-C bond lengths found in cyclopentadienide complexes. The latter behaviour is markedly different to that of transition metal (Tm) complexes of the type [Tm(allyl)Cp],where allyl ligands bond more closely than the Cp.

3

Group12

The motivation for solid-state structural studies of o-bonded complexes of Zn,21”0 Cd23 and Hg3’-38has been highly varied; many studies being of fundamental value in the investigation of new coordination chemistry or classes of complexes, while others have sought to confirm mechanistic details of new or existing inorganic or organic reactions. Two notable studies have concerned the trapping of unusual Zn salt fragments (ZnF2, MeZnF and ZnO) within supporting organometallic cage arrangements. In the first, the reaction of [Cp*TiF3] (Cp*= CSMeS),Me3SnF and ZnMe2 (8:3:6 equivalents) gives [(q5-Cp*TiF3)s(ZnF2)3]29in which three ZnF2 units are solvated by extensive Ti-F-Zn bridging from the organometallic fragments (thus overcoming the high lattice energy of ZnF2, which would normally result in precipitation of the salt itself). The reaction of [Cp*TiF3] with ZnMe2, on the other hand, gives [(q5-Cp*TiF3)4(MeZnF)2]30 in which two MeZnF units are encapsulated (the first observation of this unit within a molecular solid) (Figure 5).21 Further studies reveal that 30 is the immediate precursor to 29, 30 being formed from [Cp*TiF3] by rapid exchange of one F atom for a Me group of ZnMe2, with the remaining Zn-Me groups of 30 reacting further with Me3SnF to give 29.21 A ZnO unit is trapped within the ‘giant’ dodecanuclear cage complex [Zn2(THF)2(EtZn)6Zn&4-O)(tBuP03)8] 31 (the largest oligonuclear aggregate so far structurally characterised for Zn).22 The complex is prepared by the

Organometallic Chemistry

76 CP*

30

Cp"

Figure 5

reaction of 'BuP03H2 with ZnEt2 in the correct stoichiometric ratio, and consists of a central Zn(p4-O) fragment around which the rest of the cage is built. Novel ligand arrangements containing P/N functionalities have also attractive some attention in 1999,24-26these new arrangements providing (frequently more readily accessed) alternatives to more conventional organic frameworks. In one such study, the deprotonation of the amino-substituted cyclophosphazenes [P3N3(HNCy)6] 32 and [P4N4(HNCy)g] 33 with ZnEt2 were investigated.24 The reaction of 32 leads to complete deprotonation of all six of the HNCy groups, giving the hexanuclear Zn complex [(ZnEt)6(P3N3(NCy)s)]34. In contrast, two of the pendent NHCy groups of 33 remain protonated after treatment with ZnEt,, the product again being a hexanuclear Zn complex [(ZnEt)6{P4N4(HNCy)2(NCy)6}] 35. The terminal CyN and ring N centres of ~]~of 34 and 35 the [P3N3(NCy)6]6- and [P4N4(H N C Y ) ~ ( N C ~ )hexaanions (Figure 6) are involved in metal coordination. These unique, highly charged anions are isoelectronic with rneta-silicates, but equipped with organic groups at their teminal N-centres which impart solubility. The flexibility of these new arrangements and their ease of preparation promise extensive future applications in the coordination chemistry of a broad range of main group and

3: Group 2 (Be-Ba) and Group 12 (Zn-Hg)

77

transition metals. Also of interest in regard to readily accessible new ligands of this kind is a study of the structure and reactivity of the bis(iminophosphorano)methanide chelate complex [ZnMe{ HC. .(PPh2- .NSiMe3)2)]36, prepared in high yield by reaction of the acid CH2(PPh2NSiMe& with ZnEt2.25The reaction of this complex with AdNCO (1-adamantyl isocyanate) gives the insertion product [ZnMe{HC..-(PPh2.- s N S ~ M ~ ~ -..O). ) ~ ( C--N(Ad)}] ( 37, by means of the addition of the methanide carbon to the C=O bond (with accompanying formation of a C-C bond). This addition reaction is unique as all previously reported heteroallene insertion reactions of alkyllamido Zn complexes have involved insertion into a Zn-N bond. Of particular value is the establishing of a tripodal ligand system in one simple step. The unique properties of Hg in the +1 and +2 oxidation states were witnessed in number of recent structural studies. One highlight was the structural characterisation of the first two-coordinate, dinuclear o-bonded Hg(1) compound [(Me3Si)Me2SiHgHgSiMe2(SiMe3)] 38.31 Although compounds of the type RHgHgR (R = organic substituent) have frequently been cited as short-lived intermediates, none have previously been structurally characterised (the majority of Hg compounds being Hg(I1) complexes, like the recently characterised complex [Hg(C(SiMe3)2(SiMe2NMe2)) 21 3936). UV/ visible spectroscopy suggests that the red colour of crystalline 38 is due to an absorption at 530 nm, which can be assigned to the Hg-Hg bond in the complex and implies that the HOMO and LUMO of 38 are the o and CT* orbitals of the Hg-Hg bond [ 2.66 cf. 2.67 in Hg212].Of note also is the very deshielded nature of the Hg atoms in 38, the 199HgNMR chemical shift (6 1141.3ppm) being the highest value yet observed for Hg(1). There has been continued interest in the host/guest properties of Hg(I1) macrocyclic comp l e ~ e s . ~ 'The . ~ ~ coordination of NO3- anions within the tetranuclear 12mercuracarborand-4 host [ ((1,2-C2B10H10)Hg)4]39 has been investigated.28 The presence of H 2 0 solvation has a marked effect on the conformation of the host macrocyle and on the bonding modes adopted by the NO_?-anions in the two related complexes [ ((1,2-C2BloHlo)Hg)4(N03)2]{ K( 18-crown-6)I2.H2040 and [ {( 1,2-C2BloHlo)Hg}4(N03)2]{ K( 18-crown-6)I241. In 40 the macrocyclic C8Hg4 ring is highly puckered (a geometry which has only previously been observed in uncoordinated hosts of this type), with one of the 0 centres of one NO3- anion being coordinated to all four Hg(I1) atoms on one side of the ring and one of the 0 centres of the other NO3 anion being bonded to two adjacent Hg(I1) atoms on the other side of the cavity. The remaining coordination site is occupied by a H 2 0 molecule, which bridges the two remaining Hg(I1) centres. Remarkably the absence of H 2 0 solvation in 41 results in a planar host conformation in which the two NO3 anions adopt an unprecedented 'side-on', trihapto coordination mode at opposite sides of the cavity (Figure 7). Comparatively few studies have investigated n-bonded complexes of Group 12 metals recently.4o42 The first examples of heterometallic Pt/Cd complexes are obtained in the 1:2 reaction of [('BuqN)2( Pt(C = CPh)4}] with hydrated = CPh),} (CdC12)2] 42 and CdCl2, giving a mixture of (fB~4N)2[Pt(~-~C":r2-c ('BU~N)~[ {Pt(p-rcC*C"-C= CPh)4)2(CdC1)2]43 (the latter being obtained exclu+

A;

A

Organometallic Chemistry

78

sively in the I :1 rea~tion).~’ In 42, the square-planar [Pt(C = CPh)4]2- anion coordinates two neutral CdC12 units via 7c-bonding to the C=CPh groups in a p2-mode (in a ‘tweezer-like’ arrangement). In 43, however, the bonding of the C = CPh groups is exclusively ql- (using the a-C only), giving a highly unusual side-on coordination mode for the [Pt(C = CPh)4]2- anion [in which Pt.--Cd interactions (ca. 3.21-3.31 may also be important] (Figure 8). Like 42, aggregation in the octameric and pentameric Hg(I1) acetylide ‘clusters’ [Hg(C = CPh)2]8 44 and [Hg(C = CSiMe&I5 45 also appears to occur primarily although by Hgly-CrCR bonding between the monomer units (3.3-3.7 the relatively short 3.7-4.0 Hg.-.Hg separations in these species may suggest

A)

A);

A

43

Figure 8

some additional degree of metal.. .metal interaction (‘merc~riophilicity’).~~ Surprisingly, these are the first examples of Hg(I1) acetylides to be structurally characterised. 7c-Bonding is also a feature within the polymeric structure of the Hg(I1) anthracene derivative [HgC1(CI4H9)lco46, the monomer units being associated by a combination of Hg.--Clbonding,oanthracene n-7c stacking and trihapto n-anthracene...Hg bonding (3.35-3.48 A).42Following the structural characterisation of the non-classical carbonyl compound [Hg(C0)2l2’ 47 in 1996, high-level calculations have been used to investigate the bonding and charge distribution in this and related (observed and theoretical) Au and TI ~ a r b o n y l sThe . ~ ~ results for [Hg(C0>,l2’ are consistent with the idea that a low degree of n-back bonding between C and Hg occurs in this species. Compari-

3: Group 2 (Be-Ba) and Group 12 (Zn-Hg)

79

sion of 47 with [Au(CO)2]+and [T1(CO)2]3' (in the same period) shows that the vibrational frequency of the CO ligand is a maximum for 47 (which has the highest value yet observed experimentally, at av. 2279 cm- '). The most prolific area of research continues to be the use of Group 12 organometallics in organic synthesis. Once again this area has been dominated by the chemistry of Zn. A number of studies are of a more fundamental nature, concerning the preparation of Zn organometallics and their role in key organic reaction^.^^ However, the growth areas remain the applications of Zn organometallics and related amides and alkoxides in novel synthetic appro ache^^'-^^ and (in particular) in stereoselective s y n t h e ~ i s . ~The ~ ' importance of Zn organometallics in the search for wide-scope metal-catalysed alkyl-alkyl cross-coupling reactions has also been highlighted in a recent review.62 Owing to the interdisciplinary and diverse nature of these studies (which span the traditional areas of inorganic and organic chemistry, and transition metal catalysis) it would be impossible to do all of these recent reports justice. Instead, it is aimed here to highlight developments which have general importance and potentially far-reaching future impact in this area. The broader kinetic investigations of the reactivity of activated Zn (Zn*) with an extensive range of alkyl, aryl, vinyl, ally1 and benzyl halides (RX) provides further support for an Electron Transfer (ET) mechanism, in which the ET process is rate-determir~ing.~~ Investigations involving radical clocks (like 1-bromo-methyl-cyclopropane) and Linear Free Energy Relationships support the presence of radicals in the formation of RZnX in these reactions. The reactivity profiles also suggest that the ET has a significant inner-sphere component in the reactions involving alkyl halides, with investigations of reactions involving aryl halides (ArX) suggesting the intermediacy of radical anions [ArX.]-. The overall spectrum of reactivity of organic bromides with Zn* covers a huge range of relative rates of ca. 7 x lo'. Thus, Zn* emerges from these studies as a unique metal whose selectivity towards different types of halides (e.g. alkyl vs. aryl, n- or s-alkyl vs. benzyl, n-alkyl vs. vinyl or even talkyl vs. n-alkyl) distinguishes it from other metals (such as Li and Mg). The resulting 'reactivity line' (Figure 9) has major implications for organic and polymer synthesis, by providing simple rules for the chemoselective zincation of organic polyhalides and the subsequent functionalisation with electrophiles. A further advance in this context has been the development of a new method of preparing reactive Zn powders via sonoelectroreduction of Zn salts in H20 (the active Zn generated being protected by the 0 2 degassing effect of the ultrasound and by its replacement with dissolved H2).45The technique involves

Il-----o-o-I'---o-o--o 0.001

0.01

0.1

G

1

9-0

-

10

Relative Rate for RBr + Zn* Figure 9

I

100

RZnBr

1-1

1000

10000

80

Organometallic Chemistry

the innovative use of out-of-phase high-density current together with highintensity pulsed pressure waves (20 kHz), allowing the control of partical size by modification of the ultrasound and/or electrochemical parameters. Such Zn powders can be almost as reactive as Rieke Zn towards organic substrates (e.g. in Reformatsky, Barbier and alkyne reduction reactions). Very significantly, this process provides the means for safe and cheap, industrial-scale preparations, with the added advantage that the Zn salt byproducts generated after organic reactions can potentially be recycled. Several new studies involving synthetic transformations accomplished by organozinc compounds stand out as of particular importance. Characteristically of Zn reagents, the novel zincate [Zn'Bu2(tmp)]Li 48 (tmp = tetramethyl piperidine) has greater functional group tolerance than the lithiate [tmpLi] 49.4848 is highly effective in the ortho-metallation of mono-substituted arenes XC6H4 (X = C EN, C02R or CONR2), after the addition of electrophiles (E) the products 1,2-X-E-C6H3 being obtained in 73-99% yields. This can be compared with metallations involving 49, from which unwanted byproducts resulting from addition to X can arise. 48 is also highly useful in the direct afunctionalisation of pyridine, thiophenes, quinoline and im-quinoline. This first report of the direct a-metallation of isoquinoline (which dimerises in the presence of 49), stresses the selective nature of this new reagent. A zincate intermediate is also implicated within a new, highly enantioselective ketone alkynylation reaction mediated by the chiral Zn aminoalkoxides [(1R,2S)-NPNP}ZnOR] 50 (PNP = pyrr~lidinylnorephedrine).~~ The stereoselective reaction of c-PrC = CM (M = Li or MgX) with the amine 51 in the presence of 50 gives the recently licensed AIDS drug Efavirenz 52 with up to 99.2% enantiomeric excess (e.e.) (Scheme 2). This contrasts with the less selective course of the reaction in the absence of Zn, which requires protection of the primary amine functionality. A cautionary note is sounded, however, in an important fundamental study of the nature of [ZnMe3]Li 53 and [ZnMe4]Li2 54 in solution.46 Although 54 has been structurally characterised in the solid state, studies of the composition of' mixtures of [Zn(13CH3)2] with (13CH3)Li reveal that the predominant species in both the 1:l and 1:2 solutions is 53 (54 only being present in very small amounts in the 1:2 mixture, even after prolonged storage). This study

D

./ 1

50 51

Scheme 2

3: Group 2 (Be-Ba) and Group 12 (Zn-Hg)

81

emphasises an increasing need for in-depth solution investigations as a foundation for proper understanding of the active species present in regio- and stereoselective reactions involving organozinc reagents in general. A case in point is the recent discovery that Zn enolates generated by the acid/base reactions of ZnEt2 with CH2Y2 (Y = e.g. C02R, C = N , S02R) can greatly improve the e.e.s in Pd-catalysed allylic alkylation reactions, compared to the use of enolates prepared by transmetallation of Zn salts with Li or Na a l k ~ x i d e s . ~ ~ The improved performance of the Zn enolates is ascribed to the absence of other metals within the reaction mixtures, a conclusion which may suggest the presence of structurally different active species. Detailed mechanistic studies in this area are still relatively rare; a recent one concerned the catalytic complex formed between ZnEt, and the di-Li salt of (2S,5S)-2-isobutyl-5-isopropylpiperazine. It is found that for the dilithiate alone, rapid chaidboat equilibrium occurs for the piperazine ring.60 However, addition of ZnEt2 dramatically slows this process, with the major species in solution being 55 (Figure 10) in

55

Figure 10

which a boat-shaped ring is favoured due to chelation of the N centres to the Zn. This C2-symmetric structure appears to be essential in promoted subsequent stereoselective alkylations of ketones. The search for new chiral N, 0 and P centred ligands and promoters used in stereoselective organic synthesis involving Zn organometallics is a current growth area (especially in respect to 1,2- and 1,4-addition and reactions to ketones and a,P-unsaturated Also worthy of note in regard to new reactions involving organozinc species are recent studies of the Ni(0) catalysed reactions of 1,3-dienes and R'R2C=0, mediated by ZnR2. These show that the nature of the reactions occurring and the products formed is dependent on the Zn-bonded R - g r o ~ p . ~Reactions ~,~' involving R'R2C=0, isoprene [CH2=CHC(Me)=CH2] and ZnEt2 result in homoallylation, largely giving the products CH2=CHC(Me)CH2C(OH)R1R2 (with good regio- and stereo-selectivity with many ketones and unsaturated aldehyde^).^^ In contrast, reactions of 1,3-dienes with ZnMe2 or ZnPh2 (where there is no possibility of P-H elimination and the formation of CH2=CH2) result in an interesting three-component reaction, which arises from termination by R-group transfer to the end of the chain.50The two types of products 56 and 57 (shown in Scheme 3 for a reaction involving 1,3-butadiene) result

82

Organometullic Chemistry

from 1:l:l and 1:2:1 reactions of ZnR2 with a 1,3-diene and R'R2C=0 (respectively) (the associated disconnection involved in the latter reaction is indicated in Scheme 3).

4

[Ni(acac),] * ZnR2

+

+ R'R*C=O

25-30 "C THF

R'

R

R2

56

+

OH R' R2

57

Scheme 3

Finally, some studies of Group 12 organometallics in a more inorganic setting can be

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

14. 15. 16.

C. F. Caro, P. B. Hitchcock and M. F. Lappert, J. Chem. Soc., Chem. Commun., 1999, 1433. D. C. Green, U. Englich and K. Ruhlandte-Senge, Angew. Chem., Int. Ed. Engl., 1999,38, 354. M. Westerhausen, C. Birg, H. Noth, J. Knizek and T. Seifert, Eur. J. Inorg. Chem., 1999,2209. D. R. Armstrong, A. R. Kennedy, R. E. Mulvey and R. B. Rowlings, Angew. Chem., Int. Ed. Engl., 1999,38, 131. M. F. Hawthorne and Z. Zheng, Ace. Chem. Rex, 1997,30,267. A. Tuulments and D. Panov, J. Urganomet. Chem., 1999,575,182. V. Pallin and A. Tuulments, J. Urgunomet. Chem., 1999,584, 185. A. Tuulments and M. Sassian, J. Organomet. Chem., 1999,586, 145. V. Pallin, E. Otsa and A. Tuulments, J. Organomet. Chem., 1999,590, 149. W.-C. Zhang and C.-J. Li, J. Org. Chem., 1999,64,3230. (a) M. Rottlander, L. Boymond, G. Cahiez and P. Knochel, J. Org. Chem., 1999, 64, 1080; (b) M. Rottlander and P. Knochel, J. Comb. Chem., 1999,1, 181. J. Felding, J. Kristensen, T. Bjerregaard. L. Sander, P. Vedsa and M. Begtrup, J. Urg. Chem., 1999,64,4196. S. Kashimura, M. Ishifune, N. Yamashita, H.-B. Bu, M. Takebayshi, S. Kitajima, D. Toshiwara, Y. Kataoka, R. Nishida, %-I.,Kawasaki, H. Murase and T. Shono, J. Urg. Chem., 1999,64, 6615. S. L. Battle, A. H. Cowley, A. Decken, R. A. Jones and S. U. Koschmieder, J. Organornet. Chem., 1999,582, 66. P. L. Shapiro, K. M. Kane, A. Vij, D. Stelck, G. J. Matare, R. L. Hubbard and B. Caron, Urgunometallics,1999, 18, 3468. M. Westerhausen, M. H. Digeser, H. Noth, W. Fonikwar, T. Seifert and K. Polborn, Inorg. Chem., 1999, 38, 3207; see also M. Westerhausen, M. Digeser, H. Noth, T. Seifert and A. Pfitzner, J. Am. Chern. SOC.,1998,120,6722.

3: Group 2 (Be-Ba) and Group 12 (Zn-Hg) 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35.

36. 37. 38. 39.

40. 41. 42.

83

M. Westerhausen, M. H. Digeser, C. Cuckel, H. Noth, J. Knizek and K. Polborn, Organometallics, 1999,18,249 1. H. Schumann, J. Gottfriedsen and J. Demtschuk, J. Chem. Suc., Chem. Commun., 1999,2091. L. Bonomo, 0. Dandin, E. Solari, C. Floriani and R. Scopelliti, Angew. Chem., Int. Ed. Engl., 1999, 38, 914. M. J. Harvey, T. P. Hanusa and V. G. Young Jr., Angew. Chem., Int. Ed. Engl., 1999, 38, 217. P. Yu, P. Muller, H. W. Roesky, M. Noltemeyer, A, Demsar and I. Uson, Angew. Chem. Int. Engl., 1999,38, 3319. Y. Yang, J. Pinkas, M. Noltemeyer, H.-G. Schmidt and H. W. Roesky, Angew. Chem., Int. Ed. Engl., 1999,38, 664. S. Lullinski, I. Madura, J. Senvatoski and J. Zachara, Inorg. Chem., 1999, 38, 4937. G. T. Lawson, C. Jacob and A. Steiner, Euro. J. Inorg. Chem., 1999, 1881. A. Kasani, R. McDonald and R. G. Cavell, Organometallics, 1999, 18, 3775. S . Wingerter, H. Gornitzka, G. Betrand and D. Stalke, Eur. J. Inorg. Chem., 1999, 173. M. Westerhausen, M. Wieneke and W. Schwarz, J. Organomet. Chem., 1999,572, 249. A. A. Zinn, C. B. Knobler, D. E. Hanvell and M. F. Hawthorne, Inorg. Chem., 1999,38,2227. B. Goldfuss, S. I. Khan and K. N. Houk, Organometallics, 1999,18,2927. H. Mimoun, J. Y. de Saint Laumer, L. Giannini, R. Scopelliti and C. Floriani, J. Am. Chem. Soc., 1999,121,6158. D. Bravo-Zhivotovskii, M. Yuzefovich, M. Bendikov, K. Klinkhammer and Y. Apeloig, Angew. Chem., Int. Ed. Engl., 1999,38, 1100. P. Kocovsky, V. Dunn, A. Gogoll and V. Langer, J. Org. Chem., 1999, 64, 101. L. R. Falvello, S. Fernandez, R. Navarro and E. P. Urriolabeitia, Inorg. Chem., 1999,38,2455. F. Cecconi, C. A. Ghlardi, A. Ienco, S. Midollini and A. Orlandini, J. Organomet. Chem., 1999,575, 119. M. Tschinkl, A. Schiet, J. Riede and F. P. Gabbai, Organometallics, 1999, 18, 2040. S. S. Al-Juaid, C . Eaborn, S. M. El-Hamruni, P. B. Hitchcock and J. D. Smith, Organometallics, 1999,18,45. B. Kalyanasundari, K. Panchanatheswaran, V. Parthasarathi and W. T. Robinson, Bull. Chem. SOC.Jpn., 1999,72, 33. X. L. Cui, Y. J. Wu, C. X. Du, L. Ru and Y. Zhu, Tetrahedron Asym., 1999, 10, 1255. L. N. Saitkulova, E. V. Bakhmutova, E. S. Shubina, I. A. Tikhonova, G. G. Furin, V. I. Bakhmutov, N. P. Gambaryan, A. L. Christyakov, I. V. Stankevich, V. B. Shur and L. M. Epstein, J. Organomet. Chem., 1999,585,201. J. P. H. Charmant, L. R. Falvello, J. Forniks, E. Lalinde, M. T. Moreno, A. G. Orpen and A. Rueda, J. Chem. Soc., Chem. Commun., 1999,2045. S. J. Faville, W. Henderson, T. Mathieson and B. K. Nicholson, J. Organomet. Chern., 1999,580,364. M. Tschinkl, R. E. Bachman and F. P. Gabbai, J. Organomet. Chem., 1999,582, 40.

84 43. 44.

45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65.

Organonaetallic Chemistry

V. Jonas and W. Thiel, J. Chem. Soc., Dalton Trans., 1999, 3783, and references therein. A. Cuiarro, D. M. Rosenberg and R. D. Rieke, J. Am. Chem. Soc., 1999, 121, 4155; see also A. Guijarro and R . D. Rieke, Angew. Chem., Int. Ed. Engl., 1998, 37, 1679. A. Durant, J. L. Delplancke, V. Libert and J. Reisse, Eur. J. Org. Chem., 1999, 2845. T. A. Mobley and S. Berger, Angetti. Chem., Int. Ed. Engl., 1999,38, 3070. H. Marek, P. Schreiner and J. F. Normant, Org. Lett., 1999, 1, 929. Y. Kondo, M. Shilai, M. Uchiyama and T. Sakamoto, J. Am. Chem. Soc., 1999, 121,3539. M. Kimura, S. Matsuo, K. Shibata and Y. Tamaru, Angeti!. Chem., Znt. Ed. Engl., 1999,38, 3386. M. Kimura, H. Fujimatsu, A. Ezoe, K. Shibata, M. Shimizu, S. Matsumota and Y. Tamura, Angew. Chem., Int. Ed. Engl., 1999,38, 397. E. Erdik and T. Dakapan, J. Chem. SOC.,Perkin I , 1999, 3139. M. Nakamura, K. Hara, G. Sakata and E. Nakamura, Org. Lett., 1999,1, 1505. L. Hyldtoft, C. Storm Poulsen and R. Madsen, J. Chem. Soc., Chem. Commun., 1999,2101. K. Fuji, N. Kinoshita and K. Tanaka, J. Chem. Soc., Chem. Commun., 1999, 1895. K. Ding, A. Ishii and K. Mikami, Angew. Chem., Int. Ed. Engl., 1999,38,497. L. Tan, C.y. Chen, R. D. Tillyer, E. J. J. Grabowski and P. J. Reider, Angew. Chem., Int. Ed. Engl., 1999,38, 71 1. X. Hu, H. Chen and X. Zhang, Angew. Chenz., Int. Ed. Engl., 1999,38, 3518. H. Kleijn, E. Rijnberg, J. T. B. H. Jastrzebski and G. van Koten, Org. Lett., 1999,1, 853. H.-B. Yu, X.-F. Zheng, Z.-M. Lin, Q.-S. Hu, W.-S. Huang and L. Pu, J. Org. Chem., 1999,64,8149. J. Eriksson, P. I. Arvidsson and 0. Davidsson, Chem. Eur. J., 1999,5,2356. P. Bandt, C. Hedberg, K. Lawonn, P. Pinho and P. G . Anderson, Chem. Eur. J . , 1999, 5, 1692. D. J. Cardenas, Angew. Chem., Int. Ed. Engl., 1999,38, 3018. N. L. Pickett, D. F. Foster, N. Maung and D. J. Cole-Hamilton, J. Chem. SOC., Dalton Trans., 1999, 3005. L. Carollo and B. Floris, J. Organornet. Clzem., 1999,583, 80. R. W. Deemie, M. Rao and D. A. Knight, J. Organonzet. Chem., 1999,585,162.

4 Scandium, Yttrium and the Lanthanides BY JOHN G. BRENNAN AND ANDREA SELLA

1

Introduction

This review covers all organometallic complexes of Sc, Y and the lanthanides reported in the year 1999 and their reactions. Endohedral fullerene complexes of the lanthanides are however excluded.* 2

New Compounds - Structure and Reactivity

2.1 Cp Compounds. - Lanthanide chemistry anchored by the well-developed Cp ligand was divided among protonolysis, redox, and simple Lewis acid/base reactions. In an unusual synthetic approach to Ln-E (Ln = S, Se) bonds, the compounds Cp2Y[q3-N(EPPh2)2]were isolated from the protonolysis reaction between Cp3Y and HN(EPPh2)2 in THF. In both compounds, the [N(EPPh2)2]- ligand is bound q 3 to the Y center which is, for the sulfur compound, the first example of that mode of binding for the N(SPPh2)2 ligand. Both compounds are stable in inert environments for prolonged periods of time, and both are soluble in commonly used organic solvents.’ A second organolanthanide report describing direct bonds to sulfur outlined the reaction of Cp3Ln (Ln=Yb, Dy, Sm, Y) with 2-mercapto-benzothiazole in THF at room temperature to give Cp2Ln(SR)(THF) [Ln=Yb, Dy, Sm, yl. All these complexes have been characterized by IR and mass spectra, which indicate that they are solvated monomers. The structures of the Yb and Dy compounds were determined; each Ln coordinates two q 5 Cp groups, one oxygen from THF, sulfur and nitrogen atoms from the chelating benzothiazole-2-thiolate ligand, in a distorted trigonal bipyramidal geometry. The Ln-S bond length is the longest value found in organolanthanide complexes.2 Protonolysis of Cp3Ln with 1,3-diphenyltriazene can give products with 1,3diphenyltriazenido ligands. The absence of a detectable reaction between either Cp3Er or Cp3Lu and excess 1,3-diphenyltriazene was attributed to the insolubility of the polymeric Ln complexes in this solvent. With the monomeric,

*

Abbreviations: Ln = lanthanide; Cp = q-C5H5;Cp* = q-C5Me5; Cp’ = q-C5H4(%Me3); Cp” = q-C5H3 (SiMe3)2; Ind = r)-C9H7; COT = CxHx; COT” = 1,4-C~H6(SiMe3)2; HMPA = hexamethylphosphorustriamide; DME = 1,2-(dimethoxy)ethane; MMA = methyl methacrylate; M A 0 = methylaluminoxane; DFT = density functional theory.

Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001 85

86

Organometallic Chemistry

toluene-soluble Lewis base adduct Cp3Ln(NC5H4-4-But)(Ln = Er, Lu, reactions with 1,3-diphenyltriazene gave Cp2( 1,3-diphenyltriazenido)Ln(NC5H4-4But) as red-brown solids. Treatment of Cp3Ln with three equivalents of 1,3diphenyltriazene and pyridine in refluxing toluene afforded (1,3-diphenyltria~enido)~Ln(py)~, isolated again as red-brown solids. Results of structural investigations for both molecular classes were described, and the ‘limited’ utility of these compounds as CVD sources was e~tablished.~ Similar protonolysis reactions using substituted pyrazoles gave related product^.^ Reactions of Cp3Ln (Ln=Ho, Dy, Yb, Sm) with 3,5-dimethylpyrazole (HPzMe2) gave c p L n ( P ~ M e ~[Ln ) ~= Ho, Dy], Cp2Yb(PzMe2)(HPzMe2), and s m ( P ~ M e ~ ) ~ , respectively, indicating that the number of potential Cp protonations is largely influenced by the size of the lanthanide ion. Reaction of Cp3Er and one equivalent of HPzMe2 under the same conditions gave Cp2Er(PzMe2)(THF). In these structures, the central metal ions are coordinated to four ligands in a typical ‘bent metallocene’ geometry. The mono-Cp complexes react with dimethylsilicone grease to give the corresponding Me2Si0 insertion products, i. e. [CpLn(PzMe2)(0SiMe2PzMe2)I2[Ln = Ho, Dy]. Structural characterization of the Ho compound shows that the primary coordination sphere is composed of a Cp ligand, two bridging oxygen atoms, and three nitrogen atoms, two from the chelating PzMe2 ligand and one from the bridging 3,5-dimethylpyrazolyl ~iloxide.~ The proton transfer reaction of Cp3Ln (Ln = Yb, Tm, Er, Ho, Dy, Nd) with 2-amino-5-(p-methoxyphenyl)1,3,4-thiadiazole (L)) gave Cp2LnL. The structures of the complexes were established by IR and mass spectroscopy.6 In a continuing search for CVD sources of Ln atoms, the divalent metallocene Sm(C5H5)2 was decomposed thermally in a redox reaction that yields Cp3Sm and metallic Sm.7 Cp complexes of Ce also found applications as CVD sources in the atomic layer epitaxial growth of Ce-doped SrS phosphor layers.* The reaction of Cp2Sm(THF) with XCH2CH2X (X = Br, I) leads to an equimolar mixture of Cp3Sm(THF) and C P S ~ X ~ ( T H FStruc)~. tural characterization of CpSmBrz(THF)3 identified a formally eight-coordinate Sm atom in a distorted octahedral geometry with the centroid of the Cpring and a THF in the apical positions, with the halides transoid in the equatorial plane.’ The diazadiene complex Cp2Yb(DAD) (DAD = Bu*N=CHCH=NBut) was prepared according to three different procedures: oxidation of C P ~ Y ~ ( T H Fwith ) ~ diazadiene in THF, metathesis of Cp2YbC1 with Na2(DAD) taken in a ratio of 2:1, and by the reaction of CpZYbCl(THF) with K(DAD) taken in a ratio of 1:l.‘’ [Yb2Cp3(NPPh3)3] was isolated from the reaction of YbCp2C1 with LiNPPh3. Two of the (NPPh3)- groups bridge the Yb atoms to form a nonplanar Yb2N2 four-membered ring. The third (NPPh3)- group is terminally bonded with a short (2.142 A) Yb-N bond. Insertion of an OSiMe2 unit is observed in the synthesis of colorless, moisture sensitive vCp(NPPh3)(p-0SiMe2NPPh3)l2from YCpC12 and LiNPPh3 in boiling toluene in the presence of Baysilon paste. The Y atoms are linked viu the 0 atoms of the (OSiMe2NPPh3)- groups to form a centrosymmetric Y202 ring with asymmetric Y-0 bonds. Similarly, [Y(NPPh3)&-0Si-

4: Scandium, Yttrium and the Lanthanides

87

Me2NPPh3)I2 forms in the reaction of YC13 with KNPPh3 in THF with Baysilon.” A series of Cp3Ln and (C9H7)3Ln coordination complexes with chiral sulfoxide donors were prepared and characterized in both solution and in the solid state. While solid (CgH7)3LnO=S(Me)(4-MeC6H4) (Ln = La, Pr) contains exclusively 0-bonded sulfoxide and three q 5-coordinated indenyl ligands in a chiral arrangement around the metal ion, the indenyl ligands are involved in rapid q5-q1 exchange process. Both VT ‘H NMR and CD spectroscopy indicate that a second chirogenic centre was generated that lies closer to the metal ion than the chiral S atom of the sulfoxide ligand. In contrast, the Cp compounds (Ln=Pr, Nd, Yb) are practically CD-silent. From some very interesting NMR experiments on mixtures of indenyl complexes with (R)-(+)and (S)-( -)-sulfoxide, or/and with two different metals, it appears that there is rapid intermolecular sulfoxide exchange that is not facilitated by the presence of THF. l 2 Six new rare earth organometallic complexes [CpLn(N,N-diacetylacetoneethylenediaminato] (Ln=Y, Nd, Tb, Dy, Er, Yb) were synthesized by the reactions of the diprotic ligand with Cp3Ln. Similarly, (C5H5)Ln(N,N’disalicylideneethylenediamine) (Ln = Pr, Nd, Ho, Er, Tm, Yb) were synthesized.l4 The structure of { C~EU[CCH(COOC~H~)~][~-CH(COOC~H~>~~ ) 2 contains a pentagonal bipyramidal Eu ion.’5 2.2 Substituted Cp Ancillaries. - Treatment of [ L ~ C P ” (Ln=La, ~] Ce, Pr, Nd) with two equivalents each of [18]-crown-6 and K in benzene at ambient temperature affords the red or red-brown crystalline salts [K([181-crown6)][Ln(r15-Cp”}2(C,H6)](1) and [K([l S]-crown-6)][Cp”] as a co-product. Each of these salts is soluble in hot benzene, which allowed the ‘H NMR spectra to be recorded. The La compound is diamagnetic, while the ‘H NMR resonances of the [ 181-crown-6 moiety are only slightly shifted in the paramagnetic derivatives. Hydrolysis of these crown products yields cyclohexa-1,4-diene. The molecular structures of the isomorphous La, Ce, and Nd salts reveal that each comprises a tight ion pair with a C6H6 ligand bridging the K and Ln atoms. The K atom has close contacts to the six crown ether 0 atoms and the centroids of the 2,3- and 5,6-C atoms of the C6H6 ligand. In the reaction of [ L ~ C P ”with ~ ] K and ([181-crown-6)in benzene, EPR spectroscopy suggests the formation of at least four paramagnetic La(I1) species prior to the formation of the La(II1) product.16 Numerous structural studies were reported. The homoleptic tris q 5-C5H4(SiMe2Bu‘) compounds have been prepared for the entire lanthanide series, and characterized by multinuclear NMR and mass spectroscopy. Selected examples were also characterized by X-ray diffraction. l 7 Trivalent [ ( c ~ R ) ~ L n ( p - C l ) ] ~ (Ln = Sm, Yb, Y, Lu; CpR = (+)-neomenthylcyclopentadienyl) and [(CPR)L~X~(THF)~] (X = C1, Ln = Sm, Gd, Yb, Y, Lu; X = I, Ln = Sm, Yb) were prepared. X-ray structural analysis revealed that the monochlorides of Sm and Y are chloro-bridged dimers with the asymmetric Ln2C12plane almost perpendicular to the plane described by the four cyclopentadienyl ring

Orgunometullic Chemistry

88

centroids. X-ray structural analysis also showed that the monomeric compound C P R S ~ I ~ ( T H Fadopts )~ a pseudo-octahedral geometry with trans iodide ligands. The cationic complexes [(MeCp)2Ln(THF)2][BPh4](Ln = Sm, Yb) were prepared by oxidation of ( M ~ C P ) ~ L ~ ( T H with F ) AgBPh4 in THF and structurally ~haracterized.’~~~’ Red [ ( M e c ~ ) ~ Y b R and l orange [Cp2SmR] [R = 2,6-(2,4,6-Me3C6H2)2c~H3]were obtained by the reaction of RLi with Yb(MeCp)3 or SmCp3 in toluene. Structural characterization of both compounds reveal q5-Cp ligands, ql-coordination to the @so C atom of the aryl ligand, and intramolecular x-arene contacts to one mesityl group the nature of which depend on the size of the Ln.21The complex [(I,~-BU‘~C~H~)~EU(THF)] was prepared by the reaction of 1,3-But2C5H3Nawith EuI2 in THF. The mixed-ligand compound [(1,3-But2C5H3)Cp*Yb(THF)] was obtained by the reaction of YbT2 with NaCp* and But2C5H3Na. The reaction of 1,3-‘Bu2CjH3Li with YbC13 afforded [( 1, ~ - B u ~ ~ C ~ H ~ ) ~ Y ~ ( ~ ~ - C ~ ) ~ L The structures of all three products were established by X-ray diffraction.22 In a report strikingly similar to the description of [Cp*&m6Se13],23the halfsandwich tert-butylcyclopentadienyl (CpBut) Nd complex [(q-CpBu‘)NdClZ(THF)2]2 reacts with Na2Se5to give the organoneodymium polyselenide (2) which was structuComplex [Na(THF)6][(rl-CPBUt)6Nd6(~6-se)(~2-Se2)6], rally c h a r a c t e r i ~ e d . ~ ~ , ~ ~

But& 1

2

Reactions of metallocenes with water were noted frequently. The trichlorides of La, Nd, Sm and Gd react with [C5H4CMeRCH2CH=CH2]MgC1(R=Me, Pr) in THF to give [C5H4CMeRCH2CH=CH2]LnC12MgC12.THF (Ln = La, Nd, Sm, Gd). Recrystallization of the Nd and Gd compounds from ’moist’ TH F-hexane gives the hydrolysis product [C5H4CMeRCH2CH=CH2] Ln(OH)C1.2MgC12(Ln = Nd, Sm, Gd). These compounds were characterized by ‘H NMR spectroscopy, and the hydroxy compounds were subjected to Xray analyse~.’”~’ Partial hydrolysis of cationic organolanthanide compounds [Cp”2Sm][BPh4]and [Cp”2Sm][CB1H6Br6] gave [(Cp”zSm)2(p-O)(p-OH2)]and two distinct crystalline forms of [Cp”2Sm(pOH)]z. These new observations together with the reported structure of [Cp’’2Sm(p-OH)]2begin to outline the stepwise procedure by which organolanthanide hydroxo compounds are converted to 0x0 compound^.^ The lanthanidocene chloride complexes [(q5-

’

4: Scandium, Yttrium and the Lanthanides

89

C5H4SiMe2R)2Ln(pC1)]2(R = But, Ln = Y, Sm, Lu; R = Me, Ln = Y, Sm, Lu) were prepared. The reactions of the R = M e compounds with MeLi in a 1:4 molar ratio in THF yield monomeric (q 5-C5H4SiMe3)2Ln(p-Me)2Li(THF)2 (Ln = Y, Sm, Lu). The R = But compounds react with two LiMe to give the new dimers [(q5-C5H4SiMe2R)2Ln(p-Me)]2(R = But, Ln = Y, Sm, Lu; R = Me, L n = Y , Sm, Lu) which are 'moderately stable'. Treatment of the latter compounds with stoicheiometric H20 in toluene yields the dimeric lanthanidocene hydroxide complexes [(qS-C5H4SiMe2R)2Ln(p-OH)]2(R = But, L n = Y , Sm, Lu; R = M e , L n = Y , Sm, Lu). The Lu hydroxide was characterized by X-ray diffraction. These Me derivatives are effective precatalysts for hydrosilylation of alkenes and a l k y n e ~ . ~ ~ 2.3 Cp* Chemistry. - The one-electron reduction of SePPh3 by the sterically crowded [ S ~ C P *complex ~] suggested that redox chemistry could be done with any of the redox 'inactive' lanthanides, much as elemental S has been reduced ~] by Ln(EPh)3 to give S2- and PhEEPh. Thus, it was found that [ N ~ C P *does indeed function as a one-electron reductant: SePPh3 is reduced to Ph3P, with the concomitant formation of both (C5Me5)2 and a rare example of a molecular complex with a (SeSe)2- ligand, [(C~*~Nd)~(p:q~:q~-Se2)], (3). The ~ ] SePPh3 gave [ ((Cp*2Sm)(THF)}2(p-Se)]. analogous reaction of [ S ~ C P *with Both the Nd-Se and Sm-Se products were structurally ~haracterized.~~ Tris(peralkylcyclopentadieny1)samarium complexes with two rings connected by a Me2Si group were synthesized for comparison with [ S ~ C P * ~The ] . halide Sm13 reacts with MeZSi(CSMe4)2 in THF to give the mono-iodide which reacts further with KC5Me4R in toluene to give [Me2Si(C5Me4)2Sm(C5Me4R)] and in THF to give [Me2Si(C5Me4)2Sm(Cp*)(THF)].In a striking contrast to the reactivity of ( c ~ * ) ~ S m these , products do not ring-open THF, do not reduce 1,3,5,7-CgHgor Ph3PSe, and do not polymerize ethylene at 50 psi.34 In other redox chemistry, reactions of C P * ~ S ~ ( T H and F ) ~ benzophenone imine gave the corresponding diphenylmethylamine-coordinated amido that was isolated and charSm(II1) complex [Cp*2Sm(N=CPh2)(NH2CHPh2)] acterized by NMR spectroscopic and X-ray crystallographic techniques. This complex was probably formed via an imine radical anion intermediate. Reaction of Sm[N(SiMe3)2]2(THF)2with N-phenylfluoreneimine gave a fluorenimine-dianion samarium(II1) complex, Sm[q2-PhN-C(C12Hg)][N(SiMe3)2](THF)3, the first example of a Ln(II1) compound with an imined i a n i ~ n NdI2 . ~ ~ and Dy12 were obtained by heating a mixture of Ln and 12. Dissolving of the compounds in THF at low temperature allowed preparation of the first molecular iodides of Nd(I1) and Dy(II), Nd12(THF)5, D Y I ~ ( T H F ) ~ , and D Y I ~ ( T H F )Reduction ~. of (RO)TmIz(THF)3 ( R = t-Bu, Ph) by Na in THF affords Tm12(THF)5. The reaction C P * ~ T ~ I ( T H Fwith ) Na in DME gives an unusual complex { Na(p-MeO)2TmCp*(p-Cp*)Na(p-DME)2Na(pCp*)Cp*Tm(p-MeO)2Na(p-DME)),., which was structurally ~haracterized.~~ The reactions of [ C P * ~ S ~ ( C H ~ P ~ ) ( T Hwith F ) ] small molecules were studied, where the main objective was to detect insertion into the Ln-C bond. With N 2 0 an insertion reaction is observed, yielding the dimer

90

Organ ometa11ic Chemistry

[Cp*2Sm(ONNCH2Ph)]2,(4). The two Sm ions are linked via an (q1:q2)bridge by two PhCH2NN0 ligands. A nearly planar six-membered central Sm2N202ring is formed. Two Cp* ligands complete the coordination sphere of each Sm ion, which are thus surrounded by four ligands each and have a distorted tetrahedral coordination geometry. SCN- insertion into the Ln-C bond was not observed. Instead substitution of the benzyl ligand occurred giving a polymeric chain structure [K(1S - C ~ O W ~ - ~ ) C ~ * ~ Y ~ ( N C S ) ~ ] ~ . ~ ~ The solid state structure of { [Cp*2Nd(THF)]2(p-Cl)}BPh4consists of a cation with THF-solvated decamethylneodymocene units connected symmetrically by a chloride. The BPh4 anion does not ~oordinate.~'Reaction of neodymium metal with 3/2 I2 in iso-propanol, followed by crystallization from THF, gives NdI3(THF),, which reacts with KCp* to produce the mono-Cp* derivative Cp*NdI2(THF)3 in moderate yield. Treatment of this diiodide with an excess of pyridine in toluene gives Cp*NdI2(py)3, which reacts further with KCp' to yield the mixed-ring complex [Cp*Cp'NdI(py)]. All of the Cp* compounds were structurally characterized."

The reaction of SmC13 with three KO-2,6-But2C6H3 (KOAr) in THF produces the tris(ary1oxide) complex Sm(OAr)3(THF), which reacts further with LiCp* to give [Cp*Sm(OAr)2(THF)]. In contrast, an analogous reaction of LiCp* with the 2,6-di-iso-propylphenoxide complex Sm(OAr*)3(THF)2 (Ar* = 2,6-Pr12C6H3)leads to overall addition of the alkali metal reagent, and isolation of the lithium-containing 'ate' complex [Cp*Sm(OAr*)(p-OAr*)2Li(THF)]. The heteroleptic compounds exhibited three-legged piano-stool ge~metries.~'X-ray crystallographic and neutron diffraction studies of Cp*Y(OAr)CH(SiMe& (OAr = OC6H3But2-2,6),neutron diffraction study of Cp*La{CH(SiMe&} 2 and a density-functional study of (Cp)La{CH (SiMe3)2) are reported, which clearly show that the p-Sic agostic interaction predominates over a-CH, a-CSi, and y-CH interaction^.'^ Finally, the reaction of (2,3,4,5-tetramethylphospholyl)potassium, K(C4Me4P), with [LnC13(THF),] (Ln = Nd, n = 1.5; Ln = Sm, n = 3) in a 2: 1 ratio gave unsolvated 'ate' complexes [(C4Me4P)2LnC12K] that are analogous to known Cp* complexes. Crystallization from ether afforded { [(q5C4Me4P)Sm(p3-C1)2(p:q5,q '-C4Me4P)K(OEt2)], f , which was characterized by X-ray crystallography. Metathesis with [LiCH(SiMe3)2] gave the alkyl complexes [(C4Me4P)2LnCH(SiMe3)2](5), which can also be prepared directly by a one-pot procedure. Hydrogenolysis of [(C4Me4P)2LnCH(SiMe3)2] gave [(C4Me4P)2NdH]when Ln = Nd, whereas, when Ln = Sm, reduction occurred and [(C4Me4P)2Sm]was isolated instead.41

4: Scandium, Yttrium and the Lanthanides

91

2.4 Donor Cp Chemistry. - Most of the Cp ligands with tethered Lewis base functional units incorporated oxygen donors. Reaction of LnC13 (Ln = Sm, Yb) with three equivalents of MeOCH2CH2CSH4K in THF, followed by treatment with trans-(+)-2,2’-[1,2-cyclohexanediylbis(iminomethyl)]diphenol gave [(q5:q MeOCH2CH2C5H4Sm)]2[(p:q-OC20H20N20)]2[q5MeOCH2CH2C5H4Sm]a dimer connected by two bridging 0 atoms of the Schiff base ligands, and [(MeOCH2CH2C5H4)2Yb]2(0C20H20N20), respectively. Further studies on the reaction of (MeOCH2CH2C5H4)2DyCIwith the disodium salt of trans-(+)-2,2’-[ 1,2-cyclohexanediylbis(iminomethyl)]diphenol gave [ ( M ~ O C H ~ C H ~ C ~ H ~ ) D Y ( O C ~ O an H~O analog N ~ ~ )of ] ~ ,the Sm complex.42 The synthesis of new chiral 0-hydroxy-cyclopentadienylligands CSHSCH2CH(Rl)OH (Rl = Me, CH20Me, Ph), obtained by the nucleophilic ring opening reaction of enantiopure epoxides by C5H5-, was described. The bi-metalation of these ligands by Na, K or BuLi is facile, to give [C5H4CH2CH(R1)O]M2 (M = Li, Na, K). Further reactions with Ln13 gave ((S)-C5H4CH2CH(Me)O)LaI(THF)2 and ((S)-C5H&H2CH(Me)O)SmI(THF), where the change in geometry clearly reflects the smaller size of the Sm(II1) ion. The syntheses and X-ray structures of new Sm complexes with allenyll propargyl ligands were described. The allenyl/propargyl ligands can assume three types of coordination mode such as q3-propargyl, q’-propargyl, and q3allenyl, depending on the electronic and steric environment of the Sm center. Metathesis reactions of lithium propargylsilylcyclopentadienide with SmC13 gave propargylsilylcyclopentadiene Sm complexes that were structurally characterizede4 A synthesis and crystal structure of the Yb(I1) half-sandwich complex [ ((q5-C~Me4)SiMe20SiMe2(q ‘-O))Yb(thf)]2 (6) incorporating the new linked Cp-silanolate ligand was reported.45

’-

6

The trialkylborohydride (C5H4CH2CH20Me),Nd(HBEt3)was found to be stable in solution. By contrast, the hydride (C5H4CH2CH20Me)2NdH,formed from (C5H4CH2CH20Me)2NdCl and NaH or by hydrolysis of (C5H4CH2CH20Me)2NdR (R = CH2SiMe3 or CH(SiMe3)2), is unstable with respect to ligand redistribution and the formation of (C5H4CH2CH20Me)3Nd. While not observed directly, this hydride can be trapped with propanone or pivalone to give the alkoxides (C5H4CH2CH20Me)2NdOCHR’2(R’ = Me or CMe3).46 Structurally characterized, chiral, heterobimetallic Li[Y(q5:q I C5R4Si-Me2NCH2CH20Me)2] (R = Me, H) compounds were shown to be active in the controlled ring-opening polymerization of L-lactide to give high molecular weight poly(L-lactide)s, with little concern for transesterification and racemization processes.47

92

Organometallic Chemistry

There was only one example of a tethered donor containing a second row element, in this case a thioether derivative, and only one tethered olefin. YC13 reacts with two Na[C5H4(CH2)2SEt] to form [q5-C5H4(CH2)2SEt]2YCl. Hetero-Cp compounds can be approached in the stepwise reaction of LuC13 with Na[C5H4(CH2)2SEt]and NaCp* to give [Cp*(q-C5H4(CH2)2SEt)LuCl]. Reactions of these thioether compounds with MeLi gave the corresponding Ln-CH3 products?’ 2.5 Indene Chemistry. - The structure of [(C9H7)3Dy(THF)]was also determined, and the indenyl group is bonded to dysprosium in an ‘q3 + q2’ fashion.49 An indenyl compound was found to be an active hydroamination catalyst. Metathesis of dilithiated 1,2-bis(indenyl)ethane with either YbC13 or LuC13 in THF followed by solvent exchange with Et2O gives [(CH2CH2(qSC9H7)2)LnC13][LiC1(Et20)z] (Ln = Yb, Lu). In the Yb case, the major diastereomer formed is meso, while in the Lu reaction, the rac diastereomer predominated. Further, meso-[ethylenebis(q5-CgH7)]ytterbium(III) bis(trimethylsily1)amide was synthesized by the reaction of meso-[[ethylenebis(q5C,H7)]YbC13][LiCl(Et20)2]with NaN(TMS),; this material was characterized by X-ray diffraction, and catalyses the cyclic hydroamination of primary amino olefins in excellent yields.50 Divalent indenyl compounds also attracted interest. Redox reactions of Sm(C9H7)2with 12,(C6H5C02)2and [(C2H5)2NCS2]2cleaved 1-1, 0-0, and SS bonds, to give the extremely air and moisture sensitive Sm(II1) organometallic complexes, (CgH7)2SrnI(THF), [(C9H7)2Sm(C6H5C02)]2, and { (C9H7)2Sm[(C2H5)2NCS2]]2.51 Racemic (Me2NCH2CH2C9H6)2Sm and (Me2NCH2CH2C9H6)2Yb have been synthesized by the reaction of (Me2NCH2CH2C9H6)Kwith Ln12 (Ln=Sm, Yb). The Yb compound was structurally characterized revealing that the nitrogen atoms of both dimethylaminoethyl groups were intramolecularly coordinated to the Yb yielding an eight-coordinated Yb(I1) ion.52 Finally, metallation of 2,2-bis( 1-indenyl)propane by NaH followed by the reaction with YbC13 yields the reduced product (CgH7)2Yb.DME, a divalent complex with unlinked indenyl ligands. The reaction between (LCH2CH2L)Li2 (L = 1-indenyl, 4,7-dimethylindenyl) and YbC13 in Et2O with subsequent reduction of the product by Na metal in THF gives ~ ~ C - ( L C H ~ C H ~ L ) Y ~ ( T H F ) ~ . ~ ~ 2.6 Linked Cp Chemistry (see also section on carboranes). - A number of reports focused on structural descriptions of new compounds. The ansaytterbocene meso-Me2Si(C5H3-3-SiMe3)2YbC1(THF) desolvates when crystallized from toluene to give dimeric [meso-Me2Si(C~H3-3-SiMe3)2Yb(p2-Cl)]2, and reacts with LiBH4 in ether to give meso-meso-Me2Si(C5H3-3-SiMe3)2Yb(BH4)(THF) with a triply bridging BH4 ligand.54 Lithiation of dimethylsilyl-bridged fluorene with BuLi in Et2O followed by treatment with YC13 gave Me2Si(C13H&Y(p-C1)2Li(OEt,),, which was structurally characteri ~ e d .Reactions ~~ of LnC13 with Li2(CI3H8)CPh2(C5H4)in THF gave [Li(THF)4][LnC12{(C13HS)CPh2(CSH4)}] (Ln = Lu, Y). Treatment of

4: Scandium, Yttrium and the Lanthanides

93

[Ln(BH4)3(THF)3]with three equivalents of (C13H8)CPh2(C5H4)Li2 in THF solution gave the ionic structures [Li(THF)4][Ln(BH&{ (C13H8)CPh2(C5H4))] (Ln = La, Nd). The crystal structures of the Lu, La and Nd compounds were determined to confirm the nature of the ionic structures.s6 Racemic ansalanthanocene alkyl complexes, ~ ~ c - [ O ( C H ~ C H ~ C ~ H & ] L ~ C(Ln H &=M Y,~ ~ Lu), were directly isolated and structurally characterized. The complexes feature a rigid unsymmetrical structure with the alkyl group paralleling the bridged indenyl planes.57Reactions of the dipotassium salts K2[Me2Si(C5H3-3B U ' ) ( C ~ H ~ - ~ - ( C H ~ ) ~K2[Me2Si(C5H3-3-SiMe3)(C5H3-3-(CH2)2NMe2)], NM~~)], and K2[Me2Si(C5H2-3,5-ButMe)(C5H3-3-(CH2)2NMe2)] with LnC13(THF), (Ln = Y, La, Nd, Sm, Er, Lu) gave [Me2Si(C5H3-3-But)(C5H3-3(CH2)2NMe2)]LnCl (Ln = Y, Sm, Lu), [Me2Si(C5H3-3-SiMe3)(C5H3-3(CH2)2NMe2)]LnCl (Ln = Y, Sm, Lu), and [Me2Si(C5H2-3,5-ButMe)(C5H3-3(CH2)NMe2)]LnCl(Ln = Y, Nd, Sm, Er, Lu), respectively. In the latter group of compounds, the molecular structures of the Sm and Lu derivatives were determined by single crystal X-ray diffraction. Metathesis of the above chlorides with LiMe, LiCH2SiMe3, or LiCH(SiMe3)2 gave the alkylmetallocenes [Me2Si(C5H3-3-But)(C5H3-3-(CH2)2NMe2)]LnR (R = Me, Ln = Y, Sm, R = CH2SiMe3, Ln = Y), [Me2Si(C5H3-3-SiMe3)(C5H3-3-(CH2)2NMe2)]YMe, and [Me2Si(C5H2-3-But-5-Me)(C5H3-3-(CH2)2NMe2)]LnR (R = Me, CH2SiMe3, Ln = Lu; R = CH(SiMe3)2,Ln = Nd, Lu).58759 SiMe,

SiMe3

Me2siwMe Me

7

8

Variable-temperature 'H NMR spectroscopy was used to investigate the fluxional behavior of ansa Group 3 allyl complexes. Spectral simulations and line shape analyses suggest an allyl rearrangement mechanism involving ratedetermining C-C double-bond dissociation from the metal center, i. e. an q to q change in coordination. Activation barriers to olefin dissociation were determined for [Cp*2Sc(q3-C3H5)],meso-Me2Si(q5-C3H5-3-Bu')2Sc(q3-C3H5), meso-Me2Si[q'-C5H2-2,4-Pri2]2Sc(q3-C3H5),meso-Me2Si{ q '-3-[2-(2-Me)adamantyl]C3H5)2Sc(q3-C3H5), meso-Me2Si { q5-3-[2-(2-Me)adamantyl]C3H5)2Y (q3-C3H5), rac-Me2Si[q5-C5H2-2,4-Pri2]2Sc(q3-C3H5), and R-(C20H1202)Si(q5CSH2-2-SiMe3-4-But)2Sc(q3-C3H5).For all compounds, a range of AG = 11-16 kcal mol- at ca. 300-350 K was obtained. These dynamic processes appear to be solvent independent. A second rearrangement mechanism involving 180" rotation of the q3-C3H5 moiety was found to operate in metallocenes with ancillary ligand arrays in rigid meso geometries. Line shape analysis indicates that the rate of q3-C3H5rotation is generally more than an order of magnitude faster than olefin dissociation for a given meso metallocene. The data did not allow unambiguous assessments of the exchange mechanism(s) for the allyl derivatives of the racemic metallocenes.60

94

Ovganometallic Chemistry

2.7 Naphthalide Complexes. - Naphthalide chemistry provided two unusual synthetic approaches to alkoxide materials. (R'0)3Tm (R' = Ph or 2,4,6were products in the reactions of the naphthalene complex [(CloHs)Tm(DME)]2(C10H8) with an excess of the corresponding phenol. Also described was the synthesis of the ~ , ~ - B U ~ ~ C ~ H ~ ~ from ~ T ~ the I(DME)~ reaction of Tm12(DME)3with 3,6-di-t-butylbenzoquinone1,2 or 3,6-di-t-butylpyrocatechol, and the reactions of Tm12(DME)3with ROH (R = Ph or But) to give ROTm12(DME)2. (R0)2TmI(THF)2were synthesized from Tm13(THF)2 and ROH (taken in a ratio of 1:2).6' Similarly, the reduction of NdC13 with Li metal in THF in the presence of naphthalene produces a heterovalent aggregate with the composition pdC12(THF)2LiCl],CloHg (n = 4-7). This aggregate reacts with 2,4,6-t-Bu&jH2OH in THF to give [ {NdC12(2,4,6-tB U ~ C ~ H ~ O ) ( ~ - C ~ ) (Li(THF)2]2 T H F ) > in 70% yield.62Reactions of naphthalides with more unconventional H donors led to rare examples of compounds with Ln-Ge bonds. (Ph3Ge)2Eu(THF)4 and (Ph3Ge)2Eu(DME)3were synthesized by reacting Ph3GeH with Eu naphthalene, CloHgEu(THF)2, in THF or DME, respectively. A heteroleptic complex Ph3GeEuI(DME)2 is similarly obtained in the reaction of Ph3GeH with CloHg[EuI(DME)2]2in DME, but this compound is unstable with respect to ligand redistribution and formation of EuI2/ Eu(G~R~)~.~' Reactions of naphthalene with elemental Ln (Ln=Eu, Yb) gave a new class of complexes in which both naphthalides are coordinate to the Ln(I1) ions. Interestingly, the donated electrons are spin-paired, and ESR (EPR) spectroscopy of the Eu compound reveals a significant interaction between Eu(I1) and the naphthalide anion.64 These interactions are reminiscent of the unusual magnetic behaviour of the early bipyridine complexes Ln(N2C10H8)4(Ln = Eu, Yb).65 Related bipyridine complexes can also be obtained by displacement of naphthalide. Trimeric [ {Yb(p2-N2ClOHg)(thf)2)3] is formed by the reduction of 2,2'-bipyridine with ytterbium naphthalide as well as by the reaction of [Yb12(thf)2] with [Li2(bipy)] in THF at room t e m p e r a t ~ r e . ~ ~ 2.8 COT Chemistry. - Redox chemistry was noted in heteroleptic COT/Cp* systems. In an analysis of how electron configuration influences structure, divalent [(Cp*Ln)2(p-q8:q8-COT)](Ln = Eu, Yb) (9) were synthesized and structurally characterized. [Cp*Ln(THF)]2(p-q8:q8-COT)was prepared in the reaction of Ln12(THF)2 with KCp* and K2COT in THF to form [Cp*Ln(THF)12(p-q8:q8-COT). The THF is lost in vacuo at room temperature (Ln = Yb) or on warming (Ln = Eu). The CpLn-COT angles were 160" (Yb) and 149" (Eu). The Yb compound reduces neutral COT to give C P * Y ~ ( C O T ) In . ~ ~addition to the bimetallic COT derivatives noted above, there were reports of mixed Ln/Li and Ln/Na COT compounds. The ionic complex [Li(diglyme)2][{ 1,4-R2CsH6}2Sm2(p-C1)3](R = o-(dimethylsily1)-N,Ndimethylaniline) was synthesized by the reaction of the ligand with SmC13 and characterized by X-ray diffraction. The (p2-C1)3 unit is unique in organolanthanide systems. In the solid state the aniline functionality does not

4: Scandium, Yttrium and the Lanthanides

95

coordinate to the samarium(II1) ion, but relaxation experiments indicate some coordination in solution. DFT calculations suggest an intramolecular interaction. Reaction of Li2( 1,4-R2C&6) with [(COT)SmI(THF)2] gives the ligand redistribution product [Li(THF)3{(p-q': q8-COT)}Sm(COT).68 The first heterobimetallic organolanthanide complex, vb(THF)6][Ce(1,3,6-(Me3Si)3CsH5)2]2,was prepared by the reduction of neutral [Ce(1 ,3,6-(Me3Si)3C8H5)2] with Yb metal in THF. Both cation and anion fragments have literature pre~edent.~' Gas phase species,Ln,(COT),+l [Ln = Eu and Ho], are discussed elsewhere in this review.70 Finally, while [(COT)Ln{ N(SiMe3)2}(THF)] compounds of the later lanthanides are well documented, the red Sm analog has just been isolated from the reaction of [(COT)SmCl(THF)]2with Na[N(SiMe3)2.71

9

10

11

2.9 Miscellaneous Ancillary Ligands. - The exploration of alternatives to the cyclopentadienyl ligands continues to expand. Organometallic compounds based on a range of such ancillaries will be discussed below. 2.9.I Nitrogen-based donors. A number of different nitrogen based ligands are currently being explored. Pyrazolylborates continue to show promise. The first = hydrotris(3-t-butyldivalent lanthanide hydride, [(Tp'Bu3Me)YbH]2 (TptBu7Me 5-methyl-pyrazoly1)borate) (10) was prepared by reaction of [(TptBuVMe) Yb(CH2SiMe3)(THF)].72The synthesis of the first mixed Tp/Cp lanthanide complex, s m ( T ~ ~ ' ~ ) ~ (has C pbeen ) reported by reaction of with TlCp. Heating the mixed complex in a sealed tube gave [Sm[HB(3,5Me2Pz>2(C5H4)1(173~TPMe2)l, (1 Both chelating and macrocyclic pyrrole-based ligands have provided a number of exciting developments. The first example of a four-electron dinitrogen reduction achieved through the cooperative one-electron oxidation of four metal centers was reported. The reaction of [SmIz(THF)2] with one equivalent of diphenylmethyldipyrrolide dianion under N2 yielded [{ [pPh2C(q :q5-C4H3N)2]Sm) 4(p-q :q :q2:q2-N2)] (12). The complex remained unchanged upon prolonged exposure to heat or vacuum. The same reaction carried out under Ar afforded [{[p-Ph2C(q1:q5-C4H3N)2]2[Sm(THF)]3)(p3I)][ { [p-Ph2C(qi:q5-C4H3N)2]Sm) 5(p5-I)].Reaction of the latter with KH under N2 and resulted in an immediate color change and concomitant release of H2 giving the dinitrogen complex, elemental Sm, and KI. Reaction of diphenylmethyldipyrrolide dianion in THF with [SmC13(THF)3] followed by K metal and a catalytic amount of naphthalene gave [{[p-Ph2C(q1:q5-

96

Organometallic Chemistry

C4H3N)2]Sm)4(p4-C1) { K(THF)2}. All three complexes have been structurally characterized.74

G N - N a - N a

,'ex,:;

THF-Sm-N=N-Sk-THF

N

PI

N r P h

Ph

Dc. rii

12

13

14

Porphyrinogen ligands are being investigated. The reaction of rnesooctaethylporphyrinogen-lanthanide complexes, [{ (q 5:q1:q5 :q1 -Et,N,)M)Na(THF)2] [M = Pr, Nd], with sodium naphthalide in an ethylene or acetylene atmosphere gives dimeric species, where the metals are bridged by the [C2H4I2- (13) and [C2I2- (14) anions.75The complexation of LnfIII) ions by the rneso-octaethylporphyrinogen [Et8N4H4], has been achieved by reacting the sodium derivative [EtgN4Na4(THF)3], with [LnC13(THF)2]. The products isolated depended on the solvent used for the reaction or for the recrystallization. From THF, [{(q5:q1:q5:q1-Et8N4)Ln(THF)}-q3-Na(THF)2] [Ln = Pr, Nd, Sm, Eu, Gd, Yb] (type A) monomeric complexes were obtained. From dioxane, dimeric products (type B) were isolated with dioxane bridging the sodium cations of the [{(q5:q':q5:q '-Et8N4)Ln(DME)}-q3-Na](dioxane)l.5 [Ln=Nd Sm]. In a third category (type C), two monomeric anions [(q5:q1:q5:q'-Et&)Ln]sandwich two sodium cations in q2:q3 fashion through the pyrrolyl anions i. e. [ { (q ': q :q5:q -Et&)Ln) 2-q2:q 3-Na2] [Ln=Pr, Sm]. The recrystallization of type A complexes from DME led to dimeric organometallic complexes, where the dimerization occurred by desolvation of the Ln ion and formation of a Ln-C 0 bond with the P-carbon of a pyrrole of an adjacent Ln-porphyrinogen unit. Such dimers occur in the ion(Ln = Pr, Nd, Sm, Gd, Eu). separated form [(~5:~':~5:~*-EtgN4)2Ln2][NitS~2 Recrystallization from THF led to ion-pair derivatives in which two sodium cations are q2-bonded to the ql-pyrrolyl anions of the dimer [{(q5:q1:q5:q1Et8N4)2Ln2}-q2(NaS,)2] [Ln = Pr, Nd, Sm, Gd; S = DME, THF; n = 21. When these latter complexes were crystallized from THFIdioxane, polymeric structures were isolated, in which the cations are bridged by dioxane molecules [{(q5:q1:q5:ql-Et8N4)2Ln}2q2{Na(THF))2(p-dioxane)] [Ln = Nd, Gd]. The crystal structures of examples of all of these complexes have been obtained.76 Treating [Sm12(THF)2]with [(R8-calix-pyrrole)Li4][R = Et, (CH&] in THF gave paramagnetic, isomorphous enolate derivatives, which upon exposure to ethylene in hexane gave [[(R8-cali~-pyrrole)[(CH2=CHO)Li][Li(THF)]~Sm]~(pCH2CH2)]. Examples of each type of complex have been structurally characterized.77

'

4: Scandium, Yttrium and the Lanthanides

97

The chemistry of other lanthanide amides continues to grow in richness. The reaction of Ln[N(SiMe3)2]3(Ln = Sc, Yb, Lu) with NaN(SiMe3)2in THF leads to deprotonation of a methyl group giving the cyclic complexes [Na(THF)3LnCH2SiMe2N(SiMe3)(N(SiMe3)2f2] (Ln = Sc, Yb, Lu). The methylene carbon is in an unusual trigonal bipyramidal geometry. DFT calculations on a Sc model compound showed a very large negative charge on the pentacoordinate C atom localized in a predominantly p-character lone-pair orbital. Thus the C-Sc interaction is mainly coulombic. In a quite unusual reaction, 2,6-xylyl isocyanide can be inserted into the Yb-CH2 bond and a five-membered YbNCSiN heterocycle results (15). The exocyclic methylene group undergoes C-C coupling resulting in a dimeric structure with concomitant Yb reduction. At the same time, Na 7-methylindolate is formed, which together with paN(SiMe3)2(THF)2] forms a dimeric aggregate paN(SiMe3)2(THF)2-Na.(C9H16N)]2. All of the species have been crystallographically ~haracterized.~~ The reaction of one equivalent of dilithiated O(SiMe2-Ap)Z [Ap-H = -N(2amino-4-methylpyridine)], generated in situ, with LnC13 (Ln = Y, Sm) in THF affords O ( S ~ M ~ ~ - A P ) ~ L ~ C ~ ((Ln T H=FY, ) , n = 2; Ln = Sm, n = 3). Reaction with LaBr3, however, affords the ‘ate’ complex (O(SiMe2-Ap)2)2LaLi(THF)3. Crystal structures show the O(SiMe2-Ap) ligand to bind in a planar tetradentate manner. The yttrium complex can be derivatized using Bu4NBH4, NaBH4, or LiCH(SiMe3)2to give the corresponding ‘ate’ complexes [O(SiMe2[O(SiMe2-Ap)2Y(BH&Na(THF)2], and Ap)2Y(BH4)C1(THF)]Bu4N, [O(SiMe2-Ap)2Y(CH(SiMe3)2)2Li(THF)3], respectively. The alkyl was used as an initiator for the ring-opening polymerization of E-caprolactone or 6valerolactone. In both cases an almost linear relation between the monomerto-initiator ratio and the MW of the resulting polyester was ob~erved.~’ (Me3Si)2NI

,!\*

‘s

(Me3Si)2N‘Yb’N’

-N

N(SiMe&

~Sixt,(yb‘N(SiMe3)2

15

I 16

The chiral bidentate ancillaries are of growing importance. The yttrium bis(sily1amido)biphenyl complex [DADMB]YCl(THF)2 (DADMB = 2,2’bis((tert-butyldimethylsilyl)amido)-6,6’-dimethylbiphenyl) was prepared from Li2[DADMB].2THFand YC13(THF)3.The complex reacts with LiR (R = Me, CH(SiMe3)2) to give the corresponding alkyl derivatives [DADMBIYMe(THF)2 (16) and [DADMB]Y[CH(SiMe3)2](THF)(OEt2). Both alkyls react with phenylsilane or H2 to give the insoluble dimeric yttrium hydride ([DADMB]Y(p-H)(THF)>2.C6H6.The alkyls exhibit only limited olefin polymerization activity; however, the hydride reacts rapidly with ethylene or 1hexene to give a single insertion product. The resulting yttrium ethyl complex

98

Organometallic Chemistry

was structurally characterized.80More interestingly, the Y hydride { [DADMB]YH(THF)12 is an active olefin hydrosilylation catalyst. Initial studies of the enantioselectivity of the chiral catalyst show that 90% e.e. can be achieved in the hydrosilylation of norbornene with PhSiH3. Kinetic studies support a mechanism consistent with the generally accepted one for hydrosilylation catalysed by early transition metal species, involving rapid olefin insertion into a Y-H bond followed by a Si-C bond-forming 0-bond metathesis of the resulting Y alkyl with silane.81

2.9.2 Carborane-based ligands. The use of carboranes has resulted in a number of exciting developments. Treatment of LnI2 with K ~ [ ( C ~ H ~ C H ~ ) ~ C ~ B ~ O H ~ (K2T) gave the monomeric exo-nido-TLn(DME)3 (Ln = Sm, Yb) (17). The complexes can react with a further equivalent of Na2T to afford closo-exoYb). Reaction of Ln12 with T4Ln2Na4(THF)2 (Ln = Sm, Na2[(C6H5CH2)2C2B9H9]in THF produces the dimeric [exo-nidu((C6H5CH2)2C2B9H9)Ln(THF)3]2 (Ln = Sm, Yb). Interestingly the alkali metal carboranes can act as reducing agents. Reaction of YbC13 with two equivalents of K2T yielded the divalent complex T4Ln2Na4(THF)2,while corresponding treatment of SmC13 generated a novel mixed valence cluster closo-exo-T4Sm2Na3.Several crystal structures were obtained. This study indicates that steric factors dominate the formation of exo-nido-lanthanacarboranes and that closo- and exo-nido-lanthanacarboranesare interchangeable by altering the metal to carborane ratio.82 A rich chemistry of ansa Cp-carborane compounds has been uncovered. The readily prepared Na[Me2Si(C5H4)(C2B10H1 I)], NaXH, reacts stepwise with LnC13 in THF to give [(q5-XH)LnC12(THF)3](Ln = Nd, Sm, Er, Yb) and [(q5XH)2LnC1(THF)2] (Ln=Nd, Sm, Y, Gd, Yb). Interaction of the doubly deprotonated dianion Li2[Me2Si(C5H4)(C2BloH10)1, Li2X, with LnC13 in THF in a molar ratio of 1:l or 2:l or deprotonation of ( T ~ ~ - X H ) ~ L ~ C ~with (THF)~ MeLi in THF gave the same compounds [{ q5:O-X}~L~][L~(THF)~] (Ln = Nd, Y, Er, Yb). Treatment of NdC13 with an equimolar amount of the trianion [Me2Si(C5H4)(C2B10H1 l)]K3 in THF or reaction of [(q5-XH)NdC12(THF)3] with excess K metal in THF produced [Me2Si(q5-C5H4)(q6C2B10HII)]Nd(THF)2in which the ligand rather than the metal has been reduced. The Sm analogue was isolated from an unprecedented redox reaction of Sm12 with two equivalents of [Me2Si(C5H4)(C2B10H11)]Na in THF. Under similar reaction conditions, however, interaction of LnC13 (Ln = Sm, Yb) with [Me2Si(C5H4)(C2BloH1 l)]K3 in THF afforded the divalent compounds ([Me2Si(q5-C5H4)(q6-C2BloHl l)]Ln(THF)2}{K(THF)2) (Ln = Sm, Yb) (18). Reaction of [q5:q6-Me2Si(C5H4)(C2Bl0H1 I ) ] S ~ ( T H Fwith ) ~ excess K metal in THF also gave the reduced species. Unlike the Sm12 case, YbI2 gave [q5Me2Si(C5H4)(C2BlOH1 l)]2Yb(II)(THF)2.All of these compounds were characterized by spectroscopic and elemental analyses, and most were characterized by single crystal X-ray diffra~tion.'~ A further development in this ansa-Cpl carborane system includes a description of the first organolanthanide compound to contain an q7-carboranyl ligand, [ { [q5:q7-Me2C(C~H4)(C2Blo-

4: Scandium, Yttrium and the Lanthanides

99

Hl l)]Er}2 { Na4(THF)9}],, which was synthesized by treatment of [q5XH]ErC12(THF)3 or [q5:q6-Me2C(C5H4)(C2BloHl 1)]Er(THF)2with excess Na metal in THF. The curious array of Na+ ions can be replaced by Er3+ ions, giving the novel tetranuclear cluster [{ q5:q7-Me2C(C&)(C2B1~H11))Er&Cl)(THF)3]2. All of these compounds were characterized by X-ray crystallography.84

17

18

19

Broadly analogous chemistry has been reported for ligands in which the Cp is replaced by an indenyl group. Of particular interest is the observation that treatment of Me2Si(C9H6)(C2BloH11) with excess NaH in THF under UV light followed by reaction with one equivalent of LnC13 resulted in the isolation of unprecedented biscarborane compounds [LnC12(THF)5][p-CH(cZusu-C2BloH1l)-nido-CBloH11] (Ln = Er, Y).” Even more surprisinly, treatment of Me2Si(C9H7)(C2BloH11)with four equivalents of NaNH2 in THF, followed by reaction with LnC13, afforded the unprecedented [{ (q5-p2C9H6SiMe2NH)Ln)2(p3-Cl)(THF)]2(p4-NH) (Ln = Gd, Er, Dy) (19), which are not only rare examples of lanthanide imido complexes, but also the first examples of an organometallic clusters containing a central p4-imido group. Another type of tetranuclear cluster, [ { (q5-C9H6SiMe2)2N)(p2-NH2)Ln2(THF)2]2(p3-C1)2(p2-C1)2(Ln = Gd, Y), was obtained if the above reactions were carried out at elevated temperatures. This halogen-rich material can also be prepared by refluxing the (p4-NH) cluster compounds in THF in the presence of NaCl. Treatment of Me2Si(C9H7)(C2B10Hl 1) with eight equivalents of NaNH2 in THF, followed by reaction with LnC13 at room temperature, gave the trinuclear clusters [(q5-C9H6SiMe2)2~[p2,p2-Me2Si(NH)2](q5- p2-C9H6SiMe2NH)(p2-C1)2Ln3(THF)3 (Ln = Gd, Er). These results indicate that NaNH2 serves as both base and nucleophile in the reactions. The structures of all tetra- and trinuclear clusters were confirmed by singlecrystal X-ray a n a ~ y s e s . ~ ~ - ~ ~ Finally, The structure of the unusual neodymacarborane cluster compound, { [q5-1-Nd-2,3-(SiMe3)2C2B4H4]3[(p21-Li-2,3-(SiMe&C~B4H4)3( p3-OBut)][p2Li(THF)]3(p3-O)}has been reported.88

Organometallic Chemistry

100

2.9.3 Miscellaneous Organometallic Complexes. A rare example of an q6-arene complex, [ ( ~ l - c ~ H ~ ) N d [ N ( c ~ F(20), , ) ~ ]has ~ l , been isolated from the reaction of Nd[N(SiMe3)2]3with (C6F5)2NH in toluene. Related samarium complexes, [Sm(NHC6F5)2(THF)3]and smlr\T(siMe3)(C6F5)]3have also been prepared. The structures of these complexes reveal multiple Ln.. .F interaction^.^^ ITBonded phenyl groups have also been commonly observed in homoleptic 2,6diphenylphenolate (-Odpp) complexes. Thus the reaction of Eu or Yb metal with HOdpp in a sealed tube at high temperature gives [Eu2(0dpp)(p-Odpp)3], mb2(0dpp)2(p-Odpp)2] and the remarkable mixed-valent complex [Yb3(0dpp)7]. A range of different n-interactions were observed in these complexes.90 The feasibility of using [Zr2(0iPr)9]- as a stabilizing ancillary ligand in organometallic lanthanide complexes has been demonstrated. Complexes of the dizirconium nonaisopropoxide ligand are more soluble than analogous (CSH5)- derivatives. [([Zr2(0iPr)g]LnI}2]reacts with NaC5H5 to form the hexane-soluble complexes [ (Zr2(0iPr)g}Ln(CSH5)I (Ln = Sm; Yb), (21), which were structurally characterized. Similarly, [ { [Zr2(0iPr)9]LnI}2] reacts with K2CsHs to form hexane-soluble, hexametallic [{ [Zr2(OiPr)&n} 2(C&f8)] (Ln=Sm, Yb). The Sm complex reduces 1,3,5,7-C8Hs to form [{Zr2(0iPr)9}Sm(C8H8)],just as [{ (CSMe5)Sm}2(C8H8)]reduces CsH8. In all of these complexes, the [Zr2(0iPr)g]- unit is attached to the lanthanide metal in a tetradentate fashion.”

0 Pr‘ 20

21

Reactions of Ph2Yb(THF)2 and Ph3Ln(THF)3 (Ln=Ho, Tm, Yb) with H20, PhC-CH, C5H6, HgX2 and I2 have been studied.92 The complex (Ph3Ge)2Yb(THF)4can be synthesized in good yield of 63% by the reaction of Ph2Yb(THF)2 with Ph3GeH.93 Terphenyl (DmpH) derivatives have been prepared by reaction of DmpLi with YbC13. Addition of pyridine (py) and N-methylimidazole (N-MeIm) gave [(Dmp)YbC12(N-MeIm)2(py)].The amide derivative, Drn~Yb[N(SiMe3)~](pC1)2Li(THF)2,was also prepared. The crystal structures of both complexes were determined.94 Divalent Sm[1,3-bis(trimethylsilyl)pr0penyl]~(THF)~and Sm(1,3-diphenylp r ~ p e n y l ) ~ ( T H Fwere ) ~ synthesized by the reaction of potassium 1,3-bis(trimethylsily1)propenide or potassium 1,3-diphenylpropenide with Sm12. The aza-allyllanthanide compound was synthesized by the reaction of 2-pyridylbenzyllithium with SmC13 followed by the reaction with LiCH(SiMe3)2 to give

4: Scandium, Yttrium and the Lanthanides

101

(2-pyridylben~yl)2SmCH(SiMe~)~. 1,5-Diazapentadienyllanthanidewas prepared by the reaction of K[(C5H4N)2CPh] with YbBr2 to give Y ~ [ ( C S H ~ N ) ~ C P ~ ] ~ (22). ( T H FThe ) ~ propenyl complexes were found to be effective MMA polymerization catalysts.95Several other allylic compounds have been discussed in the Cp section.26 The reaction of the bidentate potassium alkyl { (C6H6)2K}2(C(SiMe3)2SiMe2CH212,K2L with YbI2 gave the expected chelated complex, YbL (23), which is somewhat more stable toward Et20 than the previously studied Yb { C(SiMe3)3)2.96 Finally the reductive cleavage of Se-C bonds in Ln(SePh)3 with elemental Ln, to give mixed valent (DME)4Ln4Se(SePh)* clusters (LQ = Sm, Sm2Yb2, Nd2Yb2, Yb4), has been reported. XAS and magnetic susceptibility measurements on the Yb4 compound indicated that these are localized mixed valence materia~s.’~ Ph

MezSi-SiMe2

I

-t\ yb+

Me3Si Me@

Pi

3

22

I SiMe3 SiMe3

23

Polymerization Catalysis

In [Cp*zLnHl2/[Me&(C~Me4)2LnH]2-mediated ethylene homo- or co-polymerization with other a-olefins, both primary arylsilanes (PhSiH3) and alkylsilanes (n-BuSiH3, PhCH2SiH3) function as efficient chain-transfer agents. In the case of ethylene polymerization mediated by [ ( c ~ * ) ~ S r n Hthe ] ~ mechanism , of chain transfer is supported by the observation that the weight of the capped polyethylenes formed at constant catalyst and ethylene concentration is inversely proportional to the concentration of PhSiH3.98Olefins were polymerized in the presence of H by the use of catalysts consisting bivalent C P * ~ S ~ ( T H Fand ) , organolithium and/or organomagnesium compounds.’’ Chiral silicon bridged [MeRSi(CSH4)(CSMe4)LnCl]2(R = Et, Ph; Ln = Y, La, Sm, Lu) dimers and molecular zirconocene dichlorides [MeRSi(CSH4)(CSMe4)ZrC12](R = Et, Ph) were synthesized. They react with sodium acetate to give the monomeric acetates [MeRSi(C5H4)(C5Me4)Ln02CMe](R = Et, Ph; Ln = Y, La, Sm, Lu). The zirconocenes are active catalysts for the polymerization of ethylene and propylene in the presence of MAO.’” Linked amido-cyclopentadienyl complexes of Group 3 and 4 metals constitute a class of structurally well-defined catalyst precursors for the polymerization of a variety of commodity monomers. They allow independent variation

102

Organometallic Chemistry

of both the ring- and amido-substituents and as well as the bridge." Yttrium alkyl and hydride complexes containing one linked amido-Cp ligand have been found to polymerize polar monomers such as acrylonitrile. Yttrium complexes of dibenzopyrolyl substituted Cp ligands are useful as ethylene polymerization catalysts for preparation of low molecular weight ethylene polymers having a high degree of terminal vinyl unsaturation. lo2 The lanthanide hydrides [ C P * ~ L ~are H ]highly ~ active species for the polymerization of ethylene to high molecular weight polyethylene, but they can also readily effect hydrocarbon C-H activation. The Cp*2La-systemwas found to be able to combine ethylene polymerization and C-H activation of thiophene to result in catalytic formation of polyethylene with 2-thienyl end-groups. This represents an alternative way to introduce a heteroatom functionality into polyethylene.lo3 Anionic or neutral allylic samarium or neodymium species catalyse the polymerization of styrene (catalystlstyrene ratio = 1:1000) without addition of a cocatalyst. Random syndiotactic-rich material is obtained from tetra-allyllanthanides, whereas neutral trisallyl-lanthanides or anionic ansa-bis(cyc1opentadieny1)bisallyl-lanthanides afford isotactic-rich polystyrene.'" Heterometallic complexes with general formulas [Cp*Sm(N(SiR3)2)Cp*M(THF)2]n and [Cp*Sm(N(SiR3)2)Cp*M(THF)3] (M = Na, K, R = alkyl) were used as catalysts for polymerization of styrene in PhMe at room temperature.lo5 The stereospecific polymerization of butadiene with high 1,4-cis selectivity was accomplished with a samarocene-based living polymer system achieved using modified M A 0 or AlR3/[CPh3][B(C6F5)4]as a cocatalyst.lo6 MAOactivated Nd( ~ l ~ - C ~ H ~ ) ~ ( d i oon x a nMAO-functionalized e) Si02 led to supported catalysts which allow the cis-l,4-polymerization of butadiene with a high activity of 50,000 mol butadiene/(mol Nd). The kinetics of butadiene polymerization with these supported catalysts in heptane had a first order dependence on md] and [diene]. Bisallyl ansa-Cp lanthanide complexes Me2C(q -C5H&Ln( allyl)2Li(DME) and [Ln(allyl)4]Li(dioxane)1.5 , where Ln = Sm, Nd, were used to form a copolymer of hex-1-ene and isoprene (1:lo). lo9 Gas phase conjugated dienes were also polymerized with a supported rare earth ally1 catalyst."' Methacrylates were polymerized with a variety of Ln(1I) and Ln(II1) compounds. Divalent [Sm[1,3-bis(trimethylsilyl)propenyl]2(THF)2, Sm( 1,3-diphenylpropeny1)2(THF)2, (2-pyridylben~yl)~SmCH( SiMe3)2, and Yb[(C5H4N)2CPh]2(THF)2were isolated and characterized. The divalent samarium and ytterbium complexes with bis(2-p yridylphenylme thy1)dimethylsilane were also prepared, and found to catalyse the formation of isotactic PMMA.95A proton transfer reaction of alkylsilyltetramethylcyclopentadienes with molecular w(CH2SiMe3)3(THF)2]gave a monoalkyl compound that was hydrogenated to give a dimeric p-hydrido complex. All of these compounds catalysed polymerization of But-acrylate, ethylene, and acrylonitrile. l o An AB-A copolymer comprising (meth)acrylic ester and olefin polymer blocks were prepared with [(MezSi)(MezSiOSiMe2)(4-Me&- 1,2-C6H3)2]Sm(THF)3 in toluene. Ansa-yttrocene compounds polymerized methyl methacrylate (MMA) in toluene, affording iso-rich PMMA.' l2 Fluorinated methacrylate

4: Scandium, Yttrium and the Lanthanides

103

polymers were prepared with C P * ~ S ~ M ~ ( T H asFa) catalyst,' l 3 while nonfluorinated derivatives were polymerized with C P * ~ L ~(Ln R = Sm, Y, Yb, La, Lu; R = H, Me, CH(SiMe3)2,C(SiMe3)3].' l4 The amido silyloxy complexes P a ( 12-crown-4)2][Ln(N(SiMe3)2}3(OSiMe3)] (Ln = Sm, Eu, Yb, Lu) were obtained from the trisamides Lnp(SiMe3)3]3and NaOSiMe3 in hexane in the presence of 12-crown-4; they form yellow to orange-red crystals, of which the Sm and Yb compounds were characterized crystallographically. The metal atoms of the complex anions are tetrahedrally coordinated (three N, one 0) with nearly linear M-0-Si geometries. With ethynylbenzene in the presence of NaN( SiMe3)2 in THF the trisamides M[N(SiMe3)2]3 react to form [Na(THF)3Ln(N(SiMe3)Z) 3(CCPh)] (Ln = Ce, Sm, Eu) of which the Sm derivative was characterized crystallographically and identified as an ion pair in which the terminal carbon atom of the CCPh ligand is connected with the Sm atom of the Sm[N(SiMe3)2]3group and the Na ion is side-on connected with the acetylido group. The amino derivative P a (THF)6][L~2(p-NH2)(p-NSiMe3) (N(SiMe3)2}4], which forms as a byproduct, consists of [Na(THF)6]+ions and dirneric anions, in which the lutetium atoms are connected to form a planar L u z N four-membered ~ ring via a pNH2 bridge. The vinylic polymerization of MMA catalysed by the Yb silyloxy compound gave high molecular weight PMMA with moderate yields, while the Sm analog was inactive."' A novel C,-symmetry yttrocene complex, ansa-Me2Si(r13-C13H8)(rl'C5Me4)YC12Li(OEt2)2,was isolated from the metathesis reaction of YC13 and the dilithium salt of the ansa-ligand. Structural characterization revealed an unusual q3 coordination of the substituted fluorenyl ligand. The compound reacts further with NaN(SiMe3)2 to give the corresponding bis(trimethylsily1) amide derivative Me2Si(C13H8)(r15-C~Me4)ErN(SiMe3)2.In this compound the Y-fluorenyl interaction is more conventional. The Y-N bond is described in terms of x-dative bonding, and there is a direct interaction between Y and one Me group of the amide. This compound is active for the polymerization of PMMA in toluene.' l 2 Arenethiolate complexes (Ln(SAr);! and Ln(SAr)3) were used as initiators for the polymerization of acrylonitrile in THF, giving atactic polyacrylonitriles. l 6 Alkene oxides are polymerized in the presence of Cp2LnX (X = halogen, alkyl) and organoaluminum compounds.' l 7 Ring-opening polymerization (ROP) of E-caprolactone (CL) has been investigated extensively. With Ph3Ln (Ln = Y, Nd, Sm) initiators in both bulk and solution high molecular weight polycaprolactone (PCL) can be obtained in high yield. The polymerization mechanism is through a coordinationdeprotonation-insertion process, by which the monomer inserts into the M-O bond of the Ln enolate.' l8 The catalytic activities of Cp2LnNR2 compounds have also been investigated. Both the central metals and the ligands influenced catalytic activity. For the central metal, the activity increased with increasing ionic radius of the metal; for the amido groups, NCSH10 was more effective than NPri2; and for substituted Cp ligands, CpBu' was more effective than CpMe. l9 Successful room temperature ROP of E-CL and 6-valerolactone "J

'

'

104

Organometallic Chemistry

(VL) was carried out using S m X 2 (X = I, Br, Cp) catalysts. Sm12in the presence of metallic Sm was found to have enhanced reactivity as a room temperature ROP initiator for lactones as compared to pure Sm12. SmBr2 and SmCp2 showed increased reactivity compared with the Sm/Sm12 system due to their higher reductive power.120 Oligomerization of E-CL and 6-VL was performed by using C P * ~ S ~ M ~ ( T H initiator, F ) ~ and the 26-mer, 28-mer, and 30-mer of E-CL were isolated in pure form by preparative SFC and characterized by mass spectra. In a similar manner, the 19-, 25- and 32-mers of 6-VL were isolated.67 The samarium(I1) aryloxide complexes Sm(OAr)2(THF)3 and [Cp*Sm(p-OAr)12(Ar = C6H2But2-2,6-Me-4)showed an extremely high activity for the ROP of E-CL and 6-VL. By using Sm(OAr)2(THF)3 as an initiator, polyesters with very high molecular weight and relatively narrow weight distributions were obtained. y-Butyrolactone (BL) did not polymerize under similar conditions. However, block copolymerization of BL with CL took place when both monomers were present. In all these polymerization reactions, quenching with methanol incorporatated a CH30 group into the end of polymer chain. 21 Ring-opening homopolymerization and copolymerization of 8-CL and lactide were initiated using tris(2-methylpheny1)samarium. 122 The compounds Cp*Sm2[OSi(OR)3I3, Sm[OSi(OR)3]3 or Cp*Sm3[0Si(OR)3]6 (R = aryl, alkyl) were prepared and used to catalyse the polymerization of caprolactone. 123 The synthesis and the biodegradation of optically active carbonate/&-CL copolymers using LdAlR3 catalysts was examined.124 ROP of DL-lactide (LA) was initiated with (rl3-C3H5)2Sm(~2-C1)2(~3-C1)2Mg(tmed)(~2-C1)Mg(tmed) (tmed = tetramethylenediamine). The effects of reaction conditions, such as reaction time, reaction temperature, and monomer/initiator molar ratio on the polymerization were determined. The results showed that (q3-C3H5)2Sm(p2C1)2(p3-C1)2Mg(tmed)(q2-C1)Mg(tmed) was effective for the polymerization of high molecular weight LA. The solvent affected the polymerization significantly. The polymerization mechanism was in agreement with the coordination mechanism. 12' The ring opening polymerization of E-CAor 6-VA catalysed by the Sm acetylide pa(THF)3Ln{N(SiMe3)2),(CCPh)] resulted in corresponding polylactones in quantitative yields. l5

'

4

Applications to Organic Synthesis

Divalent samarium reagents continue to find extensive applications in organic synthesis. [Cp*2Sm(THF)2] catalysed the acetylcyanation of aldehydes with acetone cyanohydrin in the presence of isopropenyl acetate under mild conditions to produce acylated cyanohydrins, e.g. hydrocyanation of compounds with a,fl-unsaturated carbonyls yield Michael addition products such as cyanoethyl methyl ketone. 12' Efficient conversion of hydroxy compounds into esters under neutral or near neutral conditions, even when tert-alcohols are used, can be accomplished with organosamarium or Group 3 metal compounds. For example, using [ C P * ~ S ~ ( T H Fcatalyst, )~] cyclohexanone oxime

4: Scandium, Yttrium and the Lanthanides

105

acetate reacts with octanol in toluene at room temperature to give octyl acetate in greater than 99% yield.127Dicarboxylic acid vinyl esters react with aldehydes to give glycol esters in the presence of organosamarium catalysts, which also effect the reaction of oxime esters with aldehydes to give glycol ester derivatives. This versatile addition reaction offers consistent reactivity for various aldehydes. For example, C P ~ S ~ ( T H Fcatalyses )~ the reaction of acetyloxyiminocyclohexane with butyraldehyde to give 3 -butyryloxy -2-et hylhexyl acetate. 12* Reductive coupling of aromatic carbonyl compounds with stoichiometric Sm(11) reagents (Sm12, Sm12/Me3SiC1, SmBr2, Sm/Me3SiBr, SmCp2) gave hydrobenzoin derivatives. Similarly, OH-functionalized poly(pxyly1ene)s were obtained by reductive coupling of aromatic dialdehydes. The use of solubilizing groups as well as the use of Me3SiX enhanced the polymerizability of the monomers under study.12’ The cycloaddition reaction of imines with epoxides in the presence of lanthanide complexes was examined. A mixture of N-( 1-methyl)ethylidenebenzylamine and isobutylene oxide in THF was reduced with Sm12 to give N-benzyl-2,2,4,4-tetramethyloxazolidine in good yield. Sm12 was found to be more efficient than organosamarium(I1) compounds.130 Intramolecular hydroamination of hindered amino olefins was catalysed by [Cp’2NdMeI2under mild conditions.13’ Enantioselective syntheses of aminoallenes, which then undergo regio- and stereoselective cyclohydroamination catalysed by the organolanthanide precatalysts Cp*2LnCH(SiMe& and Me2Si(C5Me4)(NBut)LnN(SiMe3)2, gave pyrrolidine and pyrrolizidine alkaloids. These reactive organolanthanide complexes efficiently mediate highly diastereoselective intramolecular hydroaminatiodcyclization reactions under mild conditions. The turnover-limiting step in these catalytic cycles is proposed to be intramolecular insertion into the Ln-N bond of the proximal allenic C=C linkage, followed by rapid protolytic cleavage of the resulting Ln-C bond. The rate and selectivity of the insertion process is found to be highly sensitive to the steric demand of the The synthesis and characterization of [Me2Si(q5-C5Me4)(NB~t)]LnE(TMS)2 complexes (Ln = Sm, Nd, Yb, Lu; E = CH, N) were synthesized and used as precatalysts for aminoalkene hydroaminatiodcyclization. They were found to be significantly more active than the corresponding [CP*~L~E(TMS)~] complexes.134 Cyclizatiodsilylation reactions of nitrogen-containing enynes catalysed by the complexes C P * ~ L ~ M ~ . T(Ln H F= Y, Lu) were investigated. Under the standard conditions previously developed for carbocyclic systems, Cp*2YMe suffered from poor reactivity at room temperature with nitrogen a to the alkyne. This was overcome in the current studies either by slow catalyst addition, or by using the smaller lutetium catalyst c ~ * ~ L u MThe e . use of c ~ * ~ L u Mallowed e the preparation of various nitrogen-containing ring systems in excellent yields with good to excellent diastereoselectivitiesat room temperature. The results of this study highlight the ability to tune the reactivity of an organolanthanide complex by changing the metal center.135 Dehydrogenative silylation of primary and secondary amines with Ph3SiH was catalysed by the ytterbium-imine complex fYb(q2-Ph2CNPh)(HMPA),],

106

Organometallic Chemistry

to give aminosilanes in good yields. In the reaction with diphenyl- and phenylsilanes, diaminosilanes were formed as major products. Whereas n- and sec-alkylamines were readily silylated, tert-alkylamines and aromatic amines exhibited lower reactivities. Moreover, hydrosilylation of imines has been achieved by using phenylsilane and a fluorinated imine derivative, giving rise to mono- and diaminosilanes. The two reactions gave similar selectivities and yields.136 N,N-Dibenzylamino ketones were prepared in enantiomerically pure form from non-chelation controlled reactions of a-amino acids with RCeC12 without any undesired racemization. 37 Similarly, useful intermediates in the synthesis of trans-4-cyclohexyl-~-proline, a precursor for angiotensin converting enzyme inhibitors, were prepared with in situ-generated CePh3.’389’ 39 Reactions of RYbI ( R = Me, Et, Ph) with organotin oxides and acetates have been investigated.140 The reaction of arylytterbium iodides with aromatic nitriles in the presence of excess ytterbium metal affords diarylmethylaminesin moderate yields. 14’ Monohydrosilanes can be prepared selectively in high yields from the reaction of various aryl- and alkyl iodides with ytterbium metal followed by the reaction with dihydrosilanes. Thus, reaction of Yb metal with PhI in THF gave PhYbI in situ which was reacted with MePhSiH2 to give 100% MePh2SiH. Dihydrosilanes were found to react much faster than monohydrosilanes.142

5

Theoretical and SpectroscopicStudies

5.1 Computational Studies. - Theoretical investigations focused on explaining the stability of ‘zerovalent’ compounds of the lanthanides, and on the elucidation of reaction mechanisms. Several ‘zerovalent’ lanthanide bis(arene)-sandwich complexes, Ln(q6C6H& (Ln = La, Ce, Eu, Gd, and Lu) were studied by DFT. The calculated geometries are in good agreement with the reported structures of the trialkylsubstituted derivatives. The calculated dissociation energies of the Ln-arene bonds may be considerably underestimated, but they correctly reveal the trends. Bonding can be described in terms of a relatively weak n-electron donation from benzene to Ln and by a stronger electron back-donation from Ln 5d to the benzene n*-orbitals. In contrast to earlier proposals, bond formation is characterized by electron promotion from Ln 6s to 5d. The relativistic effect only slightly influences the molecular geometry but decreases the bonding energy considerably by lowering the Ln 6s level and raising the 5d level. It enhances the trend of the bonding energy to decrease along the lanthanide series.143In a separate approach, Ln(C6H6)2(Ln = La, Ce, Nd, Gd, Tb, Lu, Th, U) were investigated with state-of-the-art quantum chemical ab initio approaches taking into account the effects of electron correlation and relativity. Ground state assignments, optimized metal-ring distances, metalring stretching frequencies, and metal-ring bonding energies were obtained,

4: Scandium, Yttrium and the Lanthanides

107

and the effects of ring substitution on the metal-ring binding energies were discussed. In direct contrast to experimental observations, the complexes of Th and U were predicted to be at least as stable as the corresponding lanthanide systems. Whereas the lanthanide systems have a 4Pe22 ground state configuration (n= 1, 3 for Ce, Nd), the corresponding actinide compounds should possess, as a consequence of stronger relativistic effects, a 5f"-'e2 ground state configuration, with a possible strong admixture of 5P-'al;e2,"2 (n= 1, 3 for Th, U). The back-donation from the occupied metal d to the empty benzene x-orbitals is the dominant bonding interaction. Whereas the lanthanide 4f orbitals are essentially localized on the metals and chemically inactive, the actinide 5f shell may also take part in the back-donation. Ethylene insertion into the Sm-C bond of (H2Si(C5H4)2)SmCH3 was studied by ab initio MO methods in an attempt to model the propagation step in olefin polymerization. The small electronegativity of the Sm atom makes the Sm-C bond ionic, the Me group being negatively charged by -0.75. The reaction passes through a loose ethylene complex with a binding energy of 15 kcal mol-' and then a tight four-centered transition state with an 'agostic' interaction between the Sm atom and one Me CH bond. A small 14 kcal mol-' activation energy is required to pass through this transition state. Compared with the reactions with Group 4 cationic silylene-bridged metallocenes, the activation energy is higher and the reaction less exothermic. The results of molecular mechanics calculations on regio- and stereoselectivities in the insertion reaction of propylene were also ana1y~ed.l~~ The reaction p;th for Sm(II1)-catalysed alkene hydroboration reaction by catecholborane has been investigated using ab initio MO methods. The stationary structures on the model reaction path for H2C=CH2,catalytic Cp2SmH,and HB(OH)2 as model borane were obtained. In the reaction, ethylene coordinates initially to the active catalyst to form a n-complex. Ethylene insertion into the Sm-H bond then gives Cp2SmC2H5after passing through a 4.2 kcal mol-' barrier. In the following step the model borane adds to Cp2SmC2H5to form a borane complex which thereafter passes through the small barrier of 1.1 kcal mol-' giving rise to a product complex. In the final step, the dissociation of C2H5B(OH)2takes place with a large endothermicity of 40.4 kcal mol-'. Because of the small activation energies, this last step may be rate determining.'46 The mechanistic details of the fluorine transfer reaction of Ln- + F-R to give LnF- + R (Ln = Ce, Ho; R = CH3, C6H5) were also investigated. Both Ce+ and Ho+ were selected as representatives for the early and rather reactive rare earth elements with low second ionization energy (IE) (Ce') and the later and less reactive elements possessing a higher second IE (Ho+). The reaction path of the defluorination process of the two fluorohydrocarbons CH3F and C6H5F brought about by these cations was mapped by determining all relevant stationary points, i. e., reactants, intermediates, saddle points, and products along the reaction coordinate. The experimental observation of a higher reactivity of fluorobenzene compared to fluoromethane (in spite of its significantly larger C-F bond strength) is rationalized by the existence of two competing reaction pathways. 147

108

Organometallic Chemistry

The equilibrium configurations and high-frequency IR spectra for the complexes HoL, (L = CO, N2, n = 1-6) were characterized by ab initio quantum-chemical calculations,148

5.2 Spectroscopic Studies. - Spectroscopic investigations of organolanthanide compounds were limited to ally1 and alkyl compounds. The absorption spectra of dimeric [((T~~-C~H~)~L~(C~H~O~))~(~-C~H~O~)] and polymeric [(q3C3H5)3Nd(C4H802)]have been measured at room and low temperatures. Comparing the spectra of both compounds, a truncated crystal field (CF) splitting pattern is derived for the Nd compound, and simulated by fitting the free parameters of an empirical Hamiltonian. The parameters derived allow the construction of experimentally based non-relativistic and relativistic MO schemes in the f range. Making use of the wavefunctions of the fit, the temperature dependence of peffcould be reproduced. The shift to lower energy of the higher multiplets in the vicinity of a charge transfer band has been attributed to a stronger mixing off- and ligand-based orbitals. 149 Chemiluminescence (CL) was noted in the reactions of O2 or (NH4)2Ce(N03)6with (Ph3C)LnC12 (Ln=Gd, Eu, and Dy), in THF and toluene. The first CL is caused by two emitters: (Ph3C)*, emitting in the green spectral region (ymax524, 550 nm), and an unstable product of substitution of the H atom in the phenyl ring of the Ph3C radical, emitting in the red region (ymax= 580 k 20 nm). The emitter of the second CL, Ph3C*, is generated in the elementary reduction of the Ce(1V) ion by Ph3C-. 150

5.3 Gas Phase Chemistry. - Organometallic clusters of lanthanides (Ln = Nd, Er, Eu, and Yb) and COT were produced by a combination of laser vaporization and molecular beam method^.'^' In the mass spectra of [Ln,(CgH8),], compounds of m = n + 1 were particularly prevalent. From mass spectrometry, photoionization spectroscopy, and photoelectron spectroscopy, it appears that these clusters adopt multiple-decker sandwich structures with alternating Ln1 COT, just as found in solution for both Ln(I1) or Ln(II1) ions and mono- or dianionic COT ligands. 524 54 Similar layered compounds were noted in gas phase sodium adducts of Ln,(C8Hs)n+l [Ln=Eu and Ho] prepared by a combination of two-laser vaporization and a molecular beam method. The number of attached sodium atoms can be reasonably explained by charge distributions of the complex, balancing charge assuming Eu(TI), Ho(III), and COT2-. From these measurements, the plausibility of isolating heterometallic LnNa COT complexes is deduced.70 Reactions of ground state Y atoms with HCCH were studied with crossed molecular beams and 1931157 nm photoionization detection. Three channels, corresponding to non-reactive decay of collision complexes, H2 elimination, and H atom elimination, were studied as a function of collision energy. Production of YC2 and H2 and decay of long-lived complexes back to reactants were observed under all conditions. Product translational energy distributions for the H2 elimination reaction demonstrate that a substantial fraction of excess energy available to the YC2/H2 product goes into relative

4: Scandium, Yttrium and the Lanthanides

109

translational energy. From related Zr and Nb experiments, it appears that a significant potential energy barrier exists in the exit channel of the YC2/H2 elimination. The reformation of Y and HCCH reactants following decay of long-lived collision complexes was found to transfer 40-50% of the initial relative translational energy into internal excitation. The YC2WH product channel required a collision energy threshold of 21(2) kcal mol-'. Since production of YC2H/H is fully spin-allowed and involves simple Y-H bond fission in the intermediate HYC2H complex, it is unlikely that any significant potential energy barrier is present in excess of the reaction end~ergicity."~ Oxides of carbon continue to serve as targets for gas phase Ln ions. Laserablated Sc atoms and ions react with CO to give primarily ScCO, ScCO-, and ScCO+ products, which have been isolated in solid argon and/or neon matrixes. Based on isotopic substitution and DFT calculations, absorptions at 1834.2cm-' in argon and 1851.4 cm-' in neon are assigned to C-O stretching vibrations in ScCO, 1923.5 cm-' in argon and 1962.4 cm-l in neon to ScCO+, and 1732.0 cm-' in neon to ScCO- (free CO absorbs at 2143 cm-'). Higher carbonyls Sc(CO), (n=2, 3, 4) and highly charged species are produced on annealing.lS6 Investigations into the fundamental character of carbon dioxide activation at metal centers were also attempted with guided ion beam mass spectrometry. The reactions of Y+ and YO+ with C02, and the reverse reactions, YO+ and YO2+ with CO, were investigated. To further probe the potential energy surfaces of these systems, Y02+ and the complexes OY(CO2)+, OY(CO)', and 02Y(CO)+ were studied by collisional activation experiments with Xe.lS7

References 1. 2. 3.

4. 5.

6. 7.

8.

9. 10.

C. G. Pernin and J. A. Ibers, Inorg. Chem., 1999,38, 5478. L.-X. Zhang, X.-G. Zhou, Z.-E. Huang, R.-F. Cai, and X.-Y. Huang, Polyhedron, 1999,18, 1533. D. Pfeiffer, I. A. Guzei, L. M. Liable-Sands, M. J. Heeg, A. L. Rheingold, and C. H. Winter, J, Organomet. Chem., 1999,588, 167. D. Pfeiffer, B. J. Ximba, L. M. Liable-Sands, A. L. Rheingold, M. J. Heeg, D. M. Coleman, H. B. Schlegel, T. F. Kuech, and C. H. Winter, Inorg. Chem., 1999,38, 4539. X.-G. Zhou, Z.-E. Huang, R.-F. Cai, L.-B. Zhang, L.-X. Zhang, and X.-Y. Huang, Organometallics, 1999, 18,4128. Z. Wu and H. Ma, Huaxue Shijie, 1999,40,413. X.-G. Zhou, R.-F. Cai, Z.-E. Huang, and Y.-S. Song, Ziran Kexueban, 1999,38, 415. G. Haerkoenen, T. Kervinen, E. Soininen, R. Toernqvist, K. Vasama, M. Glanz, and Schumann, 1999, Ger. Offen. DE 19925430 A1 1999. D. Stellfeldt, G. Meyer, and G. B. Deacon, Z . Anorg. Allg. Chem., 1999, 625, 1252. A. A. Trifonov, E. N. Kirillov, M. N. Bochkarev, H. Schumann, and S. Muehle, Russ. Chem. Bull., 1999,48, 382.

110 11. 12. 13. 14. 15. 16. 17.

18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33.

34. 35.

36.

37. 38. 39. 40. 41. 42.

Organometallic Chemistry

S. Anfang, T. Grob, K. Harms, G. Seybert, W. Massa, A. Greiner, and K. Dehnicke, 2. Anorg. Allg. Chem., 1999,625, 1853. J. Guan, J. Stehr, and R. D. Fischer, Chem. Eur. J., 1999,5, 1992. W. Zhang, Y. Cai, and H.-Z. Ma, Hecheng Huaxue, 1999,7, 1 12. W. Zhang, B.-H. Du, and X.-R. Wang, Hecheng Huaxue, 1999,7,233. Y.-Q. Yu, F.-R. Shen, Z.-C. Wu, and X.-Y. Huang, Jiegou Huaxue, 1999, 18, 119. M. C. Cassani, Y. K. Gun’ko, P. B. Hitchcock, M. F. Lappert, and F. Laschi, Organometallics, 1999,18,5539. S . Al-Juaid, Y. K. Gun’ko, P. B. Hitchcock, M. F. Lappert, and S . Tian, J. Organomet. Chem., 1999,582,143. W.-P. Leung, F.-Q. Song, F. Xue, Z.-Y. Zhang, and T. C. W. Mak, J. Organomet. Chem., 1999,582,292. F. Yuan and Q. Shen, Synth. React. Inorg. Met.-Org. Chem., 1999,29,23. F. Yuan, Q. Shen, and J. Sun, Zhongguo Xitu Xuebao, 1999,17,97. M. Niemeyer and S.-0. Hauber, Z . Anorg. Allg. Chem., 1999,625, 137. A. V. Khvostov, B. M. Bulychev, V. K. Belsky, and A. I. Sizov, Russ. Chem. Bull., 1999,48,2162. W. J. Evans, G. Rabe, and J. W. Ziller, Angew. Chem., Int. Ed., 1994,33,2110. G.-X. Jin, Y .-X. Cheng, and Y. H. Lin, Organometallics, 1999,947. G.-X. Jin, Y. Cheng, and Y. H. Lin, Organometallics, 1999,18, 5735. H. Zhang, H. Yao, S. Zhuang, and Z. Huang, Fudan Xuebao, Ziran Kexueban, 1999,38,45. J. Lin, Z.-Y. Wang, and H.-G. Wang, Wuji Huaxue Xuebao, 1999,15,751. J. Lin and Z.-Y. Wang, J. Organomet. Chem., 1999,589, 127. J. Lin, P. Zhang, Z.-Y. Wang, and H.-G. Wang, Jiegou Huaxue, 1999,18,188. J. Lin and Z.-Y. Wang, Yingyong Huaxue, 1999,16,100. Z. Xie, Z. Liu, K. Chui, F. Xue, and T. C. W. Mak, J. Organomet. Chem., 1999, 588,78. H. Schumann, M. R. Keitsch, J. Demtschuk, and G. A. Molander, J. Organomet. Chem., 1999,582,70. W. J. Evans, G. W. Nyce, R. D. Clark, R. J. Doedens, and J. W. Ziller, Angew. Chem., Int. Ed., 1999,38, 1801. W. J. Evans, D. A. Cano, M. A. Greci, and J. W. Ziller, Organometallics, 1999, 18, 1381. T.-a. Koizumi, C. Yoda, Z. Hou, S.4. Fukuzawa, and Y . Wakatsuki, Kidorui, 1999,34,284. M. N. Bochkarev, A. A. Fagin, I. L. Fedushkin, A. A. Trifonov, E. N. Kirillov, I. L. Eremenko, and S . E. Nefedov, Mater. Sci. Forum, 1999, 315317, 144. T. Labahn, A. Mandel, and J. Magull, 2. Anorg. Allg. Chem., 1999,625, 1273. W. J. Evans, C. A. Seibel, K. J. Forrestal, and J. W. Ziller, J. Coord. Chem., 1999,403. D. L. Clark, J. C . Gordon, B. L. Scott, and J. G. Watkin, Polyhedron, 1999, 18, 1389. R. J. Butcher, D. L. Clark, 0. C. Gordon, and J. G. Watkin, J. Organomet. Chem., 1999,577,228. F. Nief, P. Riant, L. Ricard, P. Desmurs, and D. Baudry-Barbier, Eur. J. Inorg. Chem., 1999,1041. Q. Liu, J. Huang, Y. Qian, and A. S . C. Chan, Polyhedron, 1999,18,2345.

4: Scandium, Yttrium and the Lanthanides

43. 44. 45. 46. 47. 48. 49. 50. 51. 52.

53.

54. 55. 56. 57. 58.

59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71.

111

A. A. Trifonov, F. Ferri, and J. Collin, J. Organomet. Chem., 1999,582,211. E. Ihara, M. Tanaka, H. Yasuda, T. Maruo, N. Kanehisa, and Y. Kai, Kidorui, 1999,34,32. A. A. Trifonov, E. N. Kirillov, M. N. Bochkarev, A. Fischer, and F. T. Edelmann, Chem. Commun.,1999,2203. M. Visseaux, D. Baudry, A. Dormond, and C. Qian, J. Organomet. Chem., 1999, 574,213. K. Beckerle, K. C. Hultzsch, and J. Okuda, Macromol. Chem. Phys., 1999, 200, 1702. H. Schumann, K. Herrmann, J. Demtschuk, and S. H. Muhle, Z. Anorg. Allg. Chem., 1999,625,1107. X.-G. Zhou, L.-B. Zhang, Z.-E. Huang, R.-F. Cai, and X.-Y. Huang, Jiegou Huaxue, 1999,18,373. A. T. Gilbert, B. L. Davis, T. J. Emge, and R. D. Broene, Organometallics, 1999, 18,2125. X. Feng, X. Zhou, Z. Huang, and R.-F. Cai, Ziran Kexueban, 1999,38,103. C . Qian, H. Li, J. Sun, and W. Nie, J. Organomet. Chem., 1999,585,59. A. V. Khvostov, B. M. Bulychev, V. K. Belsky, and A. I. Sizov, J. Orgunomet. Chem., 1999,584,164. A. V. Khvostov, V. V. Nesterov, B. M. Bulychev, A. I. Sizov, and M. Y. Antipin, J. Organomet. Chem., 1999,589,222. H. Ma, W. Zhang, and Y. Cai, Huaxue Tongbao, 1999,38. C. Qian, W. Nie, and J. Sun, J. Chem. SOC.,Dalton Trans., 1999,3283. C . Qian, G. Zou, and J. Sun, J. Chem. SOC.,Dalton Trans., 1999,519. H. Schumann, F. Erbstein, D. F. Karasiak, I. L. Fedushkin, J. Demtschuk, and F. Girgsdies, Z . Anorg. AlZg. Chem., 1999,625, 781. H. Schumann, F. Erbstein, J. Demtschuk, and R. Weimann, 2. Anorg. Allg. Chem., 1999,625,1457. M. B. Abrams, J. C. Yoder, C. Loeber, M. W. Day, and J. E. Bercaw, Organometallics, 1999,18, 1389. M. N. Bochkarev, A. A. Fagin, I. L. Fedushkin, T. V. Petrovskaya, W. J. Evans, M. A. Greci, and J. W. Ziller, Russ. Chem. Bull., 1999,48, 1782. E. N. Kirillov, A. A. Trifonov, S. E. Nefedov, I. L. Eremenko, F. T. Edelmann, and M. N. Bochkarev, 2. Naturforsch., B: Chem. Sci., 1999,54, 1379. E. E. Fedorova, A. A. Trifonov, M. N. Bochkarev, F. Girgsdies, and H. Schumann, Z . Anorg. AZlg. Chem., 1999,625, 1818. C. D. Stevenson, T. Schertz, and R. C. Reiter, J. Am. Chem. SOC.,1999, 121, 6964. G. R. Feistel and T. P. Martin, J. Am. Chem. SOC.,1968,90, 2988. I. L. Fedushkin, T. V. Petrovskaya, F. Girgsdies, R. D. Kohn, M. N. Bochkarev, and H. Schumann, Angew. Chew., Int. Ed., 1999,38,2262. W. J. Evans, M. A. Johnston, M. A. Greci, and J. W. Ziller, Organometallics, 1999,18,1460. T. G. Wetzel, S. Dehnen, and P. W. Roesky, Organometallics, 1999,18, 3835. U. Reissmann, P. Poremba, L. Lameyer, D. Stalke, and F. T. Edelmann, Chem. Commun., 1999,1865. K. Miyajima, T. Kurikawa, M. Hashimoto, A. Nakajima, and K. Kaya, Chem. Phys. Lett., 1999,306,256. M. Visseaux, A. Dormond, and D. Baudry-Barbier, Eur. J. Inorg. Chem., 1999, 10, 1827.

112

Organometallic Chemistry

72. G. M. Ferrence, R. McDonald, and J. Takats, Angew. Chem., Int. Ed., 1999, 38, 2233. 73. I. Lopes, G. Y. Lin, A. Domingos, R. McDonald, N. Marques, and J. Takats, J. Am. Chem. SOC.,1999,121,8110. 74. T. Dube, S. Conochi, S. Gambarotta, G. P. A. Yap, and Vasapollo, Angew. Chem., Int. Ed., 1999,38, 3657. 75. E. Campazzi, E. Solari, R. Scopelliti, and C. Floriani, Chem. Commun., 1999, 1617. 76. E. Campazzi, E. Solari, R. Scopelliti, and C. Floriani, Inorg. Chem., 1999, 38, 6240. 77. T. Dube, S. Gambarotta, and G. P. A. Yap, Angew. Chew., Int. Ed., 1999, 38, 1432. 78. M. Karl, K. Harms, G. Seybert, W. Massa, S. Fau, G. Frenking, and K. Dehnicke, 2. Anorg. Allg. Chem., 1999, 625,2055. 79. H. Noss, M. Oberthur, C. Fischer, W. P. Kretschmer, and R. Kempe, Eur. J. Inorg. Chem., 1999,2283. 80. T. I. Gountchev and T. D. Tilley, Organometallics, 1999,18,2896. 81. T. I. Gountchev and T. D. Tilley, Organometallics, 1999,18,5661. 82. Z. Xie, Z. Liu, Q. Yang, and T. C. W. Mak, Organometallics, 1999,18, 3603. 83. Z. Xie, S. Wang, Z.-Y. Zhou, and T. C. W. Mak, Organometallics, 1999,18, 1641. 84. Z. Xie, K. Chui, Q. Yang, and T. C. W. Mak, Organometallics, 1999,18, 3947. 85. S. Wang, Q. Yang, T. C. W. Mak, and Z. Xie, Organometallics, 1999,18,4478. 86. S. Wang, Q. Yang, T. C. W. Mak, and Z. Xie, Organometallics, 1999,18, 5511. 87. Z. Xie, S. Wang, Q. Yang, and T. C. W. Mak, Organometallics, 1999,18, 1578. 88. C . Zheng, N. Hosmane, H. Zhang, D. Zhu, and J. A. Maguire, Internet J. Chem., 1999,2, Article No. 10. 89. D. R. Click, B. L. Scott, and J. G. Watkin, Chem. Commun., 1999,633. 90. G. B. Deacon, C. M. Forsyth, P. C. Junk, B. W. Skelton, and A. H. White, Chem. Eur. J., 1999,5, 1452. 91. W. J. Evans, M. A. Greci, M. A. Johnston, and J. W. Ziller, Chem. Eur. J., 1999, 5, 3482. 92. T. A. Zheleznova, L. N. Bochkarev, A. V. Safronova, and S. F. Zhil’tsov, Russ. J. Gen. Chem., 1999,69,784. 93. V. M. Makarov, L. N. Bochkarev, E. V. Dumkina, and S. F. Zhil’tsov, Russ. J. Gen. Chem., 1999,69,88. 94. G. W. Rabe, C. S. Strissel, L. M. Liable-Sands, T. E. Concolino, and A. L. Rheingold, Inorg. Chem., 1999,38, 3446. 95. E. Ihara, K. Koyama, H. Yasuda, N. Kanehisa, and Y. Kai, J. Organomet. Chem., 1999,574,40. 96. C. Eaborn, M. S. Hill, P. B. Hitchcock, J. D. Smith, S. Zhang, and T. Ganicz, Organometallics,1999, 18,2342. 97. D. Freedman, S. Sayan, M. Croft, T. Emge, and J. Brennan, J. Am. Chem. SOC., 1999,121, 11713. 98. K. Koo, P.-F. Fu, and T. J. Marks, Macromolecules, 1999,32,981. 99. N. Kibino, M. Yamamoto, and G. Yasuda,, 1999, APPLICATION: JP 1998. 100. H. Schumann, K. Zietzke, R. Weimann, J. Demtschuk, W. Kaminsky, and A.-M. Schauwienold, J. Organomet. Chem., 1999,574,228. 101. J. Okuda, F. Amor, T. Eberle, K. C. Hultzsch, and T. P. Spaniol, Polym. Prepr. (Am. Chem. SOC.,Div. Polym. Chem.), 1999,40,371. 102. J. Soto and J. T. Patton, WO 9743294.

4: Scandium. Yttrium and the Lanthanides

113

103. S. N. Ringelberg, A. Meetsma, B. Hessen, and J. H. Teuben, J. Am. Chem. SOC., 1999,121,6082. 104. D. Baudry-Barbier, E. Camus, A. Dormond, and M. Visseaux, Appl. Organornet. Chem., 1999,13,813. 105. Z. Hou, Y. K. Chang, and Y. Wakatsuki, JP 11092487. 106. S. Kaita, Z. Hou, and Y. Wakatsuki, Macromolecules, 1999,32,9078. 107. T. Ruhmer, J. Giesemann, W. Schwieger, and K. Schmutzler, Kautsch. Gummi Kunstst., 1999, 52,420. 108. D. Baudry-Barbier, A. Dormond, and P. Desmurs, C.R Acad. Sci., Ser. IIc: Chim., 1999,2, 375. 109. R. Taube, S. Maiwald, T. Ruehmer, H. Windisch, J. Giesemann, and G. Sylvester, WO 963 1544. 110. K. C. Hultzsch, T. P. Spaniol, and J. Okuda, Angew. Chem., Int. Ed., 1999, 38, 227. 111. A. Yanagase, S. Tone, T. Tokimitsu, and M. Nodono, WO 9804595. 112. M. H. Lee, J.-W. Hwang, Y. Kim, J. Kim, Y. Han, and Y. Do, Organometallics, 1999,5124. 113. G. Yasuda and K. Kashiwagi, JP 11255829A2. 114, G. Yasuda, Gen Jpn 1999.0921. 115. M. Karl, G. Seybert, W. Massa, K. Harms, S. Agarwal, R. Maleika, W. Stelter, A. Greiner, W. Heitz, B. Neumuller, and K. Dehnicke, 2. Anorg. AlZg. Chem., 1999,625, 1301. 116. Y. Nakayama, H. Fukumoto, T. Shibahara, A. Nakamura, and K. Mashima, Polym. Int., 1999,48,502. 117. T. Asanuma, H. Yasuda, and E. Ihara, JP 11012351. 118. X. Deng, M. Yuan, C . Xiong, andX. Li, J. Appl. Polym. Sci., 1999,1401. 119. M. Xue, L. Mao, Q. Shen, and J. Ma, Yingyong Huaxue, 1999,16,102. 120. S . Agarwal, N. E. Brandukova-Szmikowski,and A. Greiner, Macromol. Rapid Commun., 1999,20,274. 121. M. Nishiura, Z . Hou, T.-a. Koizumi, T. Imamoto, and Y. Wakatsuki, Macromolecules, 1999,32,8245. 122. M. Yuan, X. Li, C. Xiong, and X. Deng, Eur. Polym. J., 1999,35,2131. 123. S . KO,Y. Wakatsuki, and M. Nishiura, JP 11255776. 124. H. Yasuda, M.-S. Aludin, N. Kitamura, M. Tanabe, and H. Sirahama, Macromolecules, 1999,32,6047. 125. M. Yuan, C. Xiong, X. Li, andX. Deng, J. Appl. Polym. Sci., 1999,73,2857. 126. Y. Kawasaki, A. Fujii, Y. Nakano, S. Sakaguchi, and Y. Ishii, J. Org. Chem., 1999,64,4214. 127. Y. Ishii and T. Nakano, JP 11080078. 128. Y. Ishii and T. Nakano, JP 11080080. 129. N. E. Brandukova-Szmikowski, S. Agarwal, and A. Greiner, Acta Polym., 1999, 50, 35. 130. T. Nishitani, H. Shiraishi, S. Sakaguchi, and Y. Ishii, Kidorui, 1999,34, 310. 131. G. A. Molander and E. D. Dowdy, J. Org. Chem., 1999,64,65 15. 132. V. M. Arredondo, S. Tian, F. E. McDonald, andT. J. Marks, J. Am. Chem. Soc., 1999,121,3633. 133. V. M. Arredondo, F. E. McDonald, and T. J. Marks, Organometallics, 1999, 18, 1949. 134. S. Tian, V. M. Arredondo, C . L. Stern, and T. J. Marks, Organometallics, 1999, 18, 2568.

114

Organometallic Chemistry

135. G. A. Molander and C. P. Corrette, J. Org. Chem., 1999,64,9697. 136. K. Takaki, T. Kamata, Y. Miura, T. Shishido, and K. Takehira, J. Org. Chem., 1999,a. 137. M. T. Reetz and A. Schmitz, Tetrahedron Lett., 1999,40,2737. 138. J. K. Thottathil, US 4734508. 139. J. K. Thottathil, DE 3814663. 140. L. F. Rybakova, 0. P. Syutkina, M. N. Novgorodova, and E. S. Petrov, Russ. J. Gen. Chem., 1999,69,85. 141. Y. Makioka, T. Nakamura, T. Kitamura, and Y. Fujiwara, Kidorui, 1999, 34, 188. 142. W . 4 . Jin, Y. Makioka, T. Kitamura, and Y. Fujiwara, Kidorui, 1999,34, 314. 143. H.-G. Lu and L.-M. Li, Theor. Chem. Acc, 1999,102, 121. 144. G. Hong, F. Schautz, and M. Dolg, J. Am. Chem. Soc., 1999,121,1502. 145. N. Koga, Theor. Chem. Acc, 1999,102,285. 146. S . A. Kulkarni and N. Koga, THEOCHEM, 1999,461462,297. 147. R. H. Hertwig and W. Koch, Chem. Eur. J., 1999,5,312. 148. A. Y. Ermilov, A. V. Nemukhin, and V. M. Kovba, Mendeleev Cornrnun., 1999, 88. 149. H. Reddmann, H.-D. Amberger, B. Kanellakopulos, S. Maiwald, and R. Taube, J. Organomet. Chem., 1999,584,310. 150. R. G. Bulgakov, S. P. Kuleshov, Z. S. Valiullina, and B. A. Mustafin, Russ. Chem. Bull., 1999,48, 1091. 151. T. Kurikawa, Y. Negishi, F. Hayakawa, S. Nagao, K. Miyajima, A. Nakajima, and K. Kaya, Eur. Phys. J. D, 1999,9,283. 152. K. 0. Hodgson, F. Mares, D. F. Starks, and A. Streitwieser, J. Am. Chem. Soc., 1973,95,8650. 153. S . A. Kinsley, A. Streitwieser, and A. Zalkin, Organornetallics,1985,4, 52. 154. S . A. Kinsley, A. Streitwieser, and A. Zalkin, Acta Cryst., 1986, C42, 1092. 155. H. U. Stauffer, R. Z. Hinrichs, P. A. Willis, and H. F. Davis, J, Chem. Phys., 1999,111,4101. 156. M. Zhou and L. Andrews, J. Phys. Chem. A , 1999,103,2694. 157. M. R.Sievers and P. B. Armentrout, Inorg. Chem., 1999,38, 397.

5 Carboranes, Including Their Metal Complexes BY ANDREW S. WELLER

1

Introduction

This review covers the 1999 literature of carboranes and metallacarboranes,’ and follows essentially the same format as adopted in previous years. Selected heteroboranes of the other members of Group 4 (Sn and Si) are also included. Carborane complexes are ordered by their C,B, formula, with metal complexes included in a separate, appropriately ordered, section. Theoretical papers are covered in Section 2 The chemical literature has been surveyed using Web of Science and the use of the Cambridge Structural Database at Daresbury is acknowledged.2 Specific reviews that have appeared in 1999 on carboranes and related compounds are special issues of Inorg. Chim. Acta (Volume 289) J. Organometallic Chern. (Volume 581) and Collect. Czech. Chem. Cummun. (Volume 64) which concentrate on boron chemistry at the end of the millennium. Each of these issues contains both review articles and newly published work, and the reader is directed towards them for further reading. A review of supramolecular assemblies formed from u-, m- and p carborane has a ~ p e a r e d A . ~ ‘highlight’ article on p~lyhydroxylated~ carboranes (see Section 3.2) has appeared. Reviews on the chemistry of cobalt bis(dicarbol1ides) complexe~,~ has appeared. A review entitled: ‘Four decades of organic chemistry of closo-boranes: a synthetic toolbox for constructing liquid crystal materials’ has appeared.6 A related review has also been publi~hed.~ A comprehensive review of the resolution of chiral deltahedral boranes by HPLC has been presented.8 The use of NMR as a tool for the estimation of electron distribution in boranes and their derivatives has been discu~sed.~ Throughout this review, the following key is used to describe the cage vertex atoms in the figures used: @ =B

0

=BH

=c

Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001 115

Organometallic Chemistry

116

2

Theoretical Chemistry

Ab initio calculations at the 3-21G*, 6-31G* and 6-31G** levels have been performed on o-, m- and p - carborane to elucidate the calculated structures, electron affinities and acidities of these compounds.lo The calculated structure of ‘free’ [C2B1oH12l2- is also reported, which shows it to have a nido-structure topped with a six-membered ring, with the C-atoms in the meta position - as found in the transition metal complexes of this dianion. An extensive study of density functional theoryhnite perturbation theory calculations of nuclear spin-spin coupling constants for polyhedral carboranes and boron hydrides has been reported.” Density functional theory has been used to predict the geometries and other energetic qualities (including stabilities) of a range of fluorinated closo monocarborane clusters.’2 The topological aspects of the skeletal bonding in ‘isocloso’ metallaboranes has been presented, and suggests that, as in closo metallacarboranes, the metal vertex provides three skeletal orbitals to cluster bonding.l 3

3

Carboranes

3.1 (CBg) and {CB1l). - The reactions of [CB9H&4]- and [CB9Hlo]- salts with the fluorinating reagent F-TEDA in the presence or absence of trifluoroacetic acid have been described.l4 The ratio of the two perfluoro-isomers produced in these reactions, [6,7,8,9,10-CB9H5F5]- and [2,6,7,8,9-CB9H5F5]-, is dramatically changed to favour the latter when trifluoracetic acid is used. The mechanism of the reaction of Cs[CB9H6F4]with F-TEDA is discussed, and 6,7,8,9-CB9H5F4while two new anions 6,7,8,9-CB9H5F4-10-NHCOCH3 10-OH, formed as side products in these reactions, are also described. The remarkable polyhydroxylated boranes, Cs2[closo-B12(OH)121 Cs[closoCB11(OH)12]and closo-l,12-C2Blo(OH)12 are formed on reaction of 30% H202 with the corresponding parent (car)borane. These fascinating complexes represent a bridge between boron oxides and boron hydrides (Figure l)?

r

L

OH

OH Figure 1

1cs

J

The crystal structures of [M(C6H6)2][CBllMe12](M=Tl, Cs, Rb, K, Na) have been determined.16The remarkable result of the isolation of protonated benzene as a room temperature stable crystalline solid, as [C~H~][CBI 1C1&], from the reaction of [Et3Si][CB11C16H6] with anhydrous HCl has been reported. l7 The structures of the monocarborane anions Ag[ I -Me-CB11H5X6]

5: Carboranes, Including Their Metal Complexes

117

(X = H, C1, Br, I) have been reported, all being one dimensional coordination polymers in the solid state.18 The synthesis of 12-alkyl and 12-phenyl derivatives of [CB11H12]- has been reported.” The tropylium ylide, 12C7H6+-CB11Hl - has been synthesised; its hyperpolarisability is found to be 10 times that of p-nitroaniline. The facile conversion of [(1l~-c&@h(c0)2] [ 1-Et-CBllF11] into the non-classical rhodium(1) carbonyl [Rh(C0)4] [ 1-Et-CBllF11] has been reported, the isolation of this complex facilitated by the very weakly coordinating properties of the fluorinated mono-carbon borane anion.20 In a related study, a bent dicarbonyl complex and a tetrahedral tetra-carbonyl complex of copper(I), isolated using polyfluorocarborane super-weak anions, have been structurally and spectroscopically characterised.2

3.2 (CzBz} and {c&) and (C2B8). - The reaction of B2H6 with ethene and ethyne has been studied by matrix isolation techniques, and showed evidence for hydrogenation but no alkylboranes were obtained.22 The reactivity of sodium hexaethyl-2,4-dicarba-nido-hexaborate( 1-) with MeOD, Et2BC1, BBr3 and FeC13 has been reported.23 The structure of the nine vertex arachno thiaborane C2SB6H10 has been established by the ab initio/IGLO/NMR method.24 The complete NMR assignment of [6-R-nido-5,6-C2B8H& has been reported.25 3.3 (C3B8) and (C,b>. - The synthesis of the new tricarborane 2-R-nido2,7, 10-C3B8Hl (R = CH2Ph, Me), resulting from protonation and (reversible) isomerisation of [7-R-nido-7,8,~ O - C ~ B ~ Hhas ~ Obeen I - ~ reported. ~ The structures of tetracarba-nido-octaborane(8) and a novel spiro derivative of 2,3,5tricarba-nido-hexaborane(7)have been e l ~ c i d a t e d . ~ ~ 3.4 {C6B6) and (C&). - The hexacarborane arachno-C&H12 and the pentacarborane arachno-CH3CSB7H12 have been synthesised and their structures elucidated by the NMR ab initiolIGL0 technique. The hexacarborane is shown to have an open structure, partway between hydrocarbon and boron cluster.28

3.5 (C2B9}. The permethylated anionic nido carborane [1,2,4,5,6,7,8,9,10,11-Me8-7,8,-nido-C2B9H2]-, formally an analogue of pentamethylcyclopentadienyl, has been reported.28More detail is given in Section 3.10. The fluoride ion promoted deboronation reactions of regioselectively deuterated closo-1,X-C2B10H12(X = 2,7) have been studied, with the position of the deuterium atom(s) in the product consistent with deboronation of the boron atom neighbouring both carbon atoms.29 Reaction of closo-1,2-C2Bl0HI2with the base HNP(NMe& eventually affords the deboronated carborane [nido-7,8-C2BgH12]- as a mixture of the [H2NP(NMe2)3]+ and [(Me2N)3PNHB{NP(NMe2)3>21+ salts (Figure 2). The intermediate in this reaction, C2BloH1iHNP(NMe2)3,has been characterised by X-ray crystallography, and represents the first step in the deboronation of

118

Organometallic Chemistry

ortho-carborane by a Lewis base.30 The novel [{ (Me2N)3PNBNP(NMe2)2) 20][C2B9H12]2 is also reported.

HNP(NMe& P

-i

borenium

salt

Figure 2

The first optically pure nido-monothiocarborane [NMe4][7-SPh-8-CH20H7,8-C2B9H has been reported, accessed via differential crystallisation of its diastereoisomericcamphanate ester derivative^.^^ 3.6 (C2BIO}.- The continued emergence of supramolecular chemistry of carboranes, especially that involved with (C2B10) fragments, has been reflected by a number of papers concerning the extended solid-state structures of neutral, closo, carboranes. The self-assembly of o-carborane with cyclotriveratrylene to form two dimensional hexagonal grid or helical chain topologies has been reported.32 A related paper reporting the host-guest interactions between o-carborane and calix[5]arenes has appeared.33 The synthesis, structure and supramolecular assembly through N- - -H-Ccageor 0,. -H-Ccagebonds respectively of the complexes 9-CN- 1,2-closo-C2BloH1 and 9-CH3CO-1,2closo-C2BloH11 has been described.34The intramolecular hydrogen bonding present in the dicage-cage o-carborane [ C ~ B ~11CH2SCH(C02CH3)]2 OH has been discussed.35 Derivitisation of the surface of C2B10H12, both at carbon and boron vertices, continues to attract attention. The synthesis and characterisation of 0-3- and m-2-substituted carboranes via boron insertion reaction has been reported.36 New, functionalised, aryl substituted bis o-carboranes have been ~ynthesised.~~ The haloaryl substituted carboranes 1-(4-Br-C6F4)-2,-R-1,2closo-C2BloHlo (R = Me, Ph, But) have been reported, and their solid-state structures described.38A full paper reporting the permethylation of o-, m-,p and bis-ortho- carborane using Friedel-Crafts conditions has been publ i ~ h e dThe . ~ ~variations in permethylation of each isomer are discussed. The ortho and meta isomers do not cleanly undergo complete methylation, the two boron atoms connected to both carbons remaining unchanged, whereas for the para isomer full B-permethylation occurs. Deboronation of the methylated ortho carborane affords a permethylated nido-{ C2B9) carborane (Figure 3). Unlike unsubstituted carborane, this reaction requires vigorous heating, deboronation only efficient in boiling DME with potassium ethoxide. The author's suggest that this nido carborane is analogous to the pentamethylcylopentadienyl [{ q5-C5Me5)-1 ligand in organo-transition metal chemistry.

5: Carboranes, Including Their Metal Complexes

119

H PPN

Figure 3

The synthesis of a range of new mono- and di-substituted o-carborane derivatives with thiolate and carbamate functionalities has been de~cribed.~' New o-carborane derivatives of the general formula 1,2-(SR)2-1,2-cZosoC2BIoHlo (SR = S2NC7H4, S2CNEt2) and 1-SR-2-(SitBuMe2)-1,2-cZosoC ~ B ~ O Hhave I O been ~ynthesised.~'The new pyridine NS2 ligand bearing 1Me02C-2-S-l,2-cZoso-C2BloHlogroups has been prepared (Figure 4), and its base degradation to form nido dianionic chelating ligands which form metal complexes with palladium chloride fragments has been reported.42

A

S

S

CMe

Mec

Figure 4

The synthesis, of the strained complex 1,2-(l', 1',2',2'-tetramethyldisilane1',2')carborane has been formed from reaction of 1,2-dilithiocarborane with dichlorotetramethylsilane. Reaction with ethanol results in SiC cleavage, while in contrast, reaction with 0 2 affords a complex in which oxygen has been inserted into the S-Si bond (Figure 5).

4

Metallacarboranes

4.1 (MCZB4). - A new, half sandwich 'carbons apart' magnesaborane, [doso1-Mg(THF)3-2,4-(SiMe3)2-2,4-C2B4H4] has been synthesised and structurally characterised.4 Half and full sandwich hafnacarboranes of the general formula [(L)((SiMe3)2C2B4H4}HfCln][L = (SiMe3)2C2B4H4or Cp"] have

120

Organometallic Chemistry

been synthesised and structurally characterised. The structures show the hafnacarboranes to have bent-sandwich structures in which the Hf atom (in the +4 oxidation state) is bound to two nido carborane ligands, a THF molecule and a chloride ligand.45The electron-transfer properties of [(fulvalendiyl)C02(Et2C2B4H&] have been studied by electrochemical and spectroscopic methods (including ESR).46There are two reversible reductions indicative of strong metal-metal interactions, while oxidation proceeds in two aniodic steps, with only the first reversible.

{MC3Bs}. - The first reported examples of ‘double-cluster’ metallatricarbollides have been synthesised, [9,9-(ButHN)~-comrno-2,2’-M-cZoso1,7,9(C3B8Hl0)-1’,7’,9’-(C3BgHlo)](M = Fe, Ru) (Figure 6). These neutral complexes are the metallacarborane analogues of ferrocene and ruthenocene, and are accessed via reaction of 7-(ButH2N)-7,8,9-C3B8Hlowith FeC12 or RuC12(DMSO) respectively, in the presence of NaH at high t e m p e r a t ~ r eIn .~~ a closely related article, a series of twelve vertex ferracarbollides [2-(q5-c5H5)9-X-clos0-2,l,7,9-FeC3B8Hlo](X = NH2, NMeH, NHtBu, NMetBu) have been synthesised by reaction of the corresponding nido tricarbollide with [CpFe(C0)2]2 in refluxing ~ y l e n e In . ~ both ~ of these papers, all of these new metalla-complexes show substantial cage carbon rearrangement to give maximum separation of carbon atoms, and are suggested to be potential precursors to molecular rods containing metallacarborane moieties. 4.2

H

H

X

Figure 6

4.3 {MC&}. - The application of the NOE experiment in the analysis of carboranes and metallacarboranes has been reported, with particular emphasis .~~ on the full spectroscopic characterisation of a pseudodoso m e t a l l a b ~ r a n eA study into the competitive extraction of selected bases by the carbollylcobaltate anion from aqueous solution has been rep~rted.~’ The ‘1,2’ to ‘1,2’ cage carbon isomerisation (equivalent to a 3,1,2-MC2Bg to 4,l ,2-MC2Bg)in a range of bisphosphine sterically encumbered carbanickelaboranes has been reported, which can be contrasted with the analogous platinum systems that undergo facile 1,2 to 1,7 isomer is at ion^.^^ The synthesis and characterisation of new Cphenyl and B-SMe2 substituted carboranes 7,8-Ph2-lO-(SR2)-7,8-nido-C2BgHlo (R2 = Me2, MeEt, Et2) has been described. The corresponding metallaborane complex of the SMe2substituted cage affords useful experimental information on the course of polytopal isomerisation in these systems.52The first examples

5: Carboranes, Including Their Metal Complexes

121

of rhenacarboranes complexed with a nitrosyl ligand, [Re(N0)(L),(q5-7,8C2B9H11)], have been reported. Reaction with Li[R] (R = Ph, C6H4Me-4, L = CO) and then [Me30][BF4] affords the alkylidene complex [Re{ =C(OMe)R}(NO)(C0)(q5-7,8-C2B9Hl 1)], while reaction with Li[Ph] (L = CNBut) and subsequent protonation affords the novel complex [Re(NO)(CNBut)(~',CT-~-C=N(H)BU~-~,~-C~B~H~~)].~~ The mixed-metal (Ru-Rh) metallacarboranes [(diene)Rh(p-H)Ru(PPh3)(q5-C2B9H1I)] (diene = COD, NBD) and [(CO)(PPh3)Rh(p-H)Ru(PPh3)2(q5-C2B9H1 1)] have been synthesised, by reaction of [exo-nido-5,6,10-(Cl(PPh3)2Ru}-5,6,lO-(p-H)3lO-H-7,8-CgBgHg] with [(diene)RhC1I2 or [(C0)2RhC1]2re~pectively.~~ The synthesis and structural characterisation of the anionic ruthenium metallacarborane [cZoso-3,3-(PPh3)23-H-3,1,2-RuC2B9H1 1][Et4N],which is the proposed key intermediate in these reactions, is also described and has been structurally characterised. The reactivity of the anionic rhenacarborane CS[R~(CO)~(~'-~,~-C~B~H~ I)] with a range of metal ligand fragments, to afford exo-nido type complexes has been reported. Reaction with [RuC12(PPh3)3], [M(C0)2(THF)(q5-C5H5)][BF4] (M = Ru, Fe), RhCl(PPh3)(L) [L = (PPh3)2, Fe(q5-C5H4PPh2)J, [CuCl(PPh3)3] and [(THF)Ag(PPh3)][BF4]affords a range of bimetallic complexes, in which the cage partakes in exo B-H-M bonding, the degree of interaction ( i e . p-H, p-H2 etc.) dependent on the metal fragment used.55The new anionic ruthenacarborane [K(1S-~rown-6)][RuH(PPh3)z(r1~-7,8-C2BgH1 I)] and its reactivity with [ R u C ~ ~ ( P Pand ~ ~[MCl(PPh3)] )~] (M = Cu n = 3, M = Au n = 1) to afford bimetallic complexes has been reported? Reaction of [M(NMe2)5] (M = Nb, Ta) reacts with nido-C2B9H13, via HNMe2 elimination, to give the dicarbollide half-sandwich complexes [M(C2B9H1 l)(NMe2)3].These complexes' reactivity with C 0 2 and CS2 - to afford triscarbamate and tris(dithi0carbamate) complexes - is described. The amide and (thio)carbamate ligands in these species show a differing orientation of ligands around each metal centre, two vertically orientated and one horizontally orientated. The electronic factors accounting for these structural features are discussed.57

(exu-MC2Bg}. - Reaction of ~is-[PdCl~(PPh~)~] with [nido-7-PPhz-S-R7,8-C2B9Hlo][NMe4] (R = Me, Ph, H) affords the novel complexes in which the diphenylphosphine has transferred from the metal of the cage, viz. [PdC1(7which has been characterised by PPh2-8-R-11-PPh2-7,8-nido-C2B9H9)(PPh3)] X-ray d i f f r a ~ t i o n . ~Reaction ~ of [1-PPh2-2-SR-1,2-cZoso-C2BloHlo] with MCl(PPh3), (M = Cu n = 2, M = Au n =1) in ethanol afforded the product of partial cage degradation, [M(7-PPh2-8-SR-7,8-nido-C2BgH10)(PPh3)~],~~ in which the coinage metal bonds either uniquely through the phosphorus (Au) or bidentate through both phosphorus and sulfur (Cu).

4.4

(MCBlo). - The synthesis, structure and reactivity of the monocarbon ruthenaborane [ R u ~ ( C O )5-7-CBl$€1 ~(~ 1)][NHMe3]has been reported, which has two B-H-Ru 3c-2e bonds. Protonation affords a hydrido cluster complex, in which the hydride straddles a Ru-Ru bond. Reaction with [PPh3MC1] (M=Cu, Ag, Au) affords novel bimetallic complexes, in which a B-H-Ru

4.5

Organometallic Chemistry

122

linkage is replaced by a B-M-Ru linkage, the hydrogen atom transferred to straddle the Ru-Ru bond (Figure 7).60

Figure 7

{MCzBlo}. - A comprehensive study of organolanthanide complexes incorporating both cyclopentadienyl and carborane (C2BlO) groups has been published.6’ In this study a range of lanthanide metals ligated with the hybrid ligands Na[MezSi(CsH4)(cZoso-C2B OH1I)], Li2[Me2Si(CsH4)(closo-C2B1OHlo)] and K3[Me2Si(C5H4)(nido-C2BloHlo)] are reported. The carborane can act as a bulky substituent, a o-ligand or a n-ligand, depending on the alkali metal and the lanthanide used. In a related study, the corresponding indenyl substituted carborane ligands have been prepared and reactivity with selected lanthanide halides r e p ~ r t e d . Exo-nido ~ ~ ’ ~ ~ and closo lanthanacarboranes (Ln = Sm, Yb) bearing the bisbenzyl substituted carborane ( C ~ H ~ C H ~ ) ~ C ~ have B ~been OH~O reported.64 The two motifs, cluso vs. exo-nido,may be controlled by appropriate choice of metakarborane ratio. In another related study, a number of complexes containing erbium6’ coordinated to q7-C2BloH11 have been also been reported, by reaction of [q5-Me2C(C5H4)(C2B10H11)]ErC12(THF)with Na metal. A uranium carborane containing the novel [q7-C2B1oH12l4-ligand has been also been reported.66

4.6

4.7 {exo-MC2Blo}. - The 16-electron complex [CpCo(S2C2BloH10)]is obtained by reaction of [CpCo(CO)I2] with Li2[S2C2B10H10]. The structure of this complex is reported, along with reactivity studies with CpCo(C2H4)2, alkynes and d i a ~ o a l k a n eThe . ~ ~ pentamethylcyclopentadienyl rhodium68 and iridium69analogues of this complex have also been prepared, along with the 18-electron PMe3 adduct and the corresponding diselenate congener. The reactivity of this electron deficient (at rhodium) complex has been studied further. Reaction with activated acetylenes affords complexes in which the acetylene is directed by the metal centre to the B(3) and B(6) positions of the cage.70The synthesis, structure, and reactivity with two-electron nucleophiles, of [Cp*IR(1,2-S2-cZoso-C2BloHlo)]has been reported.71The cyclic, bissilylated complex [(1,2-(SiMe&-l ,2-closo-C~BloHlo)-l ,2-Pt(PPh3)] is formed on reaction between [1,2-(SiMe2H)2-l,2-C2B10H10] and [Pt(C2H4)(PPh3)2],The reactivity of this complex with alkyne, dione and nitriles is reported72 to afford

5: Carboranes, Including Their Metal Complexes

123

heterocycles incorporating alkene, ketonate, imine and amine functionalities (Figure 8).

-

H

M2Si

I

\

iMe2 Ph Figure 8

A range of compounds containing intramolecularly stabilised organogallium groups appended to doso-1-[(dimethylamino)methyl]-o-carborane have been reported.73 Depending on reaction stiochiometry, mono- or biscarboranyl systems are formed. The reactivity of these new compounds towards bases such as pyridine or water is also reported. Three novel thiolate-bridged obonded indacarboranes [(C2B9H11)In(L)]2(L = S(CH2)2S(CH2)2S, SCH2CH2S, SPh) have been synthesised and structurally characteri~ed,~~ by reaction of T1[1-Tl-cZoso-2,3-C2BgH11] with InC13, followed by addition of the respective sodium thiolate salt (Figure 9). 2-

Figure 9

5

Complexes with Sn and Si

The coordination chemistry of the dianionic stannaborate [NBu4l2[SnB11H113 is described, reaction with various transition metal halides affords complexes in which the stannaborane is coordinated to the metal centre via the tin atom.75 The synthesis of monosilametallaboranes [NEt4][M(MeSiB1oH10)(NMe2)3](M = Nb, Ta) and their facile reaction with dihalomethanes to afford the novel bisamido bridged complexes pEt4][Ta(MeSiB10H8)(p-NMe2)2Br3]

124

Organometallic Chemistry

has been described (Figure 10). The mono and bis halogen substituted intermediates on this reaction pathway have also been isolated.76

-/ Me ____)

Figure 10

References 1.

2. 3.

4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

15.

16. 17.

For the previous review in this series see: A. S . Weller in Organometallic Chemistry; ed. M. Green, Vol. 27, The Royal Society of Chemistry, Cambridge, 1999. D. A. Fletcher, R. F. McMeeking, D. Parkin, J. Chem. InJ: Comput. Sci., 1996, 36, 746. P. C. Andrews, M. J. Hardie and C. L. Raston, Coord. Chem. Rev.,1999, 189, 169. C. E. Housecroft, Angew. Chem. Int. Ed., 1999,38,2717. 1. B. Sivaev and V. I. Vladimir, Collect. Czech. Chem. Commun., 1999,64,783. P. Kaszynski, Collect Czech. Chem. Commun., 1999,64,895. P. Kaszynski, A. G. Douglas, J. Organomet. Chem., 1999,581,28. J. Plesek, Inorg. Chim. Acta, 1999,289,45. S. Hermanek, Inorg. Chim. Acta, 1999,289, 20. K. Hermansson, M. Wojicik and S . Sjoberg, Inorg. Chem., 1999,38,6039. T. Onak, J. Jaballas and M. Barfield, J. Am. Chem. SOC.1999,121,2850. D. K. McLemore, D. A. Dixon and S. H. Strauss, Inorg. Chim. Acta, 1999, 294, 193. R. B. King, Inorg. Chem., 1999,38, 5151. S . V. Ivanvov, S. M. Ivanova, S. M. Miller, 0. P. Anderson, K. A. Solntsev and S . H. Strauss, Inorg. Chim. Acta, 1999,289, 76. T. Peymann, A. Herzog, C. B. Knobler and M. F. Hawthorne, Angew. Chem. Int. Ed., 1999,38, 1062. B. T. King, B. C. No11 and M. Josef, Collect. Czech. Chem. Commun., 1999, 64, 1001. C. A. Reed, N. L. P. Fackler, K.-C. Kim, D. Stasko and D. R. Evans, J. Am. Chem. Soc., 1999,121,6314.

5: Carboranes, Including Their Metal Complexes

18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36.

37. 38. 39.

40. 41. 42. 43. 44.

45. 46. 47. 48.

125

Z. Xie, C.-W. Tsang, F. Xue and T. C. W. Mak, J. Organomet. Chem., 1999,577, 197. B. Gruner, Z. Zanousek, B. T. King, J. N. Woodford, C. H. Wang, V. Vsetecka and J. Michl, J. Am. Chem. Soc., 1999,121, 3122. A. J. Lupinetti, M. D. Havighurst, S. M. Miller, 0. P. Anderson and S. H. Strauss, J. Am. Chem. SOC.,1999,121, 11920. S. V. Ivanov, S. M. Miller, 0. P. Anderson, K. A. Solntsev and S. H. Strauss, Inorg. Chem., 1999,38,3756. J. D. Carpenter and B. S. Ault, Inorg. Chim. Acta, 1999,286, 1. B. Wrackmeyer, H.-J. Schanz, W. Milius and C. McCammon, Collect. Czech. Chem. Commun., 1999,64,977. D. Hnyk, M. Hoffmann and P. von R. Schleyer, Collect. Czech. Chem. Commun., 1999,64,993. Z. Janousek, P. Kaszynski, J. D. Kennedy and B. Stibr, Collect. Czech. Chem. Commun., 1999,64,986. A. M. Shedlow and L. G. Sneddon, Collect. Czech. Chem. Commun., 1999,64,865. B. Wrackmeyer, H. J. Scahnz, M. Hofmann, P. von Schleyer and R. Boese, Eur. J. Inorg. Chem., 1999, 533. B. Griiner, T. Jelinek, Z. Plzak, J. D. Kennedy, D. L. Ormsby, R. Greatrex and B. Stibr, Angew. Chem. Int. Ed., 1999,38, 1896. L. H. Onak, T. Jaballas, U. Tran, T. U. Troung and T. H. To, Inorg. Chim. Acta, 1999,289, 1 1. M. G. Davidson, M. A. Fox., T. G. Hibbert, J. A. K. Howard, A. Mackinnon, I. S. Neretin and K. Wade, Chem. Comrnun., 1999, 1649. F. Teixidor, M. A. Flores and C. Viiias, Organometallics, 1999,18,5409. R. J. Hardie, R. D. Godfrey and C. L. Raston, Chem.-Eur. J., 1999,5, 1828. M. J. Hardie and C. L. Raston, Eur. J. Inorg. Chem., 1999, 195. L. Cracium and R. Custelcean, Inorg. Chem., 1999,38,4916. R. Macias, N. P. Rath and L. Barton, J. Organomet. Chem., 1999,581,39. W. Chen, J. J. Rockwell, C. B. Knobler, D. E. Hanvell and M. F. Hawthorne, Polyhedron, 1999,18, 1725. B. Forster, J. Bertran, F. Teixidor and C. Vinas, J. Organomet. Chem., 1999,587, 67. R. L. Thomas and A. J. Welch, Polyhedron, 1999,18, 1961. A. Herzog, A. Maderna, G. N. Harakas, C. B. Knobler and M. F. Hawthorne, Chem.-Eur. J., 1999,5, 1212. 0.Crespo, M. C. Gimeno and A. Laguna, Polyhedron, 1999,18, 1279. 0 .Crespo, M. C. Gimeno and A. Laguna, Polyhedron, 1999,18,1279. F. Teixidor, P. Angles and C. Vinas, Inorg. Chem., 1999,38, 3605. F. M. de Rege, J. D. Kassebaum, B. L. Scott, K. D. Abney and G. J. Balaich, Inorg. Chem., 1999,38,486. Z. Chong, J.-Q. Wang, J. A. Maguire and N. S. Hosmane, Main Group Met. Chem., 1999,22,361. N. S. Hosmane, H. Zhang, L. Jia, T. J. Colacot, J. A. Maguire, X. Wang, S. N. Hosmane and K. A. Brooks, Organometallics, 1999,18, 516. T. T. Chin, R.N. Grimes and W. E. Geiger, Inorg. Chem., 1999,38, 93. B. Griiner, F. Teixidor, C . Viiias, R. Sillanpaa, R. Kivekas and B. Stibr, J. Chem. SOC.,Dalton Trans., 1999, 3337. J. Holub, B. Gruner, I. Cisarova, J. Fusek, Z. Plzak, F. Teixidor, C . Viiias and B. Stibr, Inorg. Chem., 1999,38,2775.

126

Organometallic Chemistry

49.

D. Reed, A. J. Welch, J. Cowie, D. J. Donohoe and J. A. Parkinson, Inorg. Chim. Acta., 1999,289, 125. 0. Navratil, Z. Skalican, Z. Kobliha and E. Halamek, Collect. Czech. Chem. Commun., 1999,64,1111. R. M. Garrioch, P. Kuballa, K. S. Low, G. M. Rosair and A. J. Welch, J. Organomet. Chem., 1999,575, 57. S. Dunn, R. M. Garrioch, G. M. Rosair, L. Smith and A. J. Welch, Collect. Czech. Chem. Commun., 1999,64, 1013. D. D. Ellis, P. A. Jellis and F. G. A. Stone, Chem. Commun., 1999,2385. I. T. Chizhevsky, I. A. Lobanova, P. V. Petrovskii, V. I. Bregadze, F. M. Dolgushin, A. I. Yanovsky, Y. T. Stuchkov, A. L. Chistyakov, I. V. Stankevich, C. B. Knobler and M. F. Hawthorne, Organometallics,1999,18, 726. D. D. Ellis, S. M. Couchman, J. C. Jeffery, J. M. Malget and F. G. A. Stone, Inorg. Chem., 1999,38,2981. A. S. Batsanov, A. V. Churakov, J. A. K. Howard, A. K. Hughes, A. L. Johnson, A. J. Kingsley, I. S. Neretin and K. Wade, J. Chem. SOC.Dalton Trans., 1999, 3867. C. Viiias, R. Nuiiez, F. Teixidor, R. Sillanpaa and R. Kivekas, Organometallics, 1999,18,4712. F. Teixidor, R. Benakki, C . Viiias, R. Kivekas and R. Sillanpaa, Inorg. Chem., 1999,38,5916. D. D. Ellis, A. Franken and F. G. A. Stone, OrganometaElics, 1999,18,2362. Z . Xie, S. Wang, Z.-Y. Zhou and T. C. W. Mak, Organometallics, 1999,18, 1641. Z. Xie, S. Wang, Q. Yang and T. C. W. Mak, Organometallics, 1999,18,2420. S. Wang, Q. Yang, T. C. W. Mak and Z. Xie, Organometallics,1999,18,4478. Z. Xie, Z. Liu, Q. Yang and T. C . W. Mak, Organometallics, 1999,18, 3603. Z . Xie, K. Chui, Q. Yang and T. C. W. Mak, Organometallics, 1999,18, 3947. Z. Xie, C. Yan, Q. Yang and T. C. W. Mak, Angew. Chem. Int. Ed., 1999, 38, 1761. D.-H. Kim, J. KO, K. Park, S. Cho and S. 0. Kang, Organometallics, 1999, 18, 2738. M. Herberhold, C.-X. Jin, H. Yan, W. Milius and B. Wrackmeyer, J. Organomet. Chem., 1999,587,252. M. Herberhold, C. X. Jin, H. Yan, W. Milius and B. Wrackmeyer, Eur. J. Inorg. Chem., 1999,873. M. Herberhold, C.-X. Jin, H. Yan, W. Milius and B. Wrackmeyer, Angew. Chem. Int. Ed., 1999,38, 3689. J.-Y. Bae, Y.-L, Park, J. KO,K.-L. Park, S.-L. Cho and S. 0. Kang, Inorg. Chim. Acta, 1999,289, 141. Y. Kang, S. 0. Kang and J. KO,Organometallics, 1999,18, 1818. J.-D. Lee, C.-K. Baek, J. KO, K. Park, S. Cho, S.-K. Min and S. 0. Kang, Organometallics, 1999,18,2189. J. H. Kim, J. W. Hwang, Y. W. ParkandY. Do, Inorg. Chem., 1999,38,353. L. Wesemann, T. Marx, U. Englert and M. Ruck, Eur. J. Inorg. Chem., 1999, 1563. L. Wesemann, M. Trinkaus and M. Ruck, Angew. Chem. Int. Ed., 1999,38,2375.

50. 51. 52. 53. 54.

56. 57.

58.

59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70.

71. 72. 73. 74. 75.

76.

6 Group 13: Boron, Aluminium, Gallium, Indium and Thallium BY MATTHEW J. ALMOND

1

Boron

1.1 General. - There are many papers which report the use of organoboron compounds in organic synthesis and these are largely beyond the scope of this review. However, one or two examples may be noted. Pyridinium acceptors have been alkylated via thermal and photoinduced electron transfer in chargetransfer salts of organoborates, [Pyf,BR4-]. These coloured salts are readily isolated by the metathesis of LiBMe4, LiBMePh3 or NaBPh4 with a series of pyridinium triflates in aqueous solution. Thermal or photochemical chargetransfer activation of the salts leads to efficient methyl transfer to the pyridinium cations to afford the nucleophilic adducts Py-Me in good yields. Contact charge-transfer ion pairs are identified as the critical intermediates in the formal nucleophilic addition and thus play an important role in determining the regiochemistry of the alkylation. Borane chain transfer agents have been used to synthesise borane-terminated polyethylene and diblock copolymers containing polyethylene and A polar polymer.2 This work represents a recent effort in the long-standing aim of introducing polar groups into polyolefin chains. Another long-standing challenge has been that of catalytically functionalising hydrocarbons. A method has recently been reported for stoichiometric and catalytic B-C bond formation from unactivated hydrocarbons and b ~ r a n e s . ~

'

1.2 Compounds Incorporating the B(C6F& Moiety. - B(C6F5)3 is a powerful Lewis acid. There are a number of recent reports of the chemistry of this compound. It will react with naphthols to form Lewis acid adducts; this provides a means to generate stabilised forms of the keto tautomers of phenol^.^ Two examples are provided by the reactions of a-naphthol and 1,3dihydroxynaphthalene with B(C6F5)3.The structure of the a-naphthol product a is shown in 1. The key stru$ural points are a short C-0 bond (1.273(3) long B-0 bond (1.547(3) A) and a long-long-short-long-long-short array of carbon-carbon bonds around the six-membered ring of the cyclohexadienone part of the adduct molecule. A number of zwitterionic metallocycles have been derived from rac- and meso-ethylenebisindenyl zirconocene olefin complexes

A),

Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001 127

128

Organometallic Chemistry

and pentafluorophenyl-substituted b o r a n e ~The . ~ one electron oxidation of an azazirconacyclobutene in the presence of B(C6F& has been reportede6

1

2

A variety of donor adducts of B(C6F5)3 have been prepared by reaction of the Lewis acid with the appropriate Lewis base in ~ e n t a n eIn . ~ this way the nitrile complexes (C~FS)~B.NCR (R = Me, p-Me-C&, p-N02-C&), the isonitrile complexes (C6F5)3B.CNR(R = C(CH3)3, C(CH&CH2C(CH3)3, 2,6(CH&C6H3) and the phosphine adduct (C6F5)3B.P(CJ!?5)3have been prepared. The compounds have been characterised by IR and NMR spectroscopies as well as single crystal X-ray diffraction. One representative structure (R = Me) is given in 2. It is noted that coordination of the nitriles and the isonitriles leads to a substantial increase in the CN bond strength; v(CN) moves to a markedly higher wavenumber upon coordination. A small, but experimentally significant decrease in the CN bond length is noted from the X-ray studies. These experimental findings have been backed up by theoretical calculations and the work leads to the question as to whether a nonclassical main group carbonyl complex (C6F5)3B.CO may exist. B(C6F5)3 has also been used to generate adducts with the transition metal 0x0-anions wO.4l2- and [Re04]-.* The tris adduct [WO{OB(C6F5)3>3]2-and the mono adduct [Re03{OB(C6F5)3>]- have been formed in this way and the crystal structure of the salt [nPr4r\rJ2[WO{OB(C6F5)3)31, which is given in 3, has been determined. The q-cyclopentadienyl-0x0-compounds[Re(q-C5R5)03](R = H or Me) react with B(C6F5)3to give the appropriate monoadducts; the crystal structure of the form of the adduct where R = H is given in 4. Similarly the triazacyclononane compounds [LM03] (L = N,N,N’- trimethyl-1,4,7-triazacyclononane and M = M o or W) form adducts of general formula [LM02{OB(C6F5>3>]. Alkyl group effects have been studied in the ion pair formation, thermodynamics and structural reorganisation dynamics in zircocenium alkyls. One series of such species to be studied is that of the ion pairs [(I ,2-Me2Cp)2ZrR]+[CH3B(C6F5)~] (R = Me, ‘Bu, CH2SiMe3 and CH[SiMe3)2).9

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

129

4

3

1.3 Compounds Containing Nitrogen or Phosphorus Atoms. - Tris(pyrazoly1)borate ligands have been synthesised by a new route from MeBBrz and pyrazole derivatives under very mild conditions at room temperature to give TlL complexes." The structure of the complex where L = [HB(3,5-Me2pz)3]is given in 5. In a separate piece of work the synthesis and structures of the phenyl-substituted tris(3-tert-butylpyrazolyl)borato complexes [PhTptBU]M (M = Li, T1 or H) are reported." Unlike the previously reported complexes of this type where symmetric tridentate coordination of the ligand to the metal atom (see 5) is seen it is found that the complex [PhTptBu]T1exhibits an unprecedented structure (6). Specifically, one of the tert-butylpyrazolyl groups is rotated by ca. 90" and the TI atom interacts directly with the nitrogen atom attached to the boron via a p-orbital component of the aromatic mystem of the pyrazolyl nucleus. 6 is non-rigid on the NMR timescale in solution at room temperature, but cooling to - 80 "C allows 'axial' and 'equatorial' isomers to

5

6

Organometallic Chemistry

130

be identified with the descriptors denoting the position of the pyrazolyl group relative to the boat configuration of the six-membered [BN4Tl]ring. A novel organoboron compound: B2(0)(7-azain)2Ph2(7-azain = 7-azaindole anion) has been synthesised.12 The structure of one isomeric form of this compound is given in 7. The principal interest in this compound has been the observation that it shows strong blue electroluminescence. It is still the case that useful organic or organometallic blue emitters are quite rare, so 7 is potentially of use in producing organic electroluminescent devices with a full colour display. An anionic tridentate phosphinoborate - tris(diphenylphosphinomethy1) phenyldiborate - has been isolated as the Li(tmen)+ salt following the reaction of dichlorophenylborane with [Li(tmen)][CH2PPh2]in THF.l 3 This anion will act as a ligand in its reaction with SnC12,the product being the complex 8. It is possible, furthermore, to dehalogenate 8 to give the complex { [PhB(CH2PPh2)3]Sn}PF6 which still displays q 3 coordination of the Sn atom to three P atoms. n

7

1.4 Compounds Containing Oxygen Atoms. - A number of oxazaborolidinones have been prepared as single diastereoisomers.14 It is found that asymmetric memory is maintained in enolates which are derived from these compounds because the stereogenic boron resists equilibration with achiral, trivalent boron-containing species on the timescale of enolate alkylation. The importance of blue luminescence in organic and organometallic compounds has already been alluded to. This phenomenon has also recently been observed in the 7-azaindole adduct of the boroxine, B303Ph3.15The adduct (9) was prepared by the reaction of PhB(OH)2 with 7-azaindole. 9 shows that the 7-azaindole ligand is bonded to the boroxine molecule through a B-N bond and an H . . .O hydrogen bond. 9 is a fluorescent in solution and in the solid state. However, there is a significant difference in the fluorescence maximum: nm; solid h,,,=400 nm); it is also found by NMR solution h,,,=368 methods that 9 is fluxional in solution. The boroxine ring - this time substituted by methyl groups - also appears in a range of adducts that have

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

131

recently been obtained.16These adducts are of the form Me3B303.L(L = piperidine, isobutylamine, morpholine, 3-picoline and benzylamine). The structure of the adduct M ~ ~ B ~ O ~ N H ; B U . M ~ B (has O Halso ) ~ been determined. This shows an H-bond interaction between MeB(OH)2 and a ring 0 atom of the six-membered B303 ring; the direction of this interaction strongly suggesting sp2 hybridisation for this 0 atom. A novel boron-containing heterocycle has been observed in compound lo.l7 This 1,3,2,4-dioxadiborinanidewas generated by hydrolysis of the corresponding tetracoordinate 1,2-0xaboretanide. 10 has distorted tetrahedral and trigonal planar boron atoms and the sixmembered ring is boatlike. A boronate-substituted pyrrole has been synthesised and its oxidation leads to a polymer film which is found to act as a new fluoride-sensing material.l8

Mnn

10

9

1.5 Compounds Containing Metal Atoms. - Enantiometrically pure, pinenefused borabenzene derivatives have been prepared from enantiometrically pure a-pinene starting materials. l9 A range of chemical reactions are reported including isomerisation to a dihydroborinine (using catalytic quantities of HCl), methylation with MezZn, chlorination with BC13 and methoxylation with Me3SiOMe. Lithiation of the methyl derivative affords boratabenzenes and the crystalline solvate including a lithium atom (11) has been characterised. The bis( 1-methylboratabenzene) derivatives of germanium, tin and lead have all recently been synthesised.20The lead compound Pb(C5H5BMe) was synthesised by reaction of Li(C5H5BMe)with PbC12; the lighter homologues by reaction of 2-(Me3Sn)(C5H5BMe) with SnC12 or GeC12. The germanium and tin compounds are isolated as colourless liquids and the lead compound as a yellow low-melting solid. The lead analogue possesses a monomeric bent sandwich structure with a bending angle of 135.2(3)"; this represents the first structural characterisation of facial bonding of a boratabenzene to a p-element. This lead compound undergoes addition reactions with nitrogen donor bases such as tetramethylethylenediamine and 2,2'bipyridyl. The bipyridyl adduct also adopts a bent sandwich structure with a bending angle of 139.1(5)" and with the bipyridyl moiety in the pseudoequatorial plane.

Organometallic Chemistry

132

C8

12

11

The novel aminoboranediyl-bridged zirconocenes [iPr2NB(q5-C5H4)2]ZrC12 (12) and ['Pr2NB(q5-1-C9H&]ZrC12 have been prepared and structurally characterised.21Both of these compounds form highly active catalysts for the polymerisation of ethylene. The catalyst derived from the C9Hs compound converts propylene to isotactic polypropylene. The reactions of 1,l'-distannaferrocenes and chloroboranes give rise to ferrocene-based Lewis acids of general formula 1 , 2 - f ~ ( B R ~ ) ( s n RThis ~ ) . ~is~ an unexpected rearrangement reaction in which one of the SnMe3 groups from the starting organometallic compound is lost. There is again interest in such compounds as potential olefin polymerisation catalysts. In this context it is also interesting to note the activation of Cp2ZrMe2 using perfluoryl d i b ~ r a n e sIn . ~this ~ way reagents have been synthesised which are useful ethylene polymerisation catalysts when used in the presence of MeAl(BHT)2 (BHT = 2,6-di-tert-butyl-4-methylphenoxide). There has also been a report of the syntheses and structures of a range of zirconocene organoborate derivatives, namely Cp2ZrH{ (P-H)~BC~H*}, Cp2Zr(CH2Ph){ ( P - H ) ~ B C ~ H and ~ )Cp2Zr(CH2Ph)((p-H)2BC5Hlo} .24 The Bronsted acids H20.B(C6F5)3and D20.B(C6F5)3have been synthe~ i s e dReaction .~~ of neutral divalent metallocenes [M(I~-CSH~)~] (M = Cr, Fe or Co) with two equivalents of the lighter isotopomer results in oxidation of the metallocene and formation of salts containing the [M(q-CSH5)2]+ cations - , which is hydrogentogether with the hydroxoborate anion [HOB(C6F5)3] bonded to the second acid equivalent, namely [M(qC5H5)2][(F5C6)3BOH. .. H20.B(CbF&]. Other salts with p-OH bridged anions have also been prepared. The reaction of [Mn(CN)(PR3)(NO)(q-C5H4Me)] (R = Ph or OPh) with AuCl(tht) (tht = tetrahydrothiophene) in the presence of Na[BPh4] gives rise to the complex [Mn(CNBPh3)(PR3)(NO)(q-C5H4Me)] (13).26The structure of 13 shows that the triphenylboron moiety has added to the nitrogen atom of the cyanomanganese centre. The Mn ligand appears to be a relatively weak donor when compared to a range of other N and 0 ligands. Other related complexes

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

133

have been generated and their one-electron oxidation reactions on a platinum disc electrode in CH2CI2have been explored. A compound { ~ l ’ - C ~ M e ~ R e ) ~ ( p q6:q6-B4H4C02(CO)Sjincorporating a novel coordinated ‘inorganic benzene’ has been synthesised and ~haracterised.~~ This compound contains a planar six-membered B4C02 ring sandwiched between two Cp*Re fragments. Five CO groups are associated with the two Co atoms; four of these are terminal, the fifth bridges the two metal atoms. The necessity of packing of the five CO groups causes the Cp* groups to tilt and this moves the bridging CO out of the plane of the B4C02 ring. A range of borylindenides has been synthesised.28 These have been used to prepare complexes containing iron or ruthenium.

13 ,t I3

14

The reaction of l , l ’ - f ~ ( B M e(fc ~)= ~ ferrocenyl) with pyrazine gives a novel poly(ferrocene) derivative (14) which has been structurally ~haracterised.~~ This compound is a dark green colour, which is indicative of charge-transfer interactions between the iron centres and the electron-poor pyrazine adduct bridges. New 1:1 triorganophosphine silver(1) adducts containing the anionic, potential &-donor, hydrotris(3-methyl-1-imidazolyl-2-thioxo)borate (Tm) have been synthesised from K[Tm], AgN03 and tricyclohexylphosphine (PCy3), tribenzylphosphine (PBz~), tri-p-tolylphosphine (P(p-t~lyl)~)~, tris(2,4,6-trimethylphenylphosphine) (PMes3) or ethyldiphenylphosphine (PEtPh,). All complexes were characterised by a combination of analytical methods including IR and multinuclear NMR. The crystal structure of [(Tm)Ag{PCy3}](15) shows the silver atom tricoordinate with the donor Tm acting in the S2 bidentate form. The short Ag-B contact distance is suggestive of a two-electron B-H. . .Ag agostic interaction.

Organometallic Chemistry

134

15

2

Aluminium

2.1 General. - The aluminium and gallium dimethyl complexes [BptBu,MTAlMe2 and [BpfBu9Me]GaMe2 = bis(3-tert-butyl-5-methylpyrazolyl) hydroborato) are readily obtained by reaction of with Me3Al or Me3Ga. Both of the resulting complexes have been characterised by single crystal X-ray methods and the structures are very similar with the one exception that the C-M-C bond angle increases from 118.9(3)’ for the aluminium compound to 124.0(2)’ for the gallium anal~gue.~’ The Lewis acid properties of the methylene bridge dialuminium compound R2Al-CH2-AlR2 (R = CH(SiMe3)2)have been in~estigated.~~ This compound has been treated with suspensions of sodium azide or sodium acetate in diethyl ether. The Crown ether [18]crown-6 was added to the reaction mixture in order to complex the sodium ions. In both cases the dialuminiurn compound reacts as a chelating Lewis acid and six-membered rings are formed by coordination of both aluminium atoms either to the terminal nitrogen atoms of the azido group or to the oxygen atom of the aceto group. Each anionic product crystallised as a salt with the cation p a ( [ 18]crown-6)(i-Pr20)]+. The aluminatacyclopropene derivative, 16, has been synthesised by the reaction of tetrakis[bis(trimethylsilyl)methyl]dialane with lithium phenyle t h ~ n i d eThe . ~ ~ anionic carbon of this latter reagent inserts into the Al-A1 single bond of the dialane. By interaction of the second ethynide carbon atom with one of the aluminium atoms a three-membered heterocycle is formed containing an A1 atom and a C=C double bond. The synthesis and structure of a stable organotrihydroaluminate bearing a novel bowl-type substituent (17) is reported.3417 is synthesised by the reaction of BmtLi (Bmt = 4-tert-butyl-2,6bis[(2,2”,6,6”-tetramethyl-m-terphen-2’-yl)methyl]phenyl)and AlH3NMe3 in dimethoxyethane. 17 shows high activity as a reducing agent toward unsaturated compounds such as benzophenone, phenyl benzoate and benzonitrile. 1,2-Bis(trimethylstannyl)tetrafluorobenzenereacts with chlorodimethylaluminium(II1) to afford 18. This is dimeric 1,2-bis(chloromethylalurnino)tetra-

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

135

fluorobenzene. It contains two A12C3heterocycles, has a perfluorinated backbone and acts as a bifunctional Lewis acid.35

16

17

18

A theoretical study has been made of contra-binding rotation in Al+-L complexes (L = C6H6,C4H40, C5H6and C4H4NH).36In another theoretical ab initio study the transition states for the carboalumination of alkenes and alkynes have been in~estigated.~~ Ethylene insertion into an aluminium catalyst has been simulated using quantum mechanical methods.38The catalyst to be studied was [AlMe{MeC(NMe)2>]'. 2.2 Compounds Containing Group 15 Atoms. - A number of trialkylaluminium-dialkylamine adducts have been prepared and characterised by 'H NMR spectroscopy and single crystal X-ray diffra~tion.~' The adducts to be studied have the general formula R'A1.NHR22 (R' = Me, Et, i-Pr, i-Bu or t-Bu, R2= Me, Et, i-Pr or t-Bu); they were prepared by the reaction of Rl3A1 and NHR22. At high temperatures these adducts either eliminate alkane to form dimeric amides or dissociate. Increasing the bulk of R' favours alkane

136

Organometallic Chemistry

elimination. The reaction of AIR3 ( R = M e or Et) with H2NCH2CH2NMe2 leads to a number of amido- and imid~alanes.~' These include 19 and 20 which are both are prepared from Et3A1. 19 is a tetrametallic imidoalane generated by heating the adduct formed between Et3Al and H2NCH2CH2NMe2in a sealed ampoule. 19 shows one four-membered A12N2 ring and two fivemembered AlN2C2 rings of cis conformation and it has approximately C2 symmetry with the C2 axis passing through the centre of the A12N2 ring. Pyrolysis of 19 in the presence of two equivalents of H2NCH2CH2NMe2at 190 "C in a sealed ampoule gives the hexameric imidoalane 20. This consists of a hexagonal prism of an (AIN)6 cage, formed by two flat six-membered (AlN)3 rings linked together by six transverse A1-N bonds.

19

-

fgcu

20

Interest in compounds containing Group 13 and Group 15 atoms within the same molecule is often fuelled by a desire to find precursors to binary 111-V (13-1 5 ) materials by Chemical Vapour Deposition. This has certainly been the driving force behind a recent examination of the aluminium and gallium azides Bn2MN3.THF (Bn= benzyl, M = A1 or Ga).41During the course of this work the hitherto unknown amide [Bn2AINMe2I2(21) has been prepared and structurally characterised. The reactivity of triethylaluminium with a series of secondary amines has been i n ~ e s t i g a t e d .This ~ ~ leads to a series of adducts and, upon thermolysis, aminoalane dimers. Crystal structures have been obtained for the species [Et2AlN(c-C6H11)2]2 and [Et2AlNC4H*NCH&during this work. A tridentate, six-coordinate ligand has been synthesised and its coordination chemistry with a number of metals explored.43These include the formation of 22 where the ligand is coordinated to an AIMe2 moiety. A number of 1,2-~yclopentadienyldiimine-Group 13 complexes have been prepared.44These are of the form [(1,2-C,H3(C(Ph)NH)2)]MR2 (M = A1 or Ga, R = Me, Et, CH2Ph or Ph; M= Ga, R = Me). Trimethylaluminium reacts with a P-diketimine (H(LL)) to yield the aluminium complex [A1(LL)Me2], from

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

137

which the salts [A1(LL)Me(THF)][BMe(C6F5)3].0.5THF and [Al(LL)Me(OEt2)][B(C6F5)4]o. 5Et20 have been prepared, where LL = tBuC(N~P~)~.~~ CI?

c4

22

Clls

21

The potentially tridentate Schiff base ligands [3,5-t-Bu2-2(HO)C&CH=NL] (L = CH2CH2NMe2, (2-PhO)C6H4, 2-CH2C5H4N or 8C9H6N (quinoline)) on reaction with Me3Al at room temperature afford the complexes [(3, ~ - ~ - B u ~ - ~ - ( H O ) C=NL)AlMe2]. ~H~CH The structure of the complex where L = CH2CH2NMe2 is given in 23.It shows trigonal bipyramidal coordination at the aluminium centre and a very long Al.. .N(amino) linkage.46 Further reaction of these complexes with B(C6F5)3 gives cationic complexes [(~,~-~-Bu~-~-(HO)C~H~CH=NL)AIM~]+ of which those where L = CH2CH2NMe2or (2-PhO)C6& are ethylene polymerisation catalysts. An octanuclear structural analogue of a calix[4]pyrrole which contains four aluminium atoms within the ring (24)has been ~ynthesised.~~ The four aluminium atoms of the sixteen-membered ring are coplanar to within 0.19 of each other; the four near-planar AlN3C rings are inclined by 59-67' to this plane. The bonding geometries at each aluminium centre are only slightly

A

ma

23

24

138

Organometallic Chemistry

distorted from tetrahedral. An aluminium cage compound containing aluminium, fluorine and nitrogen atoms has also recently been made.48The aim of this work was to attempt to synthesise a precursor which may be used to generate both AlN and AlF3 under relatively mild conditions. Reaction of (Me2AlF)4 with four equivalents of ArNH2 (Ar = aryl) gives a compound with an eight-membered ring containing four aluminium atoms and four fluorine atoms. Each aluminium atom is attached to one methyl group and one HNAr moiety. Upon heating this compound loses two equivalents of ArNH2 to give a cubic cage (25) the six faces of which form four eight-membered AkN(p2-F)3 rings in half chair formation and two eight-membered A14N2(p2F)2rings in boat conformation. All rings consist of alternating metal and non-metal

4iB 25

26

atoms. Reactions of Me2Si(OR)(NHR) (R = 2,6-Me2Ph; R = cyclohexyl or Ph) with AlMe3 in pentane at room temperature give dinuclear aluminium that contain both nitrogen and complexes (Me2A1)2[(p.-OR)(p-NR'SiMe3)] oxygen bridging groups.49The structure of the complex where R' = cyclohexyl is given in 26. Reaction of A1Me3 with the macrobicyclic ligand 1,15-diaza3,4:12,13-dibenzo-5,8,11-trioxabicyclo[l3,3,llnonadecane (C22H28N203) in the presence of a trace of water gives a tetranuclear organoaluminium complex (Me3Al)(C22H28N203)(AlMe2)(AIMe3)(p.3-0) (27) in almost quantitative yield.50 It is found that the p.3 oxygen atom bridges three different alkyl aluminium centres in a trigonal planar geometry and the fourth aluminium centre is bonded to the ether oxygen of the macrobicycle with a dative bond length. The synthesis of a number of new aluminium complexes using the 1-aza-ally1 ligand (R) has been r e p ~ r t e d . ~The ' reaction of RLi.THF with AIMe2Cl, A1MeCl2, AlC13 and A1Br3 in Et2O or n-hexane afforded RAlMe2, RAlMeCl, RAlC12 and RA1Br2 respectively. Reaction of RAlMe2 with two equivalents of Me3SnF or I2 gives [RAlF(p-F)]2 or RAlI2 respectively. Reaction of H2C(Ph2P=NSiMe3)2 with one equivalent of AlMe3 in toluene gives a fourcoordinate aluminium complex of formula [AlMe2{ HC(Ph2P=NSiMe3)2)-

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

139

27

K~N,N’]via the elimination of methane. The complex is monomeric and the bisiminophosphoranomethane ligand binds in a bidentate manner to the aluminium.52If the reaction is repeated with two equivalents of AlMe3 then the novel bimetallic complex [AlMe2{p2-C(Ph2P=NSiMe&) -K~C,C’,N,N’] is formed in which the methylene backbone carbon has been doubly deprotonated. The syntheses and structures of a wide range of neutral and :ationic Group 13 phosphinimine and phosphinimide complexes have bee.1 performed.53 It has also been found that the trialkyl phosphates OP(OR)3 (R=Me, Et, Ph or %Me3) react with AlMe3, AlEt3 and GaMe3 in hydrocarbon solvents to form adducts of the type R3M.0P(OR)3 (M=Al or Ga, R’ = Me or Et). Thermolysis of the SiMe3-containing adducts leads to the formation of cyclic alumino- and gallophosphate d i m e r ~ The . ~ ~structure of the aluminium form of the complex is given in 28. The aluminium trialkyls AIR3 and aluminium dialkylchlorides AlR2Cl (R = Me, Et or t-Bu) react with Sb(SiMe& in a 1:l molar ratio.55The trialkyls give simple 1:l adducts. The dimethylchloride gives the six-membered ring system cyclo-[Me(Cl)AlSb (SiMe3)2I3, while the sterically more hindered diethyl and di-tert-butyl

28

Organometallic Chemistry

140

chlorides give adducts of the type R2ClA1.Sb(SiMe3)3. 2.3 Compounds Containing Group 16 Atoms. - The matrix isolation technique has been employed to isolate and characterise the initial intermediate in the reaction of Me3Al with 02.It appears that the initial product is Me2A10Me and there is no sign of Me3A102. If the reactants were heated prior to deposition this initial product was not seen; rather one or more secondary species were observed. These could not be unambiguously characterised, though the presence of the well-known dimer [Me2A1OMeI2is very likely? The aluminium alkoxides [MeClAlOEt],, [Et2A1OMeI3, [Me2A1OEtl3 and [EtClAlOEt]3 have been investigated by NMR in o-dichlorobenzene solution in order to monitor the equilibrium between these trimers and the corresponding dimerseS7It is found that all of the complexes exist primarily as trimers at room temperature but that dimer concentrations increase as the temperature is raised. A range of aluminium aryloxides have been studied.58 These have been prepared by the reaction of R2AlX (R = Me, Et; X = Cl, Br) with MDBP-H2 or MMBPMMBP-H2 (MDBP-H2= 2,2’-methylene-bis-(4,6-di-tert-butylphenol); H2 = 2,2’-methylene-bis-(4-methyl-6-tert-butylphenol). Eight-membered heterocyclic rings are formed, the shape of which is controlled by an intramolecular C-H.. .O hydrogen bond as may be seen in 29. Some of the compounds made during this work show great catalytic activities toward the reaction of cyclopentadiene with methacrolein. A wide range of aluminium ansa-indenyl metallocycles have been synthesised and structurally ~haracterised.’~ These are generated from the reaction of two equivalents of AlMe2C1with one equivalent of Li2[( 1-indenyl)zSiMe2]and various related compounds containing substituted indenyl derivatives. The products are of the form (AlMe2(THF)(indenyl)) 2SiMe2. Some dramatic structural changes have been observed upon replacement of the ester functionality by ketone functionality in a-hydroxy carbonyl compounds in donor-functionalised alkoxides of aluminium.60These include dissociation of a dimer with five-coordinate aluminium centres to a

211 Ct241

C

29

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

30

141

31

monomer with four-coordinate aluminium. This process is illustrated by the interconversion of 30 and 31. The reaction of Me2A1F with 2,6-diisopropylphenol and triethyl citrate leads to the products (R0)6&F2Me4 (R = 2,6-i-Pr2C6H3) and (ROAlFMe)2 (R = C(CH2COOEt)2(COOEt)), both containing A1202 ring systems. Diisobutyl aluminium hydride (i-Bu2A1H) similarly reacts with (Me3Si)zO to give (i-B~2AlOSiMe3)2.~l This compound (32) also contains a A1202ring and the aluminium atoms are each four coordinate. This is the first example of a structurally characterised aluminium product obtained from (Me3Si0)20 by cleavage of the Si-0 bond. In fact the particular interest in all of this work is the unexpected breaking of stable Al-F and Si-0 bonds to yield products. Compounds containing Si202 rings have also been obtained by the interaction of R2AlH with cyclic siloxanes. Thus, for example, the reaction of t-Bu2AlH with (Me2Si0)3 or (Me2SiO)5 in refluxing toluene gives [(t-B~)2Al(pOSiMe2H)J2.62 A wide range of additional chemistry has been explored in this work. The influence of bulky ligands in the synthesis of aluminosiloxanes has been explored. In this work the hitherto unknown sterically-hindered silanol (2,6-i-PrzC6H3)N(SiMe2-i-Pr)Si(OH)3 has been reacted with AlMe3 at 0 "C and with (Me3Si)3CA1Me2.THFat room temperature. The products are (i) the new cubic aluminosiloxane [(2,6-Pr2C6H3)N(SiMe2-i-Pr)SiO3Al.THF]4 and (ii) the new acyclic aluminosiloxane [(2,6-Pr2C6H3)N(SiMe2-i-Pr)SiO(OH)2J2AlC(SiMe3)3.3THF.63The cubic compound contains an Al4Si4OI2core whilst the p 0.

32

CIt11

33

142

Organometallic Chemistry

acyclic compound has an A1Si202(0H)4 unit in which the silicon atoms containing the hydroxy groups are connected by an 0-A1-0 unit. The electronic and steric factors affecting the formation of four- or fivecoordinate aluminium complexes have been studied.@ Thus, for example, the reaction of 2-phenoxyethanol with AlX3 (X = C1 or Br) gives a five-coordinate dimeric product, [(p-OCH2CH20Ph)AlX2]2, whereas the reaction of the same alcohol with Al(t-Bu), gives the four-coordinate dimer [(p-O(CH2)20Ph)Al(t-Bu)&. The synthesis of organoaluminium chalcogenides [RAl(p-E)]2 (R = N(SiMe3)C(Ph)C(SiMe3)2;E = Se or Te) from the aluminium dihydride [RAlH(p-H)]2 has been described.65 The hydride is made by reduction of RAlBr2 with an excess of LiAlH4 in Et20; it is then reacted with elemental selenium or tellurium in toluene. The structure of the selenium product is given in 33. 2.4 Compounds Containing Another Metal Atom. - A monomeric lithium aluminate with very short agostic Li.. .HC interactions has recently been prepared.66 This is the complex lithium dimethylbis(2,6-di-tert-but yl-4methy1phenoxide)aluminate. The dialkylmetal boryloxides [(pL-9-BBN-9O)MMe2I2 (M = Al, Ga or In; 9-BBN = 9-borabicylclo[3.3.llnonane) have been prepared.67 The stable, borate-bridged, ansa-zirconocene complex [Cp*Al]+[Me(Ph)B(q5-C5H&ZrC12]- has been characterised.68 This compound shows an enhanced Lewis acidity of the boron atom within its strained ansa position. The first structurally characterised organometallic compound containing a bond between aluminium and bismuth has been ~repared.~'This is the complex [Me2A1Bi(SiMe3)&. It contains a six-membered A13Bi3 ring where the aluminium and bismuth atoms adopt a distorted tetrahedral environment and the Al-Bi bond lengths range from 2.755(3) to 2.793(3) The reactions Cp2(H)Zr(p2-H)2Al(Me)Mes* between Cp2ZrMe2 and ( M ~ s * A ~ H to) afford ~ and between Cp2Zr(C1)H and [ M ~ S * A I H ~ L ~ ( T HtoF )give ~ ] ~ Cp2(H)Zr(p2H)2Al(H)Mes* have been de~cribed.~'In the methyl version the metals are connected by two hydrogen bridges and the methyl groups have been transferred from zirconium to aluminium during the course of the reaction. Two titanium-thiolate-aluminium-carbide complexes have been generated by multiple C-H bond a ~ t i v a t i o nThese . ~ ~ are the complexes [CpTi(p-SR)(p-NPi-Pr3)(C)(AlMe,)2(p-SR)AlMe] (R = Ph or CH2Ph); the structure of the phenyl form is given in 34. In both molecules the pseudo-'three-legged piano stool' coordination of the titanium atom comprises a cyclopentadienyl ring, a thiolate sulfur, a phosphinimide nitrogen and a carbide carbon. Three aluminium atoms complete the bonding sphere of the carbide carbon. The first structurally characterised coordination compound containing direct AlCr bonding has been reported. This is the complex Cp*A1-Cr(CO)5 (35).72In this complex the carbene-like ligand AlCp* binds to the Cr centre. The complex is prepared from Cr(CO),(COT) (COT = cis-cyclooctene) and AlCp*.

A.

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

143

3

34

3

35

Gallium

3.1 General. - Gallium or indium atoms have been shown to react with methane in solid argon matrices upon UV photolysis (200-400 nm) to give initially the monomethylhydride, which itself undergoes photodissociation on broad-band irradiation (200-800 nm) to yield the methylmetal(1) compounds MeM ( M = G a or In). This observation represents the first sighting of the simplest organic derivatives of Ga(1) and In(I).73 The polymeric organogallium(1) compound [Ga(CH2CMe2Ph)], has been prepared by the reduction of Ga(CH2CMezPh)2Cl using either sodium or lithium with naphtahlene in THF.74 The appearance and disappearance of intermediates in the formation of this polymer have been monitored by EPR spectroscopy. The reaction of R2GaX (R = t-Bu,Si, X = Cl or Br) with RNa in heptane leads to the formation of the dark blue radical R2-GaR which transforms at 100°C in heptane into t-Bu,Si radicals and the dark violet R,Ga4 (36).7536 contains a very compact Ga4 tetrahedron (average Ga-Ga bond length = 2.572 A). 36 reacts with oxygen to give colourless R4Ga404which contains a Ga404 heterocubane. This heterocubane is hydrolysed to give a tetrameric dihydro-

36

37

144

Organometallic Chemistry

oxogallane [RGa(OH)2]4which is shown by X-ray crystallography to consist of chains of molecules of [RGa(OH)2]4 held together by H20 molecules. Reaction of Ph2C6H3Li.2Et20with MX3 (M = Ga or In; X = C1 or I) gives (i) (Ph2C6H3)2GaI,(ii) (Ph2C6H3)21nC1,or (iii) [Li.2Et20]{(Ph2C6H3)2GaC13] depending on the reagents used.76An unusual organometallic compound (37) with a -Ga-Ga-Galinkage has been ~ynthesised.~~ 37 - [(2,4,6-i-Pr3C6H2)2C6H3]Ga{H2PGa(H)PH2)Ga[C6H~(C6H2-i-Pr3-2,4,6)2]- was made from [(2,4,6-i-Pr3C6H2)2C6H3]GaC12 and P(SiMe3)3.The Ga-Ga bond lengths in 37 are 2.5145(13) and 2.7778(14)

A.

3.2 Compounds Containing Group 15 or 16 Atoms. - Two monomeric gallium-nitrogen compounds, Et2GaNH[C6H2(2,4,6-t-B~)3] and EtGa{ NH[C6H2(2,4,6-t-Bu)3]} have been prepared by metathetical reactions between either Et2GaC1 or EtGaC12 and LiNH[C6H2(2,4,6-t-B~)3].~* Cryoscopic molecular weight determinations show that both compounds are monomeric while a single crystal X-ray study also identifies EtGa{NH[C6H2(2,4,6-tB u ) ~ ] )as~ a monomer. This compound does not decompose to form a metallacycle upon heating but it does react with GaEt3 to form Et2GaNH[C6H2(2,4,6-t-Bu)3].This last compound does decompose upon heating. The product is { E ~ G ~ N H [ C ~ H ~ ( ~ , ~ , ~ - ~ - B Uwhich )~(C contains M ~ ~ CaH ~ - ~ ) ] six-membered metallacyclic ring in a twist-boat configuration as shown in 38. Reactions of Et3SiNH2 with GaR3 in a 1:l ratio have produced dimeric silylamidogallanes {R2Ga(pNHSiEt3)]2(R = Me or Et). A mixture of cis and trans isomers is produced in each case.79However, purification of the methyl form gives only the trans isomer as colourless crystals whereas the ethyl form is always obtained as a colourless liquid containing a mixture of the two isomers. The trans to cis isomersisation of the methyl form follows first order kinetics and is markedly accelerated in the presence of a Lewis base. The reaction of the trialkylgalliums GaR3 (R=Me, Et or i-Pr) with

G

38

39

145

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

substituted hydrazines yields simple adducts at room temperature.8o Subsequent thermolysis leads to stepwise alkane loss, giving first dimeric rings and then tetrameric cages. A range of dimeric species have been synthesised in this way and one - [i-Pr2GaNHNMe2I2- has been characterised crystallographically. The tetrameric [MeGaNHN-t-BuI4has also been isolated and crystallographically characterised. It is shown to have a cage structure comprising two hexagonal and four pentagonal rings as shown in 39. Two novel Ga2N2 ring systems have been generated by reaction of pentamethylcyclopentadienylgallium (Cp*Ga) with organic azides." Theses are the dimeric iminogallane (q '-Cp*GaNXyl)2 (40) and the dimeric azide-bridged gallane [(q '-Cp*)Ga(p2N3)(NSiMe3)2}]2 (41). 40 has a planar, approximately square Ga2N2ring with the molecule, in fact, being positioned on a crystallographic centre of inver-

40

41

sion. By contrast 41 has a rhomb shaped Ga2N2ring with two small N-Ga-N angles (75.58( 19)") and correspondingly two larger Ga-N-Ga angles (104.42(10)"). The sterically crowded gallium amidinate complexes { tBuC(NR)2}GaX2 (X=Cl, Me, Et or Bz; R=i-Pr, Cy or t-Bu) have been synthesised in good yields.82 X-ray crystallographic studies show that steric interactions between the t-Bu and R groups influence the R-N-Ga angle. A P4(GaR)3 cage (42) has been prepared by the reaction of the tetrahedral gallium(1) compound Ga4(C(SiMe3)3]4with white p h o s p h ~ r u sA . ~threefold ~ insertion of monovalent gallium atoms into P-P bonds of the P4 tetrahedron occurs to give the cage 42 which has a structure reminiscent of P4S3. This comprises a homocycle of three phosphorus atoms each of which is bonded to a gallium atom. The fourth phosphorus atom resides at the apex of the cage and is pyramidally coordinated to the three gallium atoms. A range of compounds containing gallium-silicon bonds have been prepared.84 The crystal structures of Ar2GaSi(SiMe3)3(Ar = 2(dimethylaminomethyl)phenyl-) and Ph2GaSi(SiMe3)3.THFhave been obtained. In each case the gallium atom is four coordinate. In the 2(dimethylaminomethyl)phenyl compound the gallium atom is coordinated to two carbon atoms, one silicon and a nitrogen atom stemming from one of the arms of the aryl ligand. In the phenyl compound the fourth coordination site is occupied by a THF molecule bonded through oxygen. Potential single-source precursors to gallium arsenide and

146

Organometallic Chemistry

gallium antimonide have been ~ynthesised.~~ The reactions employed are those of Et2GaC1 with either A ~ ( s i M e ~ or) ~ Sb(SiMe3)3 giving [Et2GaAs(SiMe3)2]2 or [Et2GaAs(SiMe3)2]2respectively. Equilibration of these two compounds, or reaction of Et2GaCl with a mixture of A ~ ( s i M e and ~ ) ~ Sb(SiMe3)3,gives the mixed pnicogen compound Et2GaAs(SiMe&Ga(Et)2Sb(SiMe& with a fourmembered Ga-As-Ga-Sb- ring. The compound di(p-acetato)dialkyldigallium has been used as a starting material for a range of digallium derivatives containing bridged or terminally coordinated Ga-Ga single bonds? This starting material - GaR2(p-02CMe0,0')2 (R = CH(SiMe3)2)- was obtained in almost quantitative yield by the reaction of R2Ga-GaR2 with acetic acid; it has a short Ga-Ga bond (2.3785(3) bridged by two acetato groups. Reaction of GaR2(p-02CMe-O,Ol), with lithium diphenyltriazide in an equimolar ratio gives a triazenido derivative with an even shorter Ga-Ga bond of 2.3675(4) A, while a similar product is obtained by reaction with lithiated diphenylbenzamidine. Addition of hydrolysed trimethylgallium to an excess of the crown ether 18crown-6 in water affords an alkyl p-hydroxo bridged Ga(II1) trimer in solution. In the solid a hydrogen-bonded assembled supermolecule [ (Me2Ga(p-OH))3.3H20]2.18-crown-6 is obtained.87 The compounds 2,6trip2H3C6GaC12, { 2,6-trip2H&6InCl( p-Cl)} and { 2,6-trip2H3C6GaC1(pOH)}2 (2,6-trip = 2,4,6-trisopropylphenyl) have been characterised.88 It appears that analogous products, previously described, were contaminated by OH at the Cl positions. A study has been made of the mechanism of the reaction of GaMe3 with H2Se. A simple mass spectrometric sampling system has been used on an atmospheric pressure MOCVD reactor.89It appears that there is no stable Lewis acid-base adduct, although transient adduct-type species may be involved.

A)

3.3 Compounds Containing Another Metal Atom. - The compound q5phospholylgallium has been ~ynthesised.~'This represents the first monomeric polyhapto compound formed between a phospholyl ligand and a main group metal. The reaction was carried out by co-condensing the high temperature molecule GaBr with a toluene/THF mixture which was then allowed to react

6: Group 13: Boron, Aluminium, Gallium, Xndium and Thallium

147

with lithium 2,5-bis(tert-butyl)phospholide.Treatment of the product with Cr(CO)5(COT)(COT = cis-cyclooctene) in hexane gave crystals of 43. This has an q5-phospholylgallium(I) chromium pentacarbonyl structure. The phospholyl plane is tilted with respect to th,e Ga-Cr axis and this is reflected in the fact that the Ga-P distance 2.489(1) A is longer than the Ga-C distances of 2.345(3) (C-t-Bu) and 2.372(5) A (C-H). The cyclopentadienyliron- and cyclopentadienylmolybdenum-gallium compounds [CpFe(CO)2GaC12ln and [CpMo(C0)3]Ga(t-B~)~ have been prepared." The latter, which contains GaC bonds, is made by reaction of CpMo(CO)3H with Ga(t-Bu)3. It acts as a Lewis acid, forming a complex with MeCN. The reaction of Ga4[C(SiMe3)3]4 with bis(cyc1ooctadiene)nickel gives a coordination complex [Ni(GaC(SiMe3)3>4](44) which may be considered as an analogue of Ni(C0)4. 44 shows tetrahedral coordination at the Ni centre and has very short Ga-Ni

A

01

c

43

44

bonds. This suggests strong n-back donation from nickel to the empty p(n) orbitals on gallium - a supposition which is borne out by the results of quantum chemical DFT calculations. 4

Indium

The coordination chemistry of the compound Br21nCH2Brhas been investigated.93 It is found that this species will react with tetraethylammonium bromide, IP-dioxane or THF to produce adducts of general formula Br21n(L),CH2Br (L = 1,4-dioxane, THF, n = 2; L = Br -, n = 1). The crystal structure of the ionic derivative [(C2H5)41\J1[Br31nCH2Br](45) has been obtained. A compound with an Inl2 deltapolyhedron framework - a dodecaindane - has recently been ~ynthesised.~~ This complex of formula R**In12 (R* = s i ( t - B ~ ) ~is) generated by thermolysis of R*41n2at 100 "C. The twelve indium atoms are arranged in the form of a twenty-sided polyhedron, but this does not have a spherical form such as is observed, for example, in Bl2HIz2-,

Organornetallic Chemistry

148

but rather resembles a stretched ellipsoid. The four indium atoms at the ends of the ellipsoid carry one R* group each, whereas the four indium atoms at the centre of the ellipsoid have no R* groups. The compound MeZIn(C5HS) has been prepared by a metathetical reaction between Me2InC1 and Li(C5H5)in THF solution and by a methane-elimination reaction between InMe3 and C5H6 at 145 to 160"C.95An X-ray structural study shows an infinite linear polymer (46) with cyclopentadienide units bridging InMez moieties through the 1 and 3 positions of the ring. The bridging is sufficiently strong that the

Mo

46

45

polymer does not melt before thermal decomposition at 195 to 200°C and the compound is insoluble in all solvents except those that act as strong Lewis bases, e.g. THF. In THF solution the compound exists as an equilibrium mixture of Me21n(C5H5).THF,MeIn(C5H5)2.THFand InMe,.THF according to 'H NMR spectroscopic studies. The reaction of Cp*In with Cr(CO)5(COT) (COT = cis-cyclooctene) results in the formation of Cr(Cp*In)(CO)S in which the Cp*In acts as an electronpair donor.96The structure is given in 47. The chromium atom has octahedral coordination and the q5-bonding mode of the Cp* ring is maintained. The structure of this complex is compared with the gallium analogue Cr(Cp*Ga)(CO)5.

47

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

149

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.

25. 26. 27. 28. 29. 30. 31.

D. Zhu and J.K. Kochi, Organometallics, 1999,18, 161. G. Xu and T.C. Chung, J. Am. Chem. SOC.,1999,121,6763. C.N. Iverson and M.R. Smith, 111, J. Am. Chem. SOC.,1999,121,7696. D. Vagedes, R. Frohlich and G. Erker, Angew. Chem. Int. Ed., 1999,38,3362. L.W.M. Lee, W.E. Piers, M. Parvez, S.J. Rettig and V.G. Young, Jr., Organometallics, 1999,18, 3904. C.J. Harlan, T. Hascall, E. Fujita and J.R. Norton, J. Am. Chem. SOC.,1999, 121, 7274. H. Jacobsen, H. Berke, S. Doring, G. Kehr, G. Erker, R. Frohlich and 0.Meyer, Organometallics, 1999,18, 1724. G. Barrado, L. Doerrer, M.L.H. Green and M.A. Leech, J. Chem. SOC.,Dalton Trans., 1999, 1061. C.L. Beswick and T.J. Marks, Organometallics, 1999,18,2410. C. Janiak, L. Braun and F. Girgsdies, J. Chem. Soc., Dalton Trans., 1999, 3133. J.L. Kisko, T. Hascall, C. Kimblin and G . Parkin, J. Chem. Soc., Dalton Trans, 1999,1929. Q. Wu, M. Esteghamatian, N.-X. Hu, Z. Popovic, G. Enright, S.R. Breeze and S . Wang, Angew. Chem. Int. Ed., 1999,38,985. A.A. Barney, A.F. Heyduck and D.G. Nocera, Chem. Commun., 1999,2379. E. Vedejs, S.C. Fields, R. Hayashi, S.R. Hitchcock, D.R. Powell and M.R. Schrimpf, J. Am. Chem. SOC.,199,121,2460. Q.G. Wu, G. Wu, L. Brancaleon and S . Wang, Organometallics, 1999,18,2553. M.A. Beckett, D.S. Brassington, P. Owen, M.B. Hursthouse, M.E. Light, K.M.A. Malik and K.S. Varma, J. Organomet. Chem., 1999,585,7. T. Kawashima, T. Kannabe, N. Tokitoh and R. Okazaki, Organometallics, 1999, 18, 5180. M. Nicolas, B. Farbre and J. Simonet, Chem. Commun., 1999, 1881. G.E. Herberich, U. Englert, B. Ganter, M. Pons and R. Wang, Organometallics, 1999,18,3406. G.E. Herberich, X. Zheng, J. Rosenplanter and U. Englert, Organometallics, 1999,18,4747. A.J. Ashe, 111, X. Fang and J.W. Kampf, Organometallics, 1999,18,2288. F. Jakle, A.J. Lough and I. Manners, Chem. Commun., 1999,453. V.C. Willimas, C. Dai, Z. Li, S. Collins, W.E. Piers, W. Clegg, M.R.J. Elsegood and T.B. Marder, Angew. Chem. Int. Ed., 1999,38,3695. F.-C. Liu, B. Du, J. Liu, E.A. Meyers and S.G. Shore, Inorg. Chem., 1999, 38, 3228. L.H. Doerrer and M.L.H. Green, J. Chem. SOC.,Dalton Trans., 1999,4325. D. Bellamy, N.G. Connelly, O.M. Hicks and A.G. Orpen, J. Chem. SOC., Dalton Trans, 1999, 3185. S . Ghosh, M. Shang and T.P. Fehlner, J. Am. Chem. Soc., 1999,121,7451. E. Barday, B. Frange, B. Hanquet and G.E. Herberich, J. Organomet. Chem., 1999,572,225. M. Grosche, E. Herdtweck, F. Peters and M. Wagner, Organometallics, 1999,18, 4669. C. Santini, C. Pettinari, G.G. Lobbia, R. Spagna, M. Pellei and F. Vallorani, Inorg. Chim. Acta, 1999,285, 8 1 . C.M. Dowling and G. Parkin, Polyhedron, 1999,18,3567.

150

Organometallic Chemistry

32. 33. 34. 35. 36. 37.

W. Uhl and F. Hannemann, J. Organomet. Chem., 1999,579, 18. W. Uhl, T. Spies, R. Koch and W. Saak, Organometallics, 1999,18,4598. K. Goto, J. Kobayashi and R. Okazaki, Organometallics, 1999,18, 1357. M. Tschinkl, R.E. Bachmann and F.P. Gabbay, Chem. Commun., 1999,1367. D. Stockigt, Organometallics, 1999,18, 1050. J.W. Bundens, J. Yudenfreund and M.M. Francl, Organometallics, 1999, 18, 3913. M. Reinhold, J.E. McGrady and R.J. Meier, J. Chem. SOC.,Dalton Trans., 1999, 487. D.C. Bradley, G. Coumbarides, I.S. Harding, G.E. Hawkes, I.A. Maia and M. Motevalli, J. Chem. SOC.,Dalton Trans., 1999,3553. J.E. Park, B.-J. Bae, Y. Kim, J.T. Park and I.-H. Suh, Organometallics, 1999, 18, 1059. M.-A. Muiioz-Hernandez, D. Rutherford, H. Tiainen and D.A. Atwood, J. Organomet. Chem., 1999,582,103. E.K. Styron, C.H. Lake, S.J. Schauer, C.L. Watkins and L.K. Krannich, Polyhedron, 1999,18, 1595. K. Kincaid, C.P. Gerlach, G.R. Giesbrecht, J.R. Hagadorn, G.D. Whitener, A. Shafir and J. Arnold, Organometallics, 1999,18, 5360. C.M. Ong and D.W. Stephan, Inorg. Chem., 1999,38,5189. F. Cosledan, P.B. Hitchcock and M.F. Lappert, Chem. Commun., 1999,705. P.A. Cameron, V.C. Gibson, C. Redshaw, J.A. Segal, M.D. Brice, A.J.P. White and D.J. Williams, Chem. Commun., 1999, 1883. V.C. Gibson, C. Redshaw, A.J.P. White and D.J. Williams, Angew. Chem. Int. Ed., 1999,38,961. H. Wessel, H.-S. Park, P. Miiller, H.W. Roesky and I. Uson, Angew. Chem. Int. Ed., 1999,38,813. C.H. Lee and J.W. Park, Organometallics, 1999,18, 5713. Q. Zhao, H.-S. Sun and X.-Z. You, J. Organomet. Chem., 1999,572,59. C. Cui, H.W. Roesky, M. Noltmeyer, M.F. Lappert, H.-G. Schmidt and H. Hao, Organometallics, 1999, 18,2256. K. Aparana, R. McDonald, M. Ferguson and R.G. Cavell, Organometallics, 1999,18,4241. C.M. Ong, P. McKarns and D.W. Stephan, Organometallics, 1999,18,4197. J. Pinkas, D. Chakraborty, Y. Yang, R. Murugavel, M. Noltmeyer and H.W. Roesky, Organometallics, 1999,18, 523. S. Schulz and M. Nieger, Organometallics, 1999,18, 315. B.S. Ault, J. Organomer. Chem., 1999,572, 169. W.E. Rhine, D.P. Eyman and S.J. Schauer, Polyhedron, 1999,18,905. C.-H. Lin, L.-F. Yan, F.-C. Wang, Y.-L. Sun and C.-C. Lin, J. Organomet. Chem., 1999,587,151. B. Thiyagarajan and R.F. Jordan, Organometallics, 1999,18, 5347. J. Lewinski, I. Justyniak, Z . Ochal and J. Zachara, J. Chem. Soc., Dalton Trans., 1999,2909. C. Rennenkamp, H. Wessel, H.W. Roesky, P. Miiller, H.-G. Schmidt, M. Noltmeyer, I. Uson and A.R. Barron, Inorg. Chem., 1999,38, 5235. C.N. McMahon, S.G. Bott, L.B. Alemany, H.W. Roesky and A.R. Barron, Organometallics, 1999, 18, 5395, A. Klemp, H. Hatop, H.W. Roesky, H.-G. Schmidt and M. Noltmeyer, Inorg. Chem., 1999,38,5832.

38. 39. 40.

41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58.

59. 60. 61. 62. 63.

6: Group 13: Boron, Aluminium, Gallium, Indium and Thallium

64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92.

151

C.-H. Lin, B.-T. KO, F.-C. Wang, C.-C. Lin and C.-Y. Kuo, J. Organomet. Chem., 1999,575,67. C. Cui, H.W. Roesky, M. Noltmeyer and H.-G. Schmidt, Organometallics, 1999, 18, 5120. W. Clegg, E. Lamb, S.T. Liddle, R. Snaith and A.E.H. Wheatley, J. Organomet. Chem., 1999,573,305. R. Anulewicz-Ostrowska, S. Lulinski and J. Serwatowski, Inorg. Chem., 1999,38, 3796. C.T. Burns, D.S. Stelck, P.J. Shapiro, A. Vij, K. Kunz, G. Kehr, T. Concolino and A.L. Rheingold, Organometallics, 1999,18, 5432. S. Schulz and M. Nieger, Angew. Chem. Int. Ed., 1999,38,967. R.J. Wehmschulte and P.P. Power, Polyhedron, 1999,18, 1885. F. Guerin and D.W. Stephan, Angew. Chem. Int. Ed., 1999,38,3698. Q. Yu, A. Purath, A. Donchev and H. Schnockel, J. Organomet. Chem., 1999, 584,94. H.-J. Himmel, A.J. Downs, T.M. Greene and L. Andrews, Chem. Commun., 1999,2243. O.T. Beachley, Jr., M.J. Noble and R.D. Allendoerfer, J. Organomet. Chem., 1999,582, 32. N. Wiberg, K. Amelunxen, H.-W. Lerner, H. Noth, W. Ponikwar and H. Schwenk, J. Organomet. Chem., 1999,574,246. R.C. Crittendon, B.C. Beck, J. Su, X.-W. Li and G.H. Robinson, Organometallics, 1999,18, 156. X.-W. Li, P. Wei, B.C. Beck, Y. Xie, H.F. Schaefer, 111, J. Su and G.H. Robinson, Chem. Commun., 1999,453. O.T. Beachley, Jr., D.B. Rosenblum, M.W. Churchill, D.G. Churchill and L.M. Krajkowski, Organometallics, 1999,18,2543. B.-J. Bae, J.E. Park, Y. Kim, J.T. Park and I.-H. Suh, Organometallics, 1999, 18, 2513. D.W. Peters, E.D. Bourret, M.P. Power and J. Arnold, J. Organomet. Chem., 1999,582,108. P. Jutzi, B. Neumann, G. Reumann and H.-G. Stammler, Organometallics, 1999, 18,2037. S. Dagorne, R.F. Jordan and V.G. Young, Jr., Organometallics, 1999, 18, 4619. W. Uhl and M. Benter, Chem. Commun., 1999,771. N.L. Pickett, 0. Just, X. Li, D.G. Vanderveer and W.S. Rees, Jr., J. Organomet. Chem., 1999,582,119. E.E. Foos, R.J. Jouet, R.L. Wells, A.L. Rheingold and L.M. Liable-Sands, J. Organomet. Chem., 1999,582,45. W. Uhl, T. Spies and R. Koch, J. Chem. SOC.,Dalton Trans., 1999,2385. P.D. Croucher, A. Drljaca, S. Papadopoulos and C.L. Raston, Chem. Commun., 1999,153. B. Twamley and P.P. Power, Chem. Commun., 1999, 1805. N. Maung, G. Fan, T.-L. Ng, J.O. Williams and A.C. Wright, J. Mater. Chem., 1999,9,2489. A. Schnepf, G. Stosser, D. Carmichael, F. Mathey and H. Schnockel, Angew. Chem. Int. Ed., 1999,38, 1646. A.S. Borovik, S.G. Bott and A.R. Barron, Organometallics, 1999,18,2668. W. Uhl, M. Benter, S. Melle and W. Saak, Organometallics,1999,18,3778.

152

Organometallic Chemistry

93.

A.B. de Carvalho, M.A.M.A. de Maurera, J.A. Nobrega, C . Peppe, M.A. Brown, D.G. Tuck, M.Z. Hernandes, E. Longo and F.R. Sensato, Organometallics, 1999, 18, 99. N. Wiberg, T. Blank, H. Noth and W. Ponikwar, Angew. Chem. Int. Ed., 1999, 38, 839. O.T. Beachley, Jr., E.S. Robirds, D.A. Atwood and P. Wei, Organometallics, 1999,18,2561. P. Jutzi, B. Neumann, G. Reumann, L.O. Schebaum and H.-G. Stammler, Organometallics, 1999,18, 2550.

94. 95. 96.

7 Group 15: Phosphorus, Arsenic, Antimony and Bismuth BY CAMERON JONES 1

Phosphorus

Due to space restrictions a comprehensive review of organophosphorus chemistry cannot be included here. Instead emphasis has been placed on developments in low coordination phosphorus chemistry. In this area a review has appeared on ionic three-membered diphosphirenium and diphosphirenylium rings.' Various reports dealing with phosphaalkynes and related compounds have appeared which include a theoretical study of the vibrational frequencies, 31P and 13CNMR shifts of a series of phosphaalkynes. In general, good agreement was found between the calculated values and previously reported experimental data.2 The phosphaalkyne hydro-osmiation product [Os(P=CHBut)Cl(CO)(PPh3)2]has been implicated as an intermediate in the reaction of P-CBut with [OsHCl(CO)(PPh&(BTD)] 1, BTD = 2,1,3-benzothiadiazole, which ultimately gives the metallacyclic phosphaalkenyl-phosphaalkene complex [OS{ K P,K'P'P=C(Bu')P(=CHBut)}Cl(CO)(PPh&] via reaction of 1 with a further molecule of PECBU'.~ The same phosphaalkyne reacts with [{ Cp*Re(C0)2}2], Cp* =C5Me5, in the presence of an oxidising agent to yield the dinuclear rhenium complex, [Re(C0)2C5Me4CH2{ p-HC(But)P(0)}Re(C0)2Cp*] (X-ray) which contains a chiral, bridging phosphinidene oxide ligand.4 A phosphaalkyne dimerisation has been reported to occur from the reaction of [RhCl(triphos)], triphos = PPh(CH2CH2PPh2)2,with P-CBu' in the presence of TlBF4. This affords the 1,3-diphosphacyclobutadiene complex [Rh(triphos) { q4-(PCBu')2}][BF4]which can form complexes with the W(CO)5 or PtC12(PEt3)fragments through P-lone pair c~ordination.~ A phosphaalkyne pentamerisation occurs in the reaction of PGCMes, Mes = C6H2Me3-2,4,6, with [w(CO)5(THF)] to give the novel metalla-norbornadiene complex, 2, which has been structurally characterisede6The reactivity of PzCBu' toward metal imido complexes has been explored in two papers. Firstly, reaction with in situ generated [Zr(q5-Cp)2(NC6H3Me2-2,6)] leads to a [2+2] cycloaddition and formation of the hetero zirconacycle [Cp2Zr{ PC(But)N(C6H3Me2-2,6)~] (X-ray). By contrast, treating [Ti(NB~')Cl~(py)~l, py = pyridine, with P-CBu' affords [TiC12(py)(q -NBut(q3-P2C2Bu'2)}]via two [2+2] cycloaddition react i o n ~The . ~ related vanadium imido complexes, [vC13(NR)], R = Pr, CH2But, cyclohexyl (Cy), react with P-CBu', again via [2+2] cycloaddition reactions Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001

153

Organometallic Chemistry

154

2

but the products eliminate 1,2,4-azadiphosphole rings, one of which, P2C2But2NPh, has been shown to be planar by X-ray crystallography.' Phosphaalkynes, P=CR, R = But, adamantyl (Ad), have been shown to react with the perfluoroalkyne dirhodium complex [Rh2(Cp)2(p-CO)(p-q2CF3C-CCF3)] to give the phosphacyclobutadienyl complexes [RhCp{ p-q4:q PC3R(CF3)2){ Rh(CO)Cp)] 3 (X-ray). The reactions of 3 toward w(CO)5(THF)] and [Fe2(CO),] has also been reportedegOne paper describes the synthesis of a complex containing a bridging cyaphide ligand, [Pt(p-q ',q2C=P)Pt(PEt3)2]which reacts with Me1 to form the corresponding isocyaphide complex, [Pt(Cl)(PEt3)(p-C=PMe)Pt(PEt3)2(I)]. lo In related work, theoretical studies have been carried out on the 1,4-diphosphabutadiyne, P=C-C=P, 4, which show it to be a linear, thermodynamically stable molecule that is partially delocalised. The theoretical use of 4 as a ligand was also examined.' A number of reports dealing with the chemistry of species containing 02,h3phosphorus centres, e.g. phos haalkenes, have come forward. The first stable p-phosphaquinone, Mes*P=&H=C(But)C(=O)C(But)=kH, (X-ray) 5, has been prepared. This compound can be reduced chemically or electrochemically to the corresponding phosphasemiquinone radical, 5.-, in which the unpaired electron is largely localised on the phosphorus centre,l 2 A phosphaalkene, PhP=C(H)Me, has been formed within the coordination sphere of a bimetallic complex by the deprotonation of [Cp2(Co)4Mo,(p-PPhH)(p-H)] and subsequent addition of acryloyl chloride. The resulting complex, [ C P ~ ( C O ) ~ MI-,O ( ~ q2-PhP=CHMe)] (X-ray) undergoes cis / trans isomerisation.l3 Two carbonyl functionalised phosphaalkenes, RC(0)P=C(NMe2)2, R = But, Ph, have been reacted with a range of protic acids and alkylating reagents to give a variety of products, some of which have been crystallographically characterised. The reported chemical transformations were said to highlight similarities between the chemistries of these phosphaalkenes and phosphorus ylides.l4 Palladium(0) catalysed cross coupling reactions of Z-Mes*P=C(H)Br with two aryl Grignard reagents have yielded the bidentate phosphaalkenes, Mes*P=CH(3-R-Ar), R = pyridyl, carbaldimino. Upon reaction with [PdMeCl(COD)], COD = 13-c clooctadiene, the three membered palladacycles, Mes*(Me) -CH(3-R-Ar)-PdCl (X-ray), are formed by carbopalladation of the P=C bond." Several metallaphosphaalkenes have come forward this year. The addition of Grignard reagents, RMgX, across the phosphaalkyne, PrCBut, in diethyl ether affords the phosphavinyl Grignard reagents, [Z-RP=C(But)MgX(OEt2)], R = Cy, cyclopentyl, Et, Mes (X-ray) in high yields. These additions occur in a

'-

'

+

7: Group 15: Phosphorus, Arsenic, Antimony and Bismuth

155

regio- and stereoselective fashion.l 6 Treatment of Mes*P=CC12with Bu"Li in DME has been shown to give the thermally unstable phosphavinylidene carbenoid, [Mes*P=C(C1)(Li(DME)2)], 6, which spectroscopic, crystallographic and theoretical studies show to contain a C-Li bond with a low degree of covalency.l 7 The reaction of 6 with MesGeFrCHRz, CHR2 = fluorenyl, affords the germaphosphaalkene, Mes*P=C(Cl)-Ge(F)(Mes)-CHR2. Treatment of this compound with ButLi has been shown to give the novel bis(phosphaalkenyl)digermacyclobutane,7.l 8

The chemistry of a variety of compounds other than phosphaalkenes that contain a 02,h3-phosphoruscentre have been investigated. These include the first phosphasilaallene, Mes*P=C=Si(Ph)(Tip), 8, Tip = C6H2Pri3-2,4,6,which was formed by dechlorination of the silaphosphaalkene, Mes*P=C(Cl)SiCl(Ph)(Tip). Compound 8 is unstable above -30°C and dimerises to give a number of products.l9 The synthesis and characterisation of two phosphaallene tungsten complexes, [ { (Me3Si)2C(H)-P=C=C(OEt)R}{W(CO)5)], R=SnMe3, SnPh3, have also been reported.20 Reaction of the well known diphosphene Mes*P=PMes* with methyl triflate gave the first phosphanyl phosphenium ion, [Mes*P=P(Me)Mes*]+,which X-ray crystallography shows to have a close contact with the triflate counter ion. The further chemistry of this salt was also examined.21 A number of phosphinimide-titanium complexes, e.g. [c~Ti(Me)~-N=pBu~~], 9, have been prepared, When complex 9 is reacted with B(C6F5)3methyl abstraction occurs resulting in the formation of [C~T~(M~)-N=PBU'~][B(M~)(C~F~)~] which X-ray crystallography shows to be a contact ion pair. In addition, in the presence of MAO, 9 and related compounds were found to be active ethylene polymerisation catalysts.22 A series of phosphoranylidene carbenoids, [M~s*P(=E)=C(X)L~(THF)~], E=C(SiMe&, NMes*; X = F , C1, Br, have been prepared by oxidation of Mes*P=E. X-ray crystallography and multinuclear NMR studies suggest these species are carbenoids with elongated C-X bonds and weak C-Li intera c t i o n ~Similarly, .~~ the a-(lithiomethylene)phosphorane, [R2(Bu)P=C(SiMe3)Li(THF)2], R=NCy2, has been shown to result from the reaction of the stable phosphanyl carbene, R2PC(SiMe3),10, and Bu"Li. Its X-ray crystal structure and reactivity toward electrophiles were also reported.24In a closely related paper the electrophilic behaviour of the same phosphanyl carbene toward phosphorus lone pairs has been examined. For example, treating 10 with tertiary phosphines, PR'3, yields, R2P-C(=PR'3)-SiMe3, which in the case of R' = Me is readily oxidised with dioxygen to R2P(=O)-C(=PMe3)-SiMe3

156

Organornetallic Chemistry

Many reports dealing with heterocycles containing low coordinate phosphorus centres have appeared. With regard to three membered ring systems, ab initio calculations have been carried out on a diphospha-substituted cyclopropene, cyclopropenone and methylene cyclopropene. The results showed a close correlation in the energies and structures of these systems with those of their experimental counterparts.26 A phosphinophosphirene, w ( S i Me3){P(NPri2)2), has been prepared from the reaction of P=CBut with the phosphino carbene, (Pr'2N)2P-CSiMe3.The heterocycle is thermally unstable and rearranges to give a number of products. A theoretical investigation of the relative stabilities of the products was also carried A variety of diphosphirenes and diphosphirenylium salts, and tungsten carbonyl complexes of these compounds, have been pre ared and their further chemistry investigated. One of the complexes, [{ (R2Nl$%NR2)[w(CO)4])2], R = Pr', was structurally characterised and found to be dimeric in the solid statee2* The chemistry of four membered low coordinate phosphorus heterocycles has been represented by a number of reports which include that of the formation of two q4-1,3-diphosphacyclobutadienecomplexes, [MoC1(CO)(q41,3-P2C2But2)(q5-C5R5)], R = H or Me. One of these, R = H , can be oxidised with water or methanol to give the phosphaphosphonietinyl complex, [MoCl(CO)(q3,h3,,h5-PC2But2PH(0R'))(q5-Cp)], R' = Me, H (X-ray).2gSimilarly, the 1,2- and 1,3-isomers of the diphosphacyclobutadiene complex, [Fe(C0),(q4P2C2But2)]can be formed via pyrolysis and loss of FeC12 from the diphosphetane complex [{ Fe(C0)4)2{p-1,2-P2(C1)2C2(But2)2}] in the case of the 1,2isomer; and reaction of Fe(CO)5with PrCBut under UV conditions in the case of the 1,3-isomer.The coordination chemistry of both isomers was examined.,' The remarkable 1,3-diphosphabutane-2,4-diyl,Mes*PC(H)P(Mes*)&Me3 (X-ray) 11, valence isomerises in UV light to give the corresponding 2,4diphosphabicyclo[1.1.O]butane (X-ray). This in turn thermally isomerises to yield the 1,4-diphosphabutadiene Mes*P=C(H)C(SiMe3)=PMes*(X-ray).31In related work 11 has been deprotonated with LDA to give an anionic carbene, [:~P(M~S*)C(S~M~~)~M~S*I[L~(THF)~] which can form a complex with AlMe3 through the carbene centre.32 Many reports have come forward that deal with five-membered low coordination phosphorus heterocycles. Of these a number deal with phospholyl complexes such as [M{q'-PC2(Ph)2C2(SiMe3)2>(THF),I, M = Ca, n = 4; M=Sr, n = 4 ; M=Sn, n = O , all of which have been crystallographically characterised and the phospholyl ligand found to coordinate through the Pcentre in an q l - f a ~ h i o nIn . ~ contrast ~ the ligand in the monomeric gallium(1) complex [Ga { q5-PC2(Bu')2C2(H)2)],12 (X-ray), is rl 5-coordinated. The lone pair at gallium in 12 can be used to form complexes such as [12.Cr(C0)5] (Xray).34The related indium complexes, [In(1,2,4-P3C2But2)] (X-ray) and [In(1,3P2C3Buf3)]have been prepared by co-condensation of indium vapour and P=CBu' at 77 K.35The reaction of [Li{PC2(But)2C,(H)2}] with MC12, M = Pb, Sn, Ge, has been shown to yield the main group metallocenes, [M (PC2(But)2C2(H)2>2],which X-ray crystallography confirmed to be bent. The lead complex has been used as a reagent for the transfer of the heterocycle

7: Group 15: Phosphorus, Arsenic, Antimony and Bismuth

157

onto either a rhodium or an iridium fragment.36 Similarly, the ql-tin(IV) R = Ph, Me, Bu, can be prepared by complexes [R3Sn(q1-1,2,4-P3C2But2)], reaction of the ring anion [P3C2But2]- with R3SnCl. These compounds have been found to be fluxional in solution with coordination of the tin centre switching between the 1- and 2-positions of the heterocycle. The utility of the reagents in organometallic and organophosphorus chemistry was examined.37 A variety of neodymium(II1) and samarium(II1) complexes incorporating the phospholyl ligand, PC4Me4, have been prepared, e.g. [Ln(PC4Me4)2{ CH(SiMe3)2}],Ln = Nd, Sm. Treating these complexes with molecular hydrogen gave [Nd(PC4Me4)2H]when Ln = Nd but reduction to [Sm(PC4Me4)2] when Ln = Sm.38The first structurally characterised 14 electron titanocene [Ti($P3C2But2)2] has been prepared by co-condensation of titanium vapour and PzCBu' and its crystal structure revealed a centroid-Ti-centroid angle of 173.9(1)". The compound undergoes an unusual [2+2] cycloaddition reaction Several functionalised with P-CBu' at elevated temperatures affording phosphacymantrenes, e.g. [Mn(C0)3{ PC(H)CZ(M~)~C(CO~R))], R = H or Et, have been synthesised by a number of methods. Replacing one carbonyl ligand by PPh3 was found to enhance the reactivity of these complexes toward electrophilic sub~titution.~' The monophosphaferrocene [Fe(Cp){PC2(H)2C2(Me)2}],14, acts as a ligand in the formation of a series of rhodium and iridium complexes, e.g. [Rh(14)4][BF4](X-ray)?'

\But

13

The chemistry of phospholes and substituted phospholes has been well represented in the literature. For example, ab initio calculations have been carried out on the triphosphole ring system, k(Bu')P(Mes*)Pd(Bu'), which have found that it is planar, fully aromatic and should be stable if it can be experimentally isolated.42A related triphosphole has been used in the formation of the complex [Ru(C0)2(q 5-P3C2B~'2CH(SiMe3)2}] which when treated with water in the presence of CO effects a transformation of the ring to a four electron donor ligand in [Ru(C0)3{ q3-k(Bu')PP(H)CH(SiMe3)2C(But)k (O)H}] (X-ray).43Two chalcogen substituted diphospholes, EPC(Bu')PC(Bu'), E = Se, Te, were prepared by reaction of the diphosphastibolyl anion, [1,2,4P2SbC2Buf2]-with E(S2CNEt2),. The mechanism of this novel reaction could not be determined but was said to involve a redox process.44 The same heterocycles can be used as ligands in the formation of [M(CO)5(q'P2EC2But2)], M=Cr, W (X-ray), in which the metal carbonyl fragment is ligated through the phosphorus centre adjacent to the chalcogen atom.

158

Organometallic Chemistry

Theoretical studies have found that this is the most stable site of atta~hment.4~ Similar azaphosphole-metal carbonyl complexes, e.g. 15, have been synthesised and characterised by NMR data. The results of calculations detailing the preference for q '-bonding in the complexes were also Three closely related papers have described the coordination chemistry and oxidation of the diazaphospholephosphines (X,P)&PN(Me)N=C(Me), X = F, NMe2, OCH2CF3.47y48949

15

16

Six membered heterocycles containing a low coordinate phosphorus centre have featured in the literature this year. The results of theoretical studies on aza- and diazaphosphinines have been compared to those on phosphinine itself. These comparisons suggest that introduction of nitrogen at a position adjacent to phosphorus in the heterocycle reduces its degree of aromaticity. This phenomenon is discussed in terms of the various calculated heterocycles rea~tivities.~'A theoretical study has been carried out on all the 24 possible valence isomers of diphosphabenzene, P2C4H4, which have been ranked in order of stability. The most stable was found to be the ortho-diphosphinine, 1,2-P2C4H4.51Reaction of PC5H2Ph3-2,4,6 with [Pd(OAc)2] affords a Pd(0) complex of unknown structure. When this is treated with PEt, the planar Pd3 (X-ray) is formed. Each phosphinine ligand cluster [Pd3(PEt3)3(p-PC5H2Ph3)3] bridges two palladium centres and theoretical studies suggest that both 0 and n: orbitals are involved in these bridges.52Treatment of a 1-zircona-4-phosphaindene complex with PBr3 has afforded the diphosphaindene, 16. Reaction of this with lithium metal yields the related 1,4-diphosphaindenyl mono and trianions.53 A variety of tridentate ligands based on phosphinine substituted phospholes, e.g. RPC4Me2{2-PC5H2Me(SiMe3))2-2,5; R = C2H4C1, have been synthesised and their utility as ligands i n ~ e s t i g a t e d .The ~ ~ first silacalix[4]phosphinines, e.g. 17 (X-ray), have been prepared by a number of routes under high dilution conditions and were found to be fluxional in solution.55 The

\

/

Me2Si,

17

SiMe2

7: Group 15: Phosphorus, Arsenic, Antimony and Bismuth

159

same macrocycle when reacted with [AuCl(SMe2)] in the presence of GaC13 affords [Au(I)(q2-17)][GaC14](X-ray) in which the gold centre is coordinated by trans-P centres of the macrocycle. This complex was reduced chemically and electrochemically to the unstable Au(0) complex, [Au(17)], which was studied by EPR spectro~copy.~~ A number of di- and triphosphabenzene systems have been studied which include several h5,h5-1,3-diphosphabenzenesthat have been structurally characterised and their coordination chemistry studied.57 The same research group has also prepared a series of palladium(I1) complexes of the h5*h5,h5-triphosphabenzene, I ,3,5-P3(NMe2)6C3H3, one of which has been characterised by X-ray crystall~graphy.~~ Related to the triphosphabenzene, 1,3,5-P3C3But3 18, are the 1,3,5-triphosphabicyclo[3.1 .O]hexanediyl hafnium complexes, 19 (X-ray). Compound 18 is prepared by treating the hafnium complex, [Hf(COT)(P3C3But3)],COT = cyclooctateraene, with C2C16. The hydrolysis products of 19 were also identified.59A range of transition metal complexes of 18, e.g. [M0(q~-l8)(C0)~], have been prepared by displacing arene ligands from suitable precursors, e.g. [Mo(q6-C,Hs)(CO)3]. In all cases 18 acted as an q6-ligand to the transition metal centre.60 In contrast an ql-complex of 18, trans-[PtC12(PMe3)(q'-18)], was prepared by reacting 18 with [{ PtC12(PMe3)}2].When the platinum complex was recrystallised in air it was found to react with three water molecules at the same time eliminating HC1 to give [PtCl(PMe3)(P303C3H5But3)] (X-ray).6' Compound 18 also reacts with ,2} in a [1 +4] cycloaddition to give a the stable silylene, :Si((NCH2But)2C6H4-l triphosphasilabicyclo[2.2.llheptadiene (X-ray).62

But 19 L = PMe3or CNBU' n=Oorl

Other low coordinate phosphorus systems that have been investigated this year include phosphenium ions and phosphinidenes. Theoretical calculations have shown that reaction of the mono-ammine adduct of the parent phosphenium ion, [(H3N)PH2]', with ammonia proceed without an intermediate barrier to the bis-complex [(H3N)2PH2]+.63 A range of aromatically stabilised cyclic phosphenium cations that resemble 'Arduengo" carbenes, e.g. [#"(But)C(H)=C(H)fi(But)][PF6] (X-ray), have been prepared and crystallographically characterised. The degree of aromatic stabilisation in one of these systems was examined by theoretical methods? Deprotonation of [MCp(C0)2Cl(P(H)2Mes*>] or decarbonylation of [MCP(CO)~ (P(H)Mes*}] affords the phosphenium complexes, [MCp(C0)2{=P(H)Mes*}], M = Mo, W, the phosphorus hydrogen substituents of which can be exchanged for methyl or chloro groups.65 With regard to phosphinidene chemistry, ab initio calculations have been

160

Organometallic Chemistry

carried out on complexes of the type [Cr(CO)5(PR)],R = H, CH3, SiH3, NH2, PH2, OH and SH. In all cases the Cr-P bond arises from ligand to metal charge transfer while there is a varying degree of n-back donation depending on the phosphinidene substituent. The RP-Cr(CO)5 binding energies range from 216 kJ mol-' (R = NH2) to 127 kJ mol-' (R = SiH3).66The addition of the transient phosphinidene complex, [W(CO)S(PPh3)], to a series of conjugated diynes was shown to yield alkynyl substituted phosphirenes, e.g. [W(C0)5{ q '-l!(Ph)CMec(-CzCMe)>] amongst other products.67 Another group has carried out the very closely related reactions of [w(CO)5(PPh3)]with RC-C-C-CR, R = But, SiMe3, which lead to rac- and meso- mixtures of the 2,2'-biphosphirenes, [{ W(CO)s[2-PhPC(R)=C]}2]. An X-ray crystallographic study of one complex, R = SiMe3, suggests there is some delocalisation within the diene sub unit.68

2

Arsenic, Antimony and Bismuth

A review has appeared which discusses n;-bonding and the lone pair effect in compounds containing double and triple bonds from arsenic, antimony and bismuth to another element.69 An extensive review has also catalogued the structural chemistry of organobismuth compounds.70 In another literature survey that details dendrimers containing heteroatoms, some attention has been paid to organobismuth based d e n d r i m e r ~ .Finally, ~~ a feature article on metal organo-vapour epitaxy (MOVPE) discusses the mechanisms of decomposition of organo arsenic compounds in the production of GaAs from dual source precursors.72 A number of reports have appeared that describe the chemistry of cyclic and acyclic systems that contain a low coordinate arsenic, antimony or bismuth centre. With regard to acyclic systems, the first homologous series of heavier dipnictenes, ArE=EAr, E = P, As, Sb or Bi; Ar = Mes or C6H2Pri3-2,4,6, have been prepared and many have been characterised by X-ray crystallography. This systematic study has concluded that n-overlap is important in dipnictenes containing the fifth and sixth period elements of the group and that these elements are largely n~n-hybridised.~~ The reaction of RCOC1, R = Mes or Mes*, with [LiSb(SiMe&] affords mixtures of the distibabutadienes, {(R)(Me$iO)Sb=C}2, R = Mes (X-ray) and the lithium 2-stiba-l,3-dionates, [Li{OC(R)SbC(R)O)], 20. When 20, R=Mes*, is treated with HC1 the first stiba-enol, Mes*C(O)Sb=C(OH)Mes* (X-ray), results.74 The previously reported transient stibaalkene, [2-py(SiMe3)2CSb=C(SiMe3)2-py],py = pyridyl, was reacted with InEt3 affording the C-centred geminal organodimetallic complex [2-py(SiMe3)2CSb(Et)C(SiMe3)2-pyInEt2] (X-ray) via carbometallation of the Sb=C bond.75 The metallophosphaalkene and arsaalkene, [Cp*(C0)2FeE=C(NMe2)2],E = P or As, have been alkylated, protonated and silylated using a number of reagents. These reactions were found to generally give rise to ferriophosphanyl and ferrioarsanyl functionalised carbocation salts, e.g. [Cp*(C0)2FeAs(R)C(NMe2)2]X, e.g. R = Me, X = S03CF3.76The

7: Group 15: Phosphorus, Arsenic, Antimony and Bismuth

161

reactivity of the same metalloarsaalkene and phosphaalkene toward MMe3, M = Al, Ga, In, has been examined. This study revealed that coordination of MMe3 to the pnicogen centre occurred to give the adducts [CP*(CO)~F~E(MMe3)=C(NMe2)2],two of which, E = P, M = A1 or Ga, have been structurally characteri~ed.~~ A variety of acylimino-h5-bismuthanes, Ar3Bi=NC(0)R, which contain a formal Bi-N double bond have been prepared and their reactivity examined. This was found to vary depending on the nature of the aryl s ~ b s t i t u e n tVarious .~~ Ru4 clusters have been formed from the reactions of a series of alkynes with the arsinidene cluster [ R U ~ ( C O ) ~ ~ ( ~ - H ) ~ ( ~ A S C F ~ ) ] A number of these were crystallographically characteri~ed.~, Heterocyclic compounds containing low coordinate Group 15 centres that have been investigated include the 1,3-thiaarsole, e(H)=C(H)SC(H)=A;, which theoretical calculations have suggested is aromatic.80The chloroarsole, ClAsC2(SiMe3)2C2(Me)2,can be prepared by treatment of the appropriate zirconacycle with AsC13. Reacting the arsole with distilled calcium leads to the calcium arsolyl complex, [ { p.-CaCl(THF)2[AsC2(SiMe&C,(Me),]> 21 (X-ray) which is dimeric through bridging chlorides.81A range of hetero-plumbocenes, E = P or Sb, have been [Pb(q5-P3C2B~t2)2] and [Pb(q5-Cp*)(q5-EP2C2But2)], synthesised by treating either PbC12 or PbCp*Cl with the heterocyclic anions, [P3C2But2]-or [SbP2C2But2]-.The bent heteroplumbocenes were studied by X-ray crystallography and multinuclear NMR techniques.82Co-condensation of the arsinine, AsC5H5, with M, M=Ti, V or Cr, leads to the heteroarene complexes, [ M ( T ~ ~ - A S C ~one H ~ of ) ~which, ], M = Ti, has been crystallographically characterised and found to have inter-ring As-..As interactions. Ligand competition studies showed that the arsinine is a superior q6-ligand compared to benzene.83 A number of neutral and ionic compounds containing heavier Group 15 element-element bonds have been reported in the past year. The perfluorodiarsane, (CF3)2A~A~(CF3)2, has been prepared and studied by X-ray crystallography, gas phase electron diffraction and ab initio studies. Using all techniques the trans form of this compound clearly predominated. By contrast the trans and gauche forms of its phosphorus analogue were close in energy and both were found to exist in the gas phase. The difference was put down to the higher s-character lone pair in the d i a r ~ a n e The . ~ ~ cyclic tetrastibane (Bu'S~)~, 21, reacts with [Fe2(CO),] or [Mo(CO)5(THF)] to give the complexes, [Fe(C0)4(21)]and [M0(C0)~(21)](X-ray) in which 21 acts as an ~ l - l i g a n d . ~ ~ Interestingly, the analogous reactions of the cyclic arsane, (Bu'As)~, with [Fe2(CO),] gives [(But7As9){ Fe(CO)4}](X-ray), the arsa-ligand of which consists of two As four membered rings connected by an AsBut bridge. The same paper reports the co-thermolysis of (PhAs)6 with [Cp'Ta(CO)& Cp' = C5H3But2-1,3, which affords a trinuclear tantalum cluster [{ Cp"Ta}3(p-O)(pCPh)(As3)] (X-ray).86 Compound 21 and the related mixed pnicogen cyclic species, (But4As,Sb4_,), n = 1 or 2, have been prepared by treating mixtures of ButSbC12and SbC13or AsC13 with magnesium metal in THF. Reduction of 21 with potassium metal in the presence of (Me2NCH2CH2)NMe,'N3', led to the ionic complex, [K(N3)2][(B~t2Sb)2Sb] (X-ray), the anion of which contains a

162

Organometallic Chemistry

bent Sb3 chain.87In related work, scrambling reactions of Me2SbBr gave the ionic complex [Me3SbSbMe2I2[(MeSbBr3)2], the cations of which consist of pyramidal Me3Sbunits bonded to bent Me2Sb units through short Sb-Sb (2.82 bonds. The description of the complex as either a trimethylstibane adduct of the dimethylstibenium ion or a stibinostibonium salt was discussed.88A number of products result from the reaction of SbMe3 with superacidc systems, e.g. HF/SbF6. One of these is the Sb-Sb bonded species, [Me3SbSbMe3][SbF6I2(X-ray) which exists as a sulfur dioxide a d d ~ c t . ~ ~ Many reports have come forward that concern the synthesis and chemistry of compounds of the type R3-nEXn or R5--EX,, R = alkyl or aryl, X = other ligand, E = As, Sb or Bi. For example R2BiCl and RBiC12, R = CH(SiMe3)2, have been prepared by the reaction of RLi and BiC13, and the reaction of RBiPh2with HCl respectively. Both compounds have been crystallographically characterised and the former found to be monomeric whereas the latter is polymeric through chloride bridges." The reactivity of tributylallenyl tin, 22, toward EC13, E = As or Sb, in a 1:1 ratio gives the allenyl element dichlorides, (H2C=C=C(H))EC12, in high yield. Similarly, the 1:1 reaction of divinyl antimony chloride with 22 affords allenyldivinylantimony.91 Six new isobutyl derivatives of antimony have been synthesised in high yield. These include S ~ ( B U ~ S) ~ (IB~ U , ' )and ~ I S ~ ( B U ~ )AHredistribution ~.~~ reaction has been used to prepare bromodi(isopropeny1)bismuthane which X-ray crystallography shows to contain infinite helical chains formed via Bi-Br-Bi bridges.93A series of bulky phosphino(arsino)methanes,e.g. Cy2AsCH2PR2,R = (R)-menthyl (Xray) have been synthesised via metathesis reactions.94 The oxidation of R2SbBr, R = CH2(SiMe3),with Br2 yields R2SbBr3the X-ray crystal structure of which shows it to be monomeric with the two alkyl ligands in equatorial sites of a distorted trigonal bipyramid. In addition, R3SbBr2 was found to react with NH4S2PPh2 to form R3Sb(S2PPh)2 (X-ray).95 The 0x0-bridged compounds, Ar3Sb(OAsPh2)2, Ar = Ph or p-tolyl (X-ray), have been prepared by the reaction of Ar3SbBr2with Ph2AsLi and subsequent work-up in air.96 Alkenes have been shown to react with Ph2SbC1 in the presence of a catalytic amount of [Pd(OAc)2] in the air to afford the corresponding phenylated alkenes in Heck type coupling reactions. The presence of atmospheric oxygen in the reactions was found to be essential to form the catalytic intermediate, [PhPd(OAc)].97 Various ionic alkyl and aryl Group 15 complexes have been reported. These include the trimethylarsonium salts, [Me3AsH][As2F11]and [Me3AsH][SbF6] which have been formed by the reaction of Me3As with the super acidic systems, HF/EF3, E = A s or Sb. Both compounds have been characterised by X-ray ~rystallography.~~ A related arsonium salt, [MeAsF3][AsF6](X-ray), has also been prepared and studied by Raman spectro~copy.~~ The di(arsa)acetonitrilium bromide, [(Ph3As)2CCN]Br, reacts with Cu(1)Br to give [(Ph3As)2CCN][CuBr2](X-ray). Two related manganese or cobalt complexes were reported in the same paper and both were structurally characterised.lOO When PhSbI2 and Me4SbI are reacted at low temperature the stibonium salt, [Me4Sb][Ph2Sb216],results. The crystal structures of both the cis and trans

A)

7: Group 15: Phosphorus, Arsenic, Antimony and Bismuth

163

forms of this compound were discussed.'" The compounds, Ph2ECl, E = Sb or Bi, react with [Pd(L)4], L=PMe2Ph, to give the cluster compounds, [E4(PdL2)4[Ph2EC12]2, the cations of which have cubane like frameworks whose electronic structures have been examined by theoretical calculations. lo2 The first alkyl bismuthates, [Bi(CF3)3F]- and [Bi(CF3)4]- , have been prepared by treating Bi(CF3)3 with F- or CF3- ions respectively. These have been characterised by NMR techniques.lo3 The unusual compound [(Cp*2A1)(q5Cp*Bi)(p-Al14)(Al14)2](X-ray) is formed when [ ( A l c ~ * )is ~ ]treated with Bi13. The compound exhibits chain like Cp*Bi units that are bridged by Al14 units. The bismuth centres in the compound are eleven coordinate.'04 Dehalogenation of the cyclopentadienyl bismuth dichloride, [((CsHR4)BiC1(p-C1))21, R=CHMe2, occurs when it is treated with AlC13. This affords the dimeric bismuthenium compounds, [{ (CSHR4)Bi(p-Cl)}2][A1C14]2 (X-ray).lo' Tertiary pnictanes have been used as ligands in the formation of a number of main group and transition metal complexes. The first tertiary arsane complex of Ge(IV), [Gech(A~Me~)~], is formed in the 1:l or 2:l reactions of AsMe3 with GeC14. The crystal structure of the complex reveals a transoctahedral geometry. By contrast, no reaction was observed between GeC14 and AsPh3. lo6 Bromination of the osmium cluster [Os3(C0)10(AsPh3)2] afforded the salt [Os3(CO)lo(AsPh3)2(p-Br)][Os(CO)3Br~] (X-ray), the anion of which is the result of nucleophilic attack of Br- on the cluster cation.lo7The orthomanganation of Ph3As=X (X=O, S) has occurred in its reaction with PhCH2Mn(CO)Sto give complexes, 23,one of which, X = 0, has been crystallographically characterised. The analogous cyclomanganation of AsPh3 was not successful.lo8A tertiary stibane, Sb(SiMe3)3, has been utilised in the formation of a series of aluminium trialkyl adducts, [R3A1(Sb(SiMe3)3}], R = Me, Et (X-ray), But. Adducts are also formed with Et2AlCl and Bu'2AlCl but an aluminium antimonide, [(Me(Cl)Al[Sb(SiMe3>2]]31, results from the reaction of the stibane with MeAlC12.lo9 The Vaska-type complexes, [Ir(ER3)2(CO)X],can be prepared by reaction of [I~(CO)~X~][NBU~] (X = C1, Br) with ER3, E =As or Sb, R = Me, Et, Ph, under an atmosphere of CO."' Substitution of the stibane ligands in trans-[PdXPh(SbPh3)2], X = C1 or Br, with a series of N, P or As-donor ligands occurs when the reactions are carried out in refluxing CH2C12.l 1 The crystal structure of trans-[RhC12Ph(SbPh3)3] has also been reported.l12 Reaction of the organo antimony cage compound, Sb2P4C4But4, with an excess of [M(CO)s(THF)], M = Cr, Mo, W, gives the 2:l complexes 24 (X-ray), in which the cage framework remains intact. By contrast, the cage reacts with [Fe2(CO)9] to give the unusual complex 25 (Xray), which is probably formed by insertion of an Fe(C0)3 fragment into an Sb-P bond of the cage. Its crystal structure shows it to contain two qlcoordinated Fe(C0)4 fragments and an q3-1,3-diphosphaallyl fragment coordinated to an Fe(C0)3 moiety.' l 3 The coordination chemistry of the distibinomethanes, R2SbCH2SbR2,R = Me or Ph, toward manganese and rhenium carbonyls has been examined. A range of complexes resulted from this study which includes [Mn2(C0)6(Ph2SbCH2SbPh2)](X-ray).' l4 In related work a series of metal carbonyl complexes of the ditertiary bismuthane, p -

'

164

Organometallic Chemistry

Ph2BiC6H4BiPh2,L, have been prepared. These include [(M(CO)5},(L)], M = Cr or W, y1 = 1 or 2. Interestingly, if L is reacted with [CPF~(CO)~(THF)]+ cleavage of a Bi-C bond occurs and the complex [CpFe(CO)2(BiPh3)lf results.l15

23X=O,S

24M = Cr, Mo, W

25

Other organo pnicogens have been used as ligands, for example Me2SbESbMe2, E = 0, S, and MeSb(SSbMe&, all of which have been treated with [Cr(C0)4(nbd)], nbd = norbornadiene. These reactions have afforded a number of complexes which include [Cr(C0)4(Me2SbSSbMe2)2].1 l6 The X-ray crystal structures of the dithiochelate compounds, [In(S2A~R2)3], R = Me, Ph, have been reported.' l 7 Two papers have been published which discuss alkyl or aryl pnicogens actin as Lewis acids rather than Lewis bases. The Arduengo carbene, . N(Me~)c~(cl)~N(Mes), 'carb', reacts with Sb(CF3)3to form a 1:l complex, [Sb(CF&(carb)] (X-ray). The carbene has a weak interaction with the Sb centre, Sb-C(carbene) 2.821 and remarkably the Sb centre is offset by 19" from the pseudo C2 axis of the carbene ligand."* A large number of pyridine and substituted pyridine adducts of aryl bismuth(II1) halides have been prepared and their structural chemistry discussed. l9 Reports on several secondary pnictide complexes of transition and main group metals have appeared. The primary arsine, PhAsH2, has been metallated with Bu"Li in THF to give [PhAsHLi.2THF], the crystal structure of which shows the compound to exist as an infinite helical polymer in the solid state.12' Thermolysis of thioarsanes, e.g. AsMez(SPh), with a number of metal carbonyls, e.g. [Fe(C0)5], has led to a variety of p-arsenido complexes, e.g. [Fe2(Co)6(p-AsMe2)(p-SPh)](X-ray). Arsenic-sulfur bond cleavage is a feature of all reactions.12' The first beryllium arsenide, [(q 5-Cp*)BeAsBut2], has been prepared via the salt elimination reaction of [Cp*BeCl] with [LiAsBu:]. The compound was crystallographically characterised and found to be monomeric in the solid state with the AsBut2 ligand acting as a one electron donor. 122 Reaction of Et2GaC1 with either As(SiMe3)3 or Sb(SiMe3)3 affords the dimeric arsenido and stibinido complexes, [(Et2GaE(SiMe3)2}2], E = A s or Sb, the former of which was found to exist in a dimer-trimer equilibrium in solution. Thermolysis of both compounds results in the formation of nanocrystalline GaAs or GaSb respectively, via P-hydrogen elimination pathways. 123

-+ A,

7: Group 15: Phosphorus, Arsenic, Antimony and Bismuth

165

References 1. 2. 3.

D. Bourissou and G. Bertrand, Acc. Chem. Res., 1999,32,561. K. Hubler and P. Schwerdtfeger, Inorg. Chem., 1999,38,157. A.F. Hill, C. Jones and J.D.E.T. Wilton-Ely, Chem. Commun., 1999,451. 4. G. Schmitt, D. Ullrich, G. Wolmershauser, M. Regitz and O.J. Scherer, 2. Anorg. Allg. Chem., 1999,625, 702. 5. M.F. Meidine, A.J.L. Pombiero and J.F. Nixon, J. Chem. SOC.,Dalton Trans., 1999,3041. 6. P. Kramkowski and M. Scheer, Angew. Chem. Int. Ed. Engl., 1999,38,3183. 7. F.G.N. Cloke, P.B. Hitchcock, J.F. Nixon, D.J. Wilson and P. Mountford, Chem. Commun., 1999,661. 8. F.G.N. Cloke, P.B. Hitchcock, J.F. Nixon, D.J. Wilson, F. Tabellion, U. Fischbeck, F. Preuss, M. Regitz and L. Nyulaszi, Chem. Commun., 1999,2363. 9. D.E. Hibbs, M.B. Hursthouse, C. Jones, A.F. Richards, M.D. Francis, R.S. Dickson and P.C. Junk, Organometallics, 1999,18,4838. 10. W.V. Konze, V.G. Young and R.J. Angelici, Organometallics, 1999,18,258. 11. F.M. Bickelhaupt and F. Bickelhaupt, Chem. Eur. J., 1999,5,162. 12. S . Sasaki, F. Murakami and M. Yoshifuji, Angew. Chem. Int. Ed. Engl., 1999,38, 340. 13. J.E. Davies, M.J. Mays, P.R. Raithby and A.D. Woods, Chem. Commun., 1999, 2455. 14. L. Weber, S. Uthmann, H.-G. Stammler, B. Neumann, W.W. Schoeller, R. Boese and D. Blaser, Eur. J. Inorg. Chem., 1999,2369. 15. M. van der Sluis, V. Beverwijk, A. Termaten, F. Bickelhaupt, H. Kooijman and A.L. Spek, Organometallics, 1999,18, 1402. 16. D.E. Hibbs, C. Jones and A.F. Richards, J. Chem. SOC.,Dalton Trans., 1999,3531. 17. E. Niecke, M. Nieger, 0. Schmidt, D. Gudat and W.W. Schoeller, J. Am. Chem. SOC.,1999,121,519. 18. I. Pailhous, H. Ranaivonjatova, J. Escudie, J.P. Declercq and A. Dubourg, Organometallics, 1999, 18, 1622. 19. L. Rigon, H. Ranaivonjatova, J. Escudie, A. Dubourg and J.P. Declercq, Chem. Eur. J., 1999,5, 774. 20. R. Streubel, H. Wilkens, F. Ruthe and P.G. Jones, 2. Anorg. Allg, Chem., 1999, 625, 102. 21. S. Loss, C. Widauer and H. Grutzmacher, Angew. Chem. Int. Ed. Engl., 1999,38, 3329. 22. D.W. Stephan, J.C. Stewart, F. Guerin, R.E. von H. Spence, W. Xu and D.G. Harrison, Organometallics, 1999, 18, 1116. 23. T. Baumgartner, D. Gudat, M. Nieger, E. Niecke and T.J. Schiffer, J. Am. Chem. SOC.,1999, 121,5953. 24. S . Gormri-Magnet, H. Gornitzka, A. Baceiredo and G. Bertrand, Angew. Chem. Int. Ed Engl., 1999,38,678. 25. S . Gormri-Magnet, 0. Polishchuk, H. Gornitzka, C.J. Marsden, A. Baceiredo and G. Bertrand, Angew. Chem. Int. Engl., 1999,38, 3727. 26. A. Skancke and J.F. Liebman, J. Org. Chem., 1999,64,6361. 27. M. Sanchez, R. Reau, C.J. Marsden, M. Regitz and G. Bertrand, Chem. Eur. J., 1999,5,274. 28. D. Bourissou, Y. Canac, H. Gomitzka, C.J. Marsden, A. Baceiredo and G. Bertrand, Eur. J. Inorg. Chem., 1999, 1479.

166

Organomet a l k Chemistry

A.S. Weller, C.D. Andrews, A.D. Burrows, M. Green, J.M. Lynam, M.F. Mahon and C. Jones, Chem. Commun., 1999,2147. 30. F.W. Heinemann, S. Kummer, U. Seiss-Brand1 and U. Zenneck, Organometallics, 18,2021. 31. E. Niecke, A. Fuchs and M. Nieger, Angew. Chem. Int. Ed. Engl., 1999,38,3028. 32. E. Niecke, A. Fuchs, M. Nieger, 0. Schmidt and W.W. Schoeller, Angew. Chem. Int. Ed Engl., 1999,38, 3031. 33. M. Westerhausen, M.H. Digeser, H. Noth, W. Ponikwar, T. Seifert and K. Polborn, Inorg. Chem., 1999,38, 3207. 34. A. Schnepf, G. Strosser, D. Carmichael, F. Mathey and H. Schnockel, Angew. Chem. Int. Ed. Engl., 1999,38, 1646. 35. C . Callaghan, G.K.B. Clentsmith, F.G.N. Cloke, P.B. Hitchcock, J.F. Nixon and D.M. Vickers, Organometallics, 38, 793. 36. K. Forissier, L. Ricard, D: Carmichael and F. Mathey, Chem. Commun., 1999, 1273. 37. A. Elvers, F.W. Heinemann, B. Wrackmeyer and U. Zenneck, Chem. Eur. J., 1999,5, 3143. 38. F. Nief, P. Riant, L. Ricard, P. Desmurs and D.B. Barbier, Eur. J. Inorg. Chem., 1999,1041. 39. F.G.N. Cloke, J.R. Hanks, P.B. Hitchcock and J.F. Nixon, Chem. Commun., 1999,1731. 40. B. Deschamps, L. Ricard and F. Mathey, Organometallics, 1999,18, 5688. 41. X. Sava, N. Mezailles, L. Ricard, F. Mathey and P. LeFloch, Organometallics, 1999,18, 807. L. Nyulaszi and J.F. Nixon, J. Organomet. Chem., 1999,5888,28. 42 43. G.B. Clentsmith, P.B. Hitchcock, J.F. Nixon and N. Sakaraya, J. Organomet. Chem., 1999,584,58. 44. M.D. Francis, C. Jones and C.P. Morley, Tett. Lets., 1999,40,3815. 45. M.D. Francis, D.E. Hibbs, P.B. Hitchcock, M.B. Hursthouse, C. Jones, T. Mackewitz, J.F. Nixon, L. Nyulaszi and N. Sakarya, J. Organomet. Chem., 1999,580,156. 46. C.B. Jain, D.C. Sharma, N. Gupta, J. Heinicke and R.K. Bansal, J. Organomet. Chem., 1999,577,337. 47. M.D. Mikoluk, R. McDonald and R.G. Cavell, Inorg. Chem., 1999,38,2791. 48. M.D. Mikoluk, R. McDonald and R.G. Cavell, Inorg. Chem., 1999,38,3306. 49. M.D. Mikoluk, R. McDonald and R.G. Cavell, Inorg. Chem., 1999,38,4056. 50. G . Frison, A. Sevin, N. Avarvari, F. Mathey and P. LeFloch, J. Org. Chem., 1999,64,5524. 51. L. Colombet, F. Volatron, P. Maitre and P.C. Hiberty, J. Am. Chem. SOC.,1999, 121,4215. 52. M.T. Reetz, E. Bohres, R. Goddard, M.C. Holthausen and W. Thiel, Chem. Eur. J., 1999,5,2101. 53. P. Rosa, L. Ricard, F. Mathey and P. LeFloch, Chem. Commun., 1999,537. 54. X. Sava, N. Mezailles, N. Maigrot, F. Nief, L. Ricard, F. Mathey and P. LeFloch, Organometallics, 1999,18,4205. 55. N. Avarvari, N. Maigrot, L. Ricard, F. Mathey and P. LeFloch, Chem. Eur. J., 1999,5,2109. 56. N. Mezailles, N. Avarvari, N. Maigrot, L. Ricard, F. Mathey, P. LeFloch, L. Cataldo, T. Berclaz and M. Geoffroy, Angew. Chem. Int. Ed. Engl., 1999, 38, 3194.

29.

7: Group 15: Phosphorus, Arsenic, Antimony and Bismuth

57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87.

167

S. Plank, G. Heckmann, W. Schwarz, B. Neumuller and E. Fluck, 2. Anorg. Allg. Chem., 1999,625,1712. G. Heckmann, S. Plank, W. Schwarz, and E. Fluck, 2. Anorg. Allg. Chem., 1999, 625,773. P. Binger, S. Stutzmann, J. Stannek, K. Gunther, P. Phillips, R. Mynott, J. Bruckmann and C. Kriiger, Eur. J. Inorg. Chem., 1999,763. P. Binger, S. Stutzmann, J. Stannek, B. Gabor and R. Mynott, Eur. J. Inorg. Chem., 1999,83. S.B. Clendenning, P.B. Hitchcock and J.F. Nixon, Chem. Commun., 1999,1377. S.B. Clendenning, B. Gehrhus, P.B. Hitchcock and J.F. Nixon, Chem. Commun., 1999,2451. T.I. Solling, S.B. Wild and L. Radom, Inorg. Chem., 1999,38,6049. M.K. Denk, S. Gupta and A.J. Lough, Eur. J. Inorg. Chem., 1999,41. W. Malisch, U.A. Hirth, K. Griin, M. Schmeusser, J. Organornet. Chem., 1999, 572,207. S. Creve, K. Pierloot, M.T. Nguyen and L.G. Vanquickenborne, Eur. J. Inorg. Chem., 1999,107. B. Wang, K.A. Nguyen, G.N. Srinivas, C.L. Watkins, S. Menzer, A.L. Spek and K. Lammertsma, Organometullics, 1999,18, 796. N.H.T. Huy, L. Ricard and F. Mathey, J. Chem. SOC.Dalton Trans., 1999,2409. P.P. Power, Chem. Rev., 1999,99,3463. C . Silvestru, H.J. Breunig and H. Althaus, Chem. Rev., 1999,99, 3277. J.P. Majoral and A.M. Carminade, Chem. Rev., 1999,99,845. D.J. Cole-Hamilton, Chem. Commun., 1999, 759. B. Twamley, C.D. Sofield, M.M. Olmstaed and P.P. Power, J. Am. Chem. Soc., 1999,121,3357. C . Jones, J.W. Steed and R.C. Thomas, J. Chem. Soc., Dalton Trans., 1999, 1541. P.C. Andrews, P.J. Nichols, C.L. Raston and B.A. Roberts, Organometallics, 1999,18,4247. L. Weber, M.H. Scheffer, H.G. Stammler, B. Neumann, W.W. Schoeller and A. Sundermann, Organometallics, 1999,18,4216. L. Weber, M.H. Scheffer, H.G. Stammler and A. Stammler, Eur. J. Inorg. Chem., 1999,1607. Y. Matano, H. Nomura, M. Shiro and H. Suzuki, Organometallics, 1999, 18,

2580. H.G. Ang, S.G. Ang and S . Du, J. Chem. SOC.,Dalton Trans., 1999,2963. A.J. Ashe I11 and X. Fang, Chem. Commun., 1999,1283. M. Westerhausen, M.H. Digeser, C. Guckel, H. Noth, J. Knizek and W. Ponikwar, Organometallics, 1999, 18,2491. J.J. Durkin, M.D. Francis, P.B. Hitchcock, C. Jones and J.F. Nixon, J. Chem. Soc., Dalton Trans., 1999,4057. C. Elschenbroich, J. Kroker, M. Nowotny, A. Behrendt, B. Metz and K. Harms, Organometallics, 1999,18, 1495. G. Becker, W. Golla, J. Grobe, K.W. Klinkhammer, D. LeVan, A.H. Maulitz, 0. Mundt, H. Oberhammer and M. Sachs, Inorg. Chem., 1999,38, 1099. H.J. Breunig, R. Rosler and E. Lork, Z. Anorg. Allg. Chem., 1999,625, 1619. K. Mast, O.J. Scherer and G. Wolmershauser, Z. Anorg. Allg. Chem., 1999,625, 1475. H. Althaus, H.J. Breunig, J. Probst, R. Rosler and E. Lork, J. Organornet. Chem., 1999,585,285.

168 88. 89. 90. 91. 92. 93. 94. 95. 96. 97 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119.

Organometallic Chemistry

H. Althaus, H.J. Breunig and E. Lork, Chem. Commun., 1999, 1971. R. Minkwitz and C. Hirsch, 2. Anorg. Allg. Chem., 1999,625, 1674. H. Althaus, H.J. Breunig, R. Rosler and E. Lork, Organometallics, 1999,18, 328. J.C. Guillemin and K. Malagu, Organometallics, 1999, 18, 5259. A. Berry, Polyhedron, 1999,18,2609. H. Schumann and S.H. Muhle, 2. Anorg. Allg. Chem., 1999,625,629. J. Wolf, M. Manger, U. Schmidt, G. Fries, D. Barth, B. Weberndorfer, D.A. Vicic, W.D. Jones and H. Werner, J. Chem. Soc., Dalton Trans., 1999, 1867. A. Silvestru, H.J. Breunig, M. Stanciu, R. Rosler and E. Lork, J. Organomet. Chem., 1999,588,256. C.V. Amburose, A.J. Singh, N.K. Jha, P. Sharma, A. Cabrera and G.E. Perez, J. Organomet. Chem., 1999,572, 87. K. Matoba, S. Motofusa, C.S. Chao, K. Ohe and S. Uemura, J. Organomet. Chem., 1999,574,3. R. Minkwitz, C. Hirsch and T. Berends, Eur. J. Inorg. Chem., 1999,2249. R. Minkwitz and C. Hirsch, 2. Anorg, Allg. Chem., 1999,625, 1362. S. Chitsaz, B. Neumuller and K. Dehnicke, 2. Anorg. Allg. Chem., 1999, 625, 503. H.J. Breunig, M. Denker and E. Lork, 2. Anorg. Allg. Chem., 1999,625, 117. J.L. Stark, B. Harms, I.G. Jimenez, K.H. Whitmire, R. Gautier, J.F. Halet and J.Y. Saillard, J. Am. Chem. SOC.,1999,121,4409. W. Tyrra, D. Naumann, N.V. Kirij, A.A. Kolomeitsev and Y.L. Yagupolski, J. Chem. SOC.,Dalton Trans., 1999, 657. C. Uffing. A. Ecker, E. Baum and H. Schnockel, 2. Anorg. Allg. Chem., 1999, 625, 1354. H. Sitzmann, G. Wolmershauser, R. Boese and U. Blaser, Z. Anorg. Allg. Chem., 1999,625,2103. S.M. Godfrey, I. Mushtaq and R.G. Pritchard, J. Chem. SOC.,Dalton Trans., 1999, 1319. W.K. Leong and Y. Liu, Organometallics, 18,800. M.A. Leeson, B.K. Nicholson and M.R. Olsen, J. Organomet. Chem., 1999,579, 243. S. Schulz and M. Nieger, Organometallics, 18, 315. L.D. Field, E.T. Lawrenz and A.J. Ward, Polyhedron, 18,3031. A. Mentesa, R.D.W. Kemmitt, J. Fawcett and D.R. Russelib, Polyhedron, 1999, 18, 1141. R. Cini, A. Cavaglioni and E. Tiezzi, Polyhedron, 18, 669. D.E. Hibbs, M.B. Hursthouse, C . Jones and R.C. Thomas, J. Chem. SOC.,Dalton Trans., 1999,2627. A.R.J. Genge, N.J. Holmes, W. Levason and M. Webster, Polyhedron, 1999, 18, 2673. N.J. Holmes, W. Levason and M. Webster, J. Organomet, Chem., 1999,584, 179. H.J. Breunig, M. Jonsson, R. Rosler and E. Lork, 2. Anorg. Allg. Chem., 1999, 625,2 120. L.S. Dumitrescu, I.S. Dumitrescu, I. Haiduc, R.A. Toscano, V.G. Montalvo and R.C. Olivares, 2. Anorg. Allg. Chem., 1999,625, 347. A.J. Arduengo, R.Krafczyk, R. Schmutzler, W. Mahler and W.J. Marshall, Z. Anorg. Allg. Chem., 1999,625, 1813. S.C. James, N.C. Norman and A.G. Orpen, J. Chem. Soc., Dalton Trans., 1999, 2837.

7: Group 15: Phosphorus, Arsenic, Antimony and Bismuth

169

120. M.A. Beswick, Y.G. Lawson, P.R. Raithby, J.A. Wood and D.S. Wright, J. Chem. SOC.,Dalton Trans., 1999, 1921. 121. G. Conole, J.E. Davies, J.D. Kink, M.J. Mays, M. McPartlin, H.R. Powell and P.R. Raithby, J. Organomet. Chem., 1999,585, 141. 122. S.L. Battle, A.H. Cowley, R.A. Jones and S.U, Koschmieder, J. Organomet. Chem., 1999,582,66. 123. E.E. Foos, R.J.Jouet, R.L. Wells, A.L. Rheingold and L.M. Liable-Sands, J. Organomet. Chem., 1999,582,45.

8 Organic Aspects of Organometallic Chemistry BY CHRISTOPHER G. FROST AND MICHAEL C. WILLIS

1

Introduction

This chapter describes some of the leading advances in organometallic chemistry as judged from an ‘organic chemistry perspective’. The authors have attempted to highlight outstanding contributions from the most important areas but as with all reviews the content is subject to preference and limitations of space.

2

Coupling Reactions

2.1 Cross-Coupling Reactions. - One of the most significant advances in catalytic coupling is the development of efficient methods for the functionalisation of unactivated aryl chlorides. Although considerably cheaper than the brominated or iodinated equivalent, aryl chlorides have previously required much harsher conditions than would be desired in the catalytic synthesis of pharmaceuticals and other fine chemicals. An improved situation has arisen by the rational design of improved catalysts for a range of important bondforming reactions. The key to success was the observation that electron-rich, sterically-hindered monophosphines gave rise to high yields of products as clearly illustrated in Scheme 1. In combination with [Pd2(dba)3] (dba = dibenzylideneacetone), tri-tert-butylphosphine promotes the Heck-type coupling of styrene 1 with aryl chloride 2 to afford the product trans-stilbene 3 in 83% yield.2It is worth noting that both donating and accepting substituents on the aryl chloride are tolerated well under these conditions. The same catalyst system proves to be effective for the Suzuki and Stille coupling reaction^.^ Thus, vinyl groups are efficiently transferred from 4 to 5 in the presence of caesium fluoride. In a related process Hartwig and co-workers have demonstrated that electron-rich phosphines such as tricyclohexylphosphine are required to secure high yields in the palladium catalysed arylation of ketone^.^ This is shown in the formation of 7 starting from aryl chloride 2 and cyclohexanone 6. The use of 2-(di-tert-butylphospanyl)biphenylS as ligand enables palladium acetate to efficiently facilitate the Suzuki coupling of aryl chloride 9 with boronic acid 10 to afford product 11 (Scheme 2)? Also shown is the amination

’

Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001 170

8: Organic Aspects of Organometallic Chemistry

171

1 [Pd2(dbah](1.5 mol%) 6 mol% m u 3 L

C%CQ 3 83% yield

OEt Bu3Sn 4 [Pd2(dbah] (1.5 mot%)

OEt

>

Me0 5

6 mol% &u3 2.2 eq. CsF

Me0 98% yield

Oo

6 Pd(0Ack (2 mot%)

( 4 p

b

2 mot% PCy3 2

7 93% yield Scheme 1

of 9 with morpholine 12 which occurs at room temperature with the prtsented catalyst to afford high yields of product 13. Similarly, both reactions offer wide scope with regards to the various different coupling partners. The use of nucleophilic N-heterocyclic carbenes as phosphine mimics has engaged the interest of a number of research groups. Most notable is the work by Nolan and co-workers who demonstrate that bulky carbene ligands such as

Me

DC' 11 95% yield

9

(2 motyo)

H " 7 0

To

LJ 12

Pd(OAc), (1 mot%)

Me

8 (2mol%)

9

Me

M"" 13 94% yield

Scheme 2

Organometallic Chemistry

172

14 and 15 improve catalytic performance in a variety of cross-coupling protocols (Scheme 3). A general methodology for the Kumada coupling of Grignard reagents with aryl chlorides is possible by employing Pd(0) or Pd(I1) and an imidazolium chloride such as 14 as the catalyst precursor. This is CI

Me0 16

PhMgBr Pd2(dba)3(1 mol%) 14 (4 mol%) dioxane/THF

Me0 99% yield

M e H N n 17

mc'

w

Pd2(dba)3(1 rnol%)

Me

15 (4 mol%) 9

'BuOK dioxane

Me'

Me M O ) * Bq j

Me 9

Pd2(dba)3(1.5 mol%)* 15 (3 mol%) C+CQ dioxane

15

Me

DPh 96% yield

Scheme 3

exemplified by the coupling of phenylmagnesium bromide with aryl chloride 16 to furnish the product in quantitative yield.6 These remarkable catalysts have also proved effective for the coupling of secondary amines with aryl chlorides. As an example, amine 17 is reacted with 9 in the presence of carbene .~ has also reported the ligand 15 resulting in excellent yields of p r o d ~ c tNolan Suzuki cross-coupling reactions of aryl chlorides and arylboronic acids.* The success of these unusual ligands in the challenging arena of cross-coupling reactions involving aryl chlorides offers exciting opportunities in future catalytic applications. Although significantly less studied than the corresponding C-N coupling reaction, the coupling of oxygen nucleophiles with aryl halides offers a unique entry into the synthesis of aryl ethers. In keeping with the theme of utilising cheap and available aryl chlorides, Buchwald and co-workers have revealed that the ligand 18 in combination with palladium acetate is effective in C-0 bond-forming processes as described in Scheme 4. Thus, phenol 19 can be converted to arylated product 21 with aryl chloride 20.9 In a similar context, Hartwig and co-workers have developed new ferrocene-derived dialkyl phosphines for the arylation of alcohols.l o Intersestingly, the effectual tri-tertbutylphosphine promotes the synthesis of aryl tert-butyl ethers in good yield.l 1 A typical example is shown in the synthesis of 23 from 4-chlorobenzaldehyde 22 in an acceptable 60%yield. Catalytic methodologies have also been developed that allow other heterocarbon coupling reactions to occur. Lipshutz and co-workers have reported

8: Organic Aspects of Organometallic Chemistry

173

19 'Me Pd(0Ack (1 mol%)

WM 20

'BuONa Pd(0Ach (1 mol%)

OHCJ clf

/%4OBU' w

3 molyo m u 3

OHC

22

23 60% yield Scheme 4

the synthesis of triarylphosphine-boranes by the palladium catalysed coupling of secondary phosphine-boranes and aryl triflates.l 2 An alternative strategy outlined in Scheme 5 demonstrates that phosphine 24 can be coupled with vinyl triflates, for example 25 in the presence of palladium catalyst and the bidentate phosphine ligand dppb (dppb = diphenylphosphinobutane).l 3 The product can be isolated in high yield as the phosphine-borane complex 26. The first practically useful catalytic system for the formation of vicinal dithioethers has been reported. In the presence of a ruthenium catalyst methyl acrylate is treated with diphenylsulfide to afford the product 27 in reasonable yield. l4 Given that sulfur-containing compounds are useful intermediates in organic synthesis this methodology offers new opportunities. The facile synthesis of i,

Ph2PH 24, Pd(0Ack (5 mol%) m

ii, dppb (5 mol%), Bb-SM+

25

26 96% yield

Cp*RuCl(cod) (4 mol%)

SPh

PCO2Me (PhS)2,toluene

P h s A x y A e

27

aco

66% yield Pd2(dbah.CHCS(1 mol%) +

&co2Me I

(EtO)3SiH,KOAc, NMP 28

(EQ3Si 29 74% yield

Scheme 5

174

Organometallic Chemistry

stereodefined (a-alkenylsilanes has been reported using palladium(0) catalysts. In a typical example, alkenyl iodide 28 is silylated with hydrosilane to afford product 29 in respectable yield.15 An elegant entry into the synthesis of nucleic acid analogues has been realised by Hayes and Abbas in their development of a novel palladium catalysed carbon-phosphorus coupling reaction. l 6 As shown in Scheme 6, 5'deoxy-5'methylidene phosphonate-containing thymidine dimer 32 was prepared from the coupling partners 30 and 31 in the presence of palladium acetate and triphenylphosphine.

. Me

OTBDPS

6TBDPS 31

32 42% yield

Scheme 6

The synthetic potential of the Heck reaction has encouraged investigations into developing both intramolecular and intermolecular variants. Guiry and co-workers have prepared dihydrofuran 33 and studied the phenylation reaction using a range of enantiopure palladium complexes as shown in Scheme 7.17 The absence of a H-substituent at C-2 in 33 prevents the formation of isomeric products and provides a true test of reactivity and enantioselection. The product 34 could be obtained in high yield and with an impressive enantioselectivity of 98% e.e. using diphenylphosphinoferrocenyloxazoline35 as the ligand. An enantioselective reductive Heck-type reaction has been reported which allows the formation of N-protected epibatidine with good enantioselectivity.

33

Et3N Benzene

34 90% yield 98% ee (R)

Scheme 7

8: Organic Aspects of Organometallic Chemistry

Pd(0Ack (2.5mol%)

37

175

*

(R)-BINAP (5.5 mol%) Et3N, HCQH

38 66% yield 81% ee

Scheme 8

In the presence of palladium acetate and (R)-BINAP 37 is coupled with the pyridine 36 to afford the product in reasonable yield (Scheme 8).'* The emergence of automated, parallel solid phase synthesis has changed the nature of medicinal chemistry research. In this context Brase and Schroen have introduced a novel cleavage-cross-coupling strategy allowing the clean synthesis of cycloalkenyl arene derivatives as described in Scheme 9.l' The benzyl alcohol 39 bound through the triazene system was cleaved with TFA (trifluoroacetic acid) to afford the diazonium ion in situ which reacts with cyclopentene in the presence of Pd(OAc)2 to give the coupled product 40 in good overall yield. This strategy is open to further diversification and is especially suitable for automated synthesis.

Q

2.2 Allylic Substitution. - The basic process involves an allylic substrate undergoing nucleophilic substitution via an intermediate n-ally1 complex. The development of enantioselective catalysts for the palladium catalysed substitution of symmetrical substrates continues to attract attention. However, a more significant challenge is to control the regioselectivity when the reaction proceeds through an unsymmetrical intermediate. Williams and co-workers provide an attractive solution to this problem by careful ligand selection (Scheme When mono-substituted allylic acetate 41 is exposed to sodium dimethylmalonate in the presence of a palladium(0) catalyst and triphenylphosphine a mixture of isomers 42 and 43 is obtained with a preference for the linear product. By switching to tricyclohexylphosphine the alkylation proceeds with high regioselectivity in favour of the branched product 42.

Organometallic Chemistry

176 NaCH(C02Me)2 [Pd(allyl)Clh (2.5 mol%)

Me02C

-Me

+ Me

THF 41

C02Me

42

43 Ligand

42:43

pcY3

11.51

PPh3

1.2

dppe

1:1.5

Scheme 10

Alternative strategies towards obtaining branched products have focused on using different metal catalysts such as iridium,21rhodium22and molybdenum. In terms of regio- and enantioselectivity molybdenum catalysts are the most effective. This is clearly illustrated by work from the Trost group in the execution of a remarkable alkylation of polyene substrates (Scheme 11). In the presence of a molybdenum catalyst and ligand 46, polyenyl carbonate 44 reacts with a nucleophile to afford a high yield of the branched product 45 (less than 2% of the linear isomer was observed).23The enantioselectivity of the process was established as an excellent 98% e.e. In a related study Pfaltz and coworkers have revealed ligand 47 which is also effective in controlling regioand enantioselectivityin molybdenum catalysed allylic alkylation reactions.24 The enantioselective electrophilic attack of a n-ally1 palladium(I1) to a

, , -

NaCH(02Me), (EtCN),Mo(CO), (10 mol%)

Me-0C0,Me

46 (15 molyo) toluene:THF (1:1)

Me02C

Me

C02Me

a 45 81% Yield 98% ee

44

-

46

'Pr

47

'Pr

Scheme 11

stabilised prochiral nucleophile offers a succinct route to highly functionalised molecules. This has been achieved in the allylation of nucleophile 48 with cinnamyl acetate 49 catalysed by enantiopure palladium-BINAP complexes to afford product 50 pocessing a quaternary stereogenic centre at the a-carbon (Scheme 12).25 Trost and Schroeder have taken the ligand 54 developed in their laboratories and report that it is effective in the palladium catalysed allylation of nonstabilised ketone enolates.26 Thus, ketone 52 is treated with 51 to afford product 53 in excellent yield and good enantioselectivity (Scheme 12). The

8: Organic Aspects of Organometallic Chemistry

Ph-0Ac 49

NHAc [Pd(allyl)Clk (1 mol%) (R)-BINAP (2 mOl%)

177

ph

'BuOK toluene

50 87% Yield 94% ee

boAc / 51 [Pd(allyl)Clh (2.5 mol%) LiTMP (CI+J3SnCI DME 52

n

53 99% Yield 86% ee

Scheme 12

choice of base and Lewis acid was crucial to high enantioselectivity; trimethyltin chloride affords the best results under the reported conditions. The allylated products obtained are suitable for further elaboration. A concise route to enantiopure thiols relies on the palladium catalysed rearrangement reaction of O-allylic thiocarbonates (Scheme 13).27 In the presence of ligand 54 the substrate 55 rearranges in high yield and enantioselectivity to product 56. This provides an ingenious solution to the common problem concerning low reactivity of thiols in palladium(0) catalysed allylic substitution reactions.

0

S

b

Pd2dba3(1.25 mol%)

0

(1.5mol%)

55

Scheme 13

GNHMe 56 94% Yield 97% ee

178

3

Organometallic Chemistry

CarbonylationReactions

The transition metal mediated introduction of a CO unit continues to be a popular method of achieving C-C bond construction. Among the many methods that have been developed one of the most advanced is the hydroformylation of alkenes. Breit and co-workers continue to exploit this powerful transformation in a series of elegant studies detailing a range of substratedirected reactions. Scheme 14 illustrates a domino reaction combining a directed hydroformylation reaction with a Wittig olefination.28Combination of o-diphenylphosphanylbenzene ester 57 and Wittig ylide 58 under hydroformylation conditions provided the corresponding trisubstituted alkene in good yield with excellent diastereoselectivity. The high selectivity in the hydroformylation step is due to directed delivery of the catalyst by the substrate-bound phosphine group.

CJ

Q

PPh2

PPh,

RhH(CO)(PPh&, (0.7 mol%) HdCO (20 bar) Ph.jP=CMeCQEt PhMe, 50 "C

& M e

58

O A O

* Me+

CQEt

M e M e 75% yield, 96:4 dr,

57

Scheme 14

PAr2

NaQS

Na03S

PAr,

SQNa Ar = mS03Na-C6H4 BINAS

&

( l eq)

N H (aq) ~

(* eq)

[Rh(cod)Clh (0.21 mol%) H&O (78 bar) TBME, 130 "C

NH3(aq)

AN95% yield, niso99:l prim.:sec. 1:99

(8 eq)

[Rh(cod)Clh (0.21 mol%) HdCO (78 bar)

(1 eq)

TBME, 130 "C

+

H

*

t

A NH2 85% yield, niso 99:l prim.:sec. 78:22

Scheme 15

8: Organic Aspects of Organometallic Chemistry

179

A second example of a domino reaction combines a hydroformylation reaction with a reductive aminati~n.~' Thus, treatment of 1-butene with aqueous ammonia under the described hydroformylation conditions yields directly dibutylamine in excellent yield (Scheme 15). The use of BINAS as the ligand was crucial to obtain a reaction selective for the linear isomer. The authors found that by varying the a1kene:ammonia ratio they could select for production of either the primary or secondary amine. The overall transformation represents an extremely atom-economical synthesis of amines. A carbon monoxide unit is frequently introduced as a component in cycloaddition reactions; Murai has adopted such an approach to develop a synthesis of unsaturated y-la~tams.~' Reaction of t-butyl substituted unsaturated imine 59 with CO (10 atm.) and Ru3(C0)12 (2 mol.%) in toluene at 180 "C delivered the expected unsaturated lactam products 60 in good yield (Scheme 16). The reaction was shown to be general for cyclic as well as acyclic alkenes and represents the first example of a [4+1] cycloaddition of CO and simple unsaturated imines. Later in the year a similar synthesis of lactams was reported by Imhof and c o - w o r k e r ~A .~~ full account of a rhodium mediated asymmetric [4+ 11 cycloaddition of CO and vinylallenes has been published.32 A successful synthesis of y-butyrolactones featuring the ruthenium catalysed combination of a ketone, an alkene and CO has also appeared in the literature.33 CO (10 atm) Ru~(CO),~ (2mol%)

m

PhMe, 180 "C

Me

0

59

60 91% yield

Scheme 16

3.1 Pauson-Khand and Related Reactions. - The cobalt mediated combination of an alkene an alkyne and CO, the Pauson-Khand reaction, continues to be a popular method for the preparation of cyclopentenones. Until recently the majority of Pauson-Khand reactions required stoichiometric quantities of cobalt complexes. Livinghouse has previously reported that by using high purity C O ~ ( C Oonly ) ~ catalytic quantities are needed. Kraft and co-workers have since discovered that ultra high purity C O ~ ( C Ois) ~not needed provided that all glassware employed in the reaction is base-washed before use.34Using such methodology only 10 mol% cobalt complex was found necessary to achieve good yields of products. Buchwald has reported a titanium catalysed intramolecular Pauson-Khand reaction of nitrogen tethered enyne~.~' Treatment of the relevant enyne with titanocene catalyst 61 (15 mol%) delivers the cyclopentenone products in good yields with excellent levels of enantioselectivity (Scheme 17). The same catalyst could also be used to produce the corresponding carbon- and oxygen-tethered products.36

Organometallic Chemistry

180

61 Me */Me BnN

%

61 (15 mol%)

BnN

CO (1 4 psig) PhMe, 95 "C

H 82% yield, 92% ee

Scheme 17

Oxygen tethered methylene-cyclopropane-containingenynes have also been found to be suitable substrates for Pauson-Khand reactions (Scheme l 8).37 The presence of a methyl substituent on the cyclopropane ring resulted in the initially formed adducts rearranging to provide the indicated exo-alkene containing products. i. C O ~ ( C O(1) ~equiv) PhMe, rt ii. NMO, PhMe, reflux, 1 h 41Yo yield

i. Cs(CO), (1 equiv) PhMe, rt

ii. NMO, PhMe, reflux, 1 h 51% yield

Scheme 18

In related cobalt chemistry, the use of sodium methylthiolate as an efficient reagent for the deprotection of dicobalt hexacarbonyl compounds has been reported.38 4

OrganometaliicMethods of C-C Bond Formation

4.1 Metathesis Reactions. - The field of alkene metathesis is perhaps the area that has expanded most over the last year; certainly the number of publications in this area would support this. There are two main fields that continue to attract attention: the development and demonstration of new metathesis catalysts and application of existing catalytic systems to new substrates and target systems. Hoveyda and co-workers have reported a new air and moisture

8: Organic Aspects of Organometallic Chemistry

181

stable metathesis catalyst.39The catalyst is obtained by treatment of styrenyl ether 63 with Grubb's ruthenium alkylidene 62 to provide the chelated alkylidene 64 in good yield (Scheme 19). The new catalyst performs very

CH2CI2,22 "C 63

0

64(5mol%)

CH2Cb, 55 "C

Ts 65 >98?!yield Scheme 19

effectively in a range of ring closing metathesis (RCM) reactions. For example, the seven-membred cyclic amine 65 illustrated is obtained in >98% yield. An important feature of this new system is that the catalyst can be effectively and easily recycled by simple silica gel chromatography. Both Herrmann4' and G r u b b ~ ~have ' , ~ ~reported the use of ruthenium complex 66 bearing an imidazolin-2-ylidene ligand as an extremely active RCM catalysts. These new catalysts allow the formation of tetrasubstituted alkenes, a transformation not possible with the original Grubbs catalyst (Scheme 20). R-N

mN-R

P -hC JlI CI'

I

R = CHMePh

pcY3

+ E*2C

CGEt

66

EQC

66 (5mol%)

C&C12,40 "C

Me

C02Et

--Q Me

Me

96% yield

Scheme 20

All of the systems considered so far have employed preprepared catalyst systems; Furstner has reported an active catalyst that can be generated in situ. Simply combining [@-cymene)RuC12]2and PCy3 in dichloromethane provides an active RCM catalyst.43 For example, the ten-membered lactone 67 is obtained in good yield using only 2.5 mol% catalyst (Scheme 21). New highly

182

Orgartometallic Chemistry

[(pcymene)RuC& (2.5 mol%) PCy3 (5.5 mol%) CHpC12, ti

67 65% Scheme 21

active ruthenium based catalyst systems containing bis(di-t-butylphospany1)methane ligands have also been described.4 Molybdenum based catalysts continue to attract attention due to their higher reactivity. Furstner had prepared the novel trisamido-molybdenum(1V) chloride complex 68 and applied it to the RCM reaction of a series of diynes (Scheme 22).45 Preformed or in situ generated 68 was found to effectively catalyse the required transformation. When generating 68 in situ several minor Mo containing species were also found to be present.

68 [MeC =C(CH2kOOC(CH2)b

68 (10 mol%) &

CHzC12

i >91% yield

Scheme 22

The polymer bound ruthenium alkylidene 69 can be conveniently prepared by simply treating polystyrene with Grubbs complex 62 in dichloromethane at room temperature (Scheme 23).46The supported alkylidene complex was found to be a highly active catalyst in a range of RCM reactions. The catalyst functions in a 'boomerang" manner; that is initially the pro-catalyst 69 is introduced bound to the polymer support, while during the reaction the active catalyst is actually homogeneous thus providing the associated rate advantages. Upon completion of the reaction the catalyst is recaptured by the resin, thus reforming complex 69. Similar supported catalysts have been employed by Barratt in ring opening methathesis polymerisation (ROMP) applications.47 One of the problems associated with Ru metathesis chemistry is the removal of all the ruthenium residues from the products. Grubbs has described the use of the water soluble phosphine tris(hydroxyrnethy1)phosphine as an effective ruthenium scavenger to aid in p ~ r i f i c a t i o n . ~ ~ Hoveyda and Schrock recently reported the development and application of

8: Organic Aspects of Organometallic Chemistry

183

69

100% convarsion

Schemo 23

a family of chiral Mo based metathesis catalyst^.^' The range of transformations achievable with these catalysts continues to grow; Scheme 24 illustrates a tandem asymmetric ring opening metathesiskross metathesis c~mbination.~' Treatment of norbornene 71 with 5 mol% of chiral Mo catalyst 70 in the presence of 10 equivalents of p-OMe-styrene 72 delivers the enatiomerically enriched substituted cyclopentane 73 in good yield with excellent selectivity. The reaction was extended to include a range of substituted styrenes as coupling partners. Tandem reaction sequences featuring a metathesis reaction are becoming increasingly common. Scheme 25 illustrates a synthesis of stereodefined substituted pyrrolidines employing a Rh-catalysed allylic substitution followed

Me'

70

70 (5 mi%)

71

+

C6H6, fl

"0,

73 80% yield, >98% ee

OMe

72

Scheme 24

184

Orgunometullic Chemistry

Bnov RHTS 74

+

i, RhCI(PPh& (cat,) P(OMeh, 30 "C

ii, 62 (5 mol%)

Qc02Me

PhH, reflux

Ph

75% yield, 2993 dr

Ph75 Scheme 25

by a RCM reaction.51Addition of chiral amine 74 to the chiral allylic acetate 75 is mediated by RhCl(PPh3)3 and P(OMe),; this is followed by treatment with Grubbs catalyst 62 to deliver the five-membered ring products in good overall yield. The above transformation illustrates the good tolerance of the ruthenium based catalysts towards nitrogen containing substrates. Hanson continues to explore the tolerance of these catalysts towards sulfur and phosphorus containing systems. He has recently reported the preparation of cyclic sulfonam i d e and ~ ~ a~range of P-heterocycle~~~ all featuring RCM reactions. A further attractive feature of RCM chemistry is the generally mild conditions associated with the transformation. This is particularly true of reactions employing the ruthenium-based catalysts. Harrity has employed the Grubbs catalyst 62 to produce a range of spirocycles through selective RCM reactions (Scheme 26).54 The mild conditions are particularly important here as it was found that /== 62 (5 mol%)

*

CH2C12, rt 76 90% yield

62 (5 mol%)

*

CHzC12, rt

6P/o yield Scheme 26

spiroacetals such as 76 could not be formed under the traditional acidic conditions associated with acetal formation. A final example of the utility of RCM chemistry is Hoye's synthesis of d i f f e r ~ l i d eTreatment .~~ of enyne 77 with Grubbs catalyst 62 leads smoothly to diene 78 in quantitative yield (Scheme 27). Simply warming 78 triggers dimerisation via an intermolecular Diels-Alder reaction to yield the natural product. Synthetic applications of cross-metathesis are less well developed, although Grubbs has recently described the combination of a terminal alkene with an acrolein acetal via ~ross-metathesis.~~ The combination of 79 and 80 in dichloromethane with 2.5 mol% of ruthenium alkylidene 62 provided the

8: Organic Aspects of Organometallic Chemistry

185

*'? 0

& ,

00

op 0

62 (1 0 molYo) CH2C12, fl

77

~

CDCI3,5OoC

78 100% conversion

Diffemlide

89% conversion Scheme 27

coupled product in 81% yield. Treatment with formic acid cleaves the diethyl acetal to deliver an enal as the final product (Scheme 28). OBz

62 (2.5 mol%)

79

OBz

OBz

+

OEt

C&CI2,45 "C

OEt

CH2C1.2

81YOyield

d

O

E

t

80 Scheme 28

Diazo-carbenoid Chemistry. - Many of the advances in the maturing field of transition metal-carbenoid chemistry have concerned increases in selectivity and in particular the successful realisation of the highly selective production of enantiomerically enriched products. To this end Davies has introduced a new class of D2-symmetric dirhodium prolinate complexes that are highly selective catalysts for vinyl- and phenylcarbenoid cyclopr~panations.~~ One attractive feature of transition metal-carbenoid chemistry is the relatively low catalyst loadings that are usually needed. This in turn spurs the development of new transformations that employ carbenoid methodology. Marsden and co-workers have developed an efficient synthesis of silylketenes employing a rhodium-mediated Wolff rearrangement.58 Treatment of 1-diazo1-silyl ketones such as 81 with only 1 mol% Rh2(02CCTH15) provides the rearranged products 82 in high yield (Scheme 29). The procedure was shown to have good functional group and heteroatom tolerance. An excellent example of the high functional group compatibility of

4.2

81

82 80% yield Scheme 29

Organometallic Chemistry

186

C02R

0

+

Rb(OAc), (cat.) t

83 97% yield, 2.55:l dr Scheme 30

rhodium-carbenoid methodology is the work of Hanson concerning the production of heteroatom containing fused cyclopropane systems. For example, treatment of substituted diazo-phosphonate 83 with Rhz(OAc)4 delivers the corresponding cyclopropanes in excellent yield (Scheme 30).59 One area where the levels of selectivity have been increased dramatically is intermolecular C-H insertion; the related intramolecular reaction is well established, but the intermolecular version is traditionally considered to offer only poor levels of selectivity. Both Davies and Winkler have developed extremely enantioselective C-H insertion processes and both have exploited this methodology in short syntheses of the psychotropic drug r i t a h 6 ' Davies' synthesis is presented below in Scheme 31.6' Treatment of a mixture of diazo ester 84 and N-BOC piperidine with 1 mol% of the chiral catalyst Rh2(SDOSP)485 provides, after treatment with TFA, threo-methylphenidate (ritalin) in 52% yield and 86% e.e. The methodology can be extended to pyrrolidine derivatives and also to selectively provide double insertion products.

*co2Me N2 84

i, 85 (1 mol%)

ii, TFA

'"1

NH.HCI

52% yield, 86% ee thmmethylphenidate (Ritalin) Scheme 31

Two alternative methods, relying on different carbenoid reactions, have been published for the synthesis of enantiomerically enriched aldol adducts. In the first example, Davies again employs an enantioselective C-H insertion reaction, this time between diazo ester 86 and protected allylic alcohol 87

8: Organic Aspects of Organometallic Chemistry

86 TBSO-

85

N2

Ph

Hexane, rt

187

c

MeO&

/ i , / + Ph

6lBS 87

70% yield, 85% ee, 97% de

Me

73% yield, 98% ee

89

Scheme 32

(Scheme 32).62 The required aldol adduct is produced with high levels of selectivity. The Wood group use an O-H insertion reaction followed by a Claisen rearrangement to produce the required aldol motif.63Thus, treatment of a-diazo-P-ketoester 88 with chiral allylic alcohol 89 and Rh2(0Ac)4 delivers the adducts as indicated. Rhodium carbenoid reactions continue to be combined with a second process to produce powerful tandem sequences. The Hashimoto group combine carbonyl ylide formation and intermolecular 1,3-dipolar cycloadditon to produce an efficient and enantioselective synthesis of bridged tetrahydropyrans? 4.3 1,2- and 1,4-Addition Reactions. - The rhodium catalysed 1,4-addition of boronic acids and esters to enones has quickly become one of the most useful processes for carbon4arbon bond formation. Catalyst systems have been developed that afford high regioselectivity (1,4- versus 1,2-addition) and high enantioselectivity (using enantiopure phosphine ligands). Recent findings have indicated that lithium arylborates are effective as replacements for boronic acids. These can be generated in situ by lithiation of aryl bromides followed by treatment of the resulting aryl lithiums with trirneth~xyborane.~~ The enantioselective rhodium catalysed addition of similar reagents 90 has been applied to a,P-unsaturated esters. In the presence of just 3 mol% of a Rh(I)/(S)-BINAP complex the asymmetric arylation of 91 proceeds with good yield and high enantioselectivity (Scheme 33).66 It was noted that the enantioselectivity was sensitive to the steric bulk of the ester group. The protocol proved equally effective in the addition of boronic acids (e.g. 93) to cyclic a,P-unsaturated esters 94 affording the product 95 with similarly high enantioselection. By replacing aryl boronic acids with triaryl-

Organometallic Chemistry

188 Li+[PhB(OMehr 90 Rh(l)/(S)-BINAP(3 mol%)

Ph

0

dioxane/H20

91

92 64% yield 98% ee (s) 0

,OM” ( H 0 ) z B A 93

w

Rh(l)/(S)-BINAP(3 mol%)

-

dioxane/H20

94

95 91% yield 98% ee (S) (PhBOh 96 Rh(l)/(S)-BINAP(3 mol%)

0

Ph

:

*

dioxane HzO 1 eq.

I1

&‘\(OEt)z

98 94% yield 96% ee (S)

97 Scheme 33

cyclotriboroxanes 96, the 1,4-addition can be applied to a,P-unsaturated phosphonates 97 to afford enantioenriched phosphonic acid derivatives 98.67 The related rhodium catalysed 1,2-addition to aldehydes and imines has received significantly less attention. As shown in Scheme 34 the addition of /TS

JJ

PhSnMe3 [Rh(cod)(MeCNh]BF4 (2 mol%)

THF

Ph

m

HN/Ts

A

Ph

99

Ph

100 98% yield /TS

-

PhSnM% [Rh(cod)(MeCNh]BF4 (2 mol%) THF

0

EtOJTs

Ph

0

102 98% yield

101

Scheme 34

trimethyl(pheny1)stannane to N-arylsulfonyl imines 99 and 101 proceeds in excellent yield to afford 100 and 102 respectively in the presence of the phosphine-free catalyst [Rh(cod)(MeCN)2]BF4.68The major limitations associated with this reaction are imine hydrolysis and the lack of an enantioselective protocol. An interesting asymmetric multi-component tandem coupling process has been reported involving a nickel catalysed 1,4-addition reaction (Scheme 35).69 In the presence of the simple monodentate oxazoline ligand 103, the product

8: Organic Aspects of Organometallic Chemistry

189

Et-Et Me2Zn Ni(acac)* (5 mol%)

Me

+

Me &k Me Et

Bute+$ 103 (10 mol%)

Et

105 75% Yield 83% ee

Scheme 35

105 is obtained in good yield and high enantioselectivity from enone 104. The use of phosphine containing ligands was not effective in this process. The copper catalysed conjugate addition of organometallic reagents to enones is a popular method. However, a highly enantioselective catalytic version is still rare. The use of copper complexes of enantiopure phosphites such as 106 illustrated in Scheme 36 is showing considerable promise. In the

8

Etgn

Cu(l1) catalyst 106 or 109

107

108

106

Me Scheme 36

conjugate addition of diethylzinc to enone 107 the product 108 is realised with up to 90% e.e.70The use of amino-phosphine ligand 109 in the same process affords product with similar enantioselectivity.71

4.4 C-H and C-C Bond Activation. - The activation and subsequent functionalisation of C-H and C-C bonds continues to remain a considerable synthetic challenge. Although several of the previous sections have featured examples of these processes there remains several reports that do not fit readily into earlier sections. The Murai group have reported several examples of both C-H and

190

Organometallic Chemistry @Si(OEth Ru(H)2(CO)(PPh3), (10 mol%) PhMe, 135 "C

Si(OEt), 110

111 97% yield

Scheme 37

C-C bond activation, although in all of the cases studied a directinglactivating group is required. For example, Scheme 37 shows the selective activation of an ortho-C-H bond in an aromatic nitrile.72Treatment of 110 with the illustrated ruthenium catalyst (10 mol%) and triethoxyvinylsilane results in C-H activation followed by C-C coupling to deliver 111 in 97% yield. The ortho-methyl group was required to suppress double alkylation. Similar C-H activation chemistry can be performed using aromatic imidates as substrate^.^^ Aromatic imidates are also the substrates Murai has chosen to investigate selective C-C bond activation.74 Hartwig has reported the catalytic C-H activation and functionalisation of unactivated alkanes.75 Simple alkanes can be converted to the corresponding borylated compounds by treatment with diboronic ester 112 and [ReCp*C03] (2-5 mol%) under photochemical conditions (Scheme 38). The chemistry

I

hv, CO, 25 "C

M

95% yield Scheme 38

works well for simple alkanes as well as alkyl ethers and branched alkanes. Crucially, the functionalised products are obtained with high levels of regiocontrol. Jun and Lee have reported an efficient system for the selective activation of C-C bonds in unstrained ketones.76For example, combination of ketone 113, 1-hexene, Wilkinson's catalyst (10 mol%) and 2-amino-3-picoline delivers ketone 114 in 98% yield (Scheme 39). The reaction proceeds via the formation of an intermediate imine; this allows the pyridine nitrogen to direct the metal

aMe (20 mol%)

NH2

RhCI(PPh& (10 rnol%) PhMe, 150 "C

+

A

* R-BU

Me

114 9€W0yield

n-Bu Scheme 39

8: Organic Aspects of Organometallic Chemistry

191

centre to the C-C bond for activation. Dialkyl ketones can also be used as substrates although the yield of coupled products is lower (typically 6&77%). Linear, branched and cyclic alkenes can all be employed as the alkene component. 4.5 Multi-component Cyclisations. - There have been many reports of transition metal catalysed cyclisation reactions where just one of the components is an alkyne. One conceptually new strategy relies on a rhodium catalysed [2+2+2] cyloaddition process to provide functionalised indolines (Scheme 40).77 The protocol uses N-(3-butynyl)-l-alkynylamidesof the type 116 in a

H H /

115

*(y$

[RhCI(PPb)3](3 mol%)

N+SiMe3

Ts

TS

toluene

sibs

117 92% Yield

116

C02Me

C02Et

0-z

h k @ c ~ c o & k118 C02Me

Pwba3(2.5 rnol%)

\CO*Et 119

C02Et

PPh3 (5 rnol%) toluene

120 92% Yield

Scheme 40

rhodium(1) catalysed cyclotrimerisation with acetylene 115.The product 117 is obtained in excellent yield. The use of differently substituted alkynes allows for selective functionalisation around the indoline core. A related palladium catalysed [2+2+2] process involving ether 119 and alkyne 118 is efficient in providing the cycloaddition product 120.78 The classic cobalt-mediated [2+2+2] cycloaddition has been employed in an elegant route to analogues of the natural product ~ t e g a n o n e . ~ ~ As depicted in Scheme 41, when the tethered deca-1,9-diyne 122 is reacted SiMe3

Me3Si+SiMe3

121 w

CpCo(C0k hv

OW 123 20% Yield

OMe 122

Scheme 41

192

Organometallic Chemistry

with alkyne 121 under the standard irradiation conditions a modest yield of the desired product 123 was observed. An elegant approach to cyclic ethers has been reported which involves the addition of a tethered alcohol to a ruthenium-ally1 species." The initial reaction between allene 124 and methyl vinyl ketone in the presence of a ruthenium catalyst affords a ruthenacycle. T h s key intermediate is subsequently intercepted by the pendant alcohol to reveal the alkylative cycloetherification product 125 in good overall yield (Scheme 42).

4yMe 0

It

[CpRu(MeCNh}PF6(10 mol%) 124

CeCI3.7H20(15 mol%) DMF 125 82% Yield

Scheme 42

5

Oxidative and Reductive Processes

5.1 Oxidation Reactions. - The importance of diols as bulk and fine chemicals underlies the importance of the alkene to diol transformation. One of the remaining goals for this transformation is the use of oxygen as the stoichiometric oxidant, with the further proviso that both atoms of the oxygen molecule are incorporated in the diol. Beller and co-workers have reported such a system using osmium(VII1) as the catalytic oxidant? The optimised conditions involve treatment of the alkene with catalytic OsO4 (0.5 mol%), DABCO (1.5 mol%) and 0 2 (1 bar) in a two-phase tBuOHlbuffer mixture (Scheme 43). The corresponding diols are produced in excellent yield. The DABCO acts an accelerating ligand in a manner similar to the chiral ligands OsO,(0.5mol.%) DABCO (1.5 mol.%) Hex*

0,(1 bar) 50 "C phosphate buffer, BubH

*

L O H Hex 96% yield

Scheme 43

employed in the Sharpless asymmetric dihydroxylation; in the present case the use of chiral ligands produced diols of only moderate e.e. Methodology catalytic in osmium and NMO but employing H202 as the stoichiometric oxidant has also been reported.82 Directed diastereoselective dihydroxylations of allylic alcohols have been established for a number of years. Oxidations under the traditional Upjohn conditions are anti-selective. Donohoe has recently extended his hydrogen bonding dihydroxylation conditions, allowing access to syn-products, to include the oxidation of acyclic allylic alcohols (Scheme The optimal

8: Organic Aspects of Organometallic Chemistry OH

193 OH

Me

Me

Os04,TMEDA

Me

C&C12, -78 "C

OH

OH

Me

75Oh yield, 80:20dr Scheme 44

conditions involve treating the allylic alcohol with Os04 and TMEDA in dichloromethane. A current limitation to this methodology is the requirement for stoichiometric osmium. The Sharpless asymmetric dihydroxylation of alkenes is arguably the most efficient and selective method for the production of enantiomerically enriched diols, however the risk of osmium contamination of the products has limited its application in the pharmaceutical industry. To address this issue the use of supported osmium reagents has been developed; Kobayashi has recently reported a new recoverable and reusable osmium catalyst. The key to the Kobayashi system was the use of an acryonitrile-butadiene-polystyrene polymer to microencapsulate the osmium.84The resultant catalyst was highly effective in the dihydroxylation reaction delivering products with comparable yields and selectivities to the standard non-supported system (Scheme 45). Importantly, the complete recovery of all osmium entered into the reaction was possible. ABS-MC Os04 (5 mol%) (DHQDhPHAL (5 mol) Ph&

Me

H20,acetone, MeCN NMO, rt

*P h q M OH 90% yield, 92% ee

ABS-W = acryronitrile-butadiene-polystyrene microsencapsulated

Scheme 45

More recently Sharpless has developed the asymmetric aminohydroxylation of alkenes. New nitrogen sources such as amino-substituted heterocyclesg5and t-butylsulfonamides6 continue to be reported. Sharpless has extended his methodology to allow the enantioselective aminohydroxylation of unsaturated pho~phonates.'~Reversal of the usual regioselectivity observed in asymmetric aminohydroxylation of aryl esters has been noted." Methyltrioxorhenium has emerged as a very effective catalyst for alkene ep~xidation.~' It has been discovered that a variety of amine additives including pyridine and pyrazole result in a more efficient epoxidation procedure." The Shibasaki group have reported a chlorohydrin synthesis that combines epoxidation and Lewis acid promoted epoxide opening into a single operation." The optimal conditions involve treating the alkene with a mixture of bis(trimethylsilyl)peroxide, SnCb and TMSCl in dichloromethane (Scheme 46). Treatment with HCl delivers the free chlorohydrin in an impressive overall yield. The methodology tolerates cyclic as well as acyclic alkenes.

Organometallic Chemistry

194 i, SnC14(10 rnol) TMSO-OTMS, TMS-Cl CYCl,, -20 "C

*

ii, HCI, MeOH MeQC

77Y0yield Scheme 46

The final oxidative reaction we will consider is a Pd(I1) catalysed oxidative ring-cleavage of cyclobutanols (Scheme 47).92 Exposure of the required cyclobutanol to Pd(OAc)2and pyridine under an oxygen atmosphere results in selective carbon-carbon bond cleavage to deliver the resultant enone in excellent yield. The transformation is limited to the use of tertiary-cyclobutanols. A ruthenium catalysed cleavage of diols, again using oxygen as the stoichiometric oxidant has also been reported.93 PdfOAch (10 mol%) pyridine, 3 8, MS

d

P

h

PhMe, 80 "C, 0, 97% yield

Scheme 47

Reduction Reactions. - The catalytic, enantioselective hydrogenation reaction remains as the most practical and reliable method of asymmetric synthesis. Building on the success of the use of enantiopure DuPHOS ligands 128 in the enantioselective hydrogentation of dehydroamino acids, the Burk group have revealed an efficient hydrogenation of a,0, y,&unsaturated amino acids 126 (Scheme 48).94 This efficient process establishes two contiguous stereogenic centres simultaneously with excellent enantioselectivity. The products 127 are @-branchedally1 glycine derivatives. The development of water soluble DuPHOS ligands 129 allow for a cleaner hydrogenation pro~ess.'~

5.2

H2

NHAc

But

126

128

'PrOH

OH

129 Scheme 48

127 100% yield 82% ee (2S,3R)

8: Organic Aspects of Organometallic Chemistry

195

[(q-BINAP@cymene)RuCI]CI (0.01 mot%)

M e oBub2C -'vo~co2H

H2 MeOH/&O (3:l)

131 94% ee

130

Scheme 49

The crowning glory for a catalytic process is in the successful scale-up in a commercial application. The ruthenium-BINAP catalysed enantioselective hydrogenation reaction has been utilised in the key step in the manufacture of Candoxatril, an orally active metalloprotease inhibitor.96The intermediate 131 is obtained with excellent enantioselection by hydrogenation of 130. The very low catalyst loading is an added attractive feature. With the exception of tetrasubstituted N-acylaminoacrylic esters, the catalytic enantioselective reduction of tetrasubstituted alkenes has not been very successful. One possible solution has been presented that employs cationic metallocene catalysts.97Under the conditions shown in Scheme 50 the alkene H2 (1700 psig)

(EBTHI)ZrM@(8mol%) [P~MMW+[(BW~)~I-

F

dM 133 77% Yield 96% ee

132

Scheme 50

132 is reduced with extremely high enantioselectivity to afford product 133. It is proposed that the cationic nature of these catalysts renders them sufficiently electrophilic to overcome the reluctance that many metal complexes suffer in binding such hindered alkenes. The use of polymethyhydrosiloxane as a hydride source in combination with catalytic CuCl, NaOtBu and enantiopure diphosphine ligand allows for an effective enantioselective reduction of a,P-unsaturated esters.98The enantioselective reductions of (E)- and (2)-isomers (134 and 136) (Scheme 51) resulted in products (135 and 137) with similar e.e., and with the opposite enantiomer Ph'

PMHS=polymethylhydrosiloxane PMHS

OEt

CuCl(5 mol%) (3-ptol-BINAP (10 mol%)

* Ph

'BuONa 136

137 98% Yield 91O/O ee Scheme 51

196

Organometallic Chemistry

predominating. With the commercial availability of the ligand, the low cost of PMHS and simple experimental conditions, it is expected this process will be attractive to the synthetic chemist. The ruthenium complex 138 is reported to be an effective catalyst for the enantioselective transfer hydrogenation of ketones.99 The use of alternative hydride sources allows very mild reaction conditions typified by the reduction of ketone 139 to alcohol 140 with near perfect enantioselection and quantitative yield. This level of enantioselection could only be matched by the use of enzymes (Scheme 52).

M

q

M

e

'PrONa 138 (0.5 (2 mol%)

0 139

+*q

'PrOH

4 2

Me

OH 140 99% yield 99% ee (R)

. 'Pr

PPh2--RU(PPh3)C12

~

138 Scheme 52

6

Lewis Acid Mediated Processes

The discovery of more efficient or practicable metal salts for use a Lewis acids continues to be an area of much interest. The Frost group have reported the use of In(II1) triflate as a highly efficient catalysis for hetero Diels-Alder reactions.loo In the example presented in Scheme 53 a three component 0

OMe

II

n

TM'o s95% yield Scheme 53

reaction is illustrated. In(OTf)3 first mediates the in situ formation of a reactive imine which then undergoes catalysed Diels-Alder reaction with Danishefsky's diene to deliver the cycloadduct in excellent yield. Of special note is the catalyst loading that can be employed (0.5 mol0/); this is particularly impressive given the high coordinating ability of the nitrogen atom containing product. The design and preparation of new chiral Lewis acids continues to be a fruitful area of research. Two of the more successful examples reported in the last year are shown in Scheme 54. Both catalysts have been evaluated using different variants of the intermolecular Diels-Alder reaction. Kundig has

8: Organic Aspects of Organometallic Chemistry

,,,\\Ru+ (C6Hd2p 4 *o%

''

/P.(CGF&

197

Me SbF6-

Me

P h y o Ph

141

142

0

93%yield, 92% ee, 93:7 dr i, 142 (3 rnol%) 4 A MS, acetone, rt ii,TBAF

TESO

the

97% yield, 99% ee

143

Scheme 54

prepared the chiral ruthenium complex 141 containing a Cp moiety together with an electron poor chiral C2-symmetric perfluoroaryldiphosphinite.lo' Complex 141 effectively catalysed the Diels-Alder reaction between a-bromoacrolein and a range of dienes (Cp illustrated) to yield the cycloadducts with excellent levels of enantioselectivity. The Jacobsen group use the tridentate chiral Schiff base chromium(II1) complex 142 as a catalyst for hetero DielsAlder reactions. '02 In the example shown a-triethylsilyloxy acetaldehyde and diene 143 are combined to produce the corresponding dihydropyran product with impressive levels of yield and selectivity. The use of 143 as the diene component is noteworthy as it is significantly less reactive than Danishefsky's diene which would normally be employed in such reactions. In both of the examples presented the use of the SbF6 counterion was found to be crucial for the success of the chemistry. Several well established chiral Lewis acids have been exploited in new applications; the Ti-BINOL complexes developed by Mikami have been used as catalysts for the enantioselective homoaldol'03 reaction and for an enantioselective Freidel-Crafts reaction. The chiral Cu(I1) bisoxazolines pioneered by Evans have been applied to several new enantioselective reactions including 1,3-dipolar nitrone cycl~additions'~~ and Diels-Alder reactions of 2-azadienes.'06 Evans has applied these catalysts to a range of conjugate addition reactions. '07 Scheme 55 illustrates a Mukaiyama Michael addition between silyl ketene acetal 145 and fumarate 146.'08The second reaction is an example of the selective amination of the enol silane derived from acetophenone using diimide 147 as the nitrogen source.'o9 In both examples the t-butyl substituted bisoxazoline catalyst 144 was found to be optimal. A series of full accounts detailing the discovery of this highly successful catalyst family has ap-

Organometallic Chemistry

198

144

oms

145

144 (10 mol%) HFIP,36h CH2CI2, -78 "C

Me

+

0

0

C02EtO ~

0

Bu5wNAo u Me

94% yield, 99% ee, 99:l dr EQC d

N

K \ O I I

146

144 (5 rnol%) CF3CHzOH

0 ci3H2c02c 2 ' N 147

0

P h q m 0

THF, -20 "C, 1 min.

N' 0

u

T ~ H N ' N K N K O H U 96% yield, 99% ee

Scheme 55

peared.' loY1 l 1 The Kobayahi group have used these Cu(I1) complexes to catalyse a range of Mukaiyama aldol reactions in aqueous media. l 2 The aluminium-salen complexes developed by Jacobsen have been employed as catalysts in the enantioselective conjugate addition of azide to unsaturated imides. l 3 An enantioselectiveconjugate addition of thiols has also appeared.* l4 Lewis acid catalysed additions to imines are generally more challenging than additions to the corresponding carbonyl compounds; one of the major factors is catalyst turnover, with the result that often very high catalyst loadings are needed. The groups of Hoveyda and Snapper have developed a titanium based catalyst system that mediates the enantioselective addition of cyanide to a range of aromatic imines (Scheme 56).'15 High yields and selectivities can be

'

'

148

CN &NIP.

PfOH, 148 Ti(0P (10 PhMe, I')~ mol%) 4 "C

~

&NAPh /

Ph H

96% yield, 93% ee

TMS-CN Scheme 56

8: Organic Aspects of Organometallic Chemistry

199

obtained using only 10 mol% of the ligand 148. A second successful enantioselective imine addition has been reported by Leckta et al; in this case a Cu(1)phosphine complex is the catalyst of choice. l 6 Zirconium-BINOL based complexes have also been used as catalysts in enantioselective Diels-Alder reactions of imines. l 7 A significant body of work is being established that employs chiral salen complexes to catalyse a range of enantioselective additions to epoxides. The majority of these additions are either examples of enantioselective desymmetrisations or of kinetic resolutions. Scheme 57 illustrates the selective addition

'

4 But'

'But

x = (WCF313) 149

0 WC4H9

OH

150+(2.2 equiv.)

TBME, 494(4-4 A MS, mo'%) -1 5 "C

~

)pJO4Hg / Br 92% yield (based on 151), 99% ee

Br D

O 151

H Scheme 57

of phenol 151 to epoxide 150 mediated by the chiral Cr(II1) complex 149. '18 Succesful azide additions,' l9 intramolecular cyclistions,120 additions to aziridines121 and the use of polymer supported catalysts have also appeared over the last year.'22 7

Emerging Areas

7.1 High-throughput Catalyst Identification. - High-throughput and combinatorial chemistry methods have made considerable impact in many areas, perhaps most notably in the area of pharmacuetical lead identification and optimisation. Several groups are beginning to use these new technologies to identify and optimise new transition metal catalysts. Morken and Taylor have used high-throughput methodology to identify new catalysts for the reductive aldol reaction (Scheme 58).123 192 independent experiments were performed in 96-well plates, screening such variables as metal-salt, silane, ligand and solvent. The experiments revealed four combinations that provided the aldol adduct in >94% yield. The optimal system ([(cod)RhClz], Me-DuPhos, C12MeSi-H)delivered the aldol product from the combination of benzaldehyde

Organometallic Chemistry

200 0

+

$?

H-SiR' R2R3 catalyst

*

DCE, 50 "C

~~~~~~~

CI2MeSiH

]

Me 69% yield, 23:i dr

Scheme 58

and methyl acrylate in 69% yield with 23:1 diastereoselection. An important feature of the results presented in the manuscript was that the four catalyst systems identified displayed significant independence of reaction variables. The Morken group has also investigated novel approaches to the discovery of new allylation catalysts.124The system developed is illustrated in Scheme 59; treatment of allyl naphthol carbonate 152 with a metal catalyst generates a nallyl metal complex that combines with diethyl malonate to yield the desired allylated product 153. The initial reaction step also generates 1-naphthol, which reacts with the dye 'fast red" to form the bright orange azo compound 154. Simple visual inspection of the reaction vessel therefore allows the determination of the success of the reaction. The methodology identified several known catalysts as well as a novel iridium based system. Crabtree has used a related approach to identify novel hydrosilylation catalysts.12' 0

010-

152

0

qC'

+ 0

"fast red"

EtOuOEt

the 154 Scheme 59

A Japanese group have reported high-throughput methodology to identify ligands and activators for the enantioselective addition of diethylzinc to aldehydes.126 7.2 Non-traditional Solvents in OrganometallicTransformations. - The use of non-traditional solvents in metal-mediated organic synthesis is attracting a great deal of attention. The potential benefits of moving away from organic solvents include cleaner technology, increased efficiency and unique selectivities. Because of its particularly favourable environmental properties, supercritical carbon dioxide (scCO2) has been employed as a reaction medium

8: Organic Aspects of Organometallic Chemistry

20 1

0 0

II

It SCCQ, 85 'C, 1600 psi Pd(F6-acac)2 P(2-fUryl)3 DiPEA

s c c a , 40'C, 1400psi

Ph-H

156

cue12 NaOAc

155 96% yield

-

Ph

Ph

157 100% yield

Scheme 60

alternative to organic solvents. The palladium catalysed Heck reaction is a widely-used carbon-carbon bond-forming process, and as delineated in Scheme 60 the catalytic coupling of methyl acrylate with iodobenzene proceeds efficiently to afford product 155 in this unique medium.'27 A similar process using supported palladium catalysts has also been reported.128 It has been shown that copper-mediated Glaser coupling proceeds smoothly in scC02 using NaOAc instead of an amine base. Under relatively mild conditions the alkyne 156 is reacted to form the dimer 157 in quantitative yield. 29 Another expanding area involving unique solvent systems is that of fluorous biphasic synthesis (FBS). In this technique, reagents and/or catalysts are modified with long-chain fluorous pony-tails to render them preferentially soluble in the fluorous phase. As most hydrophobic and to a great extent hydrophilic products are relatively insoluble in fluorocarbon solvents a means of separation of unwanted side-products or valuable catalysts becomes apparent. Given that fluorocarbon solvents are believed to be non-toxic the strategy becomes attractive for large-scale synthesis within the confines of economics. The use of fluorous soluble catalysts has been demonstrated for hydroformylation, hydrogenation, hydroboration and alkene epoxidation. 30 The Heck coupling of iodobenzene and methyl acrylate proceeds smoothly in a mixture of fluorocarbon solvent (D-100) and acetonitrile (Scheme 61).131 The product can be separated from the palladium catalyst as a consequence of the perfluorinated pony-tailed phosphine ligand 156. In the radical cyclisation of aryl halide 158 to product 159, the use of a perfluorinated tin mediator 157 enables easy separation and recycling of the tin reagent.132 Another area of growing interest is that of using ionic liquids such as 1butyl-3-methylimidazolium hexafluorophosphate ([bmin][PFb]) as solvents. Ionic liquids have the useful property of being virtually insoluble in water and alkanes but dissolving many metal catalysts. These unique biphasic conditions can lead to facile extraction of products. Room-temperature ionic liquids have been used as solvents in a number of reactions including the dimerisation of alkanes,133 hydrogenation reactions'34 and cycloaddition processes.135 The

Organometallic Chemistry

202

a'tom M e C N l i 0 0 (1:l)

~

&om

Pd2(db)3

156

155 96% yield

P@-C6FI3)

microwave 60 W

I

\cbz 159 93% yield

cbz

158

Scheme 61

0

ionic liquid

160

(""

161 95% yield

162

CQMe PhJ

ph

163

Pd(OAc)#Ph3 K2C03

ionic liquid

Ph 164 100% yield

Scheme 62

benchmark Heck coupling process proceeds efficiently in room temperature ionic liquids as shown in Scheme 62.'36 Other palladium catalysed processes such as allylic alkylation proceed readily in [bmin][PF6]with easy catalyst and solvent recycling. An added advantage is there is no need to generate the carbanion nucleophile 162 separately, the formation of product 164 by the alkylation of 163 occurs in quantitative yield with several examples.137

References 1. 2. 3. 4.

R. Stunner, Angew. Chem. Int. Ed., 1999,38,3307. A. F. Littke and G. C. Fu, J. Org. Chem., 1999,64, 10. A. F. Littke and G. C. Fu, Angew. Chem. Int. Ed., 1999,38,2411. M. Kawatsura and J. F. Hartwig, J. Am. Chem. SOC., 1999,121, 1473.

8: Organic Aspects of Organometallic Chemistry 5. 6. 7. 8.

9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42.

203

J. P. Wolfe and S. L. Buchwald, Angew. Chem. Int. Ed., 1999,38,2413. J. Huang and S. P. Nolan, J. Am. Chem. Soc., 1999,121,9889. J. Huang, G. Grasa and S. P. Nolan, Org. Lett., 1999, 1, 1307. C. Zhang, J. Huang, M. L. Trudell and S. P. Nolan, J. Org. Chem., 1999, 64, 3804. A. Aranyos, D. W. Old, A. Kiyomori, J. P. Wolfe, J. P. Sadighi and S. L. Buchwald, J. Am. Chem. SOC., 1999,121,4369. G. Mann, C. Incarvito, A. L. Rheingold and J. F. Hartwig, J. Am. Chem. Soc., 1999,121,3224. M. Watanabe, M. Nishiyama and Y. Koie, Tetrahedron Lett., 1999,40,8837. B. L. Lipshutz, D. J. Buzard and C. S. Yun, Tetrahedron Lett., 1999,40,201. S . R. Gilbertson, Z. Fu and G. W. Starkey, Tetrahedron Lett. , 1999,40,8509. T. Kondo, S. Uenoyama, K. Fujita and T. Mitsudo, J. Am. Chem. SOC.,1999, 121,482. M. Murata, S. Watanabe and Y. Masuda, Tetrahedron Lett., 1999,40,9255. S . Abbas and C. J. Hayes, Synlett, 1999, 1124. A. J. Hennessy, Y. M. Malone and P. J. Guiry, Tetrahedron Lett., 1999,40,9163. J. C . Namyslo and D. E. Kaufmann, Synlett, 1999,804. S. Brase and M. Schroen, Angew. Chem. Int. Ed., 1999,38, 1071. A. J. Blacker, M. L. Clarke, M. S. Loft and J. M. J. Williams, Org. Lett. , 1999, 1, 1969. B. Bartels and G. Helmchen, Chem. Commun., 1999,741. P. A. Evans, J. E. Robinson and J. D. Nelson, J. Am. Chem. Soc., 1999, 121, 6761. B. M. Trost, S. Hildbrand and K. Dogra, J. Am. Chem. SOC.,1999,121,11416. F. Glorius and A. Pfaltz, Org. Lett. , 1999,1, 141. R. Kuwano and Y. Ito, J. Am. Chem. Soc., 1999,121,3236. B. M. Trost and G. M. Schroeder, J. Am. Chem. SOC.,1999,121,6759. A. Bohme and H. Gais, Tetrahedron:Asymmetry, 1999,10,2511. B. Breit and S. K. Zahn, Angew. Chem. Int. Ed., 1999,38,969. B. Zimmennann, J. Herwig and M. Beller, Angew. Chem. Int. Ed., 1999,38,2372. T. Morimoto, N. Chatani and S. Murai, J. Am. Chem. Soc., 1999,121, 1758. D. Berger and W. Imhof, Chem. Commun., 1999,1457. M. Murakami, K. Itami and Y. Ito, J. Am. Chem. Soc., 1999,121,4130. N. Chatani, M. Tobisu, T. Asaumi, Y. Fukumoto and S, Murai, J. Am. Chem. SOC.,1999,121,7160. M. E. Kraft, L. V. R. Bonaga and C. Hirosawa, Tetrahedron Lett., 1999, 40, 9171. S. J. Sturla and S. L. Buchwald, J. Org. Chem., 1999,64,5547. F. A. Hicks and S. L. Buchwald, J. Am. Chem. SOC.,1999,121,7026. H. Corlay, E. Fouquet, E. Magnier and W. B. Motherwell, Chem. Commun., 1999,183. D. S. Davis and S. C. Shadinger, Tetrahedron Lett., 1999,40,7749. J. S . Kingsbury, J. P. A. Harrity, P. J. Bonitatebus, Jr., and A. H. Hoveyda, J. Am. Chem. SOC.,1999,121,791. L. Ackermann, A. Furstner, T. Weskamp, F. J. Kohl and W. A. Herrmann, Tetrahedron Lett. , 1999,40,4788. M. Scholl, T. M. Trnka, J. P. Morgan and R. H. Grubbs, Tetrahedron Lett., 1999,40,2247. M. Scholl, S. Ding, C. W. Lee and R. H. Grubbs, Org. Lett., 1999,1,953.

204

Organometallic Chemistry

43. 44.

A. Furstner and L. Ackermann, Chem. Commun., 1999,95. S . M. Hansen, M. A. 0. Volland, F. Rominger, F. Eisentager and P. Hofmann, Angew. Chem. Int. Ed., 1999,38, 1273. A. Furstner, C. Mathes and C. W. Lehmann, J. Am. Chem. SOC.,1999,121,9453. M. Ahmed, A. G. M. Barrett, D. C. Braddock, S. M. Cramp and P. Procopiou, Tetrahedron Lett., 1999,40,8657. A. G. M. Barrett, S. M. Cramp and R. S . Roberts, Org. Lett., 1999, 1, 1083. H. D. Maynard and R. H. Grubbs, Tetrahedron Lett., 1999,40,4137. S . S . Zhu, D. R. Cefalo, D. S. La, J. Y. Jamieson, W. M. Davis, A. H. Hoveyda 1999,121,8251. and R. R. Schrock, J. Am. Chem. SOC., D. S. La, J, G, Ford, E. S. Sattely, P. J. Bonitatebus, R. R. Schrock and A. H. Hoveyda, J. Am. Chem. SOC.,1999,121,11603. P. A. Evans and J. E. Robinson, Org. Lett., 1999,1, 1929. P. R. Hanson, D. A. Probst, R. E. Robinson and M. Yei, Tetrahedron Lett., 1999,40,4761. P. R. Hanson and D. S . Stoianova, Tetrahedron Lett., 1999,40,3297. M. J. Bassindale, P. Hamley, A. Leiner and J. P. A. Harrity, Tetrahedron Lett., 1999,40,3247. T. R. Hoye, S. M. Donaldson and T. J. Vos, Org. Lett., 1999,1, 3277. D. J. O’Leary, H. E. Blackwell, R. A. Washenfelder, K. Miura and R. H. Grubbs, Tetrahedron Lett., 1999,40, 1091. H. M. L. Davies and S . A. Panaro, Tetrahedron Lett., 1999,40,5287. S . P. Marsden and W.-K. Pang, Chem. Commun., 1999,1199. P. R. Hanson, K. T. Sprott and A. D. Wrobleski, Tetrahedron Lett., 1999, 40, 1455. J. M. Axten, R. Ivy, L. Kim and J. D. Winkler, J. Am. Chem. Soc., 1999, 121, 651 1. H. M. L. Davies, T. Hansen, D. W. Hopper and S. A. Panaro, J. Am. Chem. SOC.,1999, 121, 6509. H. M. L. Davies, E. G. Antoulinakis and T. Hansen, Org. Lett., 1999,1,383. J. L. Wood, G. A. Moniz, D. A. Pflum, B. M. Stoltz, A. A. Holubec and H.-J. Dietrich, J. Am. Chem. SOC.,1999,121, 1748. S. Kitgaki, M. Anada, 0. Kataoka, K. Matsuno, C. Umeda, N. Watanabe and S . 4 Hashimoto, J. Am. Chem. Soc., 1999,121, 1417. Y. Takaya, M. Ogasawara and T. Hayashi, Tetrahedron Lett., 1999,40,6957. Y. Takaya, T. Senda, H. Kurushima, M. Ogasawara and T. Hayashi, Tetrahedron: Asymmetry, 1999,10,4047. Y. Takaya, T. Senda, H. Kurushima, M. Ogasawara and T. Hayashi, J. Am. Chem. SOC.,1999,121,11591. S . Oi, M. Moro, H. Fukuhara, T. Kawanishi and Y. Inoue, Tetrahedron Lett., 1999,40,9259. S . Ikeda, D. Cui and Y. Sat, J. Am. Chem. Soc., 1999,121,4712. M. Yan, L. Yang, K. Wong and A. S . Chan, Chem. Commun., 1999,1112. X. Hu, H. Chen and X. Zhang, Angew. Chem. Int. Ed., 1999,38,3518. F. Kakiuchi, M. Sonoda, T. Tsujimoto, N. Chatani and S . Murai, Chem. Lett., 1999,1083. F. Kakiuchi, T. Sato, M. Yamauchi, N. Chatani and S . Murai, Chem. Lett., 1999, 19. N. Chatani, Y. Ie, F. Kakiuchi and S . Murai, J. Am. Chem. Soc., 1999,121, 8645. H. Chen and J. Hartwig, Angew. Chem. Int. Ed., 1999,38,3391.

45. 46. 47. 48. 49.

50. 51. 52. 53. 54.

55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73.

74. 75.

8: Organic Aspects of Organometallic Chemistry 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107.

108. 109. 110. 111.

205

C.-H. JunandH. Lee, J. Am. Chem. SOC., 1999,121,880. B. Witulski and T. Stengel, Angew. Chem. Int. Ed., 1999,38,2426. Y. Yamamoto, A. Nagata and K. Itoh, Tetrahedron Lett., 1999,40,5035. A. Bradley, W. B. Mothenvell and F. Ujjainwalla, Chem. Commun., 1999,916. B. M. Trost and A. B. Pinkerton, J. Am. Chem. SOC.,1999,121,10842. C. Dobler, G. Mehltretter and M. Beller, Angew. Chem. Int. E d , 1999,38, 3026. K. Bergstad, S. Y. Jonsson and J.-E. Backvall, J. Am. Chem. SOC., 1999, 121, 10424. T. J. Donohoe, N. J. Newcombe and M. J. Waring, Tetrahedron Lett., 1999, 40, 6881. S. Kobayashi, M. Endo and S. Nagayama, J. Am. Chem. SOC., 1999,121,11229. L. J. Goossen, H. Liu, K. R. Dress and K. B. Sharpless, Angew. Chem. Int. Ed., 1999,38,1080. A. V. Gontcharov, H. Liu and K. B. Sharpless, Org. Lett., 1999,1,783. A. A. Thomas, K. B. Sharpless, J. Org. Chem., 1999,64,8379. A. J. Morgan, C. E. Masse and J. S. Panek, Org. Lett., 1999,1, 1949. J. H. Esperson, Chem. Comrnun., 1999,479. H. Adolfson, A. Converso and K. B. Sharpless, TetrahedronLett., 1999,40, 3991. I. Sakurada, S. Yamasaki, R. Gottlich, T. Iida, M. Kanai and M. Shibasaki, J. Am. Chern. SOC., 1999,121,1245. Y. Nishimura, K. Ohe and S. Uemura, J. Am. Chem. SOC.,1999,121,2645. E. Takewara, S. Sakaguchi and Y. Ishii, Org. Lett., 1999,1,713. M. J. Burk, K. M. Bedlingfield, W. F. Kiesman and J. G. Allen, Tetrahedron Lett., 1999,40, 3093. J. Holz, D. Heller, R. Sturmer and A. Borner, Tetrahedron Lett., 1999,40,7059. S . Challenger, A. Derrick, C. P. Mason and T. V. Silk, Tetrahedron Lett., 1999, 40, 2187. M. V. Troutman, D. H. Appella and S. L. Buchwald, J. Am. Chem. Soc., 1999, 121,4916. D. H. Appella, Y. Moritani, R. Shintani, E. M. Ferreira and S. L. Buchwald, J. Am. Chem. SOC., 1999,121,9473. Y. Nishibayashi, I. Takei, S. Uemura and M. Hidai, Organometallics, 1999, 18, 229 1. T. Ali, K. K. Chauhan and C. G. Frost, Tetrahedron Lett., 1999,47, 5621. E. P. Kundig, C. M. Saudan and G. Bernardinelli, Angew. Chem. Int. E d , 1999, 38, 1220. A. G. Dossetter, T. F. Jamison and E. N. Jacobnsen, Angew. Chem. Int. Ed., 1999,38,2398. E. 0.Martins and J. L. Gleason, Org. Lett., 1999,1, 1643. A. Ishii, J. Kojima and K. Mikami, Org. Lett., 1999,1,2013. K. B. Jensen, R. G. Hazel1 and K. A. Jorgensen, J. Org. Chem., 1999,64,2353. E. Jnoff and L. Ghosez, J. Am. Chem. Soc., 1999,121,2617. D. A. Evans, T. Rovis, M. C. Kozlowski and J. S. Tedrow, J. Am. Chem. SOC., 1999,121,1994. D. A. Evans, M. C. Willis and J. N. Johnston, Org. Lett., 1999,1, 865. D. A. Evans and D. S. Johnson, Org. Lett., 1999,1,595. D. A. Evans, M. C. Kozlowski, J. A. Murry, C. S. Burgey, K. R. Campos, B. T. Connell and R. J. Staples, J. Am. Chem. SOC.,1999,121,669. D. A. Evans, S. J. Millar, T. Lectka and P. von Matt, J. Am. Chem. SOC.,1999, 121,7559.

206

Organometallic Chemistry

S. Kobayashi, S. Nagayama and T. Busujima, Chem. Lett., 1999,71. J. K. Myers and E. N. Jacobsen, J. Am. Chem. SOC.,1999,121,8959. S. Kanemasa, Y. Oderaotoshi and E. Wada, J. Am. Chem. SOC.,1999,121,8675. C. A. Krueger, K. W. Kuntz, C . D. Dzierba, W. G. Wirschun, J. D. Gleason, M. L. Snapper and A. H. Hoveyda, J. Am. Chem. SOC.,1999,121,4284. 116. D. Ferraris, T. Dudding, B. Young, W. J. Drury I11 and T. Lectka, J. Org. Chem., 1999,64,2168. 117 S. Kobayashi, K. Kusakabe, S. Komiyama and H. Ishitani, J. Org. Chem., 1999, 112. 113. 114. 115.

64,4220. 118. J. M. Ready and E. N. Jacobsen, J. Am. Chem. SOC.,1999,121,6086. 119. H. Lebel and E. N. Jacobsen, Tetrahedron Lett., 1999,40,7303. 120. M. H. Wu, K. B. Hansen and E. N. Jacobsen, Angew. Chem. Int. Ed., 1999, 38, 20 12. 121. Z. Lei, M. Fernandez and E. N. Jacobsen, Org. Lett., 1999,1, 1611. 122. S. Peukert and E. N. Jacobsen, Org. Lett., 1999,1, 1245. 123. S. J. Taylor and J. P. Morken, J. Am. Chem. SOC., 1999,121, 12202. 124. 0. Lavastre and J. P. Morken, Angew. Chem. Int. Ed., 1999,38,3163. 125. R. H. Crabtree, Chem. Commun., 1999,161 1. 126. K. Ding, A. Ishii and K. Mikami, Angew. Chem. Int. Ed., 1999,38,497. 127. N. Shezad, S. Oakes, A. A. Clifford and C. M. Rayner, Tetrahedron Lett., 1999, 40,222 1. 128. S. Cacchi, G. Fabrizi, F. Gasparrini and C. Villani, Synlett, 1999,345. 129. J. LiandH. Jiang, Chem. Commun., 1999,2369. 130. R. H. Fish, Chem. Eur. J., 1999,6, 1677. 131. J. Moinea, G. Pozzi, S. Quici and D. Sinou, Tetrahedron Lett., 1999,40, 7683. 132. K. Olofsson, S. Kim, M. Larhed, D. P. Curran and A. Hallberg, J. Org. Chem., 1999,64,4539. 133. B. Ellis, W. Keim and P. Wassersheid, Chem. Cornmun., 1999, 337. 134. T. Fisher, A. Sethi, T. Welton and J. Woolf, Tetrahedron Lett., 1999,40, 793. 135. M. J. Earle, P. B. McCormac and K. R. Seddon, Green Chem, 1999,1,23. 136. A. J. Carmichael, M. J. Earle, J. D. Holbrey, P. B. McCormac and K. R. Seddon, Org. Lett., 1999, b, 997. 137. W. Chen, L. Xu, C. Chatterton and J. Xiao, Chem. Commun., 1999, 1247.

9 Metal Carbonyls BY JOHN A. TIMNEY

1

Introduction

This report deals with those publications from 1999 that described advances in metal carbonyl chemistry. The terms of reference for this chapter are those studies which explore the chemistry of the metal carbonyls themselves, metal carbonyl halides, pseudohalides and hydrides. Activity in this field continues to run at a fairly high level, although the number of papers noted here is slightly down compared to a high point in 1996. The general structure of this report is similar to that for previous years. This chapter, although focusing on the chemistry of the CO groups in metal carbonyls, contains information about those complexes containing Group 15 andor Group 16 donor ligands. Therefore, for example, any new chemistry about Ni(C0)2(PMe3)2would be found in this chapter, but the chemistry of Ni(PMe3)4 would reside elsewhere unless it led to the formation of a COcontaining product. There is, as in previous years, a slight bias towards Group 15 donor ligands. However, the gap between the numbers of carbonyl complexes containing P, As, Sb and Bi and those containing Group 16 donor ligands is reducing as selenium and tellurium containing compounds become more common and more amenable to exploration. The chalcogens (sulfur, selenium and tellurium) are making an increasing presence in the preparation of metal carbonyl cluster complexes. Like the report from last year, the catalytic activity of metal carbonyl complexes has not been dealt with in a separate section. Reports of any papers dealing with the use of metal carbonyl complexes as catalysts are now to be found in the section devoted to that particular metal. The practice whereby any relevant papers missed in the previous report (quite often because they were awaiting translation into English) are included in the next available report is continued. Papers about the chemistry of metal carbonyls are found in a number of journals. The most common journal for publication (by some margin) is Organometallics, followed by the Journal of Organometallic Chemistry. Workers in this field would be well advised to ensure ready access to these journals. Before Organometallics became pre-eminent, a large percentage of metal carbonyl research was published in Inorganic Chemistry and Znorganica Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001

207

Organometallic Chemistry

208

Chimica Acta. Both these journals are still represented here, but at a much lower level. Indeed, Inorganica Chimica Acta is now a virtual desert for metal carbonyl work. A sizeable fraction of the references in this chapter comes from Dalton Transactions.

2

Reviews

There has been a relative paucity of reviews from 1999 that would interest metal carbonyl chemists, but those that have been published are well worth the read. Some ten years ago, the number of new compounds featured in this chapter containing ligands where the donor atom was a Group 15 atom (predominantly phosphorus) greatly outnumbered those ligands containing a Group 16 atom (S, Se, Te). This is not the case latterly and the numbers are now more or less equal. In a long and detailed review, the synthesis, reactions and structures of complexes of metal carbonyls and cyclopentadienyl carbonyls with organotellurium ligands are all well discussed'. Of general interest to carbonyl chemists comes a large review article by Frohlich and Frenking2 dealing with theoretical models derived from ab initio calculations describing the bonding situation in transition metal complexes. Even though metal carbonyls are not the main focus, this review is well researched and repays the effort. Although very few papers within it actually fall within the terms of reference for this chapter, readers are encouraged to browse through the entire volume 578 of the Journal of Organometallic Chemistry. There is a great deal of interest contained therein. Finally, the fascinating study of ultrafast processes in organometallic chemistry using infrared techniques (especially where it relates to bond activation) has been reviewed by Harris et ~ 2 . ~

3

Theoretical, Spectroscopicand General Studies

3.1 TheoreticalStudies. - It is perhaps surprising that new theoretical insights are possible into the well-studied molecules Fe2(C0)9, Fe3(CO)12, Ru2(C0)9, Ru3(C0)12, O S ~ ( C Oand ) ~ Os3(CO)12, but this is the focus of a detailed and interesting account by Reinhold and co-workers4. Slightly off the beaten track for carbonyl chemists, but linked to much that goes on in carbonyl chemistry, is a theoretical study by Xue on the relative stabilities of transition metal alkylidene and bis(alky1idene)complexes5. Frenking and co-workers have produced three papers that are of relevance to this section: a detailed study6 of the gallium-iron bond where aryl-gallium compounds are bonded to Fe(C0)4 residues, a theoretical study of gas-phase reactions of Fe(CO)5 with OH- and their relevance for water gas shift

9: Metal Carbonyks

209

reactions7 and, finally, a most interesting insight into the molecular geometries and bond strengths of the homoleptic d" metal carbonyl cations'. There has been a re-investigation9 of the role of ohdonation as it affects CO lability in the Group 6 anions [M(C0)50H]-, [M(CO)S(halide)]-, -. [M(CO)5CH3]- ,[M(CO)5H]- and [M(CO)SNH2] There has also been a theoretical study" about the linear dicyanide and dicarbonyl complexes of the metals Au, Hg, and T1. A considerable amount of the discussion is devoted to the possible existence of a [Tl(CO),13' cation. It appears that there is no a priori reason for not being able to make these unusual species. Rarely does any metal beyond platinum make an appearance in this chapter, so it is most unusual to have an element with as high an atomic number as seaborgium (Sg) feature in here. This distant trans-uranic element has, as yet, an extremely limited chemistry but that, of course, does not stop theoretical work. Bursten' has predicted the bond lengths, vibrational frequencies and bond dissociation energies of seaborgium hexacarbonyl, Sg(CO)6. Even though Sg(CO)6 is still on the drawing board, Bursten and Andrews12 have (amongst other things) produced infrared evidence (in a solid neon matrix) of U(CO)6 and the lower carbonyls U(CO), where n = 1, 2, 3 , 4 and 5. Perhaps sg(co)6 is not too far away after all. Bursten and Li also report the reactions of thorium atoms with CO to give the first thorium carbonyl complexes.

3.2 Spectroscopic Studies. - The spectroscopy of metal carbonyls is always interesting. For example, Johnson et ~ 1 . have ' ~ produced a fascinating study of the relative reactivity and general characterisation (using mass spectrometry) of metal carbonyl cluster fragments created using a UV laser. With an intriguing title that begins 'When the ligands go marching in...'? Schultz and Krav-Ami have released details15 of successive ligand attack on the photogenerated transient species W(CO)5(cyH). They used FTIR to track the progress of the reactions. Elsewhere, the extreme sensitivity of the C = 0 vibrations in a metal carbonyl molecule have been utilised to good effect in a IR spectroscopic study16of hydrogen bonding using a metal carbonyl probe. Kaya17"* has devised a new approach to solving the CO-factored force field of M(C0)4 molecules having C3" symmetry. Although this approach does appear to get round the problem of determining four parameters from only three observed v(C0) frequencies, it is this reporter's view that there are better ways to determine CO force constants. For those who are interested, there is now an internet website which enables carbonyl chemists to have the force fields of their compounds cal~ulated'~. The service is free of charge. Matrix isolation techniques have always been fruitful with metal carbonyl molecules as the guests in the inert matrix and Zhou and Andrews2' have produced infrared spectra of RhCO+, RhCO and RhCO- in solid neon. This provides 'benchmark' points for estimating the charge on supported Rh(C0) catalyst systems. The technique of time-resolved infrared (TRIR) spectroscopy has matured

210

Organometallic Chemistry

well over the past decade and from its origins in looking at relatively simple metal carbonyl systems it is now being used in a much more sophisticated way. As evidence of this trend, a high-pressurehariable temperature infrared cell and TRIR spectroscopy have been used2' to probe the CpFe(C0)2[COCH3] system and to examine the kinetics of the intermediate CpFe(C0)2[COCH3]. TRIR has enabled much structural data to be extracted from excited states and intermediates; it has reached the femtosecond level covered by Vlek and co-workers22 in their study of the MLCT excited-state dynamics of Cr(C0)4(bpy). As might be expected, there is an excitation energy dependency between CO dissociation and simple relaxation. The structural and electronic changes accompanying reduction of Cr(C0)4(bpy) to its radical anion are discussed ~ e p a r a t e l yIt ~ ~may . be worth recalling at this point that light travels only 0.3 microns in a femtosecond and it must be an unusual situation for a chemist to be held up by the inherent slowness of light! The same time frame is used by Harris and c o - ~ o r k e r sin~ a~ study of the reaction of Re(CO)5 in chlorine abstraction. Again using femtosecond infrared technology they have explored this interesting example of a one-electron oxidative-addition reaction. Although much of a study by Davies and co-workers is devoted to the synthesis of transition metal carbonyl complexes of cyclic di- and tetraselenoether ligands, there is much to interest those who might have a more spectroscopic leaning25. Containing four osmium atoms, the water-soluble cationic cluster [Os4(pH)4(CO)10(dppH)]+(where dpp is the pyridyl-type ligand 2,3-bis(2-pyridyl)pyrazine) has been the subject of a mass spectroscopic study using electrospray techniques26. Perutz has contributed a great deal to the understanding of the photochemistry of metal carbonyls but, hitherto, the molecules he has chosen as targets have been relatively small (for example, the 16-e fragments Cr(CO)5, MO(CO)~ and W(C0)S were characterised by him in the mid-1970's). This is certainly not the case in his (and co-workers') recent study of the systematic synthesis and photochemistry of the massive tetra-aryl porphyrins monosubstituted with a transition metal ~ a r b o n y l The ~ ~ . study demonstrates the existence of a zinc porphyrin-rhenium carbonyl complex. NMR studies on metal carbonyl complexes are relatively scarce (although some extremely interesting work has been produced, especially by Heaton and co-workers, over the years and, in 1999, this group continued their valuable contribution28y29 with a detailed comparison of solid state and solution NMR of carbonyl clusters). The list of studies has been extended with the NMR detection of thermal and photochemical dihydrogen addition products of mono- and tri-nuclear ruthenium complexes containing CO and phosphine groups3'. The main method of probing these systems was through parahydrogen induced polarisation. There has also been a report31 of the observation of triple-quantum effects in the HMQC spectra of substituted derivatives of Rh6(C0)16. Perhaps the most interesting spectroscopic study of 1999 comes from Geftakis and Ball who report the direct observation of a transition metal alkane complex, CpRe(C0)2(cyclopentane),using NMR32.

9: Metal Carbonyks

21 1

3.3 General Studies. - This section contains information about the use of metal carbonyls in chemical applications. Primarily this involves organic or organometallic chemistry that makes use of carbonyls either as catalysts or to generate intermediates. In addition, in this section, we try to report studies that deal with new ligands or novel uses of existing ligands. For example, the diphosphirenes are relative newcomers as ligand and the knowledge base we have on these interesting compounds has been expanded by the release of a comm~nication~~ describing their reaction with iron carbonyl fragments. The creation of chiral carbonyl complexes has been noted a number of times during the past few years. The latest contribution points towards a method for carrying out asymmetric hydrovinylation using various phosphine catalysts via a chiral tricarbonyl(ethy1benzene)chromium complex34. Chirality is also the focus in a paper by K a t a ~ a m et a ~al. ~ The chromium group are cast as the central atoms in a paper by Angelici and c o - ~ o r k e r swho ~ ~ have prepared a series of new complexes using dimethylthiophene, benzothiophene and dibenzothiophene ligands. Some years ago there were numerous studies aimed at tagging biological molecules so that they could be detected at nanomole levels. The detection process invariably made use of the phenomenally intense v(C0) bands of the metal carbonyls around 2000 cm-’. This technique is now called ‘carbonyl metallo immuno assay’ and Jaouen and co-workers, pioneers in this type of work, have developed it as a new application for Fourier transform infrared spectro~copy~~. This work is continued in a different guise by Kerr3*et al. who have tagged several carbohydrates with the CCo3(CO)9 cluster. The metals in the iron group are usually very prominent in this section and 1999 was no exception. Adams and co-workers have been particularly active in this area (amongst others) with studies of the ring opening of 1,3-dithietane1,l-dioxide that has been achieved using a triosmium cluster39;the preparation of butene dithiolate triosmium clusters from the reaction of O S ~ ( C O ) ~ ~ (NCMe)2 with 3,6-dihydro-1,2-dithiin4; the synthesis and structural analyses of ruthenium carbonyl cluster complexes containing the bis-(trimethylsily1)hexatriene ligand, the use of semi-rigid polyyne ligands to direct the shapes of metal clusters with (for example) o-bis(phenylethynyl)benzene4’ (in this study, the mixed-metal carbonyl Pt2Ru4(C0)18was used); the catalytic transformations of vinylthiiranes using tungsten carbonyl complexes (providing a route to 3,6-dihydro-1,2-dithiin~)~~ and, finally, a study investigating the effects of a vinyl substituent on the ring opening of a tetrahydrothiophene at a trisomium centre43. Cobalt carbonyls have maintained their importance in this section. As an example, Rajesh and PeriasamyU have carried out carbonylative cyclisation of alkynes using cobalt carbonyl species prepared via reduction of CoBr2with Zn under an atmosphere of CO. Starting with the beguiling statement that ‘two dangling phosphine arms are better than one’ is a study by Keiter and co-workers4’ that deals with the induced acceleration of phosphine exchange in metal carbonyls using pendant groups of coordinated polyphosphines. Unusual phosphorus chemistry is also

212

Organometallic Chemistry

reported during the formation of iron-fluorophosphane complexes where the authors note46 a nucleophilic attack by the fluoride ion towards a trivalent phosphorus atom coordinated to a transition metal. The search for C-H and C-F activation goes on unabated with a study of the photochemical reactions of [Re(q5-C5R5)(CO)3](R = H or Me) with partially fluorinated benzenes47and a detailed and fascinating (using infrared flash kinetics as a probe technique) on the effect of alkane structure on rates of photo-induced C-H bond activation by C P * R ~ ( C Oin ) ~liquid rare gas media. In a notable first, this chapter contains a paper4' from Green Chemistry dealing with homogeneous dehydrosulfurisation under ambient conditions using Ru5C(C0)15. It has to be said that the metal carbonyls are seldom thought of as 'green' chemicals and it is interesting to see their usage in H2S removal.

4

Chemistry of the Metal Carbonyls

4.1 Titanium, Zirconium and Hafnium. - The early transition metals do not have the rich carbonyl chemistry of the later groups in the Periodic Table and the number of relevant papers dealing with titanium, zirconium and tantalum carbonyls is always restricted to a very small number. In 1999 there were no papers which would merit inclusion in this section. 4.2 Vanadium, Niobium and Tantalum. - The chemistry of metal carbonyls containing a metal from this group is usually relatively limited, and 1999 was no exception to this general rule. With the likes of V(CO)6, [v(cO),]- and V(CO),(NO) and their niobium and tantalum analogues it might have been thought that this would be a thriving section. Not so. In 1999 there were no papers which would qualify for this section.

4.3 Chromium, Molybdenum and Tungsten. - This group typically provides a large number of papers for this chapter and 1999 followed this trend. Again, as usual, the bulk of the papers deal with mononuclear species. The Group 6 metals have been used to make a variety of complexes containing a most unusual antimony-based cage ligand5* - certainly the first time that such a molecule has appeared in this report. The complexes [{Cr(C0)5)2(q1:q'-P4Sb2C4B~t4)], [ (Mo(CO)~)~(~':~'-P~S~~C~BU~~)] and [{W(CO)5>2(q':q '-P4Sb2C4But4)]have all been prepared along with an analogous iron complex. Equally novel coordination compounds containing metals from this group are to be found in a paper by Shimoi and co-workers5' who have prepared a series of monoborane Lewis base adduct complexes with the general formula M(CO)S(BH3.L) where M = Cr, Mo, W and L = NMe3, PMe3, PPh3. Angelici's work using dibenzothiophene and benzothiophene were men-

9: Metal Carbonyks

213

tioned in Section 3.3. His group have extended this type of using these thiophene ligands in reaction with Cr(C0)6. Hoff and co-workerss3have carried out a mechanistic study of the reaction of Cp*Cr(C0)3 with H2S. This yields three major products: HCr(CO)&p*, HSCr(C0)3Cp* and Cp*(C0)2Cr=S=Cr(C0)2Cp*. There is strong kinetic evidence for the production of the substituted radical complex Cr(C0)2(H2S)Cp* in these reactions. In metal carbonyl chemistry the fullerene ligands have been slow to make an impact but there is a slowly increasing body of work exploring both c 6 0 and other C, allotropes. This body of work was broadened in 1999 with the publication of a on the redox behaviour of the molybdenum and tungsten metallafullerenes Mo(q2-C60)(CO)2(phen)(dibutyl maleate) and W(q2-C60)(Co)2(phen)(dibutylmaleate) probed using spectroelectrochemistry and backed up with some detailed theoretical work. The new journal Organic Letters appeared in 1999 and, as might be expected with the increasingly blurred demarcation lines between the various disciplines in chemistry, there were papers within that would interest a carbonyl chemist. Chromium was used in its (arene)Cr(C0)3 guise to effect the synthesis of l a ~ u b i n eMolybdenum ~~. (although it tends to be the least used metal within this group) appeared as Mo(C0)3(CNBut)3 as a very efficient catalyst for regioselective hydro st an nation^^^. The preparation and control (at the nanoscale level) of molybdenum sulfide catalysts using Mo(CO)~and HZS is also reporteds7. Mo(I1) carbonyl complexes are rather rare and seven-coordinate complexes of molybdenum(I1) are rarer still. That said, seven-coordinate Mo(1I) complexes containing a trichlorogermyl ligand have been prepared5*,such as the novel [ M o ( G ~ C ~ ~ ) ~ ( C O ) ~ ( N C E ~ ) ~ ] . A di-molybdenum complex with some interesting features has been prepared by Lanfranchi and Tiripicchio5’. [Mo2(qs-CsHs)2(p-PPh2)(C0)4]is a reactive 33-electron complex (of which there are very few) and it is also a binuclear radical (also rare). In the same category, in terms of the metal atoms involved, the synthesis and structural characterisation60 of Mo2(p-SC6H&1)2(pdppm)(C0)6 and [(dppm)(Co)2Mo(~-SC6H4C1),Mo(o)l2(~-sc6H4cl)2(~-o) has been completed and the electrochemicalproperties of M02(p-SC6H&1)2(pdppm)(C0)6 have been reported. Complexes containing a single tungsten atom have been mentioned alongside their lighter Group 4 counterparts earlier in this section. Darensbourg and co-workers6’ have concentrated solely on tungsten complexes in a paper devoted to thiouracil derivatives of W(CO)6. There is an interesting theoretical perspective to this work, which lends support to the experimental findings. The crystal structure of tr~ns-[w(CO)4(q2-C2H4),1has been reported by Downs and co-workers62along with IR and NMR studies of this and the related ethene-carbonyl complexes of tungsten, w(CO)3(q2-C2H4)3], cis[w(CO)4(q2-C2H4)2]and w(CO)5(q2-C2H4)]. This reporter has a special interest in these molecules as it will enable the ligand effects on the v(C0) frequencies to be measured accurately.

214

Organometallic Chemistry

Mononuclear tungsten catalysts are not a regular feature of this chapter, but 1999 saw the electrocyclisation of aromatic enynes via vinylidene intermedia t e using ~ ~ ~the ostensibly innocent tungsten complex W(CO)s(THF). The equally simple W(C0)4(phen) has been used to i n v e ~ t i g a t ea~photochemical ~ 'race against time' between vibrational relaxation and a prompt one-electron transfer. Although the tungsten atoms are not connected by a W-W bond, a new way of linking metal centres with diimido ligands has been described. The synthesis, electronic and molecular structure and electrochemistry of organometallic ditungsten complexes [ { WC12(Ph2PMe)2(CO)) 2(N-X-N)] (X = n-conjugated organic) has been released by Hogarth and c o - w o r k e r ~ ~ ~ . Finally, in this section, a study by Richards and has produced a number of new dithiolato complexes (crystal structures are also provided): [W(SPh)2(CO)2(PEt3)2]amongst others. 4.4 Manganese, Technetium and Rhenium. - The recent flood of papers exploring the diverse photochemical and catalytic behaviour of Re(C0)3(LL)X and Mn(C0)3(L-L)X complexes (where X is a halogen atom) species has dried to a trickle although ~ ~ c - M ~ ( C O ) ~ ( P ~ ~ P C Hstill ~ Preceives P ~ ~ ) Csome I attention in an electrochemical setting67and a related study68 of the photodissociation of Mn(C0)3( 1,4-diaza-1,3-butadiene)H is noted. Electrochemical properties are also investigated in a of cis,rner-Mn(C0)3(dpm)(q2dpm)X where dpm = Ph2PCH2PPh2and X = C1 or Br. Although the dominance of the Re(C0)3(L-L)X complexes has waned, there is still much to attract the attention of workers interested in these three metals (although technetium never seems to make more than a cameo appearance). Both manganese and rhenium feature7' in a series of novel reactions of their cationic carbyne complexes with the tungsten complexes (Ph3P)2NW(CO)5NC0, (Ph3P)2NW(CO)5SCN and NaW(CO)5CN. Also noted is a study of the basic photophysics of Mn2(CO)" and Re2(CO)lo in solution7'. Mononuclear manganese complexes are on show in a of the CNR and CO insertion reactions of 2,6-xylyl isocyanide with (p-chlorobenzyl)Mn(CO)5. The first transition metal complex of a tri-telluroether also contains a single manganese atom: the complex fa~-[Mn(C0)~ { MeC(CH2TeMe)3)]CF3S03has been prepared73. A five-coordinate, sixteen-electron manganese(1) complex, [Mn(C0)3(S,S-C6H4)]- has been prepared74 with the overall structure stabilised by S,S n-donation from the chelating [S,S-C6H4I2ligand. In another study utilising relatively simple manganese-containing molecules, the reactions of cationic carbyne complexes with Et4N[Mn(CO),(CN)2] are noted75. The use of fullerenes as ligands was noted earlier (in the section devoted to Cr, Mo and W). The manganese group becomes part of this maturing picture with the synthesis and structural d e t e r m i n a t i ~ nof ~ ~the [Mn(C0)4(q2-C60)] ion (as its Na+ and PPN+ salts). Another somewhat exotic ligand attached to

9: Metal Carbonyks

215

manganese is C5(PMe2)5- a cyclopentadienyl complex with five phosphanyl substituents. The synthesis and characterisation of pentakis(dimethy1phosphany1)cymantrene [Mn{C5(PMe2)5} (CO)3], has resulted from the use of this ligand77. Cationic (sixteen electron) manganese ions of the general formula [Mn(CO)(R2PC2H4PR2)2]+have been used78 to investigate the reversible displacement of H2, N2 and SO2. The somewhat surprising finding in this study is that the activation of q2-H2 trans to a CO group is almost invariant to changes in charge and the ligands cis to the CO group. Clearly the trans effect, noted in many organometallic reactions, is overwhelming compared to cis effects. The somewhat neglected manganese(1) carbonyl halides are revisited with a detailed (involving multinuclear NMR, redox properties and crystal structures) of the reaction of this type of molecule with phosphine, arsine and stibine complexes. Cationic manganese(1) tricarbonyl complexes with Group 15 and 16 donor ligands are thoroughly investigated by Reid and co-workers" and the synthesis and structure of a paramagnetic Lewis base adduct of antimony pentachloride, trans-[Mn(CNSbClS)(C0)2{ P(OEt)3}(dpprn)][SbCl6], has also been prepared". The organometallic chemistry of technetium is, naturally, restricted by its radioactivity and very few carbonyl complexes are known. Unlike the other two metals in its group, technetium has found its main niche in bio-inorganic chemistry where, naturally, water solubility is extremely important. In 1999 we saw the first application82of ~ ~ C - [ ~ ~ ~ T C ( O H ~in ) ~bio-inorganic ( C O ) ~ ] + chemistry with the design, structure and in vitro affinity of a 5HTlA receptor ligand labelled with 99mT~. Rhenium complexes with weakly-coordinating solvent ligands (with the general formula [Re(C0)4(PR3)(L)]where L is a weakly coordinating ligand such as CH2C12, Et20, NCSFs) are founds3 to decompose to chloride-bridged dimers in the presence of CH2C12. The synthesis, structure, and reactivity of rhenium N-isocyanide complexes ReBr(CO)3(CNR)(CNNPPh3)has also been reported84. The organometallic chemistry of the boranes is dealt with elsewhere in this publication, but the surprising reactivity (with a range of metal-ligand I)]- (as its caesium fragments) of the rhenacarborane [Re(C0)3(5,7,8-C2B9H1 salt) is worth notings5. The mononuclear rhenium methyl complexes transCpRe(C0)2(Me)I, trans-CpRe(C0)2(Me)I, trans-CpRe(C0)2(Me)2, transCpRe(C0)2(Me)(Ph) and trans-CpRe(C0)2(Me)@-tolyl) have been subjected to photolysis under a CO atmosphere and the photoproducts identified86. Dinuclear rhenium complexes have a steady presence in this chapter and there is a on the formation of (C9H7)2Re2(C0)4(p-C0)and its rearrangement to (C9H7)Re(C0)2(p2,5-C9H7)Re(C0)3 to maintain the tradition from previous years. The relatively unstable 1,2-eq-eq-[Re2(Co),(THF)2], prepared quite simply, has been proposed as an Re2(CO)s 'fragment' that easily activates C-H and H-H bonds". This complex may find a considerable number of uses in coming years. Meanwhile, The reaction of [Re2(C0)8-

216

Organome t a l k Chemistry

(MeCN)2] with thiols has been found89 to lead to the formation of hydridosulfido bridged dirhenium cluster complexes [Re2(p-H)(p -sR)(Co),] (R = H, Bu, Cy, Ph, C6H4F,C6F5 or 2-naphthyl). The preparation of [Re3(p-H)3(p3-CH3)(C0)9] - is interesting in itself, but within that formula is a most intriguing ligand - the triply-bridging methyl group, p3-CH3. Backing up their arguments for this unusual structure Mercandelli and co-workersgOhave produced solid state and solution structural characterisation of the molecule.

Iron, Ruthenium and Osmium. - The iron group routinely produces a number of papers dealing with mononuclear species and a somewhat larger number of papers exploring the chemistry of complexes derived from the basic dinuclear species (e.g. Fe2(CO),) and trinuclear species (i. e. Fe3(C0)12, R U ~ ( C Oand ) ~ ~O S ~ ( C O ) ~Indeed, ~ ) . these latter three complexes are customarily used as starting materials for many compounds containing three or more metal atoms. Mononuclear iron complexes do not have a high profile in this report but the preparation, spectroscopic and structural characterisation” of the Fe(I1) carbonyl species [Fe(CO)6][Sb2F1 and [Fe(C0)6][SbF6]2more than makes up for this scarcity. Although marginally outside the frame of reference for this chapter, a study of selective metal to ring alkyl migration during irradiation of CPF~(CO)~[ CHPh(OSiMe3)]has been achieved by Nicholas92. The use of the azadiene ion in creating (a~adiene)Fe(CO)~ complexes was noted last year. A more comprehensive description of the properties and structures of these molecules is given by T e d e ~ c with o ~ ~a detailed investigation into the r d e that the electronic organization plays in the molecular structure of these complexes. Dinuclear iron complexes are represented in this section with an interesting study of double and quadruple butterfly Fe/S cluster complexes94and a study that investigates the reactivity of naphthylamines towards Fe2(C0)9 (leading to three different hydrogen migration pathways)95.The unusual complexes [(pRS)(p-S)(Fe2(C0)6)2(p4-S)](where R is one of a number of alkyl groups) have been prepared and their reactivity toward electrophiles noted96. In recent years there has been a considerable number of papers devoted to understanding the simple trinuclear systems M3(CO)12 (M = Fe, Ru, 0s) and this knowledge is added to by a full and interesting of the dynamic disorder and fluxionality in these clusters using variable-temperature X-ray diffraction techniques to probe the situation. Complete data is given for Fe,Ru3 -n(C0)12 and Fe3(C0)12. Other iron cluster compounds worthy of note are to be found in a paper98devoted to SO2-containingFe-clusters. Although marginally outside the terms of reference for this chapter, the preparation of tetra-iron clusters (and larger) by Yeh and c o - ~ o r k e r s ~ ~ deserves a mention. They have prepared functionalised (with alkyl, aryl and ferrocenyl groups) C P ~ F ~ ~ ( Ccomplexes O)~ and used these to prepare [CP3Fe4(C0)4(C5H4)12and [CP3Fe4(C0)4(C5H4)12[(C5H4)2Fel. The occurrence of monoruthenium complexes in this section tends to be

4.5

9: Metal Carbonyks

217

quite limited, so it is atypical that such an important organic reaction as the homogeneous hydrogenation of alkenes, of enormous industrial importance, should be catalysed by the ruthenium hydride complex (PCy&(CO)RuH. We shall be looking out for follow-up work based on this study'". The complex R u ( C O ) ~ ( ~ B U ~ P C ~ Hhas ~ P ~been B Uinvestigated ~) in both the solid state and in solution'". Triruthenium complexes are, as usual, well-represented here. A new approach to synthesising dodecacarbonyltriruthenium, RU~(CO)'~, using ruthenium dioxide hydrate has been published'02. Ragaini and co-workerslo3 have produced a completely revised appraisal of the reaction of R~~(CO)'~/tetraalkylammonium chloride catalysed carbonylation reactions of nitroarenes to carbamates and ureas. Group 16 ligands are routinely used to create new triruthenium complexes and the reaction of the selenium-containing ligand CH2(Ph2PSe)2(dppmSe2) with the prototype molecule R U ~ ( C O )has ' ~ been used to synthesise [Ru4(p4Se)2(p-CO)( c o )8(p-dppm)].MeOH and [RU6(p3'Se)4(CO) 12(p-dPPm)21-CH2C12 (full crystal structures are given). The fluxional behaviour of [Ru3(p3Se)2(C0)7(p-dppm)]is also overed''^. Triruthenium cluster catalysts are relatively common and Ru3(C0)12 has been shown to be able to transform unsaturated imines into unsaturated lactamslo5and to cause decarbonylative cleavage in alkyl phenyl ketoneslo6. Also, the R~~(CO)~~-catalysed reaction of yne-imines with carbon monoxide leads to bicyclic a$-unsaturated lac tarn^'^^. The large ruthenium cluster R u ~ ( ~ ~ - C H C H C C H ~ ) (has C O )been ~ ~ the studylo8 of coupling and disproportionation reactions involving ethyne. The even larger cluster R~~C(C0)~~([2.2]-paracyclophane} has been shown to react with various reagents to produce amino and bromo ring-substituted derivative~''~.The synthesis and characterisation of [RugC(C0)14] cluster complexes of some [2.2]- and [2.2.2]-cyclophaneligands is also reported' lo. Ruthenium clusters are also noted' * in the reactions of trifluoromethylphosphine and arsine compounds and the reactions' l 2 of the cluster complex [Ru5(p5-C2)(p-SMe)2(p-PPh2)2(C0)1 '1 with terminal alkynes HC=CR (R = Ph, But or SiMe3) and with ethyne incorporation into the spiked framework of the phosphinidene and arsinidene clusters [ R u ~ ( C O ) & - H ) ~ ( ~ ~ ECF3)] (E = P or AS)"^. Both osmium and ruthenium clusters are featured in a paper determining how the photochemistry of Ru3(C0)12 and Os3(CO)12 may be controlled by variation of the solvent' l4 and in the preparation of electron-deficient triruthenium and triosmium clusters from the reaction of the cluster anions [HM3(C0)11]- (M = Ru, 0s) with tricyclohexylphosphinein methanol' 15. Mononuclear osmium complexes derived from Os(C0)4(q2-C2H2) are the subject of two investigations by Jordan and co-workers' 16,117. Giving both synthetic and reaction kinetics information, this paper examines the reaction of the osmium compound above with several phosphines to investigate facile CO insertion into osmium-alkyne bonds. Osmium complexes containing three 0 s atoms have had a high profile in this

218

Organometallic Chemistry

section in recent years and the pattern continues with a comprehensive study"' of the complex reaction kinetics of O S ~ ( C O ) ~ ( Cwith ~ P ~small ~ ) Pdonor nucleophiles. An elegant piece of photochemistry' l9 has seen the insertion of a CO ligand into an 0s-N bond in clusters of the type Os3(CO)lo(L)where L is a potentially terdentate N,N-chelating diimine. The relatively simple complexes [Os3(CO)1~(PPh3)2(p-Br)]+and [Os3(CO),o(AsPh3)2(p-Br)]+have been preparedl2O. This reaction is interesting in that it is the first direct evidence for the bromonium ion (Br+) being involved in a reaction mechanism in cluster chemistry. Doubtless, other examples will follow. Stufkens and co-workers'21 have recently provided these pages with some extraordinarily interesting work on the Re(C0)3(L-L)X complexes. Keeping the same type of ligand, they have switched to triosmium clusters to make remarkably stable radical anions derived from clusters [HOs3(CO)9(L)], where L = ortho-metallated a-diimine in a spectro-electrochemicalstudy with a degree of theoretical rationalisation. Large osmium complexes are no strangers to these pages and several new hexaosmium complexes with six-membered cyclic thioether and thioxane ligands have been reported'22. The formation of hexaosmium raft clusters from [os&O) 16(MeCN)2] is also reported'23. In a detailed paper, the synthesis, structural characterisation and reactivities of [Os,(CO) 6( p3-T)2-C~H4NS)2]and [Os&o) 17(p-H)(p4-'q 2C5H4NS)I are fully discussed. The same type of raft cluster is studied by Poe et al.'24 in terms of the exceptional substitutional lability Of OS6(C0)20NCMe. 4.6 Cobalt, Rhodium and Iridium. - The cobalt group has proven very useful across the decades as a source of catalysts for a variety of organic reactions mediated by organometallic complexes. This trend continues to this day. The carbonylation of methanol is clearly a process worthy of investigation and a short c o m m ~ n i c a t i o n 'deals ~ ~ with this process using what are described as 'high activity cobalt based catalysts'. A second communication'26 from the same group details the carbonylation of methanol in supercritical C 0 2 catalysed by a supported rhodium complex and a more complete paper127on the same topic uses [RhI(CO)(PEt3)2]as the catalyst and an intermediate in the reaction, [RhMe12(CO)(PEt3)2],has been isolated and had its crystal structure determined. The mononuclear cobalt complex [(C0)4Co-GaEt2(NC7H13)]has been prepared and fully characterised by Frenking and co-workers'28. It is, to this reporter, somewhat surprising that the carbonyl-nitrosyl complexes have not had the same level of interest that the simple carbonyls have. After a flood of publications devoted to their preparation some years ago, the interest level receded dramatically. It is, therefore, pleasing to see that one of the simplest carbonyl-nitrosyl compounds, CO(CO)~(NO)has been re-visited by Brunner and co-workers' 29. Dinuclear cobalt complexes are mentioned elsewhere due to their remarkable abilities as catalysts for a wide range of reactions. They also appear here'30 in the guise of new compounds containing sulfide ligands prepared

9: Metal Carbonyks

219

from alkyne dicobalt carbonyls and as catalysts for a modified Pauson-Khand rea~tion'~'. Angelici's work using dibenzothiophene and benzothiophene was mentioned in Section 3.3. His group has extended this type of work'32 using these thiophene ligands in reaction with Co4(CO)12, in much the same way as with Cr(C0)6 described earlier. A fundamental piece of re-investigation has been carried out on C04(CO)12. A structural redetermination of Co4(CO)12 has found compelling evidence for dynamic disorder and a pathway for metal atom migration in the crystalline phase'33. Rhodium is becoming an increasingly useful metal in the context of metal carbonyl chemistry and this is typified by a paper from Liu and Garland'34 that reports the in situ IR characterisation of no less than twenty new alkynerhodium complexes after the reaction of Rh4(C0)12 with various alkynes under CO and CO/H2 mixtures. Mononuclear iridium complexes have not had a particularly high profile in recent years and Ir(II1) complexes in this section are almost unknown. However, in a break with tradition, Li and Hall have produced a further (No. 11 in the series) on transition metal polyhydride complexes dealing with the cis-trans isomerism of IrH2(CO)[C6H3(CH2PH2)2].Less oxidized Ir(1) complexes containing water soluble phosphine ligands have been prepared by A t ~ o o d ' ~ ~ . 4.7 Nickel, Palladium and Platinum. - Although tetracarbonylnickel(0) was the prototype of all the metal carbonyls, there has been little activity recently in this group from year to year. Indeed, last year, this reporter had the temerity to suggest that there seemed little scope for further work with the simple carbonyls of the metals in this group (after all, only Ni(C0)4 of the three possible carbonyls is stable at room temperature - Pd(C0)4 and Pt(C0)4 are known primarily to matrix isolation chemists). In the process of owning up to being wrong, we can report the preparation and structural characterisation' 37 of new palladium(0) carbonyl complexes with the general formulae: (R2PC2H4PR2)Pd(C0)2and ((R2PC2H4PR2)Pd} 2(p-CO). Platinum also makes an appearance13*in mononuclear form with an interesting catalytic reaction whereby propyn-2-01 undergoes a stereospecific tetramerisation using [Pt(CO)4][Sb2F 113. The reaction' 39 of the carbodiphosphorane Ph3P=C=PPh3with Ni(C0)4 is reported and provides the complexes (C0)3NiC(PPh3)and (C0)2Ni[C(PPh3)l2. Moving to polynuclear species, Zanello and c o - w o r k e r ~ (a '~~ group that has produced a large number of mixed-metal complexes that regularly appear in Section 4.9 over the years) have synthesised and investigated the electron-sink behaviour of the quite carbon-containing massive clusters ~i32c6(co)36]6and [Ni3&6(CO)42]6-. They also report the synthesis and characterisation of the anions pi32C6(C0)36]n- (where n = 5-10) and its larger relative [Ni3&6(C0)42]n- (where n = 5-9). In the same study they report the crystal This work is linked to a structure of [PPh3Me]61Ni32C6(CO)36].4MeCN.

220

Organometallic Chemistry

further interesting piece of research described in Section 4.9 where mixed-metal carbonyls are investigated for their electron-sink properties.

4.8 Copper, Silver and Gold. - The coinage metals do not form carbonyl complexes readily and the number of reports relevant to this chapter remains as small as in previous years. However, it is pleasing to report the synthesis141 of the first structurally { S02CF31). This was closely characterised copper(1) carbonyl: CU(CO)~(N followed by a paper'42 describing mono-, di-, tri- and tetracarbonyls of Cu(1). This could be a significant area for new research in the coming years.

4.9 Carbonyl Complexes Containing Two or More Different Metal Atoms - A decade ago, when this reporter took over the compilation of this chapter, the number of metal carbonyl complexes produced annually containing more than one metal atom could be numbered on one hand. In the intervening years, this section has grown greatly and regularly outstrips any other section. When one considers that other chapters in this publication also deal with the chemistry of these complexes (where organic ligands are added into the structure and carbonyl groups are less prominent), the growth in this area has been quite remarkable and, furthermore, it shows no sign of diminishing. The Group 16 (chalcogens) have become more and more useful as bridging ligands for mixed-metal cluster compounds. The synthesis and characterisation of both cis and trans isomers of the mixed chalcogen clusters CpzMo2( p ~ - Tbeen e ) reFe2(C0)8(C13-S)(C13-Se) and C ~ ~ M o ~ F e ~ ( c o ) ~ ( p ~ - S ) have ported 143. The syntheses of Co,Pt, Co2Pd and MoPd2 mixed-metal clusters with the PN-P assembling ligands (Ph2P)2NH (dppa) and (Ph2P)2NMe(dppaMe) have been reported'44 along with the crystal structure of [Co2Pt(C1L,-Co)(Co),(C1dPPa)lLinked to a study by Zanello and c o - ~ o r k e r s described '~~ in Section 4.7 is an elegant piece of work exploring the electron-sink properties of a series of metal carbonyl cluster anions (see also reference 140 in the section on Ni, Pd and Pt) containing nickel and platinum, namely [H6-nNi32Pt6(C0)48]n(where n can be 4,5 or 6). The iridium-ruthenium complex [ R U ~ I ~ ~ H ( C Ohas ) ~ been ~ C ~prepared ] by the reaction of ruthenium carbonyl chloride with iridium tetracarbonyl anion. The synthesis, crystal structure and characterisation of this unusual a heterometallic tetranuclear butterfly cluster with chloride bridge is fully d e ~ c r i b e d ' ~ ~ . Osmium and rhodium have been coupled (using a variety of ligands) to make [N(PPh3)21[oS6Rh(C1-H)2(C0)201, [Os6Rh(p-H)7(C1-CO)(CO)lS], [ o ~ ~ R h ( p - H ) ~ ( c Oand ) ~ ~ [OS~R~(~CO)(CO)~(P~C~P~)(P~C~P~H)] ] Full details of synthesis, characterisation and crystal structures are given'47. Ruthenium and osmium are coupled with mercury elsewhere'48 although the mercury atoms do not contain CO groups. The tungsten-iridium clusters formed by reaction of [Cp2W21R2(CO)lo]with trimethyl phosphite have been identified and the X-ray crystal structures of

9: Metal Carbonyks

221

[Cp2W21R2(p-CO)3(CO)5(P(OMe)3)2] and two modifications of [CpWIR3(p-

CO)3(CO)7{P(OMe)3)]have been ~ompleted'~'. Rhodium and platinum are partners in the synthesis and structural charand acterisation of the mixed-metal clusters [Rh2Pt3(p-C0)5(C0)4(PPh3)3] [Rh2Pt2(p-C0)3(C0)4(PPh3)3],with the crystal structure of [Rh2Pt3(pC0)5(C0)4(PPh3)3]being reported' 50. Platinum (although it is not bonded to any CO groups in these molecules) is twinned with rhenium to make a set of mixed-metal c ~ m p l e x e s ' ~[(Re~: (Co)3]3(PtMe3)(oH)41, [(Re(C0)312(PtMe3)2(OH)4] and [(Re(C0)31@Me3)3(OH)4].This is the first set of hetero-bimetallic hydroxy-cubane complexes. Only a few years ago the synthesis of a new mixed-metal cluster was worthy of a sizeable paper. This endeavour has matured somewhat and, now, a fair fraction of papers involving mixed-metal compounds deal with fluxionality and other molecular dynamics. An example of a study of this type has been released by Waterman and Humphrey'52 who (as No. 10 in a series of papers on mixedmetal cluster chemistry) deal with the isomer distribution and ligand fluxionality in the molecules CpWIr3(p-C0)3(C0)7(PPh3),CpWIr3(p-C0)3(C0)6(PPh3)2, CpWIr3(p-C0)3(C0)7(PMe3), and CpWIr3(~-C0)3(C0)6(PPh3)2. Tungsten also takes a central role (with ruthenium in this instance) in the ~ r e p a r a t i o n ' ~ ~of tetrathiotungstate clusters such as [ (Cp*Ruwith (CO)) 2(WS4){ W(CO)4)] by the reaction of [Cp*2Ru&] [W(C0)3(NCMe)3] and in the reactions of tungsten complexes with cobalt carbonyls described by Bruce et al.'54 Complexes containing silver have a relatively small impact on this section from year to year but 1999 saw the synthesis, chemical characterisation and the full molecular s t r ~ c t u r e 'of ~ ~[Ag3(p3-Fe(C0)4)(dppm)3][NO,] and its gold-containing partner [ A u {~p-Fe(C0)4)(dppm)2][Cl]. Gold also makes an appearance in the reactions of spiked and open chain cluster hydrides with Au complexes. In this study, the skeletal rearrangement and crystal structures of [AU~RU~(CO)~~(~~-PCF~)(PM~~)~ and the heterometallic clusters [ A u ~ R u ~ ( C O ) & - P C F ~ ) ~ ( P Pare ~ ~also ) ~ ] studiedlS6. Each year this section produces some truly massive molecules. In 1999 there were two heavyweight contenders to match anything from previous years and both made use of gold, palladium and nickel'57: [AU6Pd6(Pd6-xNix)Ni2o(C0),l6- (where x = 1,2, 3,4, 5) and [Au~Ni~~(C0)44]~-. Also containing gold'58 (even though the gold bears no carbonyl groups) are the high nuclearity clusters of osmium and ruthenium containing the [ A u ~ ( P ~ ~ P C H ~ P P ~ ~ ) ] + 1 1Au2(Ph2PCH2PPh2)]and gold-ruthecation: gold-osmium in [OS~H~(CO) nium in [ R u & ( C O ) ~ ~ A U ~ ( P ~ ~ P C H ~ P P ~ ~ ) ] .

References 1. 2.

I. D. Sadekov, A. I. Uraev and A. D. Garnovskii, Rum. Chern. Rev., 1999,415. N. Frohlich and G. Frenking in Solid State Organometallic Chemistry: Methods

222

Organometallic Chemistry

and Applications, M Gielen and B. Wrackmeyer (eds), Wiley-VCH, New York, 1999, pp 173-226. 3. H. Yang, K. T. Kotz, M. C. Asplund, M. J. Wilkens and C. B. Harris, Acc. Chem. Res., 1999,32, 55 1. 4. E. Hunstock, C . Mealli, M. J. Calhorda and J. Reinhold, Inorg Chem., 1999, 38, 5053. 5. Z. Xue, Organometallics, 1999,18, 5488. 6. C. Boehme and G. Frenking, Chem. Eur. J., 1999,5,2184. 7. M. Torrent, M Sola and G. Frenking, Organometallics, 1999,18,2801. 8. A. J. Lupinetti, V. Jonas, W. Thiel, S . H. Strauss and G. Frenking, Chem. Eur. J., 1999,5, 2573. 9. S. A. McGregor and D. MacQueen, Inorg. Chem., 1999,38,4868. 10. V. Jonas, W. Thiel, J. Chem. SOC.,Dalton Trans., 1999,3783. 11. B. E. Bursten, J. Am. Chem. SOC.,1999,121,10830. 12. M. Zhou, L. Andrews, J. Li and B. E. Bursten, J. Am. Chem. SOC., 1999, 121, 9712. 13. J. Li and B. E. Bursten, J. Am. Chem. Soc., 1999,121,12188 14. G. Critchley, P. J. Dyson, B. F. G. Johnson, J. S. McIndoe, R. K. O’Reilly and P. R. R. Langridge-Smith, Organometallics,1999, 18,4090. 15. R. H. Schultz and S. K r a v - h i , J. Chem. Soc., Dalton Trans., 1999,115. 16. E. Peris, J. A. Mata and V. Moliner, J. Chem. SOC.,Dalton Trans., 1999, 3893. 17. C. Kaya, J. Organomet. Chem., 1999,575,209. 18. C. Kaya, J. Organomet. Chem., 1999,582,254. htm 19. http://www.johntimney.fsnet.co.uk/carbonyl. 20. M. Zhou and L. Andrews, J. Am. Chem. SOC.,1999,121,9171. 21. S. M. Massick and P. C . Ford, Organometallics, 1999,18,4362. 22. I. R. Farrel, P. Matousekand A. Vlek, J. Am. Chem. SOC.,1999, 121, 5296. 23. S. Zali, C. Daniel, A. Vlcek, Jr., J. Chem. Soc., Dalton Trans., 1999, 3081. 24. H. Yang, P. T. Snee, K. T. Kotz, C. K. Payne, H. Frei and C. B. Harris, J. Am. Chem. SOC.,1999,121,9227. 25. M. K. Davies, M. C . Durrant, W. Leaveson, G. Reid and R. L. Richards, J. Chem. SOC.,Dalton Trans., 1999, 1077. 26. Y-Y. Choi and W-T. Wong, J. Chem. Soc., Dalton Trans., 1999,331. 27. C. J. Aspley, J. R. Lindsay Smith and R. N. Perutz, J. Chem. Soc., Dalton Trans., 1999,2269. 28. T. Eguchi and B. T. Heaton, J. Chem. SOC.,Dalton Trans., 1999,3523 29. J. V. Barkley, T. Eguchi, R. A. Harding, B. T. Heaton, G. Longoni, L. Manzi, H. Nakayama, K. Miyagi, A. K. Smith, A. Steiner, J. Organomet. Chem., 1999, 573, 254. 30. C. J. Sleigh, S. B. Duckett, R. J. Mawby and J. P. Lowe, Chem. Commun., 1999, 1223. 31. B. T. Heaton, J. A Iggo, I. S. Podkorytov, D. J. Smawfield, S. P. Tunik, and R. Whyman, J. Chem. SOC.,Dalton Trans., 1999, 1917 32. S. Geftakis and G. E. Ball, J. Am. Chem. SOC.,1999,121, 6336. 33. D. Bourissou, Y. Canac, H. Gornitzka, A. Baceiredo and G. Bertrand, Chem. Commun., 1999,1535. 34. E. B. Eggeling and D. Vogt, Organometallics,1999,18,4390. 35. T. Katayama, Y. Morimoto, M. Yuge, M. Uno and S. Takahashi, Organometallics, 1999, 18, 3087.

9: Metal Carbonyks

36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54.

55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69.

223

M. A. Reynolds, I. A. Guzei, B. C. Logsdon, L. M. Thomas, R. A. Jacobson and R. J. Angelici, Organometallics, 1999,18,4075. A. Vessieres, M. Salmain, P. Brossier and G Jaouen, J. Pharm. Biomed. Anal., 1999, 21,625. J. L. Kerr, B. H. Robinson, J. Simpson, J. Chem. SOC.,Dalton Trans., 1999,4165. R. D. Adams and W. Huang, J. Organomet. Chem., 1999,573,14. R. D. Adams and J. L. Perrin, J. Organomet. Chem., 1999,582,9. R. D. Adams, W. Fu and B. Qu, Inorg. Chem. Commun., 1999,2,1. R. D. Adams and J. L. Perrin, J,Am. Chem. SOC.,1999,121,3984. R. D. Adams, 0. Sung Kwon and J. L. Perrin, J. Organomet. Chem., 1999,584, 223. T. Rajesh and M. Periasamy, Organometallics, 1999,18, 5709. R. L. Keiter, J. W. Benson, E. A. Keiter, W. Lin, Z. Jia, D. M. Olson, D. E. Brandt and J. L. Wheeler, Organometallics, 1999,18, 5194. K. Kubo, K. Bansho, H. Nakazawa and K. Miyoshi, Organometallics, 1999, 18, 431 1. F. Godoy, C. L. Higgitt, A. H. Klahn, B. Oelckers, S. Parsons and R. N. Perutz, J. Chem. SOC.,Dalton Trans., 1999,2039. B. K. McNamara, J. S. Yeston, R. G. Bergman and C. B. Moore, J. Am. Chem. SOC., 1999,121,6437. A. J. Bailey, S. Basra and P. J. Dyson, Green Chem., 1999,31. D. E. Hibbs, M. B. Hursthouse, C. Jones and R. C. Thomas, J. Chem. SOC., Dalton Trans., 1999,2627. M. Shimoi, S. Nagai, M. Ichikawa, Y. Kawano, K. Katoh, M. Uruichi and H. Ogino, J. Am. Chem. SOC.,1999,121,11704. J. Chen and R. J. Angelici, Organometallics, 1999,18, 5721. K. B. Capps, A. Bauer, T. D. Ju and C . D. Hoff, Inorg. Chem., 1999,38,6130. P. Zanello, F. Laschi, M. Fontani, C. Mealli, A. Ienco, K. Tang, X Jin and L. Li, J. Chem. SOC.,Dalton Trans., 1999,965. H. Ratni and E. P. Kundig, Org. Lett., 1999,1, 1997. U. Kazmaier, D. Schauss and M. Pohlman, Org. Lett., 1999,1, 1017. M. R. Close, J. L. Petersen and E. L. Kugler, Inorg. Chem., 1999,38, 1535. T. Szymanska-Buzar, T. Glowiak, I. Czelusniak, J. Organomet. Chem., 1999,585, 215 - 224 M. Lanfranchi and A. Tiripicchio, J. Am. Chem. SOC.,1999,121,4060. G. Pan, B. Zhuang, L. He, J. Chen, J. Lu, J. Organomet. Chem., 1999,581,313. D. J. Darensbourg, B. J. Frost, A. Derecskei-Kovacs and J. H. Rebenspies, Inorg. Chem., 1999,38,4715. T. Szymanska-Buzar, K. Kern, A. J. Downs, T. M. Greene, L. J. Morris and S. Parsons, New J. Chem., 1999,407. K. Maeyama and N. Iwasawa, J. Org. Chem., 1999,64,1344. E. M. Lindsay, C. H. Langford and A. D. Kirk, Inorg. Chem., 1999,38,4771. G. Hogarth, D. G. Humphrey, N. Kaltsoyannis, W. Kim, M. Lee, T. Norman, S. P. Redmond, J. Chem. Sac., Dalton Trans., 1999,2705. P. K. Baker, A. I. Clark, M. G. B. Drew, M. C . Durrant and R. L. Richards,, Inorg. Chem., 1999,38, 821. J. C. Eklund and A. M. Bond, J. Am. Chem. SOC.,1999,121,8306. D. Guillaumont and C. Daniel, J. Am. Chem. SOC.,1999,121, 11733. J. C. Eklund, A. M. Bond, R. Colton, D. G. Humphrey, P. J. Mahon and J. N. Walter, Inorg. Chem., 1999, 38,2005.

224

Organometallic Chemistry

70. Y. Tang, J. Sun and J. Chen, Organometallics, 1999,18,2459. 71. M. Sarakha and G. Ferraudi, Inorg. Chem., 1999,38,4605. 72. T. M. Becker, J. J. Alexander, J. A. Krause Bauer, J. L. Nauss and F. Wireko, Organometallics, 1999,18, 5594. 73. W. Leaveson, S. D. Orchard and G. Reid, J. Chem. SOC.,Dalton Trans., 1999, 823. 74. C-M. Lee, G-Y. Lin, C-H. Hsieh, C-H. Hu, G-H. Lee, S-M. Peng, W-F. Liaw, J. Chem. SOC.,Dalton Trans., 1999,2393. 75. Y. Tang, J. Sun and J. Chen, Organometallics, 1999,18,4337. 76. G. D. Enright, Organometallics, 1999,18,2950. 77. IS.Siinkel, C. Stramm, S. Soheili, J. Chem. SOC.,Dalton Trans., 1999,4299 78. W. A. King, B. L. Scott, J. Eckert and G. J. Kubas, Inorg. Chem., 1999,38,1069. 79. S. J. A. Pope and G. Reid, J. Chem. SOC.,Dalton Trans., 1999, 1615. 80. J. Connolly, A. R. J. Genge, W. Levason, S. D. Orchard, S. J. A. Pope and G. Reid, J. Chem. SOC.,Dalton Trans., 1999,2343 81. D. Bellamy, N. C. Brown, N. G. Connell and A. G. Orpen, J. Chem. SOC.,Dalton Trans., 1999,3191. 82. H-J. Pietzsch and B. Johannsen, J. Am. Chem. SOC.,1999,121,6076. 83. J. Huhmann-Vincent, B. L. Scott and G. A. Kubas, Inorg. Chem., 1999,38,115. 84. J-S. Fan, F-Y. Lee, C-C. Chiang, H-C. Chen, S-H. Liu, Y-S. Wen, C-C. Chang, S-Y. Li, K-M. Chi, K-L Lu, J. Organomet. Chem., 1999,580,82. 85. D. D. Ellis, P. A. Jellis and F. G. A. Stone, Organometallics, 1999,18,4982. 86. D. Sutton, Organometallics, 1999, 18, 339. 87. J. R. Shapley, Organometallics, 1999,18, 1353 88. G. D’Alfonso, Organometallics, 1999,18,2091. 89. H. Egold, D. Schwarze, U. Florke, J. Chem. Soc., Dalton Trans., 1999, 3203. 90. P. Mercandelli, M. Moret and A. Sironi, J. Am. Chem. SOC.,1999,121,2307. 91. E. Bernhardt, B. Bley, R, Wartchow, H. Willner, E. Bill, P. Kuhn, I. H. T. Sham, M. Bodenbinder, R. Brochler and F. Aubke, J. Am. Chem. SOC.,1999, 121, 7188, 92. K. M. Nicholas, Organometallics, 1999,18, 1569. 93. E. Tedesco, Organometallics, 1999,18, 736. 94. L-C. Song, G-L. Lu, Q-M. Hu and J. Sun, Organometallics, 1999,18, 5429. 95. W. Imhof, Organometallics, 1999,18,4845. 96. Z-X. Wang, C-S. Jia, Z-Y. Zhou and X-G. Zhou, J. Organomet. Chem., 1999, 581, 201. 97. F. Grepioni, Organometallics, 1999,18, 5022. 98. R. W. Eveland, C. C. Raymond, T. E. Albrecht-Schmitt and D. F. Shriver, Inorg. Chem., 1999,38,1282. 99. W-Y. Yeh, C-Y. Wu and L-W. Chiou, Organometallics, 1999,18, 3547. 100. C. S. Yi and D. W. Lee, Organometallics,1999,18, 5152. 101. H. Gerard and 0. Eisenstein, J. Am. Chem. SOC.,1999,121,3242. 102. I. Shimoyama, T. Hachiya, M. Mizuguchi, T. Nakamura, M. Kaihara and T. Ikariya, J. Organomet. Chem., 1999,584, 197. 103. F. Ragaini, A. Ghitti and S. Cenini, Organometallics, 1999,18,4925. 104. D. Cauzzi, C. Graiff, G. Predieri, A. Tiripicchio and C. Vignali, J. Chem. Suc., Dalton Trans., 1999, 237. 105. T. Morimoto, N. Chatani and S. Murai, J. Am. Chem. Soc., 1999,121, , 1758. 106. M. Chatani, Y. Ie, F. Kakiuchi and S. Murai, J. Am. Chem. SOC.,1999, 121, 8645.

9: Metal Carbonyks

225

107. N. Chatani, T. Morimoto, A. Kamitani,Y. Fukumoto, S . Murai, J. Organomet. Chem., 1999,579,177. 108. M. I. Bruce, B. W. Skelton, A. H. White and N. N. Zaitseva, J. Chem. SOC., Dalton Trans., 1999, 13. 109. P. Schooler, B. F. G. Johnson and S . Parsons, J. Chem. SOC.,Dalton Trans., 1999,559. 110. P.Schooler, B. F. G. Johnson, L. Scaccianoce and R. Tregonning, J. Chem. SOC., Dalton Trans., 1999,2743. 1 1 1 . H. G. Ang, S. G. Ang, S. Du, B. H. Sow and X. Wu, J. Chem. SOC.,Dalton Trans., 1999,2799. 112. C . J. Adams, M. I. Bruce, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton Trans., 1999,2451. 113. H. G. Ang, S. G. Ang and S. Du, J. Chem. SOC.,Dalton Trans., 1999,2963 114. N. E. Leadbeater, J. Organomet. Chem., 1999,573,211. 115. G. Suss-Fink, I. Godefroy, V. Ferrand, A. Neels, H. Stoeckli-Evans, S. Kahlal, J-Y. Saillard and M. T. Garland, J. Organomet. Chem., 1999,579,285. 116. T-F. Mao, Z. Zhang, J. Washington, J. Takats and R. B. Jordan, Organometallics, 1999,18, 2926. 117. T-F. Mao, Z. Zhang, J. Washington, J. Takats and R. B. Jordan, Organometallics, 1999,18,2331. 118. A. J. Poe and C. Moreno, Organometallics, 1999,18, 5518. 119. J. Fraanje, Organometallics, 1999,18,4380. 120. Y. Liu, Organometallics, 1999,18, 800. 121. J. Nijhoff, F. Hartl, J. W. M. van Outersterp, D. J. Stufkens, M. J. Calhorda and L. F. Veiros, J. Organomet. Chem., 1999,573, 121. 122. K. Leung and W-T. Wong, J. Chem. SOC.,Dalton Trans., 1999,2077. 123. K. S-Y. Leung and W-T. Wong, J. Chem. SOC.,Dalton Trans., 1999,2521. 124. D. H. Farrar, A. J. Poe and R. Ramachandran, J. Organomet. Chem., 1999,573, 217. 125. C. Marr, E. J. Ditzel, A. C . Benyei, P. Lightfoot and D. J. Cole-Hamilton, Chem. Commun., 1999, 1379. 126. R. J. Sowden, M. F. Sellin, N. De Blasio and D. J. Cole-Hamilton, Chem. Commun., 1999,251 1. 127. J. Rankin, A. C. Benyei, A. D. Poole and D. J. Cole-Hamilton, J. Chem. Soc., Dalton Trans., 1999, 3771. 128. R. A. Fischer, A. Miehr, H. Hoffmann, W. Rogge, C. Boehme, G. Frenking and E. Herdtweck, 2. Anorg. Allg. Chem., 1999,625, 1466. 129. H. Brunner, P. Faustmann and B. Nuber, J. Organomet. Chem., 1999,579, 1 130. X. Verdaguer, A. Moyano, M. A. Pericas, A. Riera, A. Alvarez-Larena and J-F. Piniella, Organometallics, 1999,18,4275. 131. Y-T. Shiu, R. J. Madhushaw, W-T. Li, Y-C. Lin, G-H. Lee, S-M. Peng, F-L. Liao, S-L. Wang and R-S. Liu, J. Am. Chem. SOC.,1999,121,4066. 132. J. Chen and R. J. Angelici, Organometallics, 1999, 18, 5721. 133. L. J. Farrugia, D. Braga and F. Grepioni, J. Organomet. Chem., 1999, 573, 60. 134. G. Liu and M. Garland, Organometallics, 1999, 18, 3457. 135. S. Li and M. B. Hall, Organometallics, 1999,18, 5682. 136. J. D. Atwood, Organometallics, 1999,18, 123. 137. R. Trebbe, R. Goddard, A. Rufiska, K. Seevogel and K-R. Porschke, Organometallics, 1999,18,2466.

226

Organometallic Chemistry

138. L. Weber, M. Barlmeyer, J-M. Quasdorff, H. L. Sievers, H-G. Stammler and B. Neumann, Organometallics,1999,18, 2497. 139. G. Frenking, Organometallics, 1999, 18,619. 140. F. Calderoni, F. Demartin, F. Fabrizi de Biani, C. Femoni, M. C . Iapalucci, G. Longoni and P. Zanello, Eur. J. Inorg. Chem., 1999,663. 141. 0. G. Polyakov, S. M. Ivanova, C. M. Gaudinski, S. M. Miller, 0. P. Anderson and S. H. Strauss, Organometallics,1999,18, 3769. 142. S. M. Ivanova, S. V. Ivanov, S. M. Miller, 0. P. Anderson, K. A. Solntsev and S. H. Strauss, Inorg. Chem., 1999,38, 3756. 143. P. Mathur, S. Chatterjee, S. Ghose, M. F. Mahon, J. Organomet. Chem., 1999, 587, 93. 144. I. Bachert, I. Bartusseck, P. Braunstein, E. Guillon, J. Rose and G. Kickelbick, J. Organomet. Chem., 1999,587, 144. 145. F. Fabrizi de Biani, C. Femoni, M. C. Iapalucci, G. Longoni, P. Zanello and A. Ceriotti, Inorg. Chem., 1999,38,3721. 146. A. U. Harkonen, M. Ahlgren, T. A. Pakkanen and J. Pursiainen, J. Organomet. Chem., 1999,573,225. 147. W-T. Wong, Organometallics, 1999,18, 3474. 148. F-S. Kong and W-T. Wong, J. Chem. SOC.,Dalton Trans., 1999,2497. 149. S. M. Waterman, M. G. Humphrey and D. C. R. Hockless, J. Organomet. Chem., 1999,582,310 - 318 150. F. M. Dolgushin, E. V. Grachova, B. T. Heaton, J. A. Iggo, I. 0. Koshevoy, I. S. Podkorytov, D. J. Smawfield, S. P. Tunik, R. Whyman and A. I. Yanovskii, J. Chem. Soc., Dalton Trans., 1999, 1609 151. U. Brand, C. A. Wright and J. R. Shapley, Inorg. Chem., 1999,38,5910. 152. S. M. Waterman and M. G. Humphrey, Organometallics, 1999,18,3116. 153. M. Yuki, M. Okazaki, S. Inomata and H. Ogino, Organometallics, 1999, 18, 3728. 154. M. I. Bruce, B. D. Kelly, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton Trans., 1999, 847. 155. V. G. Albano, C. Castellari, M. C. Iapalucci, G. Longoni, M. Monari, A. Paselli and S. Zacchini, J. Organomet. Chem., 1999,573,261. 156. H.-G. Ang, S.-G. Ang, S. Du, J. Organomet. Chem., 1999,589, 133. 157. N. T. Tran, M. Kawano, D. R. Powell, R. K. Hayashi, C. F. Campana and L. F. Dahl, J. Am. Chem. SOC.,1999,121,5945. 158. A. J. Amoroso, M. A. Beswick, C-K. Li, J. Lewis, P. R. Raithby and M. Carmen Ramirez de Arellano, J. Organomet. Chem., 1999,573,247.

10 Complexes Containing MetaI-Carbon a-Bonds of the Groups Titanium to Manganese, Including Carbenes and Carbynes BY PATRICK C. MCGOWAN, ELIZABETH M. PAGE, MICHAEL K. WHITTLESEY AND JASON M. LYNAM

Part I: Group 4 by Patrick C. McGowan This article will concentrate on the formation and reactivity of o-carbon bonds of Group 4. Much has been published and discussed about the catalytic activity of many of these complexes (including in some of the papers examined in this review), but space restrictions do not allow coverage of this. A recent monograph has covered many catalytic aspects of Group 4 and includes some of the authors covered in this review.' The bis(tri-tert-butylphosphinimide) complexes ( B u ~ ~ P N ) ~ Tand ~C~~ ( B u ~ ~ P N ) ~were T~M prepared ~~ and characterised crystallographically. Stoichiometric reactions of ( B u ' ~ P N ) ~ T ~with M ~ PhNMe2H[B(C6F5)4] ~ in the while reaction presence of PMe3 afforded [(Bu'~PN)~T~M~(PM~~)][B(C~F~)~], of ( B u ' ~ P N ) ~ T with ~ M ~B(C6F5)3 ~ affords ( B u ' ~ P N ) ~ T ~ M ~ ( ~ - M ~ ) Of B(C~F~)~ significance is the fact that these catalysts represent the first non-cyclopentadienyl, single-site catalysts competitive with derivatives of metallocenes under relevant polymerisation conditions.2 Bis(alky1) derivatives of Ti and Zr [(Ar0)2MR2] 1 (M=Ti, Zr; R=Me, CH2Ph; ArO = various 2,6-disubstituted phenoxides) were synthesised and their reactivity towards the Lewis acid [B(C&5)3] was examined. The benzyl compounds generate stable zwitterionic species such as [M(OC6HPh2-2,6-R23,5)2(CH2Ph)][r16-C6H5cH2B(C6F5)3] (M = Ti, R = H, or Me 2; M = Zr, R=Me,). Structural studies of 2 show the boron anion n-bound to the metal centre through the original benzyl phenyl ring. Treatment of the benzyl compound [Zr(OC6H3B~'2-2,6)2(CH2Ph)2] with [B(C6F5)3] leads to the cyclometalated compound [Zr(OC6H3Bu'-CMe2CH2)(oc6H3Bufz-2,6)][r16C6H5CH2B(C6F5)3] 3 which was structurally characterised. In contrast to this behaviour the titanium bis(methy1) species react with [B(C6F5)3] to produce unstable Me cationic intermediates which decompose to a mixture of [Ti(OAr)2Me(C&5)] and [MeB(C6F5)2]. The titanium zwitterionic benzyl compounds 2 react with alkynes and a-olefins to produce mono-insertion products such as [Ti(OC6H3Ph2-2,6)2(CMeC(Ph)CH2(q6-Ph))][PhCH2BOrganometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001 227

Organornetallic Chemistry

228

(C6F5)3]. In these compounds 1,2-insertion of olefins occurs followed by chelation of the original benzyl group to the metal ~ e n t r e . ~

2B(c6F5)3

-CH

3

The chemistry of the titanium derivatives has been further explored by the reactivity of [Ti(OC6H3Ph2-2,6)2Me2] 4 and titanabicyclic compounds [(Ar0)2Ti(CH2CH(C4H8)CHCH2)] (Ar=2,6-Ph2C6H3, 2,3,5,6-Ph&H; CH2CH(C4H8)CHCH2= trans-1,2-dimethylcyclohexane-ol,a’-diyl) (formed by transcoupling of 1,7-0ctadiene)toward organic isocyanides was studied. Compound 4 reacts with one equivalent of 2,6-dimethylphenyl isocyanide (xyNC) to produce a cyclometallated product [Ti(OC6H3Ph2-2,6)(0C6H3Ph-q C6H4)(N(xy>CHMe2)] 5. Compound 5 is believed to arise via C-H bond activation within an intermediate q2-imine(azatitanacyclopropane)formed by transfer of both Me groups to the isocyanide. With an excess of xyNC, 6 produces an intermediate bis(q2-iminoacyl) 7,which slowly converts into the enediamide [Ti(OC6H3Ph2-2,6)2{ N(xy)CMeCMeN(xy))] 8. The solid-state structure of 8 shows a folded diazatitanacyclopent-3-enering formed by intramolecular coupling of the two iminoacyl groups. Titanabicyclic compounds [(Ar0)2Ti(CH2CH(C4H8)CHCH2)]react with ButNC and xyNC respectively to generate products Ti(OC6H3Ph2-2,6)(OC6H3Ph-(q2(C6H4)CNR’)){ R’NCH(C8H14))I (R’ = Bur, 2,6-Me2C6H3), which both

’-

4

XY

8

7

10: Complexes Containing Metal-Carbon a-Bonds

229

contain amide ligands derived by CH bond activation and an iminoacyl group formed by insertion into the new Ti-C bond. The solid-state structure of { Oc6H3Ph-(q2-(C6H4)CNBu')} { BufNCH(C8H14)}) shows [Ti(OC6H3Ph2-2,6) a trans-fusion between the five- and six-membered C rings as found in the initial titanabicycle. The treatment of 4 with xyNC in the presence of excess 3hexyne or styrene produces azatitanacyclopent-2-ene and azatitanacyclopentane derivatives, respectively. These arise via coupling of the alkyne or olefin with an intermediate q2-imine. The solid-state structure of [Ti(OC6H3Ph22,6)2{N(xy)CMe2CEtCEt)lhas been determined.4 Reaction of solvent-free [(Ph3Si0)2ZrC12],with CH3Li in the presence of 2,2'-bipyridine yielded the organometallic compound [(Ph3Si0)2Zr(CH3)2(bpy)](t~luene)~ whose molecular structure has been determined by X-ray crystallography. A series of five-coordinate bis(pheno1ate) titanium hydrocarbyl complexes (MBP)Ti(q2-R)R' (MBP = 2,2'-methylenebis(4-methyl-6-~ert-butylphenolate), R = C6H4(o-CH2NMe2); R = C1, OS02CF3, Me, CH2CMe3 9; R = CH2C6H4(u-NMe2);R' = C1, Me 10) were prepared. A structure determination of (MBP)Ti[q2-C6H4(o-CH2NMe2)]OS02CF3 showed the metal to have a distorted trigonal-bipyramidal coordination geometry. Cationic fourcoordinate derivatives [(MBP)Ti(q2-R)]' were generated by reacting the R' = Me derivatives with the Lewis acid B(C6F5)3. These cations were found to undergo stoichiometric insertions of ethene and propene into the Ti-C bond, as seen by 1D and 2D NMR spectroscopy and quenching reactions with CD30D.6

'

9

'

10

Bis alkoxide derivatives have been prepared by the addition of Ind-2-4,6-ditert-butylphenol (Ind-2 = 2-inden-3-yl) to CpTiC13 in the presence of excess pyridine giving [Cp2Ti(OC6H4Bu'2-4,6-Ind-2)C12]. Zirconium alkyl complexes containing the 2-(indenyl)-4,6-di-tert-butylphenoxideligand were also prepared. The complexes prepared represent three distinct bonding modes for the ligand 2-(indenyl)-4,6-di-tert-butylphenoxideat early d-block metal centre^.^ Insertion of optically pure (R,R)-and meso-(R,S)-1,3-bis(1-phenylethyl)carbodiimide into a Ti-CMe bond of (q5-C5R5)TiMe3provides the compounds (q 5-C5R5)TiMe2-N, N-bis( 1-phenyl)acetamidinates (R,R) (R = H), (R, R) (R = Me), (R,S)( R = H ) and (R,S) (R = Me) 11, in high yield. Reaction 1-tert-butyl-3-(1-phenylethyl)carbodiimide and (q5-C5H5)TiMe3 between (R)yields analogous compound 12 in a similar fashion. Variable-temperature H NMR studies unequivocally establish that a low-energy amidinate ring twisting

230

Organometallic Chemistry

pathway is the exclusive origin of configurational instability in this class of piano-stool complexes. Further, evidence for a dynamic process involving amidinate ring conformation is obtained for (R,S)-ll (R = Me) by a similar study. R

R

11

12

The chemistry of amidinate ligands with a pendant pyridine functionality has been described. Reaction of p-toluoyl- or p-But-benzoyl chloride with 2aminoethylpyridine generates the amides 2-Py-(CH2)2NHCO(p-RPh)(R = Me, But); these amides are then converted into the amidines ~ - F ' Y ( C H ~ ) ~ N H C ( ~ RPh)NR' (R = Me, R' = Ph) (LMeH); R = Bu', R' = 3,5-dimethylphenyl (LBuH)) by reaction with PC15 followed by R'NH2. Reaction with the homoleptic metal-alkyl Zr(CH2Ph)4 yields the mono-amidinate) complex (L'BU)Z~(CH~P ~ )This ~ was characterised by 'H NMR and IR spectro13. scopy, elemental analyses and X-ray crystallography. The X-ray crystal structure of 13 shows it to be monomeric, with the pendant pyridine coordinated intramolecularly coordinated and the ligand arranged in a meridional fashion to the metal centre.' Several Ti(II1) complexes incorporating the chelating diamidoamine ligand [(Me3SiNCH2CH2)2NSiMe3]2-[NN2] are described. The reaction between Li2?JN2] and TiC13(THF)3 gave the dimeric Ti(II1) chloride { TiClw2]}2, from which the monomeric Ti(II1) alkyl Ti(CH(SiMe3)2}[NN2]14 could be synthesised via a salt metathesis route. The alkyl complex 14 reacted with H2 to form the thermally stable, dimeric, diamagnetic Ti(II1) hydride (TiHwN2]}2 . Density functional calculations on a simplified model system of (TiH[NN2]j2indicated the presence of a weak Ti-Ti o-interaction. lo The reaction of TiC14 with the bis-phosphinimine Me3SiN=P(Ph)2CH2CH2P(Ph)2=NSiMe3 proceeds with evolution of HCl and metalation of

MesSi,

0'

13

14

23 1

10: Complexes Containing Metal-Carbon a-Bonds

one CH2 group to give TiC13{Me3SiNP(Ph)2CHCH2P(Ph)2NSiMe3) 15. The crystal structure determination of 15 has been carried out and shows a comparatively long Ti-C bond. Complexes of the type (Me3SiN-o-C6H4)20MMe2 have been prepared where M=Ti, Zr or Hf. Although cations prepared by addition of [Ph3C][B(C6F5)4]or [PhNMe2H][B(C6F5)4]to (Me3SiN-o-C6H4)20ZrMe2or (Me3SiN-o-C6H4)20HfMe2 could not be observed in NMR studies, addition of [(q5-C5H4Me)2Fe][B(C6H5)4] to (Me3SiN-o-C~H4)20HfMe2in the presence of THF led to isolation of { (Me3SiN-o-C6H4)20HfMe(THF)2} [B(C6H5)4] 16. An X-ray study showed the cation to be a distorted octahedron in which the (Me3SiN-o-C6H4)20- ligand is in the mer arrangement and is significantly twisted from a planar NC20C2N arrangement.l2 +

15

16

The analogous isopropyl substituted derivatives have been studied extensively. A variety of five- and six-coordinate Ti and Zr dialkyl complexes that contain the [(Pr%I-o-C6H4)20I2-([PriN0Nl2-) ligand were prepared, among them [PriNON]Ti(CH2CHMe2)2, [Pr'NON]Ti(CHzCMe&, [PriNON]ZrEt2 and [PriNONfZr(CH2CHMe2)2.These species serve as sources of complexes 2(p-N2) 17, [PriNON]Ti(CHCMe3)(PMe3)218, such as { [PI-'NON]T~(PM~~)~} [PriNON]Zr(CH2CHMe2)2(PMe3) and [PriNON]Zr(H2C=CMe2)(PMe3)2 19. The reaction between [PriNON]Ti(CH2CMe3)2 and MezPCH2CH2PMe2 But

(dmpe) in the absence of dinitrogen yields (Pr'NC6H4)(Pr'NC6H40)Ti(dmpe), a pseudo-octahedral species in which one aryl-0 bond has been cleaved. In all structurally characterised complexes in which the [Pr'N0Nl2- ligand is intact, it adopts a mer configuration in which the donor 0 atom is planar. Analogous dialkyl complexes [CyNON]MR2(Cy = cyclohexyl; M = Zr, R = Me, Et, Bu', CH2CMe3,allyl; M = Ti, R = Me, CH2CMe3,Bu') also were prepared. Decomposition of [PriNON]ZrEt2 in the absence of phosphine proceeds in a firstorder manner to yield { [Pr'NONIZrEt } 2(.~-C2H4)via rate-limiting P-H abstraction to give transient [PriN0N]Zr(CH2CH2) followed by either intermolecular

232

Organometallic Chemistry

selective P-H transfer or Et group transfer from [Pr'NON]ZrEt2 to [Pr'NON]Zr(CH2CH2),as suggested by 2H and 3C labelling studies. Decomposition of [Pr'NON]ZrR2 complexes is dramatically accelerated in the presence of PMe3. One equivalent of PMe3 is proposed to bind to give a pseudo-octahedral adduct, [PriN0N]ZrR2(PMe3), in which the two alkyl (R) groups are pushed close to one another and P-H abstraction is thereby a~ce1erated.l~ Increasing the size of the alkyl groups attached to the NON ligand has a dramatic effect on the chemistry. Titanium, zirconium and hafnium dialkyl complexes that contain the [(Bu'-d6-N-o-C6H4)20I2- ([BufN0NI2-) ligand have been prepared. [Bul\TON]ZrR2and [BufNON]HfR2complexes could be isolated in which (for example) R = Me, Et, or Bu', but only [Bu'NON]TiMe2. X-ray crystallography studies showed [Bu'NON]MMe2 structures (M = Ti or Zr) to be of the 'twisted fac' 20 variety in which two amido nitrogens occupy equatorial positions in a distorted trigonal bipyramid. However, in solution all such species show equivalents alkyl groups on the NMR time-scale as a consequence of formation of an intermediate mer structure 21 that contains a planar oxygen donor. In analogous complexes that contain the ([Me(CD3),CNC6H4][Me(CD3)2CN-2,4-Me2C6H2]o}2or ([Me(CD3)2CNC6H4][Me(CD3)2N-EtC6H3]0} 2 - ligand the two metal alkyl groups are inequivalent on the NMR time-scale. Addition of trimethylphosphine to [Bu'NONIZ T ( C H ~ C H ~yields )~ structurally characterised, pseudo-octahedral [ButN O N ] Z ~ ( T ~ ~ - C ~ H ~ )Addition ( P M ~ ~ of ) ~B(C6F5)3 . to [BuNON]ZrMe2 yields structurally characterised ([Bu'NONIZrMe) [MeB(C6F5)3]22, while addition

of [PhNMe2H][B(C6F5)4]to [Bu'NON]ZrMe2 in bromobenzene-d5 generates '([ButNON]ZrMe(PhNMe2)}[B(C6F5)4]'.An X-ray structure of ([Bu'NONIZrMe(THF)2}[B(C6F5)4] shows it to be a pseudo-octahedral species in which the [ButN0Nl2- ligand adopts a 'twisted mer' geometry, while the X-ray structure was of the 'twisted fac' of { [[ButNON]ZrMe(MeOCH2CH20Me)][B(C,F,),I} variety. In the case of hafnium, pseudo-octahedral cationic bis-THF or DME complexes can be isolated even when the anion is [B(C6H5)4]-.14 Addition of LiNH(2,6-Me2C6H3) (LiNHAr') to cis-2,5-bis((tosyloxy)The reaction methy1)tetrahydrofuran gave c~~-~,~-(A~'NHCH~)~(C~H~O). between Zr(NMe2)4 and H2-cis-2,5-(Ar'NHCH2)2(C4H60) yielded cis-2,5(Ar'NHCH2)2(C4H60)Zr(NMe2)2, from which cis-2,5-(Ar'NHCH&were prepared readily. (C4H@)ZrC12 and cis-2,5-(Ar'NHCH2)2(C4H60)ZrMe2 cis-2,5An unsymmetric derivative of H2-cis-2,5-(Ar'NHCH2)2(C4H60),

10: Complexes Containing Metal-Carbon

IS-

Bonds

233

(Ar'NHCH2)(ArNHCH2)(C4H60)(Ar = 2,6-Pri2C6H3), was also prepared via the imine of 5-(hydroxymethy1)furaldehyde. { C~S-~,S-(A~'NHCH~)~(C~H~O Me(PhNMe2)}[B(C6F5)4] and { cis-2,S-(Ar'NHCH,)(ArNHCH,)( C4H60)ZrMe(PhNMe2)}[B(C6F5)4] were prepared in the reaction between the dimethyl species and [PhNHMe2][B(C6F5)4].l5 Zr complexes that contain the [(2,4,6-Me3C6H2NCH2CH&NRl2([Mes&NRI2; R = H or Me) ligand, along with [Mes2N2NH]TiMe2 and [Mes2N2NH]HfMe2complexes 23, were prepared. The crystal and molecular structures of [Mes2N2NMe]ZrMe2were determined by X-ray crystallography. l6

23

24

A new synthesis of PhP(CH2CH2NH3C1)2is reported that involves the addition of two equivalents of BuLi to a mixture of PhPH2 and two equivalents of ClCH2CH2(cyclo-NSiMe2CH2CH2SiMe2). The reaction between PhP(CH2CH2NH3Cl), and four equivalents of BuLi followed by two equivalents of Me3SiC1then yielded (Me3SiNHCH2CH2)2PPh (H2[N2P]) quantitatively. The alkyl complexes that were prepared include [N2P]Zr(THF)MeCl, [N2P]Zr(Bui)Cl, w2PlZrMe2, [N2P]Zr(CH2Ph)2 and p2P]Zr(CH3)(CH2Ph), compounds 24. An X-ray diffraction study showed that the basic structure of [N2P]Zr(Me)(CH,Ph) is a distorted trigonal bipyramid in which the Me group is in the apical position trans to phosphorus and the q2-benzyl group is cis to phosphorus. Compounds of the type PhP(CH2SiMe2NHR)2(R = Bu' or 2,6-Me2C6H3;H2[RzNPN]) were prepared by treating ClCH2SiMe2Clwith LiNHR to give ClCH2SiMe2NHR followed by a reaction between PhPH2, C1CH2SiMe2NHRand butyllithium. Zirconium complexes that were prepared include [Bur2NPN]ZrMeCl,[Ar2NPN]ZrMeC1 and [Ar2NPN]ZrMe2.X-ray studies of [Bur2NPN]ZrMeC1and [Ar2NPN]ZrMeCl demonstrate that extensive steric crowding exerted by a Bu' group in complexes of this type contributes to the inability to form a simple complex such as [PhP(CH2SiMe2NBu?2]ZrMe2.l7 The thioethers (Bu'-d6-NH-o-C6H4)2S(H2[Bu'NSN]) and (P ~ ' N H - o - C ~ H ~ ) ~ S (H2[PriNSN]) have been prepared in three steps in good yield. Zirconium complexes that contain the [Bu'NSw2- ligand [Bu'NSN]ZrMe2) were prepared readily, but this is unstable, and no higher alkyl homologues could be prepared. In contrast, [PriNSN]ZrMe2and priNSN]Zr(CH2CHMe2)2are both stable, even at elevated temperatures. An X-ray study of [PriNSN)ZrMe2 showed it to have approximately a square-pyramidal structure with a methyl group in the apical position. Low-temperature solution 'H and 13C NMR spectra of [Bu'NSN2- and [Pr'NSN12- species are consistent with the solid-

234

Organometallic Chemistry

state structures, although inversion at sulfur on the NMR time-scale results in equilibration of the two metal substituents (e.g. methyl groups). Cationic complexes prepared from [RNSN]ZrMe2 precursors (R = But, Pr') were not stable at 22 OC.18 Six-coordinate [TiMe2(Me2ATI)2] and piPh2(Me2ATI)2]25 were synthesised and structurally characterised, where Me2ATI is N,N'-dimethylaminotroponiminate. The mono-alkyl complexes [TiClR(Me2ATI)2], R = Me, CH2SiMe3 26,were prepared, and the alkyl-aryl complex [TiMePh(Me2ATI)2] was prepared by treatment of fTiClR(Me2ATI)2], the former with PhMgC1. The solid-state structures of most of these complexes were determined and reveal slightly distorted, trigonal-prismatic coordination geometry. Attempts to prepare alkyl complexes containing 9-hydrogen atoms resulted instead in the isolation of [Ti(MezATI)3] or [Ti2C12(Me2ATI)4], depending on the alkyl reagent and stoichiometry. Because of the modest steric requirements of the { Ti(Me2ATI)2)2+ fragment, five-coordinate Ti(1V) complexes were only generbeing a ated with a bulky a-2n donor ligand, [Ti(2,6-NPrz2C6H3)(Me2ATI)2] specific example. Attempts to prepare the isoelectronic 0x0 analogue afforded l9 only dimeric [Ti~02(Me~AT1)~].

25

26

The reactivity of these complexes was reported in another paper by the same authors. Reaction of piR2(MeZATI)2] with CO or RNC in the presence of various organic electrophiles was studied. The compounds TiMe2(MeZATI)2 and TiPh2(Me2ATI)2react with CO and aldehydes or ketones to afford unsymmetric diolate complexes 27 that convert into the corresponding vicinal diols after hydrolysis. Phenylacetylene also reacts to form the oxametallacyclopentene complex [Ti(OCMe2CH=CPh)(Me2ATI)2]. Treatment of TiMe2L2 with RNC yields the free imine and a source of low-valent Ti. Trapping this intermediate with two equivalents of benzaldehyde or benzil affords the Ti diolate or enediolate complex, respectively. When one equivalent each of benzophenone and either N-tosylbenzaldimine or acetone were added to the intermediate, ~~(OCP~~CHP~N(SO~~O~)HP~)(M~~ATI)~] and [Ti(Ph2COCOMe2)(Me2ATI)2], respectively, were obtained. The Ti thiolato-alkoxide complex [Ti(Ph2CSCOMe2)(Me2ATI)2]was prepared using thiobenzophenone and acetone. This chemistry allows for the preparation of unsymmetric diols and oxametallacyclopentene complexes from Ti(1V) dialkyls, CO and either carbonyl compounds or alkynes. Amido-alkoxide and thiolato-alkoxide complexes can be prepared by the reaction of Ti(1V) dialkyl complex, two equivalents of benzophenone and either an imine or a thioketonee2' A novel, multicomponent method to prepare vicinal diols from titanium dialkyl com-

10: Complexes ContainingMetal-Carbon a-Bonds

235

plexes such as 27, CO and carbonyl compounds is presented. The reaction involves sequential coupling of aminotroponiminate-supported titanium dialkyl complexes, carbon monoxide and carbonyl compounds to yield vicinal diols following hydrolysis of the diolate complexes. In one example, 2-methyl3-phenylbutane-2,3-diolwas prepared in 69% yield.2' The synthesis and structural characterisation of Ti(1V) dialkyl complexes ligated by a new tetradentate C2-symmetric aminotroponiminate ligand are reported. Included are rare examples of thermally stable Ti diethyl and dibutyl complexes and an q2-imine complex 28. The crystal and molecular structures of TiR2L (R = Me, Et) and (q2-Bu'N=CMe2)TiL were determined by X-ray crystallography. (q2-Bu'N=CMe2)TiLreacted with two equivalents of benzophenone to give Ti(OCPh2CPh20-0,0')L 29.22

I

\

0

28

Y

0

29

The organometallic chemistry of titanium macrocycles was investigated using meso-octaethyl mono(pyridine)-trisbyrrole), [Et8(C,H3~(C4H2NH)3], as a ligand for titanium(1v). The metallation of this with LiBu followed by the reaction with TiC14.thf2led to [Et8(C5H3N>(C,H2N),Ticl~,which was alkyl) ~The T~M T ~i ]4 bond in 30 underwent a ated to [ E ~ ~ ( C S H ~ N ) ( C ~ H ~ N30. migratory insertion reaction with BdNC and carbon monoxide. In the former case the corresponding q2-iminoacyl was isolated and structurally charac-

Bu'NC

30

31

236

Organometallic Chemistry

terised as [Et8(C5H3N)(C4H2N)3Ti(q2-C(Me)NBu')], 31, while the reaction of 30 with carbon monoxide led to the homologation of one pyrrolyl anion, thus converting the mono(pyridine)-tris(pyrro1e)into a cis-bis(pyridine)-bis(pyrro1e) macrocycle and the oxotitanium(iv) functionality in [Et8(m-MeC5H2N)(C5H3N)(C4H2N)2Ti=O]. The homologation occurs via a carbenium ion q2acyl which was not i n t e r ~ e p t e d . ~ ~ The cis-dichloro-rneso-hexaethylporphodimethene-Zr(1V) complex was functionalised to the corresponding dialkyl derivatives 32 [R = Me, PhCH2, Ph] displaying a variety of migratory pathways. In the case of the benzyl derivative of 32, the spontaneous migration of the first benzyl to the ligand is followed by the second one, photochemically induced, thus forming a Zrporphyrinogen complex. The Me derivative of 32 undergoes thermally induced methane elimination with the metalation of the rneso Et chains. Migration of both Me groups was observed in the reaction of 32 with Bu'NC, with the preliminary formation of q2-imine, rearranging to the corresponding enamine 33.24

Et

Bu'NC _____)

Et

32

33

The compounds Cp*TiMe2E (Cp* = q5-C5Me5;E = Me, C&5, OC6F5, C1) react with t rityl tetrakis(perfluorophenyl)borate, [Ph&] [B(c6F5)4], to form the thermally unstable dititanium complexes [(Cp*TiMeE)2(p-Me)][B(C6F5)4],all of which behave as sources of the highly electrophilic species [ c ~ * T i M e E l ' . ~ ~ Alkylation of complexes (q5-C5H4R)TiC13(R = CMezPh, CMe2CH2Ph, SiMe2Ph, CHPh2) and (C5H4CMe2CH2Ph)ZrC13.dmereadily affords the corresponding trimethyl and tribenzyl derivatives; the crystal structure of (q5C5H4CHPh2)Ti(CH2Ph)3 34 was determined. Treatment of (q5-C5H4R)MMe3 [M = Ti, Zr] with [Ph3C]'[B(C6F5)4]- in dichloromethane at low temperatures generates the cationic [(q 5-C5H4R)MMe2]+complexes; the complexes are stabilised by mcoordination to the Ph ring to give ansa-arene complexes with one- and two-carbon linkages 35.26 The mono- and bis-ring substituted zirconocenes with pendant Ph groups [Zr(q-C5H5)(q-C5H4CMe2Ph)Me2], [Zr(q-C5H5)(q-C5H4CMe2C6H4Me-~)Me2, [Zr(q -C5H4CMe2Ph)2Me2]and [Zr(q-C5H4CMe2C6H4Me-~)2Me2] were prepared. These compounds react with Me abstracting reagents such as B(C6F5)3 or [Ph3C]' [B(CbF5)4]- to form cationic zirconocene complexes as solvent separated ion pairs as shown by low temperature NMR spectroscopy. For the cationic complexes [Zr(q-C5H5)(q-C5H4CMe2Ph)Me]" [RB(C6F5)3](R = Me or C&) and [Zr(q-C5H5)(q-C$€4CMe2C6H4Me-p)Me]t

10: Complexes Containing Metal-Carbon o-Bonds

237

[RB(C6F5)3]- (R = Me or C6F5) evidence for the coordination of a Ph group to the Zr centre via agostic C-H-M interaction was obtained by NMR spectroscopy. The cationic complexes [Zr(q-CsH&Me2Ph)2Me]+ [RB(C6F5)3](R = Me or C6F5) and [Zr(q-C5H4CMe2C6H4Me-p)2Me]+ [RB(C6F5)3](R = Me or C6F5),respectively, exhibit more complex b e h a ~ i o u r . ~ ~ Low temperature NMR studies indicate that the dicationic salts [Zr(qC S H ~ C M ~ ~ C ~ H ~ M ~ - P ) ~ ] ~and + [[Zr(q-C5H4CMe2Ph)2]2+M ~ B ( C ~ F ~ ) ~ ] ~ [MeB (C6F5)3]2are formed when the neutral compounds [Zr(q-C5&CMe2C6H4M e - ~ ) ~ Mand e ~ l[Zr(q-C5H4CMe2Ph)2Me2] are treated with two equivalents of B(C6F5>3.28

34

35

36

The reaction of 6,6-dimethylfulvene with M(CH2Ph)4 (M = Zr, Hf) in 36 (M = Zr, Hf) without benzene gives [q5-C5H4(CMe2CH2Ph)]M(CH2Ph)3 any observable by-products. A similar reaction for M = Ti is not observed. The shows a single-crystal X-ray study of [q5-C5H4(CMe2CH2Ph)]Zr(CH2Ph)3 three-legged piano-stool geometry with an q2-bound benzyl ligand. A second equivalent of 6,6-dimethylfulvene does not react with either derivative of 36. The bulkier 6,6-diphenyfulvene only reacts cleanly with the more Lewis acidic Hf(CH2Ph)4to give [q 5-C5H4(CPh2CH2Ph)]Hf(CH2Ph)3 .29 Reactions of the chloro complexes C12M(q5-C5R5)[(C5H4)(SiMe2)2(q5C5H3)]( R = H , Me; M=Ti, Zr, Hf) with various alkylating agents afforded the chloroalkyl compounds ClM(R)(q5-C5H5)[(C5H4)(SiMe2)2(q5-C5H3)] (M=Ti; R=Me, Et; M = Z r , R=Me, Et, CH2Ph; M=Hf, R=CH2Ph) and dialkyl compounds Me2M(q5-C5R5)[(C5H4)(SiMe2)2(q 5-C5H3)] (M = Ti; R = H, Me; M = Zr; R = H). Formation of the heterodinuclear complex (q5C5H5)ZrC12(q5-C5H3)(SiMe2)2(q5-C5H3)Ti(NMe2)3 with amine elimination was observed by 'H NMR spectroscopy when complex C12M(q5C5H5)[(C5H4)(SiMe2)2(q5-C5H3)] was treated with Ti(NMe2)4.30 The mixed cyclopentadienyl-phosphinimide analogues (Cp')TiC12(NPR3) (R = cyclohexyl, CHMe2, CMe3) and the analogous dimethyl derivatives (Cp')TiMe2(NPR3)were prepared. For example, Tic14 was added to a solution of cyclopentadiene and heated to 60°C for 30 min. Me3SiN=PtBu3was then added, producing (But3P=N)TiC12Cpin 94% yield. MeMgBr was then added to a benzene solution of (Bur3P=N)TiC12Cpat room temperature and stirred for 12 h, yielding (But3P=N)TiMe2Cp37 (87%). 37 was added to B(C6F5)3 producing p i (But3P=N)(Cp)(Me)(MeB(C6F5)3)] 38 in 85% yield. The preparation and reactions of [CP('P~~PN)T~(SR)~] (R = Ph, CH2Ph) with AlMe3 are described. The result is an unprecedented triple C-H bond activation of a Me group to yield Ti-Al-carbide clusters. [Cp(Prz3PN)Ti(SR)2]

are readily prepared by reaction of [Cp(Prz3PN)TiC12]with the Li thiolates LiSPh or LiSCH2Ph. The X-ray structural data for the products with AlMe3 confirmed that they are analogous and can be formulated as [CpTi(p-SR)(pNPPr'3)(C)(A1Me2)2(p-SR)AlMe] 39. In both of these molecules, the pseudothree-legged piano stool coordination sphere of Ti comprises a cyclopentadienyl ring, a thiolate S, a phosphinimide N and a carbide C. Three A1 atoms complete the bonding sphere of the carbide C atom. The geometry about the carbide is severely distorted tetrahedral.32 The compounds c ~ T i ( R ) ( o c ~ H ~(R P r=~Bu', ~ ) ~Bus, Bun, Me) were prepared and characterised. Reactions of CpTiC12(OC6H3Pri2)2 with AlMe3 revealed stepwise formation of CpTi(Me)C1(OC6H3Pr'~) and CpTi(Me)2(OC6H3Pri2),while subsequent addition of A1Me3 afforded complete conversion into CpTi(Me)2(0C6H3Pri2), with formation of the A1 species [A1Me2(OC6H3Prz2)]n. In contrast, the catecholate complex CpTi(02C6H4)Cl reacts with AlMe3 yielding the paramagnetic species [CpTi(02(C,&)).A1C1Me2]2.33 Reactions of the q5-cyclopentadienyl-q'-amid0 dimethyl Ti derivative [Ti(q5-C5H4SiMe2[q '-N(C6H3Me2)]}Me21 40 with B(C6F5)3 in hexane at room temperature yielded a thermally stable bright yellow microcrystalline solid identified by elemental analysis as [Ti(q5-C5H4SiMe2[q'-N(C6H3Me2)]}Me(MeB(C6F5)3}] 41. A solution of 40 in CD2C12 at - 78 "C affords the ionpair complex 41, while in C6D6 it is slowly converted into the new neutral complex pi(q5-C5H4SiMe2-[q'-N(C6&Me2)]} (CH2B(C6F5)2>(c&)] 42. Complex 42 is the unique product obtained after stirring compound 41 or a mixture of complex 40 and B(C6F5)3 in toluene or benzene for 12 h at room temperature.34 Me,Si

4Q \

I

239

10: Complexes Containing Metal-Carbon a-Bonds

Treatment of 6-(dimethylamino)-6-methylfulvene with MeLi followed by the reaction of the resulting [C5H4CMe2NMe2]Lireagent with CpZrC13 gave [(q5-C5H4CMe2NMe2)CpZrC12].Its treatment with two molar equivalents of MeLi furnished [(q5-C5H4CMe2NMe2)CpZrMe2],which was reacted with B(C6F5)3by Me group transfer. The in situ [Zr]+-Me cation system generated in this manner proved to be unstable under the reaction conditions and instantaneously eliminated methane with formation of 43. In this reaction a N-Me hydrogen atom was abstracted. 43 was stabilised by the addition of one equivalent of the alkyl isocyanide RN-C (R=CMe3, Bu, CMe2CH2CMe3) to yield the respective adducts 44. 44 (R = CMe3) was characterised by an X-ray crystal structure analysis. It exhibits an q2coordination the pendant formaldiminium moiety to Zr (d(ZrN) = 2.318(7) A, d(Zr-C) = 2.272(7) The (q2-R2NCH2)Zrmoiety shows a characteristic 15N NMR chemical shift (6 -376 ppm), deshielded by ca. A6 z -40 ppm relative to the "NMe2 NMR resonance found for [(q5C5H4CMe2NMe2)CpZrMe2].43 reacts with butadiene or isoprene by insertion into the Zr-CH2 bond of the (q2-forma1diminium)Zr moiety to form metallacyclic (x-ally1)metallocene complexes. [(q5-C5H4CMe2NMe2)2ZrMe2] reacts analogously: upon treatment with B(C&5)3 in a 1:I ratio, CH3 is transferred from Zr to B, and one equivalent of methane is liberated to give complex 45 (15N NMR signals at 6 -357 and -372 ppm). 45 was also characterised by X-ray diffraction. It shows coordination of both N atoms to Zr: i. e. the presence of a (q2-R2NCH2)Zr+ three-membered-ring system, formed by C-H activation, and a KN-coordinated intact pendant CMe2NMe2 group. The latter is displaced upon the addition of tert-butyl isocyanide to yield the (~C-isonitrile)(q2-formaldiminium)metallocenecation 46.35 Group 4 metal complexes M(q5:q '-C5R4SiMe2NCH2CH2SMe)C12(R = H, M = Ti; R = Me, M = Ti, Zr) containing the thioether-functionalised linked amido-cyclopentadienyl ligand were synthesised and characterised by 'H- and 13C NMR spectroscopy, mass spectrometry and elemental analysis. Reaction of Ti(q ':q '-C5H4SiMe2NCH2CH2SMe)C12with Mg(CH2)Ph)2(THF)2 yielded Ti dibenzyl Ti(q5:ql-C5Me4ZNCH2CH2SMe)(CH2Ph)2 (Z = SiMe2, CH2SiMe2) 47. Reaction of 47 and B(C6F5)3 in C6D5Br resulted in the clean

A).

43

44

45

Me

-Me

46

240

Organometallic Chemistry

/

SMe 48

47

formation of the solvent-separated ion pair [Ti(q5:q'-C5Me4ZNCH2CH2SMe)(q2-CH2Ph)]'[(PhCH2)B(C,F,),I- 48.36 A paper deals with the organometallic chemistry of Zr, with the cyclopentadienyldiphosphine ligand [q5-C5H3-1,3-(SiMe2CH2PR2)2], abbreviated as [RP2Cp] (R = Pr' or Ph). The Zr(1V) complex [PrP2Cp]ZrC13undergoes reduction with NdHg to form the trivalent Zr derivative, [PrzP2Cp]ZrC12,which undergoes a metathetical reaction with MeMgBr to yield the monomethyl derivative [PrzP2Cp]ZrMeCl 49. The reaction of the Zr(II1) complex [PriP2Cp]ZrC12with excess CO results in disproportionation to the Zr(1V) complex, [PriP2Cp]ZrCl3and the Zr(I1) compound [Pr'P2Cp]Zr(C0)2C1.This reaction is reversible, and upon removal of CO the starting material, [PriP2Cp]ZrC12, is formed.37

. ..

49

50

The reaction of [PrzP2Cp]ZrC13 with two equivalents of KCH2Ph generates an equilibrium mixture of alkyl complexes consisting of [PrzP2Cp]ZrC12(CH2Ph),[Pr'P2Cp]ZrC1(CH2Ph)2and [PriP2Cp]Zr(CH2Ph)3.Thermolysis of this mixture yields the alkylidene complex [P2Cp]Zr=CHPh(C1)50 in 85% overall yield. The reaction of [PrZP2Cp]ZrCl3 with two equivalents of LiCH2EMe3(E = C, Si) produces a similar equilibrium mixture as observed for the benzyl analogues, consisting of [Pr'P2Cp]ZrC12(CH2EMe3), [PriP2Cp]Z T ( C H ~ E M ~ and ~ ) ~ [Pr'P2Cp]ZrC1(CH2EMe3)2.3* The reaction of [Pr'P2Cp]Zr=CHR(C1) (R = Ph, SiMe3) with ethylene follows second-order kinetics to give the ethylene complex [Pr'rP2Cp]Zr(q2-C2H4)C1, the structure of which was determined by X-ray crystallography. Addition of acetone to 50 generates the alkene RCH=CMe2, although the anticipated Zr 0x0 species could not be isolated from this reaction. An insertion of CO into the Zr=C bond of 50 yields the ketene complex [PriP2Cp]Zr(q2-C,O-OC=CHR)Cl, while the reaction with tert-butyl isocyanide gives the analogous ketenimine complex [PriP2Cp]Zr(q2-C,N-Bu'NC=CHR)C1.The structure of ketene [Pr'P2Cp]Zr(q2C,O-OC=CHPh)Cl, determined by X-ray diffraction, exhibits the E geometry, with the position of the ketene unit with respect to the ancillary [PrzP2Cp] ligand being opposite to that in the configuration of the precursor alkylidene 50. The ketene complex [P2Cp]Zr(q2-C,0-OC=CHR)Clreacts with ethylene to

10: Complexes Containing Metal-Carbon cr-Bonds

24 1

give [PriP2Cp]Zr((q2-C,0-CH2CH2C(0)=CHR)Cl.The molecular structure of [Pr'P2Cp]Zr((q2-C,0-CH2CH2C(0)=CHSiMe3)C1was obtained by X-ray diffraction and reveals a five-membered zirconaoxacycle arising from the insertion of ethylene into the Zr-C bond of the ketene, which is subsequently coordinated to the metal as an enolate ligand. [PriP2Cp]Zr(q2-C,0CH2CH2C(0)=CHSiMe3)C1undergoes a final insertion reaction with CO to give the q2-acyl-ylidecomplex. For each reaction detailed above, dissociation of a labile pendant phosphine donor provides an open site for reactivity.39 [C5H3(CONHCMe3)2]Na adds to CpzZr(Me)Cl to yield Cp2Zr(Me)[C5H3(CONHCMe3)2]51. Here, the C5H3(CONHCMe3)2ligand is bonded

HN

,

51

R

to Zr through one of its carboxamido 0 atoms (KO-coordination). Treatment of [C5H3(CONHCMe3)2]Nawith C P Z ~ C ~ ~ ( T Hyields F ) ~ CpZrC12[C5H3(CONHCMe3)2](THF), where the [C5H3(CONHCMe3)2]moiety serves as a C,-symmetric chelate ligand, binding to Zr through both carbamoyl 0 atoms (~20,0'-coordination).~ Boc-Gly-Val-OMe and Boc-Ala-Val-OMe selectively add [Cp2ZrMe]+to the carbonyl 0 atom of the N-terminal amino acid residue [~-C(4):0 coordination] upon treatment with [Cp2ZrMe(THF)]+BPh4- in CH2C12 at low temperature (
'

'

242

Organometallic Chemistry

cations [Cp2Zr(p-q1-O:q2-C,0-RCHO)(p-N=CHR1)ZrCp2J+. Similarly, treatment with RNCO (R = CMe3, %Me3, 4-MeC6H4,adamantyl) gave the related p-formamidato complexes.42

H-zrcp,

H-;zrcp2

Me 53

52

The (q2-forma1dehyde)zirconocene dimer 54 cleanly adds one or two equivalents HB(C6F5)2by insertion of the H-[B] unit into the Zr-C bond of the metallaoxirane moieties to form the mono- 55 and bis-insertion 56 products, respectively. These systems contain five-membered heterocyclic rings that are built up by connecting H, B, C, 0 and Zr. (Butadiene)zirconocenereacts with HB(C6F5)2in a similar way by insertion of the H-[B] unit into the (butadiene)C(4)-Zr linkage to form the respective metallacycle 57.43Treatment of a variety of bis(alkyny1)metallocenes Cp2M(C’CR)2 (M = Ti, Zr, Hf; R = Me, Pr, Bu, cyclo-C6H11) with B(C6F5)3 yields metallocene(p-RC4R)borate betaines 58. These seem to be in an endothermic equilibrium with their methylenecyclopropene isomers - derived by an intramolecular alkyne insertion reaction which are very effectively trapped by the reaction with tert-butyl isocyanide to yield the complexes 59 that exhibit a methylenecyclopropene derived o-ligand framework. The hydrolysis of 59 (R=Me, Pr, Bu) gave the respective metal free systems that exhibit a pronounced cyclopropenylium-borate-betainecharacter Treatment of the alkyl Group 4 metallocene cation reagent [ZrCp2{CH2SiMe3)(THF)]+[BPh4J- with bis(propyny1)zirconocene yielded the cationic { p-~c~-C’CCH~siMe,>l’ 60 dimetallic complex [ ( Z ~ C p ~ ) ~ ( p:q2-MeCCMe) -q

55

54

cMe3

I

R

N

111

terkbutylisocyanide cp*2zrJ&

57

56

R

E(C6H5)3

58

,cMe3

C

‘1

Cp2Zr

-

R

59

B(c6F5)3

10: Complexes Containing Metal-Carbon a-Bonds

243

Me

I

/%

c -Me

cp2zr-

I

I

Me&i -CH2 - C =C --ZrCp2

/%

R-N=C b

Cp2Zi-N I Me&i -CH2 -C C -2rCp2 E

60

61

with a B P b - anion. 60 contains a planar four-coordinate C atom, which is stabilised by the interaction with both Group 4 metal centres. Finding the CH2SiMe3 substituent, that originates from the alkylzirconocene reagent, attached to the p-acetylide ligand in the final product is unusual. A reversible alkynyl carbometalation sequence is proposed to account for the observed selective formation of 60. 60 reacted with alkyl isocyanides RN‘C (R = CMe2CH2CMe3, CMe3, cyclohexyl) by replacement of the p-q1:q2MeCCMe ligand to form the p-isocyanide complexes [(ZrCp2)2(p-q‘-C:q2C,N-RNC) ( ~ - K ~ - C ’ C C H ~ S ~(with M ~ ~BPh4} ] + anion) 61, of which one was characterised by a crystal structure analysis.45 The zirconium and hafnium diene complexes Cp”MC1(q4CH2CMeCR’CH2) react with benzylmagnesium chloride to give the benzyl complexes Cp”M(q4-CH2CMeCR’CH2)(CH2Ph) (M = Zr, R’ = Me 62, H; M = Hf, R’ = Me) which react with B(C6F5)3 selectively under benzyl abstraction to give the zwitterionic products Cp”M(q4-diene)( T ~ ~ - P ~ C H ~ B ( C ~ F ~ ) ~ The zirconium derivative exists as a mixture of two isomers which interchange via ring-flipping of the diene ligand, whereas the Hf compound is rigid. The isoprene analogue Cp”Zr(CH2CMeCHCH2){ PhCH2B(C6F5)3}decomposes at room temperature under C-H activation and C6F5 migration from boron to zirconium to give toluene and the structurally characterised boryldiene complex Cp”Zr(C6F5){ CH2CMeCHCHB(C6F5)2} 63. In the hafnium (but not zirconium) complexes, the [PhCH2B(C6F5)3]- anion is displaced by CH2C12. The addition of diethyl ether leads to the ionic compound [Cp”Hf(2,3-Me2C4H4)(OEt2)]+[PhCH2B(C6F5)3] which was characterised by X-ray d i f f r a ~ t i o n . ~ ~

62

63

Thermolysis of [(q5-C~HMe4)2Ti(q2-BTMSA)] or [(q5-C~Me5)2Ti(q2BTMSA)] with TMOD in rn-xylene at 130-140 “C for 2-5 h gave the olefinic complexes 64 (R = H or Me) in 8-84?40yield (BTMSA = bis(trimethysily1acetylene), TMOD = 2,2,7,7-tetramethyl-3,5-octadiyne).Also, thermolysis of the complex 64 in rn-xylene at 130 “C for 48 h produced 65 (R = Me) in 80% yield. 64 is likely formed as an intermediate in the thermolysis of [(q5-C,MeS),Ti(q2BTMSA)] to form 65 (R =

244

Organometallic Chemistry

130 "C

65

64

Unusual, but still stable, five-membered zirconacyclocumulenes (q4-diyne complexes, zirconacyclopenta-2,3,4trienes) Cp*,Zr(q4- 1,2,3,4-RC4R) (R = Ph, %Me3) were prepared using new synthetic routes. The permethylzirconocene bisacetylides Cp*2Zr(C= CR)2, R = Ph, SiMe3, rearrange in sunlight to form the stable five-membered zirconacyclocumulenes c ~ * ~ Z r (1,2,3,4-RC4R) q~(R = Ph, SiMe3) 66.The alternative route to 66 is the reduction of c ~ * ~ Z r C 1 2 with Mg in the presence of the adequate disubstituted butadiynes RC=CC 3 CR. Both methods failed to produce the analogous titanacyclocumulenes, which seemed extremely unstable. Nevertheless, distinct products employing the reduction pathway with perrnethyltitanocene were obtained. For R = %Me3, the novel titanacyclopropene (q2-complex) c ~ * ~ T i (1,2-Me3q~SiC2C=CSiMe3) 67 was isolated. For R=Ph, an activation of both pentamethylcyclopentadienyl ligands was observed resulting in the complex [q5CSMe4(CH2)-]Ti[-C(=CHPh)C(=CHPh)CH2-q5-C5Me4] 68. The reaction of 68 with carbon dioxide led to the Cp*-substituted titanafuranone Cp*Ti[-OC(=O)C(Ph)C(-)C(=CHPh)CH2-q5-CSMe4] 69. The zirconacyclocumulene 66 (R = SiMe3)surprisinglyinserted two molecules of C02 to give the unprecedented cumulenic dicarboxylate Cp*,Zr[-OC( =O)C(%Me3)=C=C=C(SiMe3)C(=O)O-1. The q2-complex 67 (titanacyclopropene) took up one molecule of carbon dioxide to afford the titanafuranone Cp*2Ti[OC(=O)C(SiMe3)=C(C= CSiMe3)-Ia4* ,SiMe3

R 66

67

68

69

The reaction of [ c ~ * ~ T i Cwith l ~ ]equimolar amounts of Mg in the presence of Me3SiC = C-C = CSiMe3 yields the first early transition metal q3-enyne complex [ c ~ * ~ Tq3-Me3SiC i{ = C-C=C(C = CSiMe3)SiMe3}]70 which probably is an intermediate in early transition metal catalysed oligomerisation reactions of alk- 1- ~ n e s . ~ ~ Cp2Ti(q2-Me3SiC2SiMe3)has also been reacted with different 1,4-~ubstituted 1,3-butadiynes RC = C-C = CR, by substitution of the acetylene in a one to

10: Complexes Containing Metal-Carbon a-Bonds

245

one complexation of titanocene and the diyne, yielding different five-membered titanacyclocumulenes Cp2Ti[q4-(1-2-3-4)-RC4R]. While these complexes are very stable for R = Bur,the metallacyclocumulenewith R = Ph is unstable in solution and stabilises by dimerisation to dinuclear isomers: a fused titanacyclopentadiene-titanacyclopentene complex and a compound 71 (R = Cp) consisting of two fused titanacyclopentadiene ring systems and thus possessing a Ti substituted radialene structure. Reaction of the monomethylwith PhC = Ccyclopentadienyl complex (H4MeC5)2Ti(q2-Me3SiC2SiMe3) C r CPh gave the Ti substituted radialene 71 (R = C5H4Me)in a low yield among some other as yet unidentified c o m p l e ~ e s . ~ ~

Ph

71

Ph

Reactions of the branched polyynes tris(tert-butylbutadiyny1)benzene (1,3,5(Bu'C = CC = C)3C6H3) with the metallocene sources Cp2Ti(q2-Me3SiC= C%Me3) and Cp2Zr(THF)(q2-Me3SiC= CSiMe3) led to diverse novel organometallic Ti6 72, Zr3 73 and Zr6 complexes depending on the metals, the polyynes and the stoichiometries employed in the conversions. The new complexes were characterised spectroscopically.51 Bd

72

But

73

The reactions of c ~ * ~ M ( q ~ - M e=~CSiMe3) siC (M = Ti, Zr; Cp* = q5CSMeS) with H 2 0 and C 0 2 were studied and compared with those of corresponding Cp2M(L)(q2-Me3SiC= CSiMe3) (M = Ti, L = -; M = Zr, L = THF) to understand the influence of the ligands, Cp and Cp*, and of the metals on the reaction pathways and the obtained products. The reaction of C ~ * ~ z r ( q ~ - M e= ~ CSiMe3) SiC with H 2 0 gives CP*~Z~(OH)C(S~M~~)=CH%Me3. In the reaction of Cp*2Zr(q2-Me3SiC=CSiMe3)with C02, a mononuclear insertion product, a 5-zircona-2-furanone, was formed by coupling of C02 and the acetylene. In contrast, Cp2Zr(THF)(q2-Me3SiC= CSiMe3) by an analogous reaction, yields a dinuclear complex. c ~ * ~ Z r ( q ~ - P=hCSiMe3) C reacts with C02 resulting in a mixture of regioisomeric 5-zircona-2-furanones.

246

Organometallic Chemistry

The Zr-C bond of the latter was hydrolysed to give Cp*2Zr(OH)02CC(SiMe3)=CHPhand Cp*2Zr(OH)02CCPh=CHSiMe3.52 Thermally induced elimination of bis(trimethylsily1)acetylene from its titano2Ti(q2-Me3SiCE CSiMe3)] 74 afforded the cene complex [{ q 5-C5Me4(SiMe3)) stable titanocene [(q5-C5Me4(SiMe3))2Ti''] in high yield under mild condi2Ti11]exhibits paramagnetic line broadening of 'H tions. [{ q5-C5Me4(SiMe3)) NMR signals, although it is silent in EPR spectra down to -196 "C. The solidstate structure determination revealed an exactly parallel arrangement of the cyclopentadienyl rings in [ { q 5-C5Me4(SiMe3))2Ti1'] due to crystallographically imposed symmetry. [ (q5-C5Me4(SiMe3))2Ti1'] reacts with ethylene to give the yellow q2-ethylene complex [{ q5-C5Me4(SiMe3))2Ti(q2-CH2=CH,>I.The structures of 74 and [{ q5-C5Me4(SiMe3)) 2Ti(q2-CH2=CH2)],determined by single-crystal X-ray diffraction, show the bent-titanocene moieties with the q2coordinated Me3SiC= CSiMe3 and CH2=CH2 ligands, respe~tively.~~ Cp2Ti(q2-C60)was synthesised in 29% yield by reaction of Cp2Ti(q2Me3SiC= CSiMe3) with an equimolar amount of fullerene-60 in toluene at room temperature under Ar. An X-ray diffraction study of the complex showed that it has the structure of a titanacy~lopropane.~~ Cp2Ti(q2-Me3SiC= CSiMe3) reacts with B(C,jF5)3 in toluene to give CpTif(q5-C5H4B-(C6F5)(q'-CgF5)2), which was characterised by X-ray crystallography. An ortho fluorine of each of two C6F5 groups coordinates to the titanium centre. Me3SiC = CSiMe3, Me3SiCH2CH2SiMe3and H2 were also formed in the reaction.55

74

75

76

A number of substituted-titanocene-alkynyl-alkenylcomplexes, [(q5C5Me4R'hTi(q'-C = CR2)(q'-(E)-CH=CHR2)] (R' = H, Me, Ph, Bz; R2= CMe3, %Me3,ferrocenyl) 75, were obtained by reacting the corresponding bis(trimethylsily1)ethyne complexes [(q 5-C5Me4R')ZTi( q 2-Me3SiC= CSiMe3)] with 1-alkynes R2C=CH in the dark at 60°C. The complexes undergo a coupling of the carbyl ligands upon exposure to sunlight to give titanocene complexes with 1,4-disubstituted but- l-en-3-ynes, [(q5-C5Me4R')2Ti(3,4-qR2C=CCH=CHR2)] 76. In contrast to A type complexes that do not react further with an excess of tert-butylethyne and (trimethylsily1)ethyne in the dark, 76 induces rapid dimerisation of these terminal alkynes to 2,4-disubstituted but-1-en-3-ynes (head-to-tail dimers). This implies that the known dimerisation of 1-alkynes in the presence of [(q5-C5Me4R')2Ti(q2-Me3SiC= CSiMe3)] (R' = H, Me) performed in diffuse daylight is initiated by 76 originating from photoinduced conversion of the initially formed 75. Titanocene complexes with 2,4-disubstituted but-l-en-3-ynes, [(q5-C5Me4R1)2Ti(3,4-q-

10: Complexes Containing Metal-Carbon o-Bonds

247

R2C= CC(R2)=CH2)] (R' = H, Me, Ph; R2= SiMe3), were also prepared and their participation in the catalytic cycle was dem~nstrated.'~ The synthesis of heterobimetallic {[Ti](C- CR')2}MX (M = Cu, R' = %Me3: X=SCF3; X=SEt; M=Ag, R'=Buf : X=OC(O)Me; X = N 0 3 ; M=Ag, R1 = %Me3: X = OC(O)Me, X = OC(0)Ph; X = NO3} 77 is described. These compounds together with { [Ti](C= CR')2}CuX (R' = SiMe3, X = SC6H4CH2NMe2-2; R' = But, X = SC6H4CH2NMe2-2)can be used for the preparation of a large variety of different organo-copper(1) and -silver(I) species. The titanium-copper complexes { [Ti](CEE CR')2}CuR2 [R' = %Me3: R2 = C6F5; R2 = C6H2(CF3)3-2,4,6; R2 = C,H,Ph,-2,4,6; R' = But: R2= C6HzPh3-2,4,6;R2= Me] are accessibl'e by the reaction of 77 with suitable organic nucleophiles to give 78. Monomeric organo-silver(1) compounds can be prepared by using different starting materials: The heterobimetallic titanium-silver acetylide { [Ti](CZE CSiMe3)(C= CAg)} is formed by nucleophilic substitution of one of the alkynyl Me3Si groups, whereby %Me4is eliminated. Moreover, compounds 77 react with Br2 to produce R2Br along with ([Ti](C = CR')2}MBr (M = Cu; R' = But; R' = SiMe3; M = Ag, R' = %Me3).

The reduction of (q5-CSHS_,Me,)2TiCl2 ( n = O , 4, 5) complexes by Mg metal in THF and in the presence of [(trimethylsilyl)ethynyl]ferrocene or [(phenyl)ethynyl]ferroceneaffords the (qs-CSHS,Me,)2Ti(q2-FcC = CR) complexes [Fc = (q5-CSHS)Fe(qs-C5H4),R = %Me3, Ph] 79. Crystal structures show a titanacyclopropene-like mode of coordination of the acetylenes. Bonding of the acetylenes to the titanocene unit results in a remarkable downfield shift of 13C NMR resonances of the acetylenic C atoms and in a large red shift of the v(C ZE C) wa~enumber.'~ Reaction of { [Ti](CICBU?~} CuCH3{ p i ] = (qs-CSH4SiMe3)2Ti} with 1,l'(q'-CSH4C02H)2Fe gave either heterotrinuclear { [Ti](C= CBut)2}CuO2C(q CSH4)Fe(q5-CSH4CO2H) 80 or the pentametallic complex [([Ti](C = CBut)2}C U O ~ C ( ~ ~ - C ~81, H ~depending ) ] ~ F ~ on the stoichiometric ratio of the reactants. Compound 81 can also be obtained by reacting 80 with one equivalent of 78 (R = Cu, X = Me). When 80 is reacted with a stoichiometric quantity of { [Ti](C= CSiMe3)2}CuMe, the asymmetric complex { [Ti](C= CBu?2}CuO2C(q'-CSH4)Fe(q5-C5H4)CO2Cu{ (Me3SiC= C),[Ti]} was pr~duced.'~ The titanocene(II1) complexe Cp2TiMe(PMe3) is readily synthesised by comproportionation reactions of Cp2Ti(PMe3)2 and Cp2TiX2. The products are characterised by EPR spectrosc~py.~~ The reaction of [CPh3][B(C6F4R)4]with [ C P ' ~ Z ~ H(Cp' ~ ]= ~ CsH4SiMe3)

'-

Organometatlic Chemistry

248 ,But

80

81

'

But

gives the new binuclear hydrido complexes [ C P ' ~ Z ~ ~ H ~ ] [ B ( C (R ~ F=~F, R)~] SiPr'3). The structure of the trinuclear hydride [Cp'5(q ':q5-C5H3SiMe3)Zr3H4]+[B(C6F4SiPr'3)4]- is reported.6o Alkyl zirconocenes [ Z T ( ~ - C ~ H ~ R(R ) ~=X CH2Ph, ~] X = C1, Me; R = CHPh2, X = CI, Me; R = Si(SiMe&, X = C1, Me) and for comparison [Zr(q-C5H5)(qC5H4CH2Ph)CI2]were prepared and characterised. The reactions of these compounds with the methide abstracting reagents B(C6F5)3, B(o-C&5C6F4)3 and [Ph3C]'[B(C6F5)4]- were studied by low temperature NMR spectroscopy. [ z r ( ~ & H ~ c H ~ P h ) ~ Mreacts e ~ ] with [Ph3C]'[B(C6F5)4]- to form homodinuclear [ (Zr(q-C5H4CH2Ph)2Me} 2(p-Me)]+[B(C6F5)4]-. The related compound [{ Zr(C5H4CH2Ph)2Me} 2(p-Me)]'[MeB(C6F5)3]- was formed from the reaction of [Zr(q-C5H4CH2Ph)2Me2]with 0.5 equivalents of B(C6F5)3. Reaction between [Zr(q-C5H4CH2Ph)2Me2]and one equivalent B(C6F5)3 gave [Me(q-C5H4CH2Ph)2Zr(p-Me)B(C6F5)3]and the ion pair [Zr(q-C5H4CH2Ph)2Me][MeB(C6F5)3], which are in equilibrium with each other.61 Isotopically labelled alkyl zirconocene complexes (CpR,)2Zr(CH2CDR'2)(X) (CpR, = alkyl-substituted cyclopentadienyl; R' = H, alkyl group; X = H, D, Me) undergo isomerisation of the alkyl ligand as well as exchange with free olefin in solution under ambient conditions. Increasing the substitution on the Cp ring results in slower isomerisation reactions, but these steric effects are small. In contrast, changing X has a very large effect on the rate of isomerisation. Pure o-bonding ligands such as Me and hydride promote rapid isomerisation, whereas .n-donor ligands inhibit P-H elimination and hence alkyl isomerisation. For ( ~ l ~ - C ~ H ~ ) ~ z r ( Rinternal > ( c l ) , alkyl complexes were observed for the first time. The rate of isomerisation depends on the length of the alkyl group: longer alkyl chains (heptyl, hexyl) isomerise faster than shorter chains (butyl). The transient intermediate species were identified by a combination of isotopic labelling and 'H, 2H and 13C NMR experiments. The solidstate structure of the zirconocene cyclopentyl chloride complex 82, Cp2Zr(cyclo-C5H9)(C1),was determined by X-ray diffraction.62 Substantial Zr-alkyl group (R) effects on ion pair thermodynamic stability as well as on ion pair solution structure and structural dynamics are reported in the [(1 ,2-Me2Cp)2ZrR]+[CH3B(C6F5)3]-series, where R = Me, CH2CMe3, CH2SiMe3 and CH(SiMe3)z. These quantitative results underscore the effects such R moieties are likely to play in Group 4 metallocene-mediated olefin polymerisation catalysis.63 Reaction of the bridged (dimethylsilanediy1)dicyclopentadienyl dilithium

10: Complexes Containing Metal-Carbon

0-

Bonds

249

salt [(SiMe2)(C5H4)2Li2]with MC14, in toluene, gave the Zr and Hf complexes [M{(SiMe2)(q5-C&)2}C12] (M = Zr, Hf). Addition of two equivalents of M'R (M' = MgC1, R = Me; M' = Li, R = CH2CMe2Ph; M' = MgBz, R = CH2Ph) to toluene or diethyl ether solutions of [M { (SiMe2)(q5-C5H4)2> C12] afforded the dialkyl derivatives [M((SiMe2)(qS-C~H4)2}R2](R = Me, M = Zr, Hf; R = CH2CMe2Ph, M = Zr, Hf; R = CHZPh, M = Zr) 83. [Zr{(SiMe2)(q5C5H4)2)C12]reacted with LiMe and Mg(CH2Ph)2(THF)2in the presence of a stoichiometric amount of H20 to give the p-0x0 derivatives [Zr{(SiMe2)(q5C5H4)2)R]2(p-0) (R = Me, CH2Ph). The X-ray molecular structure of [Zr{ (SiMe2)(q'-CSH4)2} (CH2Ph)I2(p-0) was determined by diffraction methods. Its most remarkable feature is the planarity of the Bz-Zr-0-Zr-Bz and the linearity of the Zr-0-Zr systems.@

82

84

83

85

A series of permethylated [Me2Si] ansa bridged titanocene complexes has been synthesised and structurally characterised by X-ray diffraction; the dialkyl complexes [Me2Si(C5Me4)]TiR2 are thermally unstable towards elimination of alkane (RH), thereby yielding fulvene derivatives [Me2Si(C5Me4)(CsMe3CH2)ITiR P-bridged ansa-metallocene complexes of Ti, Zr and Hf, [PhP(C5Me4)2]MX2 and [Ph(E)P(C5Me4)2]MX2(X=Me, CO, E = O , S, Se) 85, were synthesised. Structural characterisation by X-ray diffraction indicates that, in comparison to their non-ansa counterparts (C5Me5)2MX2,the cyclopentadienyl groups in P-bridged complexes are displaced from symmetric q 5-coordination toward q3-coordination. Such q3,q3-coordination creates more electrophilic metal centres than those in their permethylcyclopentadienylcounterparts, as judged by the v(C0) stretching frequencies of the Zr dicarbonyl complexes Cp*2Zr(C0)2 (1946 and 1853 cm-') and [PhP(C5Me4)2]Zr(C0)2(1959 and 1874 cm- 1).66 In contrast to reactions of the bis(pentamethylcyclopentadieny1)titanium system, substituted allyl complexes of the electron-rich bis(2-piperidinoindenyl)titanium(IrI) template, e.g. 86 (R = Ph, Me) are converted into 2,3disubstituted titanacyclobutane complexes, e.g. 87 (R = Me, Ph; R' = Pr', cyclohexyl, Bu? by free radical alkylation at the allyl central carbon.67

fp-: F

L? ! e ; I 3

R'X

____)

Qk 86

a N+

?

-

R 87

Ni3

250

Organometallic Chemistry

Trimethylphosphine stabilised ethylene complexes, 88, of the ethylenebisindenyl-supported zirconocene fragment are prepared via magnesium reduction of rac-(EBI)ZrC12 in the presence of ethylene and PMe3. When the reaction is halted after 6 h, good yields of a mixture containing rac-(EBI)Zr(q2CH2=CH2)PMe3,rac-88 and the racemic diastereomer of the zirconacyclopentane derivative (EBI)Zr(q2-CH2CH2CH2CH2),rac-89, are obtained. This mixture may be converted into pure rac-88 if treated with excess PMe3. If the magnesium reduction of rac-(EBI)ZrC12 is left for three days in the presence of magnesium chloride, complete epimerisation to rneso-88 is observed. Thus,

both diastereomers of 88 are available. The coordinated ethylene ligands in compounds 88 are susceptible to electrophilic attack by the pentafluorophenylsubstituted boranes HB(C6F5)2and B(C6F5)3, forming zwitterionic metallocene products. For reactions involving HB(C6F5)2, the products meso-90 and rac-90 are characterised by a strong zirconium-hydrido borate interaction, as well as a weak Zr-Cp bonding. Upon treatment of rac-90 with B(C6F&, a more chargeseparated zwitterion, rac-91, was formed. In addition to retaining its PMe3 ligand, the complex is stabilised by a strong P-CH;! interaction, as determined by X-ray crystallography and NMR spectroscopy.68 Treatment of the ansa-metallocene dichloride rac-Me2Si(C5H3Me)ZrC12

with 'butadiene-magnesium' gave a 82:8: 10 mixture of the respective (s-transq4-butadiene)metallocenes and the (s-cis-butadiene)Me2Si(CsH3Me)2Zr isomer 92. One of the (s-trans-diene)metallocene isomers was characterised by X-ray diffraction. The bond lengths and angles are to be regarded as typical for (s-trans-q4-butadiene)Group 4 metallocene complexes.69 Treatment of the (s-cis-q4-butadiene) complex 92 with B ( C ~ F Sgives ) ~ an ansa-metallocene-(p-C&)-B(C6F5)3 betaine, which was characterised by Xray diffraction and showed a distorted (o,z-type) ally1 ligand, bonded to zirconium, that bears a syn-oriented CH2B(C6F5)3 substituent. An ortho C-F

10: Complexes Containing Metal-Carbon a-Bonds

25 1

substituent of one of the C6F5 groups at boron coordinates to the electrondeficient zirconium centre. Of particular note from this paper is the observation that the first propene insertion reaction at the rac-[Me2Si(1-inden~l)~]Zr derived single-component Ziegler catalyst system is not stereoselective, whereas all subsequent propene insertion steps show a high degree of stereose~ectivity.~' The complex (Cp2Zr)2(p-NHBut)(p-N=CH2)was obtained when the stoichiometric reaction between Cp2(THF)Zr=NBu' and PhCH=NMe was carried out. The crystal structure of (Cp2Zr)2(p-NHBu3(p-N=CH2)shows two Cp2Zr fragments bridged in a moderately symmetric fashon by a -NHBut group, and in an extremely asymmetric fashion by a -N=CH2 (methyleneamido) group. The methyleneamido fragment exhibits an unusual coordinationomode: it is bound to one Zr atom in a linear fashion (LZrl-Nl-C21=176.9(6)) and to the second Zr atom (Zr2) in a side-on fashion.71 The structures of novel complexes resulting from one- and two-step [2 + 21 cycloaddition reactions of four Group 4 imides with the phosphaalkyne BdCP are described. Thus, treatment of the transient imide complex, [Zr(q5C&15)2(NC6H3Me2-2,6)], prepared from the thermolysis of [Zr(q5C5H5)2(NC6H3Me2-2,6)2] with an excess of Bu'CP in toluene at 100°C for 48 h, yielded the orange crystalline complex [Zr(q5-C5H5)2(PCBu'NCgH3Me22,6)]. A single crystal X-ray diffraction study on [Zr(q5-C5H&(PCButNC6H3Me2-2,6)]established that its molecular structure contains the four-membered planar metalacycle resulting from the [2+2] phosphaalkyneimide cycloaddition, in which the phosphorus is bonded to the nitrogen of the imide function, consistent with the bond polarity of the unsaturated reactive sites.72 Unprecedented Zr(I1) complexes bearing tethered olefin-phosphine ligands were synthesised and characterised. For example, n-butyllithium was added to a solution of Cp2ZrC12 in THF at -78°C and stirred for 1 h. 4(Dipheny1phosphino)-1-butene was then added and the mixture was warmed to room temperature and stirred for 1 h, giving Cp2Zr(CH2=CH(CH2)2PPh2) in 82% yield. The molecular structures of the newly synthesised complexes (q 5- 1,2-Me2C5H3)2Zr(CH2=CHCH2CH2PPh2) and Cp2Zr(CH2=CHCH2CH2CH2PPh2)were determined by single-crystal X-ray diffraction methods. The stability and reactivity of complexes Cp2Zr(CH2=CH(CH2)nPR2)(n = 2, 3; R = Et, Ph) were examined. The complex Cp2Zr(CH2=CHCH2CH2CH2PPh2) showed simultaneously both sufficient stability and high reactivity .73 Phosphinozirconocene complexes 93 react with isocyanides to give tricyclic P-phosphino imines 94 and 95 through three successive and controlled steps. Spectroscopic and chemical evidence for the formation of the first neutral qlimine zirconocene complexes in the reductive elimination reaction sequence is presented. Formal [3+2] cycloaddition reactions between the a-phosphino zirconaindene 93 and various cumulenes [COZ, CS2, CyN=C=NCy (Cy = cyclohexyl), RN=C=S (R = Me, Ph), RN=C=O (R = Ph, Bu?] afford stable zwitterionic monomeric five-coordinated anionic bis(cyclopentadieny1) zirco-

252

Organometallic Chemistry

nium complexes, e.g. 96 and 97, of which single-crystal X-ray structures are reported. A related bis zwitterionic zirconocene complex is prepared through the reaction of carbon disulfide with the tricyclic a-phospholane zirconaindane; in this case cycloaddition reactions take place on the two carbon-sulfur double bonds of CS2. Formal [3+2] cycloaddition reactions between various aldehydes and 2-phosphino-1-zirconaindene 93 lead to stable anionic zwitterionic zirconocene complexes 98. Extension of this method to the reaction of internal or terminated aldehyde containing dendrimers with 93 allows the preparation of the first dendrimers and multidendritic macromolecules containing zwitterionic [phosphonium anionic zirconocene(rv)] comp~exes.~~ H

d 95

A convergent route to allylzirconocene reagents by insertion of silylsubstituted carbenoids LiCR(SiMe3)(Cl) into vinylzirconocene chlorides is reported. The product silylated allylzirconocenes react with aldehydes and ketones with high anti-selectivity to afford vinyl- (R = H) or allyl- (R = Me, Pr) silanes which may be converted into 4,5-trans-disubstituted y-lactones and stereodefined d i e n e ~ . ~ ~ 1,l-Dihalo-1-1ithio species (halo carbenoids) undergo double insertion into the C-Zr bonds of a zirconacyclopentane to give 99 or zirconacyclopentene to produce, after hydrolysis, bicyclo[3.3.0]octanesand bicyclo[3.3.0]octenes.78 The cuboctameric hydroxysilsesquioxane ( C - C ~ H ~ ) ~ S ~ ~ Oobtained ~~(OH), after hydrolysis of ( C - C ~ H ~ ) ~ S and ~~O triphenylsilanol ~~C~, have been applied as model supports for silica-grafted olefin polymerisation catalysts. The ligands were introduced on Group 4 metals by either chloride metathesis or protonolysis. Protonolysis of Cp”MR3 with the silanol (c-C5H9)7Si8O12(OH) and Ph3SiOH yielded the corresponding silsesquioxane bis(alky1) complexes C~”[(C-C~H~)~S&O (R~=~CH2Ph) ] T ~ R ~and triphenylsiloxy bis(alky1) compounds Cp”[Ph3SiO]MR2(M = Ti, R = CH2Ph, Me; M = Zr, R = CH2Ph) and the monobenzyl complex Cp”[Ph3Si0]2ZrCH2Ph.79 Reaction of P b M (M=Zr, Hf) with CsH5BPMe3 in C6D6 gave

10: Complexes Containing Metal-Carbon a-Bonds

99

253

100

( C S H S B C H ~ P ~ ) M ( C H100, ~ P ~whereas )~ similar reaction with Zr(NMe& gave (CSH5BNMe2)Zr(NMe2)3 .80

References 1. 2.

3.

4. 5. 6. 7. 8. 9.

10. 11.

12. 13. 14. 15.

16. 17. 18. 19. 20. 21. 22.

Topics Catal., 1999,7. D. W. Stephan, F. Guerin, R. E. V. Spence, L. Koch, X. L. Gao, S. J. Brown, J. W. Swabey, Q. Y. Wang, W. Xu, P. Zoricak and D. G. Harrison, Organometallics, 1999,18,2046. M. G. Thorn, Z. C. Etheridge, P. E. Fanwick and I. P. Rothwell, J. Organomet. Chem., 1999,591,148. M. G. Thorn, P. E. Fanwick and I. P. Rothwell, Organometallics, 1999,18,4442. B. Schweder, H. Gorls and D. Walther, Inorg. Chim. Acta, 1999,286, 14. E. Gielens, T. W. Dijkstra, P. Berno, A. Meetsma, B. Hessen and J. H. Teuben, J. Organomet. Chem., 1999,591,88. M. G. Thorn, P. E. Fanwick, R. W. Chesnut and I. P. Rothwell, Chem. Commun., 1999,2543. L. A. Kotenvas, J. C. Fettinger and L. R. Sita, Organometallics, 1999,18,4183. K. Kincaid, C. P. Gerlach, G. R. Giesbrecht, J. R. Hagadorn, G . D. Whitener, A. Shafir and J. Arnold, Organometallics, 1999,18, 5360. J. B. Love, H. C. S. Clark, F. G. N. Cloke, J. C. Green and P. B. Hitchcock, J. Am. Chem. SOC.,1999,121,6843. M. J. Sarsfield, M. Thornton-Pett and M. Bochmann, J. Chem. Soc., Dalton Trans., 1999,3329. R. R. Schrock, L. C. Liang, R. Baumann and W. M. Davis, J. Organomet. Chem., 1999,591,163. R. Baumann, R. Stumpf, W. M. Davis, L. C. Liang and R. R. Schrock, J. Am. Chem. SOC.,1999,121,7822. R. R. Schrock, R. Baumann, S. M. Reid, J. T. Goodman, R. Stumpf and W. M. Davis, Organometallics, 1999,18, 3649. M. A. Flores, M. R. Manzoni, R. Baumann, W. M. Davis and R. R. Schrock, Organometallics, 1999,18,3220. L. C . Liang, R. R. Schrock, W. M. Davis and D. H. McConville, J. Am. Chem. SOC.,1999,121, 5797. R. R. Schrock, S. W. Seidel, Y. Schrodi and W. M. Davis, Organometallics, 1999, 18,428. D. D. Graf, R. R. Schrock, W. M. Davis and R. Stumpf, Organometallics, 1999, 18, 843. D. P. Steinhuebel and S. J. Lippard, Inorg. Chem., 1999,38, 6225. D. P. Steinhuebel and S. J. Lippard, J. Am. Chem. Suc., 1999,121, 11762. D. P. Steinhuebel and S. J. Lippard, Organometallics, 1999, 18, 109. D. P. Steinhuebel and S. J. Lippard, Organometallics, 1999,18, 3959.

254

Organometallic Chemistry

23.

R. Crescenzi, E. Solari, C. Floriani, N. Re, A. Chiesi-Villa and C. Rizzoli, Organometallics, 1999,18, 606. L. Bonomo, G. Toraman, E. Solari, R. Scopelliti and C. Floriani, Organometallics, 1999, 18, 5198. S. W. Ewart, M. J. Sarsfield, E. F. Williams and M. C. Baird, J. Organomet. Chem., 1999,579, 106. J. Sassmannshausen, A. K. Powell, C. E. Anson, S. Wocadlo and M. Bochmann, J. Organomet. Chem., 1999,592, 84. L. H. Doerrer, M. L. H. Green, D. Haussinger and J. Sassmannshausen, J. Chem. Soc., Dalton Trans., 1999,2111. M. L. H. Green and J. Sassmannshausen, Chem. Commun., 1999,115. J. S. Rogers, R. J. Lachicotte and G. C. Bazan, Organometallics, 1999, 18, 3976. R. Gomez-Garcia and P. Royo, J. Organomet. Chem., 1999,583,86. D. W. Stephan, J. C. Stewart, F. Guerin, R. Spence, W. Xu and D. G. Harrison, Organometallics, 1999,18, 1116. F. Guerin and D. W. Stephan, Angew. Chem., Int. Ed., 1999,38,3698. A. V. Firth, J. C. Stewart, A. J. Hoskin and D. W. Stephan, J. Organomet. Chem, 1999,591,185. R. Gomez, P. Gomez-Sal, P. A. del Real and P. Royo, J. Organomet. Chem., 1999,588,22. J. Pflug, A. Bertuleit, G. Kehr, R. Frohlich and G. Erker, Organometallics, 1999, 18, 3818. J. Okuda, T. Eberle, T. P. Spaniol and V. Piquet-Faure, J. Organomet. Chem., 1999,591, 127. M. D. Fryzuk, L. Jafarpour and S. J. Rettig, Organometallics, 1999,18,4050. M. D. Fryzuk, P. B. Duval, S. Mao, M. J. Zaworotko and L. R. MacGillivray, J. Am. Chem. Soc., 1999,121,2478. M. D. Fryzuk, P. B. Duval, S. Mao, S. J. Rettig, M. J. Zaworotko and L. R. MacGillivray, J. Am. Chem. Soc., 1999,121, 1707. K. Klass, L. Duda, N. Kleigrewe, G. Erker, R. Frohlich and E. Wegelius, Em-. J. Inorg. Chem., 1999, 1 1. J. Wonnemann, M. Oberhoff, G. Erker, R. Frohlich and K. Bergander, Eur. J. Inorg. Chem., 1999, 1111. U. Blaschke, F. Menges, G. Erker and R. Frohlich, Eur. J. Inorg. Chem., 1999, 621. U. Blaschke, G. Erker, R. Frohlich and 0. Meyer, Eur. J. Inorg. Chem., 1999, 2243. W. Ahlers, G. Erker, R. Frolich and U. Peuchert, J. Organomet. Chem., 1999, 578, 115. J. Pflug, R. Frohlich and G. Erker, J. Chem. Soc., Dalton Trans., 1999,2551. G. J. Pindado, M. Thornton-Pett, M. B. Hursthouse, S. J. Coles and M. Bochmann, J. Chem. Soc., Dalton Trans., 1999,1663. M. Horacek, P. Stepnicka, R. Gyepes, I. Cisaroca, M. Polasek, K. Mach, P. M. Pellny, V. V. Burlakov, W. Baumann, A. Spannenberg and U. Rosenthal, J. Am. Chem. SOC.,1999,121,10638. P. M. Pellny, F. G. Kirchbauer, V. V. Burlakov, W. Baumann, A. Spannenberg and U. Rosenthal, J. Am. Chem. Soc., 1999,121,8313. P. M. Pellny, F. G. Kirchbauer, V. V. Burlakov, A. Spannenberg, K. Mach and U. Rosenthal, Chem. Commun., 1999,2505.

24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45, 46. 47.

48. 49.

10: Complexes Containing Metal-Carbon a-Bonds 50. 51.

52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77.

255

P. M. Pellny, V. V. Burlakov, N. Peulecke, W. Baumann, A. Spannenberg, R. Kempe, V. Francke and U. Rosenthal, J. Organomet. Chem., 1999,578,125. P. M. Pellny, V. V. Burlakov, W. Baumann, A. Spannenberg, R. Kempe and U. Rosenthal, Organometallics, 1999,18,2906. P. M. Pellny, V. V. Burlakov, W. Baumann, A. Spannenberg and U. Rosenthal, 2. Anorg. Allg. Chem., 1999,625,910. M. Horacek, V. Kupfer, U. Thewalt, P. Stepnicka, M. Polasek and K. Mach, Organometallics, 1999,18, 3572. V. V. Burlakov, A. V. Usatov, K. A. Lyssenko, M. Y. Antipin, Y. N. Novikov and V. B. Shur, Eur. J. Inorg. Chem., 1999, 1855. V. V. Burlakov, S. I. Troyanov, A. V. Letov, E. I. Mysov, G. G. Furin and V. B. Shur, Russ. Chem. Bull., 1999,48, 1012. P. Stepnicka, R. Gyepes, I. Cisarova, M. Horacek, J. Kubista and K. Mach, Organometallics, 1999,18,4869. P. Stepnicka, R. Gyepes, I. Cisarova, V. Varga, M. Polasek, M. Horacek and K. Mach, Organometallics, 1999,18, 627. W. Frosch, S. Back and H. Lang, Organometallics, 1999,18,5725. L. J. Hao and J. F. Harrod, Inorg. Chem. Commun., 1999,2,191. A. G. Carr, D. M. Dawson, M. Thornton-Pett and M. Bochmann, Organometallics, 1999,18,2933. M. Bochmann, M. L. H. Green, A. K. Powell, J. Sassmannshausen, M. U. Triller and S . Wocadlo, J. Chem. SOC.,Dalton Trans., 1999,43. P. J. Chirik, M. W. Day, J. A. Labinger and J. E. Bercaw, J. Am. Chem. SOC., 1999,121,10308. C. L. Beswick and T. J. Marks, Organometallics, 1999,18,2410. T. Cuenca, P. Gomez-Sal, C. Martin, B. Roy0 and P. Royo, J. Organomet. Chern., 1999,588,134. H. Lee, J. B. Bonanno, T. Hascall, J. Cordaro, J. M. Hahn and G. Parkin, J. Chem. SOC.,Dalton Trans., 1999, 1365. J. H. Shin, T. Hascall and G. Parkin, Organometallics, 1999,18,6. C. A. G. Carter, R. McDonald and J. M. Stryker, Organometallics, 1999,18, 820. L. W. M. Lee, W. E. Piers, M. Parvez, S. J. Rettig and V. G. Young, Organometallics, 1999,18, 3904. M. Dahlmann, G. Erker, R. Frohlich and 0. Meyer, Organometallics, 1999, 18, 4459. M. Dahlmann, G. Erker, M. Nissinen and R. Frohlich, J. Am. Chem. SOC.,1999, 121,2820. R. L. Zuckerman, S. W. Krska and R. G. Bergman, J. Organomet. Chem., 1999, 591,2. F. G. N. Cloke, P. B. Hitchcock, J. F. Nixon, D. J. Wilson and P. Mountford, Chem. Commun., 1999,661. A. Yamazaki, Y. Nishihara, K. Nakajima, R. Hara and T. Takahashi, Organometallics, 1999,18, 3105. V. Cadierno, M. Zablocka, B. Donnadieu, A. Igau, J. P. Majoral and A. Skowronska, J. Am. Chem. SOC.,1999,121,11086. V. Cadierno, M. Zablocka, B. Donnadieu, A. Igau and J. P. Majoral, Organometallics, 1999,18, 1882. V. Cadierno, A. Igau, B. Donnadieu, A. M. Caminade and J. P. Majoral, Organometallics, 1999,18, 1580. A. N. Kasatkin and R. J. Whitby, Tetrahedron Lett., 1999,40,9353.

256

Orgunometallic Chemistry

78. 79.

N. Vicart and R. J. Whitby, Chem. Commun., 1999,1241. R. Duchateau, U. Cremer, R. J. Harmesen, S. I. Mohamud, H. C. L. Abbenhuis, R. A. van Santem, A. Meetsma, S. K.-H. Thiele, M. F. H. van To1 and M. Kranenburg, Orgunometallics, 1999,18,5447. J. S. Rogers, R. J. Lachicotte and G. C . Bazan, Orgunometallics, 1999,18, 3976.

80.

Part 11: Group 5 by Elizabeth M. Page 1

Reviews

The chemistry of biscyclopentadienyl hydride derivatives of niobium and tantalum has been reviewed.' The syntheses, reactivity and spectroscopic properties are discussed, the latter being influenced mainly by the nature of the Cp ring and the metal centre. Elimination reactions of the H2 unit and insertion reactions into the M-H bond are of interest to the field of organic synthesis. Complexes of the type Cp2MH(olefin)have been widely investigated as they provide good models for the study of beta-elimination reactions and the reverse olefin insertion process. A review has appeared of the coordination chemistry of vanadium as related to its biological functiom2 The review describes the binding of vanadium to protein side-chains, modelled by complexes with varying ligand sets which mimic possible intermediates and structures in vanadium-nitrogenase, vanadium-dependent haloperoxidases and other reactions. A comprehensive review of the literature of the past decade has been published presenting many aspects of niobium chemistry relating to the preparation, characterisation and application of niobium complexes in heterogeneous catalysis.

2

Alkyl Complexes

A new potent ethylene polymerisation catalyst, (2,6-bi~[2,6-('Pr)~PhN=C(Me)]2(2-MeC~H3N)}VC12.0.5(toluene) has been produced. Further reaction of the complex with strong alkylating agents such as MeLi occurs at the pyridine ring to either remove the Me group or place an additional Me group on the ring meta-position. Both processes must involve two-electron reduction of the metal centre with the formation of the V(1) derivatives {2,6-bis[2,6-('Pr)zPhN=CMe]2(C,H,N)>V(CH3)(p-CH3)[Li(Et,0)3 and the ionic (2,6-bis[2,6(iPr)2PhN=CMe]2(2,3-Me2C,H3N)}V(CH3)2][Li(THF)2(TMEDA)~].O. 5(Et20). The structures of both compounds were determined crystallographically. In contrast to the extensive chemistry of alkyltantalumchlorides very little work has been published on the corresponding alkylfluorides. A study has been made of convenient synthetic routes to different types of alkyltantalumfluorides by halogen exchange reactions using trimethyltin fluoride as a fluorine source. The results showed the reactions to be highly dependent upon the number of organic ligands on the Ta atom as well as the electronic and

10: Complexes Containing Metal-Carbon

0-Bonds

257

steric nature of the substituents. Complexes of general formula (RCH2)3TaF2 (R = Ph, p-Tol, Me3Si) and the first alkyltantalum tetrafluoride, (Me3Si)2CHTaF4(1) have been reported. The structure of (1) consists of zigzag chains of (Me3Si)2CHTaF4 units connected by bridging fluorine atoms, thus resulting in Ta atoms in slightly distorted octahedral environments.'

1

Dimeric tantalum alkyl and aryl derivatives, [Ta2{ p-ptBu-calix[4]-(0)4}2R2] (R = alkyl or aryl), have been obtained by alkylation of p a 2{ p-p-'Bu-calix[4](0)4}2C12] by standard procedures. The complexes are in equilibrium with the monomeric species in solution. Alternatively the monomers can be prepared by pyridine assisted demethylation of [TaIp-'B~-calix[4]-(OMe)(O)~} R2] obtained by alkylation of [Ta(p-'Bu-calix[4]-(OMe)(0)3}C12]. The monomeric alkyls undergo migratory insertion reactions with CO and 'BuNC to give the corresponding q2-ketonesand q2-imines.6

3

Alkylidene Complexes

The [Nb'I1=Nb1''] dimer [(p-'B~-calix[4]-(0)~} 2Nb2Na2]has been found active in the synthesis of niobium alkylidene complexes via reaction with ketones and aldehydes. The complexes formed, [(p-tBu-calix[4]-(0)4}Nb=CRR']Na, (R=Ph, Cp2Fe, "Pr; R'=Ph, Me, H, CH2Ph; RR'=(CH2)4) are easily separated from the oxoniobium(V) product [ Ip-tBu-calix[4]-(0)~}~Nb=ONa] thus affording a useful synthetic route to Nb alkylidene complexes. The alkylidene [(p-tBu-calix[4]-(0)4}Nb=CPhH]Na undergoes a reversible protonation and deprotonation reaction yielding the corresponding benzyl derivative [ (p-'B~-calix[4]-(0),}2Nb-CH2Ph] and the bridging alkylidyne [ (p-'Bucalix[4]-(O), } 2Nb2( p-PhC),Na4]. The T a m trimethyl complex [P2N*]TaMe3 (2), ([P2N2] = PhP(CH2SiMezNSiMe2CH2)2PPh) has been obtained by reaction of [P2N2]Li2.C4H802 (C4HsO2 = 1,4-dioxane) with TaMe3C12. The X-Ray crystal structure of (2) shows that it consists of a seven-coordinate capped trigonal prism. UV photolysis of (2) yields [P2N2]Ta=CHZ(Me) (3) with the elimination of

258

Organometallic Chemistry

methane. The geometry of this complex is intermediate between octahedral and trigonal-prismatic. In solution the double bonded methylidene moiety was shown by variable-temperature NMR studies to exibit fluxional behaviour with a barrier of 33.5 f.0.6 kJ mol-'.8

3

2

Scheme 1

10: Complexes Containing Metal-Carbon a-Bonds

259

Pl8)

4

S

In an analogous study to that carried out on dialkylzirconocenes the reactions of the methyl methylene complex Cp2Ta(=CH2)CH3, with HB(C6F5)2have been reported. Results from the zirconocene systems show that electrophilic attack on these hydrocarbyl ligands occurs at the sterically more accessible portions of the HOMO. In Cp2Ta(=CH2)CH3the HOMO is comprised mainly of the Ta methylene n: bond and attack of electrophiles is expected to occur in an analogous manner. It was found that reactions of Cp2Ta(=CH2)CH3with HB(C6F& are dependent upon the conditions employed and the ratio of borane used. Direct reaction with two equivalents of HB(C6F5)Z in toluene at RT gave the fully characterised dihydride (4). Reaction of Cp2Ta(=CH2)CH3with one equivalent of borane in toluene followed by ‘BuNC (Scheme 1) leads ultimately to Cp2Ta(=C=N‘Bu )(CH2B(C6F5)2)(5). Observations from both sets of reactions suggest that the borane ligand attacks the endo face of the Ta=CH2 unit. In Scheme 1 the second borane is then thought to engage in an alkyllhydride exchange with the Ta-CH3 group with the accompanying liberation of methane.g Similar reactions have been investigated involving attack of pyridine Noxides on the methylidene Ta complex [ T O ~ C ( N S ~ M ~ ~ ) ~ ] ~ T ~ (InCthe H~)CH~. (CH one ~ )equivalent CH~ of pyrireaction between [ T o ~ C ( N S ~ M ~ ~ ) ~ ] ~ T ~and dine N-oxide at RT the methylene group is transferred regioselectively to the pyridine N-oxide to leave the tantalum 0x0 complex [ T ~ l c ( N S i M e ~ ) ~ l ~ Ta(O)CH3 and methylpyridine (equation (i)). Reactions of the structurally similar nitrones (RR’C=N(O)R’’) with [ T o ~ C ( N S ~ M ~ ~ ) ~ ] ~ T ~were (CH~)CH~ also investigated. When heated to 45 “C for 40 h N-tert-butyl-a-phenylnitrone undergoes reaction with [ T o ~ C ( N S ~ M ~ ~ ) ~ ] ~ T ~ (to CH produce ~ ) C H ~styrene and an organometallic complex formulated as [ T o ~ C ( N S ~ M ~ ~ ) ~ ] ~ T ~ ( O ) (N‘BuMe) on the basis of NMR, IR and mass spectroscopic techniques (equation (ii)). The reaction is thought to proceed in the same manner to that with the pyridine oxides in which the oxide moiety first forms a Lewis acidbase adduct at the Ta centre.”

Organometallic Chemistry

260 0

equation (i)

equation (ii)

4

Alkyne Complexes

New niobocene alkyne complexes [Nb(q5-C~H4SiMe&(Cl)(q2( C, C)R’CECR’’)] have been prepared by reaction of Nb(q 5-C5H4SiMe3)2Clwith the diynes R-CEC-CEC-R (R = SiMe3 or Ph) and 1,Shexadiyne. The enyne C,C)-R'Cr CR") containing niobocene complexes Nb(q5-C5H4SiMe3)2Cl(q2( have been prepared in a similar manner by reaction of Nb(q s-C5H4SiMe3)2C1 with the appropriate enyne reagent. The X-ray structures of [Nb(q5-C5H4SiC,C)-PhC-CC=CPh’)] (6) and [Nb(q5-CSH4SiMe3)2(C1)(q2Me3>2(C1)(q2( (C,C)-PhC=CCH2CH=C(CH&)] (7)have been reported.”

6

7

The same group have synthesised the novel lithium compound [(Li(H20)(bdmpza)>4] (8) (bdmpza = bis(3,5-dimethylpyrazoly-l-yl)acetate) and tested its coordinative ability with niobium complexes. The compound is an example of a ‘scorpionate’ ligand analogous to tris(pyrazoly1)borate and capable of facially-coordinating metal centres. The lithium compound (8) was found to react at RT with [NbC13(dme)(PhC=CMe)] in THF to give the complex [NbC12(bdmpza)(PhC=CMe)) (9). The ‘H NMR spectrum of the

10: Complexes Containing Metal-Carbon o-Bonds

261

complex was found to exhibit two resonances for each of the different pyrazole protons indicating that the two rings from the ligand are non-equivalent. The X-ray crystal structure of (9) showed the Nb atom to be in an octahedral environment surrounded by an N, N, 0-coordinated 'scorpionate' ligand, an alkyne group and two chloride ligands.12

4

8

1,

9

\-I

Nitrile adducts of the type Tp*Nb(CO)(PhC-CMe)(RC=N) (Tp* = hydridotris(3,5-dimethylpyrazolyl)borate) have been prepared by CO displacement from Tp*Nb(C0)2(PhCrCMe). X-ray crystallography and NMR studies showed both the nitrile and the alkyne ligands to act as q3 donors in an unprecedented fashion. Thermal displacement of PhCrN from Tp*Nb(CO)(PhCrCMe)(PhC-N) by PMe2Ph or PhCECMe gives Tp*Nb(CO)(PhC=CMe)(PMezPh) or Tp*Nb(CO)(PhCrCMe)2. Protonation of Tp*Nb(CO)(PhCrCMe)(EtCrN) with HBF4 was studied and was found to induce nitrile/alkyne coupling to give the niobacycle Tp*NbF[CPhCMeCPhNH] via an 2-iminoacyl alkyne cation which was isolated and characterised by NMR. l 3 The d2-d2 homobimetallic complex ( c p ~ V ) ~q(:4q 3 -Me3SiC-C-C=CCrCSiMe3) (10) has been synthesised from Me3SiCrC-C-C-CKSMe3 and Cp2V and has been characterised by X-ray crystallography and magnetic measurements from 300-2 K. Unusually the vanadium atom is in the +3

262

Organometallic Chemistry

oxidation state. The two vanadocene moieties are attached to both internal C atoms of the triyne giving a near linear -C-CrCSiMe3 unit. The reactivity was unexpected due to the odd parity of the number of C r C bonds in Me3SiC-CC=C-C=CSiMe3. 14

10

The reactivity of three Ta dihydride aryloxide complexes towards olefins and alkynes has been investigated and was found to be highly dependent upon the nature of the ancillary aryl oxide ligand. [Ta(OC&Ph2-2,6)2(H)2Cl(PMe,>,l reacts with styrene to produce one equivalent of ethylbenzene and the adduct fra(OC6H3Ph2-2,6)2(q2-CH2=CHPh)CI(PMe3)] (11). With 3-hexyne the same compound forms the analogous alkyne complex, [Ta(OC6H3Ph2-2,6)2(r2EtC=CEt)Cl(PMe3)] (12), by elimination of H2. The structures of (11) and (12) show them to have square planar geometry with an axial olefin (alkyne) unit lying along the C1-Ta-P axis . The parameters around the Ta atoms suggest a tantalum cyclopropane(cyc1opropene) bonding geometry. Reaction of styrene with the dihydride [Ta(OC6HiPr2-2,6]2(H)2C1(PMe2Ph)2] yields the dihydrogenation product [Ta(OC6H~Pr2-q2CMe=CH2)(0C6H~Pr2-2,6)Cl(PMe2Ph)2] (13) along with PhEt and hygrogen. The 2,6-di-tert-butylphenoxidecompound [T~(OC~H~~BU~-~,~)~(H)~C~(PM~P~~)] undergoes reaction with styrene to give the mono-cyclometallated complex [Ta(OCsH3’BuCMe2CH2)(Oc6~~Bu22,6)(CH2CH2Ph)C1]whose structure was also determined.l5 Olefin insertion and reductive elimination reactions of [MezSi(CsMe4)2]TaH3 and [Me2Si(C5Me&]Ta(q2-C2H4)H have been compared with those of their permethyltantalocene counterparts.* It appears that incorporation of the [Me2Si]ansa bridge substantially enhances the rates of both types of reactions. It is thought from spectroscopic studies that the [Me2Si]ansa bridge causes a reduction in the electron density at the Ta centres in ([Me2Si(C5Me&]Ta} complexes as compared to their [ C P * ~ Tcounterparts. ~] l6 The reactivity of catecholborane (HBCat, Cat = l,2-02C6H4)with endo- and

10: Complexes Containing Metal-Carbon a-Bonds

263

C24

C

12

11

C3P

wC163

13

em-tantalocene and niobocene olefin complexes, Cp2M(CH2=CHMe) has been compared and monitored by 'H and "B NMR spectroscopy. The reaction between endo- and exo-Cp2NbH(CH2=CHMe) with HBCat is thought to proceed via the formation of the intermediate Cp2Nb(H)(q2HBCat).17 The sodium amalgam reduction of cis-rner-[Ta(OC~H~Pr-2,6)2Cl,(dcpm)] (dcpm = bis(dicyclohexy1phosphino)methane) in hydrocarbon solvent leads to the compound ~a(OC~H~Pr-q2-CMe=CH2)Cl(dcpm)]. The X-ray structural determination of this complex shows that the Ta atom adopts a metallacyclopropane bonding mode via an q2interaction with the vinyl group."

5

Butadiene and Similar Complexes

The (q4-s-trans-butadiene)tantalocenecation reacts with isonitriles to yield the [(q2-butadiene)(C=NCMe3)TaCp2]' complex according to Scheme 2. The cyclohexyl isocyanide was characterised by X-ray diffraction and shows the

264

Organometallic Chemistry

q2-butadiene ligand oriented at the front of the Cp2Ta+ bent metallocene wedge. The Ta-CGN-R unit is almost linear. Photolysis of [(butadiene)TaCp2]+with excess cyclohexyl isocyanide followed by thermal treatment at 45 "C yields the pseudotetrahedral [CP~T~(C-NR)~]+ cation. Both Ta-CrN-R units are slightly bent at the N atoms. The bonding situations were analysed by density functional calculations.l 9

Scheme 2

The half-sandwich 1,4-diaza-1,3-butadiene (dad) complexes, MC12(qsC5Rs)(q4-supine-p-MeOC6H4-dad) (M = Nb, Ta) (14) have been obtained by treatment of MC14(qs-CSRs)with one equivalent of the dilithium salt of 1,4bisb-methoxypheny1)-1,4-diaza-1,3-butadiene (p-MeOC6H4-dad)in THF. The dad complexes can also be obtained by treatment of the dinuclear Ta(II1) complex, [TaC12Cp*]a with p-MeOC6H4-dad.The mode of coordination of the dad ligand with a variety of half metallocene complexes has been investigated including the conformation of the 02,p-endiamidoligand which can adopt two conformations (supine or prone) relative to the q5-C5R5ligand.20

6

Imido Complexes

The reaction of Cp*TaC14 with Li[MeC(NiPr)2] in THF yields Cp*[MeC(NiPr)2]TaC13whose structure was determined. Reaction of c~*[Mec(N'Pr)~]TaC13 with excess MeMgCl yields the trimethyl Ta complex Cp*[MeC(N'Pr)2]TaMe3. Reaction of Cp*[MeC(NiPr)2]TaC13with AgSbF6 yields the cation [Cp*[MeC(NiPr)2]TaC12]+in which the amidinate orientation is completely reversed with respect to that in the reactant and the trimethyl Ta complex such that the amidinate ligand and the Cp* group are almost parallel. Cp*[MeC(NiPr)2]TaC13 was found to be active in the polymerisation of ethylene upon treatment with M A 0 in isobutane.21

10: Complexes Containing Metal-Carbon a-Bonds

265

Reactions of the chloro-imido complex [Nb(q5-C5H4-SiMe2C1)(CH2Ph)C1(NtBu)] with LiNH'Bu and N H ~ ~ Bhave u been investigated. With LiNH'Bu selective substitution of the Nb-Cl bond occurs giving [Nb(q5-C5H4SiMe2C1)(CH2Ph)(NH'Bu)(N'Bu)]whereas preferential reaction at the Si-Cl bond occurs with NH;Bu to produce [Nb(q5-C5H4-SiMe2(NHtBu))(CH2Ph)C1(NtBu)] which is transformed into [Nb{q5-C5H4-SiMe2(NHtBu)) (CH2Ph)(NHtBu)(N'Bu)] on further reaction with N H ~ B u .Intermolecular rearrangements between Si-Cl and Nb-NH'Bu bonds and conversion of q2iminoacyl complexes into vinylamido derivatives are also reported.22 The imido complexes Cp(VN2MeC6H4)C12and CpNb(N;BuC6H4)C12 have been tested as procatalysts for the polymerisation of ethylene in combination with diethylaluminium chloride or methylaluminoxane (MAO) co-catalysts. The V precursor was relatively active but short-lived giving high MW polyethylene with little branching. Treatment of the appropriate precursors with alkylating agents gave the dialkyls Cp*Nb(N-(2,6-'Pr&H3))Me2 and Cp*Ta(N-'Bu)(CH2Ph)2which were also investigated as precursors to welldefined cationic alkyl catalysts.23 Gradient corrected levels of density functional theory and 51VNMR shifts have been used to compute barriers for insertion of ethylene into a V-C bond of V(NR)Me3 (R = H, %u, C(CF3)3, C6H5, p-C6H@Me, p-C6H4N02, o,pC6H3(N02)2, o-C6H4(COMe)). Interesting neighbouring group effects were found allowing predictions to be made of known compounds and their activity as polymerisation catalysts.24 A study has been made on the metal mediated cleavage of the N=N bond in organic diazenes to give metal imido compounds. It has been generally assumed that the reaction proceeds via the formation of an q2-diazene or diazametallocyclopropane complex which activates the N=N bond and reduces its multiplicity. In this investigation methyl tantalocene complexes Cp2Ta(L)CH3 (L = Cp2Ta(=S)CH3,PMe3, ethylene) were treated with azobenzene or azotoluene (ArN=NAr) leading to loss of L and the formation of Cp2Ta(q2-ArN=NAr)CH3 (15) and Cp2Ta(=NAr)CH3 (16) (Scheme 3). Mechanistic studies were carried out which showed that (15) cannot be an intermediate in the formation of (16) and an ql-azoarene complex was proposed as an intermediate. 25 Reaction of NbCp'C14 (Cp' = q5-C5H4SiMe3)and TaCp*C12Me2 (Cp* = q5C5Me5)with two equivalents of NHR'SiMe3 and CNR' respectively gave the dichloroimido-derivatives [MCpC12(NR1)].The monochloroimido-derivatives, /L CRTa

ArN=NAr

\

CH3

-L

/"\"'

NAr

Cp2Ta-NAr

\CH3

+

\

CH3

16

15

I Scheme 3

ChTa'/

V

A

266

Organometallic Chemistry

[MCpClR(NR')] were obtained by treatment of the dichloro-derivatives INbCpCl2(N(2,6-'Pr2c6H3))] and [TaCp*C12(N(2,6-Me2C6H3))] with the appropriate amount of alkylating reagent. Further reactions produced the dialkylamido-derivatives,[MCPR~(NR*)].~~ The imido-niobium complexes [Nb(=NAr)C13(dme)] (Ar = C6H4Me4, C6H40Me4) have been prepared and characterised. The half-sandwich complex [Nb(=NtBu)CpC12]has been synthesised by a new method involving the reaction of NaCp and INb(NtBu)C13(py)2]. Similarly the novel complex [Nb(=NC6H4Me4)CpC12]has been prepared by reaction of NaCp with [Nb(=NC6H4Me4)Cl,(dme)]. The structures of several of these sandwich and half-sandwich niobium-imido complexes have been determined. 27 Single crystal X-ray analyses have been carried out on two N , N f , N f tri(isopropy1)guanidinate complexes of Ta(V) with imido ligands. The alkyl (17) was obtained by complex { [~1-(N'Pr)3C]2TaMe(N'Pr)}(Mg2C12).4C6D6 halogen exchange with two equivalents of MeMgX (X=Cl, Br) on TaCl(NiPr)[(NiPr)2C(NH'Pr)]2. The second complex, {(p-q2:q2 ('PrN)3C)Ta(NiPr)Cl}2,(18), was obtained from the reaction between TaC15 and in situ generated monolithium guanidinate. This is a binuclear complex possessing bridging dianionic tri(isopropy1)guanidinate ligands each showing a previously unknown chelating coordination mode.28

17

7

Other Complexes

Reduction of (silox)3NbC12 (silox = tB~3SiO)in the presence of 4-picoline yielded (S~~OX)~N~(~~-N,C-~-NC~H~CH~), considered as a source of (silox)3Nb. - N(silox)3Ta C~H~CH~) 4-picoline was abstracted from ( S ~ ~ O X ) ~ N ~ ( ~ ~ - N , C - ~ by p:q2,q2-C6H60and (silox)3Ta(q2-N,C-4-NC5H4CH3) .29 to give { (silo~)~Nb}2(

10: Complexes Containing Metal-Carbon a-Bonds

267

18

Carbonylation of Cp*(ArN=)Ta[Si(SiMe3)3]H produces the adduct Cp*(ArN=)Ta(CO)[Si(SiMe3)3]H whose X-ray crystal structure was investigated along with 'H and 13CNMR spectra. On standing at room temperature for 24 h, pentane solutions of Cp*(ArN=)Ta(CO)[Si(SiMe3)3]H quantitatively transform to the six-membered tantalacycle (19) in which the former carbonyl and silyl ligands are incorporated into the ring.30

19

A report has appeared of the synthesis of the first dinitrosyls of Nb and Ta (M), ~is-[M(N0)~(CNXyl)~l+, by direct nitrosylation of [M(CO)G]- with two CNXyl. equivalents of [NO]+ in the presence of 2,6-dimethylphenylisocyanide, The new complexes are thermally stable but air, moisture and light sensitive. The IR, 'H,13CNMR and X-ray crystal structures of the complexes have been determined. The reaction of [Cp*TaC14] with the potassium salt of carbazole (cbK) in hydrocarbon solvents led to the formation of [(C5Me4CH2)Ta(cb)2C1]in which one of the ring methyl C-H bonds of the Cp* ligand has been cleaved along with free cbH. Alkylation of [(C5Me4CH2)Ta(cb)2C1] with LiCH2SiMe3 or PhCH2MgCl leads to the corresponding monoalkyl derivatives [(C5Me4CH2)Ta(~b)~(R)l (R = CH2SiMe3 or CH2Ph). Structural studies showed all three complexes to exhibit an q ':q5-CH2CSMe4 description for the metallated ligands with slippage towards an q ':q3-CH2C5Me4 resonance

'

Organometallic Chemistry

268

References 1.

2. 3. 4. 5.

6. 7. 8. 9. 10. 11.

12.

13. 14. 15.

16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27.

28.

A. Antiiiolo, F. Carrillo-Hermosilla, M. Fajardo, J. Fernandez-Baeza, S. GraciaYuste and A. Otero, Coord. Chem. Rev., 1999,195,43. D. Rehder, Coord. Chem. Rev., 1999,182,297. I. Nowak and M. Ziolek, Chem. Rev., 1999,99,3603. D. Reardon, F. Conan, S. Gambarotta, G. Yap and Q.Y. Wang., J. Am. Chem. SOC.,1999, 121,9318. 0.1. Guzyr, M. Schormann, J. Schimkowiak, H.W. Roesky, C . Lehmann, M.G. Walawalkar, R. Murugavel, H-G. Schmidt and M. Noltemeyer, Organometallics, 1999,18, 832. B. Castellano, E. Solari, C. Floriani, N. Re, A. Chiesi-Villa and C. Rizzoli, Chem. Eur. J., 1999,5, 722. A. Caselli, E. Solari, R. Scopelliti and C. Floriani, J. Am. Chem. SOC.,1999, 121, 8296. M.D. Fryzuk, S.A. Johnson and S.J. Rettig, Organornetallics,1999,18,4059. K.S. Cook, W.E. Piers and S.J. Rettig, Organometallics, 1999, 18, 1575. S.M. Mullins, R.G. Bergman and J. Arnold, Organometallics, 1999, 18, 4465. C. Garcia-Yebra, F. Carrero, C. Lopez-Mardomingo, M. Fajardo, A. Rodriguez, A. Antiiiolo, A. Otero, D. Lucas and Y. Mugnier, Organometallics, 1999, 18, 1287. A. Otero, J. Fernandez-Baeza, J. Tejeda, A. Antiiiolo, F. Carrillo-Hermosilla, E. Dez-Barra, A. Lara-Sanchez, M. Fernandez-Lopez, M. Lanfranchi and M.A. Pellinghelli,J. Chem. SOC.,Dalton Trans., 1999, 3537. M. Etienne, C. Carfagna, P. Lorente, R. Mathieu and D. de Montauzon, Organometallics, 1999, 18, 3075. R. Choukroun, C. Lorber, B. Donnadieu, B. Henner, R. Frantz and C. Guerin, Chem. Commun., 1999,1099. D.R. Mulford, J.R. Clark, S.W. Schweiger, P.E. Fanwick and I.P. Rothwell, Organometallics, 1999,18,4448. J.H. Shin and G. Parkin, Chem. Commun., 1999,887. D.R. Lantero, S.L. Miller, J-Y. Cho, D.L. Ward and M.R. Smith, Organumetallics, 1999,18, 235. P.N. Riley, J.R. Clark, P.E. Fanwick and I.P. Rothwell, Inorg. Chim. Acta, 288, 35. C. Strauch, B. Wibbeling, R. Frohlich, G. Erker, H. Jacobsen and H. Berke, Organometallics, 1999,18,3802. K. Mashima, Y. Matsuo and K. Tani, Organometallics, 1999,18, 1471. J.M. Decker, S.J. Geib and T.Y. Meyer, Organometallics, 1999,18,4417. M. I. Alcalde, M.P. G6mez-Sal and P. Royo, Organometallics, 1999,18, 546. M.P. Coles, C.I. Dalby, V.C. Gibson, I.R. Little, E.L. Marshall, M.H.R. da Costa and S. Mastroianni, J. Organomet. Chem., 1999,591, 78. M. Biihl, Organometallics,1999,18,4894. M.A. Aubart and R.G. Bergman, Orgunometallics,1999, 18,811. A. Castro, M.V. Galakhov, M. Gomez and F. Sanchez, J. Organomet. Chem., 1999,580,161. A. Antiiiolo, M. Fajardo, C. Huertas, A. Otero, S. Prashar and A.M. Rodriguez, J. Organomet. Chem., 1999,585, 154. N. Thirupathi, G.P.A. Yap and D.S. Richeson, Chem. Commun., 1999,2483.

10: Complexes Containing Metal-Carbon a-Bonds

29. 30. 31. 32.

269

S. Veige, T.S. Kleckley, R.M. Chamberlin, D.R. Neithamer, C.E. Lee, P.T. Wolczanski, E.B. Lobkovsky and W.V. Glassey, J. Organomet. Chern., 1999,591, 194. U. Burckhardt and T.D. Tilley, J. Am. Chem. Suc., 1999,121,6328. M.V. Barybin, V.G. Young Jr., and J.E. Ellis, Organometallics, 1999, 18,2744. P.N. Riley, J.R. Parker, P.E. Fanwick and I.P. Rothwell, Organometallics, 1999, 18,3579.

Part 111: Group 6 by Michael K. Whittlesey

A number of review articles have appeared which contain material of relevance to the organometallic chemistry of chromium, molybdenum and tungsten. The application of non-metallocene catalysts in alkene polymerisation has been described' while the use of metal vinylidene complexes as catalysts for [2+2] cycloaddition, alkyne dimerisation and nucleophilic addition to alkynes has been reviewed.2 Cycloisomerisation of alkynols by transition metal complexes, including Group 6 compounds, has been re~iewed.~ Two reviews of carbene chemistry has been published. Firstly, recent developments in annulation reactions of chromium carbene complexes have been described4 and then a more general review on carbene transfer reactions has also a ~ p e a r e dReviews .~ of early-late heterobimetallic systems6and calix[4]arene complexes as models for metal 0x0 surfaces7contain some material of relevance to the current chapter. Time-resolved IR spectroscopy using a step-scan FT instrument has been used to study' the substitution kinetics of cyclohexane by a range of ligands including alkenes and thf in W(C0)5(CbH12). Density functional theory (DFT) has been used to probe the energetics of CO dissociation from [M(CO)5X](X=OH, F , CH3 etc.). Loss of CO from [M(CO)5CH3]- is computed to require between 144 and 165 kJ mol-'.9 DFT has also been used to study the singlet and triplet spin states of (q-C5H5)(NO)(PH3)W(=CH2).The singlet is calculated to be 10 kJ mol-' lower in energy." DFT has been used to investigate the preference for coplanarity of the q2-alkenyl ligand and one of the Mo-L bonds in of (q-C5H5)(P(OMe)3)2Mo(q2-CMe=CH2) and of (q-

CSH~)(PH~)~MO(T~~-CH=CHZ).'~ There continue to be extensive studies of Group 6 metal alkyl complexes. Treatment of [Tp'BU*MeCrPh] (TptBuyMe = hydrotris(3-tert-butyl-5-methylpyrazoly1)borate) with excess 0 2 at -45 "C results in a colour change from blue to red and formation of the paramagnetic d2 0x0 complex, [Tp'BU9MeCr(0)(OPh)].l 2 Addition of sodium cyclopentadienyl dimethoxyethane or one equivalent of R2Mg (R = q '-C5H5, CH2SiMe3, CH2Ph, Ph, CPh=CHZ, C-CCMe3, CSCPh) to (q-C5H5)Cr(NO)(NiPr2)(OC(0)Ph)yields the lowspin 18-electron complexes (q-C5H5)Cr(NO)(NiPr2)R.The electronic configuration can be explained by the strong field nature of the nitrosyl and amide ligands.l3 The reaction of Cr(NO)(NiPr2)(OC(0)Ph)2with two equivalents of R2Mg (R = CH2SiMe3, CH2Ph) affords the diamagnetic 14-electron species

270

Organometallic Chemistry

Cr(NO)(NiPr2)(CH2SiMe3)2and Cr(NO)(NiPr2)(CH2Ph)2, both of which have been structurally characterised.l4 Addition of alkyl halides RX to CrMep(SiMe2CH2PPh2)2] results in one electron oxidation to give Cr(II1) alkyl halide complexes CrMe(X)[N(SiMe2CH2PPh2)2]. Treatment of CrCl(CH2SiMe3)p(SiMe2CH2PPh2)2] with LiCH2SiMe3 yields Cr(CH2SiMe&[N(SiMe2CH2PPh2)2], which is only stabilised because of the bulky alkyl groups (CrMe2[N(SiMe2CH2PPh2)2]cannot be prepared). The alkyl halide complexes show no activity for alkene polymerisation; Cr(CH2SiMe3)2[N(SiMe2CH2PPh2)2] shows some short-lived catalytic behaviour. l4 The activation of solvent C-H bonds by the transient species (q-C5Me5)W(NO)(q2-PhCrCPh) has been investigated upon its generation by reductive elimination of SiMe4 from (q-C5Me5)W(N0)(q2-CPhCH2)(CH$3iMe3).Thus, in toluene, products from both aromatic and aliphatic C-H cleavage are seen with the formation of (q -C5Me5)W(NO)(q 2-CPhCH2)(C6H4-p-Me), (q -C5Me5>-W"O)(q2CPhCH2)(C6H4-o-Me)and (q-C5Me5)W(NO)(q2-CPhCH2)-(CH2C6H5) in the ratio 57:38:5. Dual C-H bond activation of aliphatic hydrocarbons occurs to give the metallacycles (q -C5Me5)W(NO)(q 2- CH(q 2-Ph)CH2CH(R) CH2) (R="Pr, n B ~ ,tBu, OEt) as shown in 1. In reactions with alkenes, CMe2=CMe2 affords (q -C5Me5)W(NO)(q3-endo-CH2C(Me)C(Me)CH2(q ICPhMe)), 2. Attempts to trap the transient alkyne complex with PMe3 have resulted in the formation of the metallacyclopropane complex (q-C5Me5)W(NO)(CH2SiMe3)(q 2-CH2CPh(PMe3)).

am5 aMe5 R = "Pr. "Bu. 'Bu. OEt I

I

1

.

I

2

The trisalkyl complexes MoR3(NNPh2)(0C6F5) [M = Mo, R = CH2CMe2Ph; M = W, R = CH2SiMe31 have been prepared by reaction of MoC14(NNPh2) with RMgCl followed by addition of C6F50H. Both complexes are catalysts for the ring-opening metathesis polymerisation (ROMP) of norbornene.l 6 The bis(2,6-diisopropylphenylimido) complex (NR)2MoMe2 reacts with thf, C5H5N, PMe3 or PMe2Ph to give the five-coordinate species (NR)2Mo(L)Me2.17 Both the starting material and the PMe2Ph adduct have been subject to X-ray crystallography. The molecular structures of Mo(NAr)2(0CMe2-2-py)(CH2SiMe3)and Mo(NAr)2(OMe)2Me (Ar = 2$Pr2C6H3) have been reported. * The five coordinate bisimidoaryl complexes M o ( N A ~ )C-N)X ~( (Ar = 2,6-h2C&3; C-N = C6H4(CH2NMe2)-2;X = Me, Et, Bu, CH2SiMe3,c6&-p-Me, C-N) have been rep~rted.'~ Upon reaction with R'Li (R' = Me, "Bu, C6H4-p-Me),the lithium molybdates 3 are produced. The same authors have also described the preparation of Mo(q2-C,NNCN)(NAr)2Me (NCN = [C6H3(CH2NMe2)2-2,6] - ; Ar = 2,6-iPr2C6H3).20 Photolysis of the ansa-bridged metallocene [Me2Si(C5Me4)2]MoH2 in C6H6

27 1

10: Complexes Containing Metal-Carbon a-Bonds

yields the phenyl hydride product.21 This contrasts with (q5-CSH5)2MoH2 which does not give the analogous reaction. Photolysis of [Me2Si(CSMe4)2]M~H2 in CH3CN results in C-C bond cleavage of the solvent to give 4. The high-valent 0x0 complex W02(L')(CH2SiMe3) (HL = 2-N-(2-pyridylmethy1)aminophenol) has been synthesised and characterised crystallographically.22Addition of B(C6F5)3to cis-[(p-'Bu-calix[4]-(04))W(CH3)2] affords the monomethyl cation 5. Sodium reduction of the starting dimethyl complex ultimately yields [@-'Bu-ca1ix[4]-(O4))Na2W(CH3)2]. Crystallisation of the complex from pyridine/DME gives crystals suitable for X-ray diffraction; the

3

4

5

6

structure shows two crystallographically independent [(p-'Bu-calix[4]-(04))Na(DME)W(CH&]- ions interacting through one of the calix oxygen atoms with a sodium cation.23Room temperature isomerisation of the bistrimethylsilyl complex 6 (C, symmetry) occurs in solution over days to the structure with C1 symmetry. The dimethyl and dibenzyl analogues are formed directly in the C1 Thermolysis of the alkyl complexes at 60°C leads to a-H elimination to form alkylidene complexes which will catalyse ROMP of norbornene. Similarly heating solutions of the alkyl complexes (q-C5R5)W(N'Bu)R3 (R = Et, nPr), formed by reaction of (q-C5R5)W(NtBu)C13with three equivalents of RMgCl, at between 25-80 "C yields the alkylidene derivatives (q-C5R5)W(NtBu)(CHR)R.25 Protonation of the tungsten propargyl complexes (q7-CgH5)(C0)3WCH2C-CR (R = Me, Ph) with triflic acid at low temperature and warming to room temperature for 10 hours, followed by addition of water or amine, yields the carbonylation products (q-C5H5)(C0)2W(q1,q2-CH2CHCHR-Y-CO-) (Y = 0, NR).26 The long chain tungsten alkyls (q-C5H5)(C0)3WR (R = nCsH13, n-C7HI5,n-C8H17)can be prepared by addition of [(q-CgH5)(C0)3Wto the respective alkyl bromides or iodides.27 A range of alkene rearrangements have been demonstrated using [(p-'Bucalix[4]-(04)}W(q2-C2H4)] as a model for alkene absorption upon metal 0x0 surfaces. Thus, deprotonation with BuLi gave the anionic alkylidyne [(p-'Bucalix[4]-(04))W(CMe]Li, which is protonated, not back to the starting material, but to the alkylidene, [@-tBu-calix[4]-(04)} W=CH(Me)]. The intermediacy of a metallacyclopropane species in the deprotonation reaction comes from isolation of [@-'Bu-~alix[4]-(0,)}W(C(PhCHPh)]Li, which can be prepared from [(p-'Bu-ca1ix[4]-(O4))W(q2-CHPh=CHPh)]. Both [(p-'Bu-calix[4](04)) W(q2-C2H4)]and [(p-'Bu-calix[4]-(04))W(q2-CHMe=CHMe)]react with ethene and propene under catalytic electron transfer conditions to give the

272

Organometallic Chemistry

metallacyclopentanes [ (p-'Bu-calix[4]-(04)1W(CH2CH(R')CH(R)CH2)] ( R = R ' = H ; R=Me, R'=H; R=R'=Me). In the case of the R = R ' = H complex, deprotonation with BuLi yields [ (p-'Bu-calix[4]-(04)}W(CH(CH2)2CH2)]Li,which can be converted photochemically to [ (p-'Bu-calix[4](04)) W=CH("Pr)] and [(p-'Bu-ca1ix[4]-(O4)) W(C"Pr]Li.28 A series of (q-CSMeS)W(NO)containing 1-metallacyclopropene and q vinyl complexes have been prepared2' and compared to literature examples through their X-ray and NMR data. The nature of the tungsten-vinyl interaction has been found to be dependent upon the donor strength of the 1electron X or 3-electron LX donor ligands also present. A series of trisalkenyl chromium complexes of the general structure 7 have been prepared that incorporate sterically encumbered adamantyl derived groups.30 The reaction of ((~-c5H5>w(cO)3)2(~-cS) with [Co2(p-dppm),(CO)8-2~] (x = 0, 1) gives a range of complexes arising from addition of [Co2(p-dppm),(C0)6- 2x]to one or two C-C bond^.^' The flyover metallacycle 8 has been structurally characterised from the reaction of [(q-C5H5)2M02(p-SMe)3(CH3CN)2]with

7

8

two equivalents of (p-CH3C6H4)C=CHin dichloromethane solution at room t e m p e r a t ~ r e .The ~ ~ reaction involves the coupling of two alkynes and one thiolate bridge to give an 8-electron donor ligand. The synthesis, cyclic voltammetry and EPR of the 17 and 18-electron c cloheptatrienyl molybdenum com lexes (q-C7H7)Mo(dppe)( CH2CH2CH2 )I+, [(q-C7H7)Mo(dppe)(CeH2CH2CH2 - 6 )I2+, [(rl-C7H7)Mo(dPPe)CH31+ and [(q-C7H7)Mo(dppe)(C=CPh)I2' have been de~cribed.~' Protonation of (q-C5H5)W(CO)3(CH2C_C(CH2)xAr)(x = 0, 1) with triflic acid at low temperature in dichloromethane results in addition of the aryl C-H bond to one of the carbonyl ligands to afford the carbonylation products, (qC5H~)W(C0)2(n;-cyclopentenonyl) and (q-C~H~)W(CO)~(n:-cyclohexenonyl). 34 Addition of LiCrC-C=CSiMe3 to a thf solution of (q-C5Hs)(dppe)Mo(CO)C1 yields (q-C5HS)(dppe)Mo(CO)(C=C-CSiMe3), which reacts with Bu4NF to form (q-CSH5)(dppe)Mo(CO)(C~C-C~CH).35 UV photolysis of (q6-arene)M(C0)3 (arene = 1,2,3,5-C6H2Me4, 1,2,3C6H3Me3, 1,3,5-C&3Me3, C6H6, C6Me6; M = Cr, Mo) in the presence of Me3SiCdSMe3 yields the vinylidene complexes (q6-arene)M(C0)2(=C=C(SiMe3)2).36These undergo 1-electron oxidation to the alkyne cations [(q6arene)M~(CO)~(q'-Me~SiC=CSiMe~)]+, which can then be reduced to the neutral alkyne complexes, which in turn slowly isomerise to the neutral

10: Complexes Containing Metal-Carbon o-Bonds

273

vinylidene compounds. The preparation of (dmpe)2ClW(C-C6H4-p-C=CH)37 has allowed the subsequent formation of poly(aryleneethyn1ene)s via functionalisation at both the metal and the ethynyl group. Treatment of [Tp’W(O)(I)(HCrCMe] (Tp’ = hydridotris(3,5-dimethylpyrazoly1)borate) with “BuLi and an electrophile (MeLi, HCl) affords the vinylidene complexes [Tp’W(0)(I)(=C=CMe2)] and frp’W(0)(I)(=C=CHMe)].38 The reactivity of functionalised tungsten alkylidenes has been studied39 through the synthesis of 9. This has allowed the preparation of phosphanyl, amino, alkynyl and trialkylidenes. The amino and phosphanyl complexes show an q2-interaction with the tungsten centre, which can be used for intermolecular binding to other metals. One such copper complex (10) has been structurally characterised.

9

10

Deuterium labelling studiesm have demonstrated that NaBH4 addition to (OC)5Cr=C(OEt)(CH=CHPh)leads to hydride addition to the carbene carbon followed by 1,3-rearrangement of the chromium centre and protonation. In the case of borohydride reaction with (OC)5Cr=C(OEt)(CrCPh), hydride addition gives the allenyl intermediate (OC)sCr(CPh=C=CH(OEt)) followed by protonation. Further light has been shed on the mechanism of reaction of Fischer carbenes with alkynes to give phenols, using (OC)5Cr=C(OMe)(2OMeC6H4),which has allowed the first demonstration that the regioisomeric vinyl carbene intermediates equilibrate during the benzannulation reaction.41 Rate constants for the reversible deprotonation of (OC)5M-C(SMe)Me (M = Cr, w)by OH-, H20, RNH2, R2NH and RC02- have been reported. They show that, in comparison with (OC)SM=C(OMe)Me,incorporation of the SMe group leads to (i) increased thermodynamic acidity, (ii) increased dependence of pK, on M and (iii) decreased intrinsic rate constants for proton transfer.42Kinetic studies have been used to probe the reactions of (OC)5M=C(0R’)Ph (M=Cr, W, R’=Me, Et) with RS- (R=”Pr, HOCH2CH2, Me02CCH2CH2,Me02CCH2). At low [RS-] and pH < pKaRSH,the substitution products (OC)SM=C(SR)Ph are formed. At high [RS-] and pH (pKaRSH, the tetrahedral species, [(OC)5MC(OR’)(SR)Ph]- is produced, which immediately converts to the substitution products upon addition of acid.43 The half-sandwich chromium carbene complex 11 has been prepared by reaction of ( ~ l - c ~ H ~with ) ~ C1,3-dimesitylimadazoliurn r chloride? Addition of PhMgCl leads to the phenyl complex, which has been characterised by Xray crystallography. Related products cannot be made from (q-C5Me&Cr, presumably due to steric constraints. In a related (q-CSH&Cr reacts

274

Organometallic Chemistry

with 1,3-dimesitylimidaz01-2-ylideneto give 12, whereas reaction with tetramethylimidazol-2-ylidene gave a biscarbene complex. Treatment of [W(NPh)C14(Et20)] with Zn { C6H3(CH2NMe2)2-2,6) yields pNC12(NPh){ C6H3(CH2N(Me)CH2)-2-(CH2NMe2)-6],in which one of the NCN ligands is bonded in an q3-meridonal arrangement to the tungsten centre. This reacts with two equivalents of LiCH2SiMe3to give the alkylidene complex 13.46

11 Ar = 2,4,6-M@C6H2

12 Ar = 2,4,6-Me&H2

13

Novel biscarbene binuclear tungsten complexes with linking alkynediyl units have been prepared via two routes involving (a) reaction of [(OC),W=C(NMe2)C-CLi] with W(CO)6 and subsequent addition of MeOTf or (b) palladium catalysed coupling of two (OC)5M=C(NR2)(C=C), units. Method (b) yields the hexayndiyl species (OC)5W=C(NMe2)(C=C)6C(NMe2)W(C0)5.47 The reaction of Mo(=CHtBu)(=NAr){ OCMe2(CF3)2) (Ar = CbH3-2,6-'Pr2) with pyrroline results in imine ring-opening metathesis polymerisation (ROMP) via the pyrroline adduct Mo(=CHtBu)(=NC4H7){OCMe2(CF3)2).48 The Fischer carbenes (OC)5W=CHR (R = C6H5, P - C H ~ C ~ H p-MeOC6H4) ~, react with (q-C5H5)(C0)3WH to form the benzyl complexes (qC5H5)(C0)3WCH2R.In the case of (OC)5W=CH(p-MeC6H4),reaction with yields (q-C5H5)2W(H)(CH2-p-MeC6H4)W(CO)5 in which the hydride ligand acts as a 3-centre-2-electronlink.49 Reaction of (OC)5M=C(OEt)-C=C-&CHCH2(CH2)n~H2 (M = Cr, Mo; n =1, 2, 3) with HNMe2 or (29-(methoxymethy1)pyrrolidine affords 4-amino-1metalla-l,3,Shexatrienes, which cyclise to give 14 through anti addition of the M=C unit to the C=C bond of the metalla-hexatriene fragment?' Carbene transfer occurs upon reaction of (OC)5M=C[N(R)CH2]2 (M = Cr, Mo, W; R = ethyl, allyl, benzyl, 4-pentenyl) with (PhCN)ZPtCl, to form cis[N(R)CH2I2C=Pt(CO)Cl2. The X-ray structure is reported for R = benzyL51 Addition of azolyllithiums to (OC)5ML (M=Cr, Mo, W; L=CO, thf, Cl) followed by methylation provides a route to Fischer type c a r b e n e ~ The .~~ alkyne complex [(OC)5M(q2-HC-CPh)] (M = Cr, Mo, W) reacts with RN=C(Ph)H (R = Et, 'Pr) to form the 2-azetidin-1-ylidene complexes [(OC)5M=cNRC(Ph)Hc(Ph)H] with high stereoselectivity (syn:anti 2 9), and with RN-C-NR (R = c clohexyl, 'Pr) to give 3-imino-2-azetidin-1-ylidenes [(OC)5M= - NRC(=NR)H . (Ph)H].53 Reaction with the Group 15 elementocarbene com lexes [ ( q - C 5 H 5 ) ( C O ) ( P M e 3 ) q P h 2 ] + and [(qCSHS)(C0)2V -C(R)-AsPh2]+ e (R =p-CH&H4, C6H5, CH3) react with CF3C02H or C13CC02Hto form the hos hino- and arsinomethanide complexes [(q-C5H5)(CO)(PMe3)X C(H)(R)- Ph$ and [(q-C5HS)(CO),X+C(H)(R)-AsPh2]+ (X = CF3C02,C13CC02).54

*

10: Complexes Containing MetalLCarbon a-Bonds

275

The reaction of anionic tungsten alkylidynes [(p-'Bu-calix[4]-(04)1W(CR]M (R=Ph, M=OS Mg; R="Pr, M=Li; R=SiMe3, M=Li) with acid leads to the corresponding alkylidenes, which can be reversibly deprotonated? The alkylidynes can be functionalised with AgN03 to afford dimetallic alkylidenes [(p-'Bu-calix[4]-(04)}W(C(R)Ag]], while reaction with electrophiles such as PhCHO or Ph2C=C=O give complex structures, such as 15 in the case of

14 M = Cr, W

15

diphenylketene. The influence of ligand type on the site of protonation of the Fischer carbyne complexes [(q-C5H5)L2Mo(CBu] and ppL2Mo(CBu] (L = CO, P(OR)3) has been described. As the electron density at the Mo centre is decreased by incorporation of more carbonyl groups, the carbyne carbon becomes protonated in preference to the metal centre.56The hydroxycarbyne [W2(p-COH)(q-C5H5)2(C1-PPh2)2]+and methoxycarbyne [W2(p-COMe)(qCsH&(p-PPh2)2]+ have been prepared upon addition of HBF4.0Et, and MeOTf respectively to w2(y-CO)(q-CSH5)2(p-PPh2)2].57 Low temperature protonation of w2(q-C5Hs)2(C0)2(p-dppm)]+with HBF,.OEt, in CH2C12 in gives the hydroxycarbyne complex w2(p-COH)(q-C5H5)2(CO)2(p-dppm)]+ quantitative yield.58 The same reaction does not occur in toluene, where a bridging hydride species is formed. If the protonation in CH2C12 is performed with 1,8-diazabicyclo[5.4.O]undec-7-ene(DBU), the known cyclopentadienylidene complex w2(m-H)(p-q ,q5-CsH4)(q-C5H5)(C0)3(p-dppm)] is formed. Internal electron transfer from palladium has been used to explain the quenching of emission from the tungsten fragment in the trinuclear complex [(tmeda)(CO)ClW= C6H4-NG CI2PdX2(X = C1, Br).59Electron transfer from the excited state of (q-C5H5){P(OPh)3}(OC)W= CPh to a series of electron acceptors has been investigated.60The dn* excited state of the complex is found to be a potent reducing agent (E1/2(m*/m+.) = - 1.7 0.2 V). Synthesis and characterisation of the arsaalkenyl carbyne complexes TP'(CO)~M=CAS=C(NM~~)~ and [Tp'(C0)2M-CAs(Me)C(NMe2)2]+ has been reported.61

References 1. 2. 3.

G. J. P. Britovsek, V. C. Gibson and D. F. Wass, Angew. Chem., Int. Ed. Engl. 1999,38,428. C . Bruneau and P. €3. Dixneuf, Acc. Chem. Res. 1999,32,311. B. Weyershausen and K.-H. Dotz, Eur. J. Inorg. Chem. 1999, 1057.

276 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33.

Organometullic Chemistry K.-H. Dotz and P. Tomuschat, Chem. SOC.Rev. 1999,28, 187. S.-T. Liu and K. R. Reddy, Chem. SOC.Rev. 1999,28,315. N. Wheatley and P. Kalck, Chem. Rev. 1999,99,3379. C. Floriani, Chem. Eur. J . 1999,5, 19. R. H. Schultz and S. Krav-Ami, J. Chem. SOC.,Dalton Trans. 1999, 115. S. A. Macgregor and D. MacQueen, Inorg. Chem. 1999,38,4868. K. M. Smith, R. Poli and P. Legzdins, Chem. Eur. J. 1999,5, 1598. S.-H. Choi and Z. Lin, Organometallics 1999,18,2473. A. Hess, M. R. Horz, L. M. Liable-Sands, D. C. Lindner, A. L. Rheingold and K. H. Theopold, Angew. Chem., Int. Ed. Engl. 1999,38, 166. E. W. Jandciu, J. Kuzelka, P. Legdzins, S. J. Rettig and K. M. Smith, Organometallics 1999, 18, 1994. M. D. Fryzuk, D. B. Leznoff, S. J. Rettig and V. G. Young Jr., J. Chem. SOC., Dalton Trans. 1999, 147. J. D. Debad, P. Legzdins, S. A. Lumb, S. J. Rettig, R. J. Batchelor and F. W. B. Einstein, Organometallics 1999,18, 3414. J. R. Dilworth, V. C. Gibson, C. Redshaw, A. J. P. White and D. J. Williams, J. Chem. SOC.,Dalton Trans. 1999,2701. V. C. Gibson, C. Redshaw, G. L. P. Walker, J. A. K. Howard, V. J. Hoy, J. M. Cole, L. G. Kuzmina and D. S . De Silva, J. Chem. SOC.,Dalton Trans. 1999, 161. J. A. M. Brandts, J. Boersma, A. L. Spek and G. van Koten, Eur. J. Inorg. Chem. 1999,1727. J. A. M. Brandts, M. van Leur, R. A. Gossage, J. Boersma, A. L. Spek and G. van Koten, Organometallics 1999,18,2633. J. A. M. Brandts, M. van Leur, R. A. Gossage, J. Boersma, A. L. Spek and G. van Koten, Organometallics 1999,18,2642. D. Churchill, J. H. Shin, T. Hascall, J. M. Hahn, B. M. Bridgewater and G. Parkin, Organometallics 1999, 18,2403. Y.-L. Wong, J.-F. Ma, F. Xue, T. C . W. Mak and D. K. P. Ng, Organometallics 1999,18,5075. L. Giannini, S. Dovesi, E. Solari, C. Floriani, A. Chiesi-Villa and C. Rizzoli, Angew. Chem., Int. Ed Engl. 1999,38,807. Y. Nakayama, H. Saito, N. Ueyama and A. Nakamura, Organometallics 1999, 18, 3149. S. Acebron, M. V. Galakhov, P. Gomez-Sal, A. Martin, P. Roy0 and A. Vazquez de Miguel, J. Orgunomet. Chem. 1999,580,110. R. J. Madhushaw, S. R. Cheruku, K. Narkunan, G.-H. Lee, S.-M. Peng and R. S. Liu, Organometallics 1999, 18, 748. X. Yin and J. R. Moss, Inorg. Chim. Actu 1999,286,221. L. Giannini, G. Gillemot, E. Solari, C. Floriani, N. Re, A. Chiesi-Villa and C. Rizzoli, J. Am. Chem. SOC.1999,121,2797. P. Legdzins, S. A. Lumb and S. J. Rettig, Organometallics 1999,18,3128. J. R. Brock, A. L. Odom, S. R. Klei and C. C. Cummins, Organometallics 1999, 18, 1360.3 M. I. Bruce, B. D. Kelly, B. W. Skelton and A. H. White, J. Chern. SOC.,Dalton Trans. 1999, 847. J.-F. Capon, P. Schollhammer, F. Y. Pktillon, J. Talarmin and K. W. Muir, Organometallics 1999,18, 2055. G. M. Aston, S. Badriya, R. D. Farley, R. W. Grime, S. J. Ledger, F. E. Mabbs,

10: Complexes Containing Metal-Carbon

0-

Bonds

277

E. J. L. McInnes, H. W. Morris, A. Ricalton, C. C. Rowlands, K. Wagner and M. R. Whiteley, J. Chem. SOC.,Dalton Trans. 1999,4379. 34. Y.-R. Wu, G.-H. Lin, R. J. Madhushaw, K.-M. Horng, C.-C. Hu, C.-L. Li, F.-L. Liao, S.-L. Wang and R.-S. Liu, Organometallics 1999,18,3566. 35. C. Moreno, J. L. Gbmez, R.-M. Medina, M.-J. Macazaga, A. Arnanz, A. Lough, D. H. Farrar and S. Delgado, J. Organomet. Chem. 1999,579,63. 36. I. M. Bartlett, N. G. Connelly, A. J. Martin, A. G. Orpen, T. J. Paget, A. L. Reiger and P. H. Reiger, J. Chem. SOC.,Dalton Trans. 1999,691. 37. K. D. John and M. D. Hopkins, Chem. Commun. 1999,589. 38. T. W. Crane, P. S. White and J. L. Templeton, Organometallics 1999,18, 1897. 39. S . Dovesi, E. Solari, R. Scopelliti and C. Floriani, Angew. Chem., Int. Ed. Engl. 1999,38,2388. 40. M. J. Mancheiio, M. A. Sierra, N. Gomez-Gallego and P. Radrez, Organometallics 1999,18,3252. 41. M. L. Waters, M. E. Bos and W. D. Wulff, J. Am. Chem. SOC.1999,121,6403. 42. C. F. Bernasconi and M. Ali, J. Am. Chem. Soc. 1999,121,3039. 43 C. F. Bernasconi, K. W. Kittredge and F. X. Flores, J. Am. Chem. SOC.1999, 121,6630. 44. M. H. Voges, C. Rarmming and M. Tilset, Organometallics 1999,18, 529. 45. C. D. Abernethy, J. A. C. Clyburne, A. H. Cowley and R. A. Jones, J. Am. Chem. SOC.1999,121,2329. 46. J. A. M. Brandts, E. Kruiswijk, J. Boersma, A. L. Spek and G. van Koten, J. Organomet. Chem. 1999,585,93. 47. C. Hartbaum, E. Maw, G. Roth, K. Weissenbach and H. Fischer, OrganometalEics 1999,18,2619. 48. G . K. Cantrell, S. J. Geib and T. Y. Meyer, Organometallics 1999, 18,4250. 49. H. Fischer and H. Jungklaus, J. Organomet. Chem. 1999,572,105. 50. R. Aumann, R. Frohlich, J. Prigge and 0. Meyer, Organometallics 1999, 18, 1369. 51. R.-Z. Ku, J.-C. Chuang, J.-Y. Cho, F.-M. Kiang, K. R. Reddy, Y.-C. Chen, K. J. Lee, J.-H. Lee, G.-H. Lee, S.-M. Peng and S.-T. Liu, Organometallics 1999, 18,2145. 52. H. G. Raubenheimer, Y. Standar, E. K. Marais, C. Thompson, G. J. Kruger, S. Cronje and M. Deetlefs, J. Organomet. Chem. 1999,590, 158. 53. M. M. Abd-Elzaher and H. Fischer, J. Organomet. Chem. 1999,588,235. 54. T. Lehotkay, P. Jainter, K. Wurst and F. R. KreiDl, J. Organomet. Chem. 1999, 583, 120. 55. L. Giannini, E. Solari, S. Dovesi, C. Floriani, N. Re, A. Chiesi-Villa and C. Rizzoli, J, Am. Chem. SOC.1999,121,2784. 56. K. E. Torraca, I. Ghiviriga and L. McElwee-White, Organometallics 1999, 18, 2262. 57. M. E. Garcia, V. Riera, M. T. Rueda, M. A. Ruiz and S. Halut, J. Am. Chem. SOC.1999,121,1960. 58. M. A. Alvarez, M. E. Garcia, V. Riera and M. A. Ruiz, Organometallics 1999, 18, 634. 59. A. Mayr, M. P. Y. Yi and V. W.-W. Yam, J. Am. Chem. SOC.1999,121,1760. 60. L. Weber, G. Dembeck, R. Boese and D. Blaser, Organometallics 1999, 18,4603. 61. C. C. S. Cavalheiro, K. E. Torraca, K. S. Schanze and L. McElwee-White, Inorg. Chem. 1999,38,3254. *

278

Organometallic Chemistry

Part IV: Group 7 by Jason M. Lynam A study of the rhenium complexes of the fascinating isonitrile CNNPPh3 has been reported.’ Treatment of ReBr(C0)3(CNR)(CNMe) (R = Ph or Pr”) with CNNPPh3 results in a simple substitution reaction and formation of ReBr(CO)3(CNR)(CNNPPh3), 1. Reaction of 1 with ketones O=CR’R” in the presence of a catalytic amount of HBF4 gives ReBr(CO)3(CNR)(CNNCR’R’’) (R’ = R” = Me, R’ = Me, R” = Ph and CR’R’= C(CH&]. The reaction of 1 with NH2Pri was also reported. The rhenium bis-isonitrile complex ReCl(4CN-3,5-Pri2-C6H2C-CH)2(CO)3,2, has been prepared by the reaction of ReCl(CO),(thf), with 4-CN-3,5-Pri2-C6H2C~CH.2 This is one of a series of complexes in which the isonitrile contains groups which might act as ligands to a second metal centre, the aim being to use them as building blocks in molecular arrays. The reaction between [Mn(CN)(PR3)(NO)(q5-C5H4Me)](R = Ph or OPh), NaBPh4 and AgCl(tht) results, surprisingly, in the formation of [Mn(CN(BPh3)(PR3)(NO)(q5-C5H4Me)], which was characterised by X-ray ~rystallography.~ These complexes may also be formed by direct reaction of [Mn(CN)(PR3)(NO)(q 5-C5H4Me)]with BPh3. A discussion, using structures from the Cambridge Structure Database, of the bonding in adducts L+BPh3 was also made. Similar complexes have been reported from the reaction of [Mn(CN)(C0)2(P{OEt)3)(dppm)] with an excess of SbCl,; this results in the formation of the paramagnetic Lewis base adduct trans[Mn(CN-+SbC15)(CO)2(P{ OEt}3)(dppm)][sbC16].4 The complex was characterised by IR, EPR and a single crystal X-ray crystallography and forms part of a discussion on the nature of L+SbC15 interactions. A kinetic study into the alkylation of metal-cyanide complexes by 4nitrobenzenesulfonate has been r e p ~ r t e d A . ~ range of metal complexes were investigated, including Mn(cO)(dp~m)~(CN),Mn(C0)2({PPh2CH2)3CCMe3)(CN), Re(C0)3(dppm)CN and Mn(CN)(C0)3(T16-CgMe6). The reaction was shown to be first order in both metal complex and 4-nitrobenzenesulfonate, consistent with a mechanism involving nucleophilic attack by the nitrogen atom of the cyanide ligand on the alkylating agent. The alkylation of [NB~~][trans-Re(CN)~(dppe)~] to give tran~-[Re(CNR)2(dppe)~] has been subjected to a kinetic study.6 It was found that the first alkylation step to give tran~-Re(CNR)(CN)(dppe)2was more rapid than the second alkylation and that the presence of NaI inhibited the reaction, presumably due to the formation of ion pairs such as [Re(cN)(CNNa)(dp~e)~]. The crystal structures of pBu4][trans-Re(CN)2(dppe)2] and trans-Re(CN)2(dppe)2 were also reported. Reaction of [Mn(salen)(H20)]C104with NaCN results in the formation of a one-dimensional coordination polymer [ { Mn(salen)(CN)}x].7 The polymer was studied by SQUID magnetometery and appeared to possess an equal number of uniformly distributed high spin (S = 2) and low spin (S = 1) Mn centres. There has been continued interest in the use of methylrhenium trioxide (MTO) as an oxidation catalyst, and a review article on its chemistry has

10: Complexes Containing Metal-Carbon c-Bonds

279

appeared.8 Trifluoroethanol has been shown to be an excellent solvent for the epoxidation of alkenes by the MTO system, giving higher rates than similar reactions in CH2C12.' In the presence of PPh3, MTO has also been shown to catalyse the desulfurisation of thiiranes to give alkenes. Pre-treating the solution with H2S results in an increase in the rate of desulfurisation leading to the belief that the active species in the reaction mixture is a Re(VI1) compound with a Re=S bond." MTO has been shown to oxidise trialkylsilanes to silanols, which reaction was subjected to a kinetic and theoretical investigation. l 1 MTO also oxidises P(4-Me-C6H5)3to OP(4-Me-C6H5)3.'2 This study crucially proved that methylrhenium dioxide (andor its phosphine adduct) reacts with 02.Methylrhenium dioxide has been shown to abstract an oxygen atom from tertiary hydrogen peroxides giving MTO; again the reaction was subjected to a kinetic study,l3 as was the MTO-catalysed sulfoxidation of thioketones and ~ulfines.'~ MTO and hydrogen peroxide do not appreciably catalyse the oxidation of alcohols; addition of a catalytic amount of Br-, however, greatly enhances the rate.15 A kinetic study established that the Br2 was probably the active oxidising agent in the system. A theoretical investigation, using ab initio methods, into the mechanism of the rearrangement of allyl alcohols catalysed by MTO, has been reported? Studies of the epoxidisation of allyl alchols by MTO has also been de~cribed.'~ The selective oxidation of terminal alcohols to aldehydes using a four component (MTO, H202, HBr, TEMP) system has been described; this system is particularly useful for oxidation reactions involving carbohydrates. * Reaction of MTO with picH (picH = 2-pyridinecarboxylicacid) affords [Re(CH3)0(pi~)~] which is an active catalyst for alkene epoxidation.'' Treatment of MTO with AdNCO results in the formation of Re(CH3)(NAd3) which reacts with aromatic aldehydes to give ArC(H)=NAd.20The rhenium-containing product of the reaction was MTO, formed by sequential oxygen transfer reactions. Reaction of Re(CH3)(NAd3) with imines results in metathesis. In the presence of H202and acetic anhydride, MTO catalytically oxidises 2-methylnapthalene to 2-methyl-1,4naphthoquinone (Vitamin K3) with acetic acid as solvent.21The reaction was subjected to a kinetic study and the influence of acetic anhydride was investigated. The optically pure chiral-at-rhenium complex [Re(CH3)(NO)(PPh3)(q5CSMe4Pin)l {Pin= (+)-pinany11 has been prepared and the presence of the Pin group has been used to probe its stereochemical behaviour.22 Fractional crystallisation of the diastereoisomeric complex [Re(CONHCH(CH3)CloH7)(NO)(PPh3)(qS-CsMe4Pin)]afforded optically pure product. Treatment of the (RRe) complex with NaOMe and CF3C02H gave optically pure [Re(CH3)(NO)(PPh3)(q'-C5Me4Pin)]. Reaction of the methyl complex with HBF4 in CD2C12 results in the formation of [Re(CD2C12)(NO)(PPh3)(q 5CSMe4Pin)][BF4].At -80 "C the product is predominantly one diastereoisomer; however, on warming to -4O"C, a 1:l mixture of diastereoisomers was obtained indicating that the complex [Re(CD2C12)(NO)(PPh3)(qSCSMe4Pin)][BF4]has a low conformational stability. Reaction of [M(CH2Ph)(CO)5](M = Mn or Re) with Ph3P=NPh gives good

280

Organometallic Chemistry

yields of the cyclometalated complexes 3 (see Scheme 1). It is of interest to note that the manganese complex shows thermochromic b e h a ~ i o u rSimilar . ~ ~ reactions were observed between [Mn(CH2Ph)(CO),] and Ph3As=X ( X = O or S) although yields were lower in these two cases. Reaction of [Mn(CH2Ph)(CO),] with AsPh3 does not lead to a selective reaction. However, from the reaction mixture crystals of 4 were isolated. Ph

Ph

3 Scheme 1

The complex fa~-Re(CO~H)(Co)~(dmbpy), 5 , readily converts into facfacRe(C0)3(dmbpy)(C{0}O)Re(C0)3(dmbpy), 6, in DMF solution at room temperature. Treatment of 6 with C02 yields fac-Re(OC(O}OH)(C0)3(dmbpy), as does a similar reaction of Re(OH)(C0)3(dmbpy).H20 with C02.24A series of manganese and rhenium trifluoroacetoxymethyl complexes have been prepared; for example, reaction of fa~-Mn(CH~oCH~)(CO)~(dppp) with trifluoroacetic acid results in formation of fac-Mn(CH20C { 0}CF3)(CO)3(dppp) and methanol.25 Similarly, the iodomethyl complex facMn(CH21)(C0)3(dppp) can be prepared by reaction of fac-Mn(CH20CH3)(C0)3(dppp) with Si(CH3)31, the other product from the reaction being (CH3)3SiOCH3. Reaction of the rhenium imido complex [ReTp(N-p-tol)X2]with organolithium, Grignard or organozinc reagents results in the formation of either [ReTp(N-p-tol)RX] (X=Cl, Br, I, R = P h , Me, Et, Pr' or Bun) or [ReTp(N-ptol)R2] (R = Me or Ph) depending on the reaction conditions and nature of the organometallic nucleophile employed.26 The halides in many of these complexes may be exchanged for triflate by reaction with AgOTf. Fascinatingly, a similar reaction of [ReTp(N-p-tol)PhI] with AgPFB does not result in halide abstraction, but gives the silver bridged dimer [ (ReTp(N-p-tol)PhI}2Ag]PF6.A kinetic study of the reaction of [ReTp(N-p-tol)R(OTf)] with pyridine to give [ReTpW-p-tol)R(py)]was also reported. A study of the reaction of the complexes [keR(CO){q5-C5H4C2H4&H(CH3))]+ (R=CH2C(O)CH3, CH3) with amines has been reported.27 In the case where R = CH2C(0)CH3the reaction with Bu"NH2 leads to the reversible

281

10: Complexes Containing Metal-Carbon a-Bonds

formation of [ReR{C(0)NHBu") { q5-C5H4C2H4NH(CH3{]+; heating t y mixture in CH2C12 solution resulted in the formation of [ eR(NHBu"){q C5H&H4$JH(CH3)}]+. When the reaction was repeated with the complex in was obtained. A which R = CH3 [keH(NH2Bu")(q5-C5H4C2H4fiH(CH3))1+ reaction of either of the two parent complexes with hydrazine resulted in the eventual formation of the isocycanate complexes [keR(N=C=O){ q5C5H4C2bAH(CH3))1' Reaction of [Re12(CO)2(q5-C5Me5)] with methylcopper results in selective monomethylation to give [ReMeI(C0)2(q5-C5Mes)].28 Also, photolysis of [ReMePh(C0)2(qS-C5Me5)]under a CO atmosphere in cyclohexane solution results in the formation of [Re(C0)3(q5-C5Me5)],benzene and methane. In CC14 solution, under a CO atmosphere, photolysis of [ReMe(p-tol)(CO)2(q5whereas a similar C5Me5)] gave CHC13 and [Re(p-t~l)Cl(CO)~(q~-C~Me& reaction with [ReMe2(CO)2(q5-C5Mes)] gave mostly [ReC12(CO)2(q5-C5Me5)] and CHC13. Reaction of LiRe(NO)(PPh3)(q'-C5H5) with excess C02 results in the formation of 7 (see Scheme 2).29 Complex 7 may also be formed by the reaction of Re(NO)(PPh3)(q5-C5H5)(C02)Kwith either C02 or [Re(NO)(CO)(PPh3)(q5-C5H5)]+.The reactions of 7 with silanols, water and alcohols are reported.

ON'

Re 'PPh3

Scheme 2

Nucleophilic attack of the deprotonated barbituic acid 8 with [Re(q2C2H4)(CO)5][BF4] results in the formation of complex 9 (see Scheme 3).30 The barbituric acid derivatives are N-protected hence preventing the formation of hydrogen-bonded arrays. It is hoped that transition metal complexes such as these may be used as detectors for barbiturate drugs. S

S

8

9

Scheme 3

The q2-thioaldehyde complexes [Re(NO)(PPh3)(q2-S=CHR)(q5-C5H5)1[PF6] (R = CH2Ph, C02Et, CH2C02Me, CH2C(O)NHCH2Ph, (R)-CH(NC8H4O2)CO2Me,(S,S-CH(Me)C(0)NC4H7C02Me, C4H30) have been obtained by hydride abstraction from [Re(NO)(PPh3)(S=CH2R)(q5-C5H5)] by

282

Organometallic Chemistry

[Ph3C][PF6];single stereoisomers were formed in these reactions (except in the case where R = C02Et).31Subsequent reactions with nucleophiles and dienes (in a Diels-Alder-type reaction) resulted in attack at the thioaldehyde ligand, although they proceeded with low diastereoselectivity. Reaction of ReOC1(CH3)2(PMe3)2 with 2,2’-bipyridine (bpy) in the presence of pyridine N-oxide resulted in the formation of ~is-ReOCl(CH~)~(bpy) .32 In contrast, reaction of ReOC13(bpy)afforded trans-ReOCl(CH3)2(bpy). Heating the cis-isomer in [2H6]benzenesolution resulted in the trans isomer as the only product: a kinetic study of this reaction was undertaken. Both of these complexes are catalytic precursors for ethene polymerisation. Reaction of the cis-isomer with Ag+ in acetonitrile solution results in the formation of cisReOC1(CH3)2(bpy)(NCMe)]+;the acetonitrile ligand is labile and may be replaced by phosphine and phosphite ligands. Group 7 metal complexes have again been used to probe the mechanism of hydrodesulfurisation. Reaction of diphenyl-2-thienylphosphine, 10, with Mn2(CO)loin refluxing xylene leads to the formation of ll.33 The analogous reaction with Re2(CO)lo requires more forcing conditions (refluxing decane) and gives 12.

Ph2 10

11

Ph2

12

Perutz and co-workers have continued their study of the reaction of halfsandwich rhenium complexes with fluorinated aromatic corn pound^.^^ For example, photochemical reaction of [Re(C0)3(q5-C5H5)]with C6F5H yields [Re(C0)2(r15-C5H5)(C6F5)H] as the major photoproduct. This is in contrast to the previously reported reaction with C6F6 which affords an q2-C6F6 complex; the balance between C-H and C-F activation is discussed. There has been a continued interest in the chemistry of manganese and rhenium complexes with metal-carbon multiple bonds, particularly focusing on their optical and electronic properties. A review article describing the expanding field of luminescent metal acetylide complexes has appeared, and includes several examples of Re(1) actylide complexes.35 The paramagnetic complex [I(dppe)2Mn-C-C-C=C-MnT(dmpe)2],which has a triplet ground state, has been prepared by the reaction of [MnI(dmpe)(q5C5H4Me)]with M ~ ~ S ~ - C ~ C - C Z C - SCyclic ~ M voltametry ~ ~ . ~ ~ and synthetic studies show that [I(dppe)2Mn-C-C-CrC-MnI(dmpe)2]can be selectively, and reversibly, oxidised to [I(dppe)2Mn-C-C-C=C-MnI(dmpe)2]+ and [I(dppe)2Mn=C=C=C=C=MnI(dmpe)2]2+ which possess one and no unpaired electrons respectively. Due to this electrochemical behaviour, these complexes represent a further advance towards well-defined one-dimensional conducting polymers and materials for non-linear optics. In an elegant study, treatment of manganeseocenes M ~ ( T ~ ~ - C(R ~= HH~ or R Me) ) ~ with one equivalent each of

283

10: Complexes Containing Metal-Carbon o-Bonds

dpme and alkynes R'C-CR2 (R'=Ph, SiMe3, R 2 = H , SnMe3) results in the formation of Mn(-C-CR')(dmpe)(q5-C5H4R) and elimination of C5H4RR2.37 Treatment of these acetylide complexes with a further equivalent each of dpme and R'C=CR2 results in elimination of a second C5H4RR2and formation of Mn(-CSR')z(dmpe)2: this complex could also be obtained by treating Mn(q5C5H4R)2with two equivalents of dpme and R'C-CR2. The mono acetylide complexes undergo reversible one-electron oxidation to give [Mn(-CrCR')(dmpe)(q5-C5H4R)]'. The complexes Mn(-C=CR')(dmpe)(q5C5H4R) readily undergo hydrogen radical scavenging reactions to give the vinylidene complex Mn(=C=CR'H)(dmpe)(q'-C5H4R); however, this reaction is in competition with carbon-based radical couplings which give the dimeric complexes (q 5-C5H4R)(dmpe)Mn(=C=CR-R C=C=)Mn(dmpe)(q 5-CsH4R). The electrochemical and structural properties of these dimeric complexes were examined Reaction of Re(C0)3(bpy)(-C=CPh) with [M(CNMe)4]+ (M = Cu, Ag) results in formation of complexes [{ q2-Re(C0)3(bpy)(-CrCPh))2M]+.3* The crystal structures of both complexes and their luminescent behaviour were reported. Treatment of Re(CO)2(triphos)(OTf) with propargyl alcohol HCECCRR'OH results in the formation of a series of complexes containing Re-C multiple bonds.39 For example, reaction with HCGCCPhR'OH (R' = Me or Ph) yields [Re(C0)2(=C=C=PhR')(triphos)][OTf]. However, an intriguing reaction occurs with HCECCH~OH:in MeOH the product is 13, whereas in CH2C1214 is produced. The sp carbon chain in the complex Re(q5-

' '

OC' L O H2C-C,-H H 13

L

14

C5Me5)(NO)(PPh3)(-CrC-C=C-SiMe3) has been shown to be easily expanded to give Re(q5-C5Me5)(NO)(PPh3)(-C-C-C=C-C=C-C=C-SiR3) (R = Me, Et).40The silyl groups may then be replaced by aromatic groups to give the complexes Re(q5-C5Me5)(NO)(PPh3) (-C=C-(C&-),-p-tol } (n = 2, 15; 3, 16). Fascinatingly, the crystal structures of these compounds show that the spcarbon chains are bent (see Figure l), the bending being thought to be due to crystal packing forces. Protonation of complex 15 with HBF4.OEt2 leads to the vinylidene complex Re{=C(H)C=C-C=C-p-tol}(NO)(PPh3)(q5-C5Me5). Treatment of Re(-CrC-CrCR)(NO)(PPh3)(q5-C5Me5)(R = Me or H) with (Bu~O)~W(W(OBU')~ results in a smooth metathesis reaction to give

284

Organometallic Chemistry

Figure 1 (Reprinted from J. Organomet. Chem., 578, R. Dembinski, T. Lis, S. Szafert, C.L. Mayne, T. Bartik and J.A. Gladysz, ‘Appreciably bent sp carbon chains: synthesis, structure, and protonation of organometallic 1,3,5-triynes and 1,3,5,7-tetraynes of the formula (q5-C~Mes)Re(NO)(PPh,)((CC)~-C6H4Me)’, p. 229, 0 1999, with permission from Elsevier Science)

Re(-C=C-C( W(OBu‘) 3(NO)(PPh3)(q 5-C5Me5) and RC(W(OBU‘)~ .4 The crystal structure of the complex shows that it exists as a solvated tert-butoxy bridged dimer in the solid state. Atomic manganese has been reacted with CH2N2 in argon matrices. The formation of MnCH2 and Mn(CH2N2) complexes has been observed by FTIR?2 Photolysis of the matrix (A >, 400 nm) results in the destruction of all the complexes except for one of the Mn(CH2N2) complexes. Treatment of the rhenium carborane complex [Re(N0)(CO),(q5-7,8C2B9H1 17 with LiR (R = Ph, C6H4-4-Me)followed by [Me30][BF4]results in the formation of the carbene complex [Re(=C(OMe)R)(CO)(q 5-7,8n

Bu’NC’

\ NO

18

285

10: Complexes Containing Metal-Carbon a-Bonds

C2B9H11)].43 The two carbonyl ligands in 17 can be replaced by a range of other donor ligands, such as phosphines and isonitriles, to give [Re(NO)LL'(q 5-7,8-C2BgH1 Protonation of [Re(NO)(CNtBu)2(q 5-7,8C2B9Hll)]results in insertion into the carborane cage to give 18. Reaction of [Mn{=C(OEt)CH2}(C0)2(q5-C5H4Me)]-, 19, (generated by deprotonation of [Mn{=C(OEt)CH3}(CO)2(q5-C5H4Me)])with aldehydes, such as PhCHO) affords [Mn{=C(OEt)CH=CHPhf (CO)z(q5-C5H4Me)l,20. The reaction is a general one giving analogous products for a range of ferrocenyl and vinyl substituted aldehydes.4q Reaction of 20 with TfOH affords [Mn{q2-HC(0)CH=CHPh}(C0)2(qS-C5H4Me)], 21, which, on treatment with PPh3 or acetonitrile, results in decomplexation of the vinyl aldehyde. All the synthetic steps (which are summarised in Scheme 4) occur in reasonable yield making this route an excellent one for the conversion of aldehydes into vinyl aldehydes.

20

19

I

t-c/ H

R-9

4 H

'b

TfoH

+ PPhQ

H 21 Scheme 4

Reaction of the manganese carbyne complex [Mn((CPh)(C0)2(q5-C5H5)]+, 22+, with MeN(H)CH2CH=CH2 affords [Mn(=C(Ph)N(Me)CH2CH=CH2}(C0)2(q5-C5H5)],23, which on photolysis gives [Mn{=C(Ph)N(Me)CH2(q2CH=CH2}(C0)(q5-C5H5)],24 (see Scheme 5).45 In contrast, photolysis of [Mn(=C(Ph)N(Me)CH2CH=CHCH20H}(C0)2(q5-C5H5)] (prepared by the reaction of 22+ with MeN(H)CH2CH=CHCH20H) does not result in the loss

Scheme 5

286

Organometallic Chemistry

of CO and formation of a chelate complex. The cationic metal carbyne complexes [M((CPh)(C0)2(q5-C5H5)J+ (M = Mn, 22+ or Re, 25') have been shown to be useful building blocks in the construction of metal cluster compounds. For example, reaction of 22+ with [Fe(C0)4(CN)]- results in the formation of 26 (see Scheme 6), whereas treatment with [Mn(C0)4(CN),]results in the formation of the tri- and tetranuclear complexes 27 and 28 (Scheme 6).46Reaction of 22+ with w(CO)s(NCO)]' gives 29 whereas reaction of 23+ yields 30. When 22+ is reacted with [w(CO)5(SCN)]' loss of the sulfur atom occurs to give 31; interestingly 32, an isomer of 31, is formed by the analogous reaction with [w(CO)s(CN)]'.47

f

26

. ..

Scheme 6

NH

29

31

Ph

Ph' 30

32

10: Complexes Containing Metal-Carbon a-Bonds

287

References 1. 2. 3. 4. 5. 6. 7.

8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31.

J. S. Fan, F. Y. Lee, C. C. Chiang, H. C. Chen, S. H. Liu, Y. S. Wen, C. C . Chang, S. Y. Li, K. M. Chi and K. L. Lu, J. Organometal. Chern., 1999,580,82. L. Yang, K. K. Cheung and A. Mayr, J. Organometal. Chem., 1999,585,26. D. Bellamy, N.G. Connelly, 0. M. Hicks and A. G. Orpen J. Chem. SOC.,Dalton Trans., 1999,3185. D. Bellamy, N. C. Brown, N. G. Connelly and A. G. Orpen, J. Chem. Soc., Dalton Trans., 1999, 3191. L. A. Cardoza and R. J. Angelici, Inorg. Chem., 1999,38, 1708. M. Fernanda N. N. Carvalho, M. T. Duarte, A. M. Galviio, A. J. L. Pombeiro, R. Henderson, H. Fuess and I. Svoboda, J. Organometal. Chem., 1999,583,56. N. Matsumoto, Y. Sunatsuki, H. Miyasaka, Y. Hashimoto, D. Luneau and J.-P. Tuchagues, Angew. Chem., Int. Ed., 1999,38, 171. J. H. Espenson, Chem. Commun., 1999,479. M. C. A. van Vliet, I. W. C. E. Arends and R. A. Sheldon, Chem. Cornrnun., 1999,821. J. Jacob and J. H. Espenson, Chem. Commun., 1999, 1003. H. Tan, A. Yoshikawa, M. S. Gordon and J. H. Espenson, Organometallics, 1999,18,4753. M. D. Eager and J. H. Espenson, Inorg. Chem., 1999,38,2533. K. A. Brittingham and J. H. Espenson, Inorg. Chem., 1999,38,744. R. Huang and J. H. Espenson, J. Org. Chem., 1999,64,6374. J. H. Espenson, Z. Zhu and T. H. Zauche, J. Org. Chem., 1999,64,1191. S. Bellemin-Laponnaz, J. P. Le Ny and A. Dedieu, Chem. - Eur. J. 1999,5, 57. H. R. Tetzlaff and J. H. Espenson, Inorg. Chem., 1999,38,881. W. A. Herrmann, J. P. Zoller and R. W. Fischer, J. Organometal. Chem., 1999, 579,404. A. Deloffre, S. Halut, L. Salles, J.-M. BrCgeault, J. R. Gregorio, B. Denise and H. Rudler, J. Chem. Soc., Dalton Trans., 1999,2897 W. D. Wang and J. H. Espenson, Organometallics, 1999,18,5170. W. A. Herrmann, J. J. Haider and R. W. Fischer, J. Mol. Catal. A , 1999, 138, 115. A. Salzer, A. Hosang, J. Knuppertz and U. Englert, Eur. J. Inorg. Chem., 1999, 1497. M. A. Leeson, B. K. Nicholson and M. R. Olsen, J. Organometal. Chem., 1999, 579, 243. D. H. Gibson and X. Yin, Chem. Commun., 1999, 1411. D. A. Brown, S. K. Mandal, D. M. Ho, T. M. Becker and M. Orchin, J. Organometal. Chem, 1999,592,61. W. S. McNeil, D. D. DuMez, Y. Matano, S. Lovel, and J. M. Mayer, Organometallics, 1999, 18, 37 15. T.-F. Wang, C.-C. Hwu, C.-W. Tsai and Y.-S. Wen, Organometallics, 1999, 18, 1553. C. Leiva, A. H. Klahn, F. Godoy, A. Toro, V. Manriquez, 0. Wittke and D. Sutton, Organometallics, 1999, 18, 339. S. M. Tetrick and A. R. Cutler, Organometallics, 1999, 18, 1741. 0. E. Woisetschlager, K. Sunkel, W. Weigand and W. Beck, J. Organometal. Chem, 1999,584, 122. N. Burzlaff and W. A. Schenk, Eur. J. Inorg. Chem., 1999, 1435.

288

32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47.

Organometallic Chemistry

J. H. Jung, T. A. Albright, D. M. Hoffman and T. R. Lee, J. Chem. SOC.,Dalton Trans., 1999,4487. A. J . Deeming, M. K. Shinhmar, A. J. Arce and Y. De Sanctis, J. Chem. SOC., Dalton Trans., 1999, 1153. F. Godoy, C. L. Higgitt, A. H. Klahn, B. Oelckers, S. Parsons and R. N. Perutz, J. Chem. SOC.,Dalton Trans., 1999,2039. V. W. W. Yam, K. K. W. Lo and K. M. C. Wong, J. Organometal. Chem, 1999, 578, 3. S. Kheradmandan, K. Heinze, H. W. Schmalle and H. Berke, Angew. Chem., Int. Ed., 1999,38,2270. D. Unseld, V. V. Krivykh, K. Heinze, F. Wild, G. Artus, H. Schmalle and H. Berke Organometallics, 1999, 18, 1525. V. W. W. Yam, S. H. F. Chong, K. M. C. Wong and K. K. Cheung, Chem. Commun., 1999,1013. C. Bianchini, N. Mantovani, A. Marchi, L. Marvelli, D. Masi, M. Peruzzini, R. Rossi and A Romerosa Organometallics, 1999,18,4501. R. Dembinski, T. Lis, S. Szafert, C . L. Mayne, T. Bartik and J. A. Gladysz, J. Organometal. Chem., 1999,578,229. R. Dembinski, S. Szafert, P. Haquette, T. Lis and J. A. Gladysz, Organometallics, 1999,18,5438. W. E. Billups, S. C. Chang, J. L. Margrave and R. H. Hauge Organometallics, 1999,18,3551. D. D. Ellis, P. A. Jelliss and F. G. A. Stone, Chem. Commun., 1999,2385. C. Mongin, Y. Ortin, N. Lugan and R. Mathieu, Eur. J. Inorg. Chem., 1999,739. S.-E. Eigemann and R. Schobert, J. Organometal. Chem., 1999,585, 115. Y. Tang, J. Sun and J. Chen, Organometallics, 1999,18,4337. Y. Tang, J. Sun and J. Chen, Organometallics, 1999,18,2459.

Organo-Transition Metal Cluster Complexes BY MARK G. HUMPHREY AND MARIE P. CIFUENTES

1

Introduction

This chapter covers the chemistry of metal carbonyl and organometallic clusters containing three or more metal atoms. The treatment is in Periodic Group order, homometallic compounds being followed by heterometallic clusters. The numbered compounds are illustrated. Ligands are not shown for high-nuclearity clusters, emphasis being placed on core geometry. 2

General Reviews

The first reference set on cluster chemistry, a three volume collection covering synthesis, structure, dynamics, and applications, has appeared, the synthesis, structure and chemistry of tri- and tetranuclear clusters with face-capping C7H7and C8Hs ligands ligands have been reviewed,2and the recent chemistry of large clusters, their application to nanoscale devices, and their use as precursors to nanoparticles have been ~ummarised.~ The synthesis, characterisation, and catalytic application of transition metal nanoparticles have also been r e v i e ~ e d . ~

3

SpectroscopicStudies

3.1 IR. - Spherical (SHM) and tensor (THM) harmonic models have been applied to interpret the terminal v(C0) spectra of a range of tetrahedral clusters; although equally applicable to the clusters surveyed, THM behaviour becomes increasingly rare as cluster size increases, and the SHM is therefore the more generally relevant.5 Subtractively normalised interfacial FTIR spectroscopy (SNIFTIRS), which affords absorbance difference spectra induced by changes in electrode potential, has been employed for the first time with metal carbonyl complexes; studies with (CO)9C03(p-C2)Co3(CO)9 agree with results using conventional OTTLE techniques, but provide more information of the dominant species on chemically important time scales.6

Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001 289

290

Organometallic Chemistry

3.2 NMR. - The dynamic and structural information available from solidstate multinuclear NMR measurements has been compared and contrasted with data obtained from solution NMR and other spectroscopic and structural measurements for tetra- and higher-nuclearity transition metal carbonyl clusters, solid-state NMR providing useful information in the absence of twinning and disorder problems as there is a resonance for each crystallographically distinct site.7 Inverse detected multiple quantum coherence (HMQC) experiments have been performed on substituted derivatives of Rh6(CO)16;cross peaks are displaced from the true chemical shift, additional cross peaks are seen, and the intensity of the coherence is zero at the conventional mixing delay of 1/(2J), the authors concluding that the spin system must be analysed carefully to determine the optimal mixing delay in situations where coupling of the detector nucleus to several insensitive spins can occur.' Para-hydrogen induced polarisation has been used to enhance NMR signals in the R U ~ ( C O ) ~ ( P P ~system, ~ ) ~ / H the ~ enhanced hydride resonances demonstrating the existence of R u ~ ( ~ - H ) ( H ) ( C O ) ~ ( Pwhich P~~)~ subsequently fragments to afford R u ( H ) ~ ( C O ) ~ ( P P ~ ~ ) . ~ 3.3 MS. - The application of electrospray mass spectrometry (ES MS) to the study of metal carbonyl cluster complexes has been further developed, previous studies having shown the utility of MeO- as a derivatisation agent. Replacing MeO- with N3- usually affords the corresponding isocyanate-containing compounds following elimination of N2, but in some instances [M + N3]- is observed, and hydride-containing clusters can undergo competitive proton abstraction; the technique is therefore not as general or useful as the alkoxide derivatisation procedure, but may have utility in guiding subsequent preparative studies.lo A series of 'electrospray-friendly' ligands [PPh,(C6H40Me- ~ )been ~ ] synthe4)3 --n, PPh,(C6H4NMe2-4)3--n (n = 0-3), A s ( C ~ H ~ O M ~have sised, with their cluster adducts affording [M + H]+ ions in their spectra, in contrast to their PPh3-containing analogues." ES MS has been used to monitor the synthesis of [MogRh2(p3-0)~(~.~-0)4(p-OMe)2(0)1&p*2]~-,the intermediacy of [Mo~Rh(p~-O)(p3-OMe)(~-O)2(p-OMe)~(0)~(OMe)2Cp*]~ being established.l 2 Laser vaporisation of Fe, Co or Ni, followed by cooling and reaction with benzene vapour, affords binary clusters, the photo-ions from which have been mass-analysed by a reflection time-of-flight mass spectrometer; the observed mass peaks are consistent with transition-metal clusters surounded by benzene ligands. 3.4 Theory. - Density functional theory (DFT) has been applied to several cluster systems. The series M ~ ( P ~ - E ) ~(M=Cr, C P ~ Mo; E = 0 , S) has been examined; the sulfur-containing clusters have 12 cluster valence electrons (c.v.e.) delocalised in six M-M bonds, giving a tetrahedral core, whereas for the M = Cr, E = 0 example these electrons remain localised on the Cr atoms, and no strong Cr-Cr bonds exist. Low-lying excited states for the chromiumcontaining clusters result in this bonding pattern being reversed in the excited

1 I : Organo-Transition Metal Cluster Complexes

29 1

state - six M-M bonds for E = 0 , none for E = S.14 Although only one example of M ~ ( P ~ - E ’ ) ( ~ ~has - E )been ~ L ~synthesised thus far, results from a DFT study suggest that other examples should be accessible, with likely c.v.e. counts of 120 or 122, the former being favoured for E=early main-group element, and the latter for E = late main-group element. The high connectivity in these clusters is predicted to favour open-shell configuration^.'^ A DFT study of [Fe,Pt3(CO)I $- (n = 0-2) reproduces experimental geometries, and suggests a Pt-Pt antibonding character of the HOMO, with delocalised cluster magnetisation for the mono-anion.l6 Comparative calculations at the selfconsistent field (SCF), second-order Moller-Plesset (MP2) and DFT levels of theory show that only the last-mentioned is able to properly describe the energetics of all members of M3(CO)12 (M = Fe, Ru, Os), structural preferences for terminal vs bridge bonding for CO ligands being determined by a balance of metal-bridge bonding, metal-metal bonding, and intermetallic repulsion.l 7 Extended Huckel (EH) and DFT calculations on Pdg(p-A~2)~(PPh3)8, the core of which has an interstitial Pd atom (Pdi) in a &,-distorted Pd8 cube, reveal that the bonding of Pdi with As is more important than bonding of Pdi with Pd8, in contrast to related metal-centered cubic M9(p4-E)6L8 clusters.l8 EH and DFT calculations on triangular electron-rich 50-electron M3L, clusters reveal weak M-M bonding, with n-donor bridging ligands enhancing stability and terminal or n-acceptor ligands decreasing stability.l 9

4

Structural Studies

A quantum theory of atoms in molecules (QTAM) analysis of the experimental electron density of C O ~ ( ~ - C O ) ~ ( C O ) ~has (PP shed ~ ~ light ) on the differences between supported and unsupported M-M interactions, confirming that the M-C-M bonds in the former are delocalised three-centre interactions and that M-M bonding is indirect because it is achieved through the C0.20 X-ray structural studies of the following complexes have been reported: Fe3(p3-r12-C=C’CPh2)2(co)8,21 (PMePh3)2[R~3(~-CO)(CO)l~]~2 Ru3(ti dppm)(CO)g{ PPh2(C G H ~ NCHPh-2) = 1,23 Os3(C0)1O(PPh3)2 (two isomers), OS~(~-H)(~-~~-OCNHM~)(CO)~(NM~~),~~ OS~(~-H)(~-OCH~CH~OH)c04(P-co)3(co)9,27 CU4@3-X)4~P(OPh)314(X = c1, Br),28 [Au3(p3O)(PPh3)d”CSH2-3,5-(N02)2-4-01,29 WAg3(CL3-Br)(P3-Se)3(pph3)3(Se),30 WAg3(P3 -1)(p3- s)3(PPh3)3(s), Re2Ag(P-PCY2)( c o )8(PPh3),32 FePt2(P3Se)(C0)5(PPh3)2.33

5

Large Clusters

Interest in clusters with nuclearity > 10 continues, but progress is relatively slow as a result of the comparative difficulties of characterisation, together with the lack of general methods of preparation. In this account, the chemistry

292

Organometallic Chemistry

of the more interesting large complexes is gathered together in one place, most of the metal cores being illustrated in Figure 1. Reaction of [IRlo(C0)21I2- and [IR(CO)4]- affords [IRl l(p-CO)9(CO)14]3(1) in very low yields. Cluster 1 and its rhodium analogue possess D3hsymmetric frameworks comprised of three fused octahedra, and have 148 c.v.e., as predicted by the Polyhedral Skeletal Electron Pair Theory (PSEPT); however, the carbonyl disposition in 1 differs from the two isomeric forms of the rhodium cluster.34 Structural studies and variable temperature solid-state H- and 3C-NMR spectra for the previously-reported clusters (NMe4)4-,[Ni12(p6-H)x(pCO)12(CO),] (x = 1, 2) (2) have confirmed that the hydrides are located in octahedral cavities, and displaced toward the central Ni3 triangle, with no evidence for the hydride in the mono-hydrido cluster oscillating between octahedral cavities.35 Re-investigation and optimisation of synthesis of the previously-reported [HNi38C6(C0)42]5- has also afforded the corresponding hexa-anion and dihydrido tetra-anion clusters, protonation of the last-mentioned giving the unstable trihydrido cluster tri-anion. The cluster hexa-anion reacts almost quantitatively with CO to afford the known cluster [Nij2(pgc)6(co)36]6- (3), a structural study of which shows that the truncated octahedral Ni32(pg-C)6 framework is almost identical to the corresponding fragment in [HNi38(pg-C)6(C0)42I5-. Chemical and electrochemical reduction Of these Clusters affords ~i32(p&)(j(co)36]"(n = 7-1 0), [HNi38(pLgC)6(CO)42]"- (n = 6-8) and [Ni3&&)6(C0)42]"(n = 7-9), with many of these redox processes electrochemically rever~ible.~~ Reaction of one equivalent of NOBF4 with [Pt1g(CO)22l4- gives [Ptl9(CO)21(N0)l3- (4), the cluster core of which has the same connectivity as its precursor, namely three apically-fused pentagonal bipyramids; the 236 c.v.e. for 4 is two less than that of the precursor, the electron counts for these clusters being rationalised by EH MO calculations. Addition of two equivalents of NOBF4 to 4 under a CO atmosphere affords [Pt38(Co)u]2- (5); this possesses the largest homometallic core exclusively stabilised by CO ligands, the structure of which is based on a cubic close-packed (c.c.P.) metal core with an inner octahedron with each of the surface Pt atoms bearing a terminal CO ligand, and the coordination completed by 12 edge-bridging C O S . Platinum ~~ nanoparticles have been stabilised previously by alkanethiol interactions, and this has now been extended to isocyanides as capping ligands to afford organometallic nanoparticles, the resultant alkyl isocyanide-protected platinum particles being characterised by transmission electron microscopy (TEM) and time-of-flight mass spectrometry (TOF MS); these studies reveal 2.0 & 0.4 nm metallic cores and clusters of approximately 150 atoms.38 Reactions of copper(1) chloride with RSeSiMe3 (R = Ph, mesityl) and bidentate phosphines afford a series of copper-selenium clusters, amongst which are the crystallographically-characterised cu38Se&ePh)1~(dppb)~ [dppb = Ph2P(CH2)4PPh21, [Cu25Se4(SePh)I 8(dPPP>2]- [dPPP = Ph2P(CH2)3PPh21, Cu36Se5(SePh)26(dppa)4 (dppa = Ph2PC=CPPh2), and cU58se16(SePh),,(dppa),; in these clusters, the Cu-Cu bonding is weak.39 Similar

I I : Organo-Transition Metal Cluster Complexes

293

a

0 Au

*0 \

'O-$,,;O \ *

cu Pt

Ni 0 Au 0 Pd 0

(12) = Ni (13) rn = Ni/Pd disorder

294

Organometallic Chemistry

reactions of CuX (X = C1, SCN) and PR3 (R = Et, Pri), and employing mixtures of RSeSiMe3 (R = Ph, Bu) and Se(SiMe&, afford the crystallographically ~(PP~'~)~, Cu&e35confirmed C U ~ ~ S ~ ~ ( S ~ B U ~ ) ~Cu~OSe20(SeBut)lo(PPri~)~~, (SePh)3(PPri3)21 c u 140Se70(PEt3)34 and c u 14OSe7O(PEtd36s40 The luminescent [Aul2(p3-S)4(p-dppm)6]4+ (6) is formed from the reaction between Au2(p-dppm)C12 and H2S in ethanol/pyridine. Excitation of the macrobicyclic 6 in the solid state and in solution at wavelengths > 350 nm produces long-lived orange-red and green luminescence, respectively; the long lifetime is suggestive of emission from triplet states with LMCT character mixed with metal-centred (ds-dp) states modified by A d . , .Au' interaction^.^^ TEM and small-angle X-ray diffraction has been applied to micro-crystals of Ligand exchange at this cluster by Na2(B12H11SH) under phase-transfer conditions affords the water-soluble [Au&16(B&11 SH)]24- as its sodium salt. Cation exchange of Na+ by pN(oct~l)~]+ results in solubility in polar organic solvents.43 Ligand exchange using 1-pentadecylamine affords gold nanoparticles of expanded (to ca. 5 nm), but reproducible, core size.44 [ R u ~ P ~ ~ ( C Ohas ) ~been ~ ] ~supported on mesoporous silica and decarbonylated by heating, to afford an active catalyst for hydrogenation of alkenes and naphthalene .45 Treating [Mlo(p6-C)(CO)24]2-with Au2(p-dppm)C12in the presence of an [M = Ru (7),Os], with excess of TlPF6 affords M10A~2(p6-C)(p-dppm)(C0)24 the ruthenium example being structurally characterised. The osmium-containing cluster reacts with nucleophiles PR3 by loss of the capping gold units to form [0s 1O( p6-c)(co) 241 - .46 Chemical and electrochemical studies of the previously-reported bimetallic clusters [H6-nNi38Pt6(C0)48]n-[n= 4, 5 (8), 61 are consistent with 'electronsink' behaviour in up to six oxidation states. An almost constant difference in formal electrode potentials for consecutive redox couples in two examples ( n = 5 , 6) is consistent with the absence of a well-defined HOMO-LUMO gap, and is an indication of semiconductor rather than metallic character; it is suggested that an increase of about 50% in currently available nuclearities should suffice for the transition to metallic b e h a ~ i o u r .Reaction ~~ of [Ni6(CO)12]2- with [PtC14I2- (molar ration 2.5: 1) affords co-crystallised mi36Pt4(C0)45]6- (9) and [Ni37Pt4(C0)46]c (10) in 27% yield. The mixture is degraded by 1 atm CO to give [Ni9Pt3(CO)21]4-, and oxidation with [PtC14I2- yields [H6- nNi38Pt6(C0)48]n-, side-products in the synthesis of 9 and 10. Clusters 9 and 10 are stable over several chemical reduction and reoxidation steps.48The dimeric Pt4Cu8(p-q2-C2Ph)1z9and trimeric Pt&u12(pq2-CzPh)24 (11)50 are photoluminescent; unsupported Pt-Pt interactions which link octahedral Pt2Cu4 units are crucial for the photoluminescent behaviour . Reaction between AuC1(PPh3) and N~(OAC)~, followed by treatment with non-stoichio[Ni6(C0)12l2-, affords [ N ~ ~ ~ A U ~ ( C(12). O ) ~The ] ~isostructural metric INi20+xPd12--Au6(C0)44]6- (13) is formed in similar reactions with Pd(OAc)2 or P ~ ( O A C ) ~ / N ~ ( Omixtures, A C ) ~ and is the first high-nuclearity trimetallic carbonyl cluster. These clusters have 38-atom cores which consist of

11: Organo-Transition Metal Cluster Complexes

295

the hexagonal close-packed (h.c.p.) stacking of two inner Ni6M3Au3and two outer Pd3 layers along with two Pd3-capped and six AuNircapped Ni atoms. The disorder in 13 is found at six specific non-adjacent M sites, with x ranging from 2.1 to 5.5 across seven crystals sampled?

6

Group4

The methylation of TiMeC13 under ether-free conditions affords the heterocubane cluster Ti4(p3-C1)4Me4.52Treating TiC14(dmpe) with two equivalents of Bu‘MgC1 gives Ti3(p-C1)3C13(dmpe)3, in which all edges of the triangular Ti3 core are bridged by chlorine atoms and the coordination at each Ti is completed by a terminal chlorine atom and a chelating dmpe ligand.53

7

Group5

Reduction of VCl2(0)Cp* by alkali or alkaline earth metals affords a mixture of the heterocubane cluster V4(p3-0)4Cp*4 (favoured in thf as solvent) and the adamantane cluster V&-O)&p*4 (favoured in toluene), with the latter accompanied by v3(pL-C1)6cp*3. The cubane cluster is paramagnetic (per= 2.35 pg at 300 K).54

8

Group6

8.1 Chromium. - Reaction of Cr2(C0)&p2 with P4Se3 affords 14 and 15, together with lower-nuclearity products; 14 and 15 are also obtained from reaction between Cr2(p-Se)(CO)4Cp2and P4Se3 or P4S3. Heating 14 gives 15, which in turn gives Cr4Se4Cp4,also obtained from heating Cr2(CO)4Cp2 (CrECr) with P4Se3.55

\ j

CpCr,-Se \

8.2 Molybdenum and Tungsten. - Co-thermolysis of Mo2(C0)&p2 and W2(CO)&p2 with grey arsenic affords all four clusters of composition M2M’(p3-As)(C0)&p3 [M, M’ = Mo, W (16)], together with bimetallic products, the reaction presumably proceeding by way of M(=As)(C0)2Cp; the higher yield of the tungsten-containing clusters reflects the greater strength of

296

Organornetallic Chemistry

tungsten-containing bonds compared to molybdenum-containing linkages.56 H ~ ) ~reacted ] ~ + , with triethyl The inorganic cluster [ M o ~ ( ~ ~ - S ) ( ~ - S ) ~ ( Owhen orthoformate in the presence of a catalytic amount of p-toluenesulfonic acid followed by TlCp, gives [M03(p~-S)(p-S)~Cp~lf. This triangular cluster cation is capped on reaction with M’(C0)3(NCMe)3(M’ = Cr, Mo, W), affording the heterocubane clusters [ M o ~ M ’ ( ~ ~ - S ) ~ ( C O ) ~ C ~ ~ ] + . ~ ~ Thermolysis of the metallaborane WH3Cp*B4H8affords 17, with a highlycapped W3 triangle structure analogous to that of a known Rull cluster.58 Three-component reaction of W2(0CH2But)6, W(CO)5(thf) and P-CC6H2But3-2,4,6 gives the triangular W~(CL~-P)(~-OCH~BU~)~(OCH~ and the P-ligated cluster W3 { p3-PW(CO)5}(p-OCH2But)3(0CH2But)6; the former is converted to the latter on reaction with W(C0)5(thf).59

9

Group7

9.1 Manganese. - Reaction between MII~(CO)~O and TeO?- in methanol affords the octahedral cluster dianion 18. Treating 18 with MeOS02CF3gives the Te-metallated cluster anion 19, rather than the expected Te-methylated product; the intermediacy of [Mn(TeMe2)(CO)4]+,presumably from fragmentation of 18 upon methylation, has been shown.60

9.2 Rhenium. - The chemistry of tri-, tetra- and hexanuclear rhenium sulfide clusters has been reviewed, and comparisons with molybdenum sulfide clusters have been drawn.6l A selective synthesis of Re3(p-H)3(CO)12, by hydrogena-

11: Organo-TransitionMetal Cluster Complexes

297

tion of Re2(CO)loin n-octane (350 psi, 170°C) in an autoclave, has appeared; importantly, contamination with Re4(p-H)4(CO)12 is avoided.62 Reaction of Re2(CO)lowith the reducing agent Sm(BH(3,5-dimethylpyra~ 0 1 ~ 1in) ~ toluene ) ~ at 80 "C, followed by crystallisation from toluene, affords the electron precise 64 c.v.e. spiked triangular cluster [Re4@-H)(CO)171- .63 The cyclic oligomer series (ReH(C0)4), (n = 3-5) has now been extended to the n = 6 example. Treating Re2(p-H)2(C0)8 with [Re&-H)2H2(CO)*] affords [Re4(p-H)3H2(C0)16]-,which reacts with an equimolar amount of Re2(CO),(thf), to give 20 in up to 40% yields amongst a complex mixture of products. The electron precise 96 c.v.e. cluster 20 adopts a cyclohexane-like chair conformation in the solid state.64

The unsaturated cluster anion [Re3(p3-H)(p-H)3(CO)~]-reacts with diazomethane to afford 21 in 90% yield. Cluster 21 contains only the second example of a p3-methyl in a triangular cluster. It is suggested that the stability of 21 derives from two factors: the bridging hydride ligands on all Re-Re interactions prevent C-H oxidative addition, and the bridging CH3 and hydride ligands hamper CH4 e l i m i n a t i ~ n . ~ ~

10

Group8

10.1 General. - The proposed fluxional mechanisms in M3(CO)12 clusters continue to attract attention. The structures of Fe3(C0)12 (123 K) and FenRu3_,(C0)12 [n= 1 (223 K, 323 K), 2 (173 K, 291 K)] have been determined, with the solid-state results providing supporting evidence for both the Johnson and Mann proposals for Fe3(C0)12fluxionality. The disorder in the structures of the mixed iron-ruthenium clusters has been shown to be dynamic in origin, both clusters undergoing phase transitions from ordered structures to disordered 'Star of David' structures on warmingM The syntheses, structures and isolobal relationships of c ~ o ~ ~ - M ~ ( R C ~ R 'and ) ~ (nidoCO)~ M2(RC2R')2(C0)6(M = Fe, Ru, 0s) pentagonal bipyramidal complexes (considering the alkynyl carbon atoms as core atoms) have been reviewed, and their role in organic synthesis and catalysis discussed.67 The reactions of M O ~ ( ~ - ~ ~ - C ~ ~ H (containing ~ ~ ) ( C O a) ~coordinated C~~ cyclotetradeca-l,8-diyne)with a variety of trinuclear Group 8 clusters have

298

Organometallic Chemistry

been contrasted; reactions with M3(C0)12 (M = Fe, Ru) afford Fe3{ p,p3-q2,q2c14H20M02(C0)4CP21(co)9 and RU3(p-H) { p, p3-q2,q3-C14H19M02(C0)4CP~)(CO)~, whereas reactions with M3(CO)lo(NCMe)2(M = Ru, 0s) give RU3(pL-H) { p,p3-q2,q3-C14H19Mo2(C0)4Cpd(co)9 and os3 { p9p3-q2,q2C14H20M02(C0)4Cp2} (CO)lo. The former ruthenium cluster is attached to the hydrocarbyl ligand by an allyl interaction, whereas the latter is bonded via an allenyl linkage; warming the allenyl cluster affords the allyl cluster? 10.2 Iron. - The chemistry of selenium- and tellurium-containing iron carbony1 clusters has been reviewed.69 10.2,l Trinuclear Clusters, C-ligands. Fe3(C0)12 reacts with cyclotetradeca-l,8diyne to give Fe3(p3-q2-C14H20)(C0)9. This cluster fragments upon heating to give known mono- and binuclear complexes. In contrast, reaction of the same hydrocarbon with Os3(CO)lo(NCMe)2 gives 22 and { 0s3(C0)l0}2(p3,p3-q2,q2C14H20).Cluster 22 undergoes C-H activation on heating to give 0~3(p-H)(p3q3-C14H19)(CO)9 and C-C coupling on irradiation with further cyclotetradeca1,s-diyne to give 0 s 3{ p-q4-C4(C2H20)2)(C0)9.70

Heating Fe2(p-q2-C2But)(p-PPh2)(C0)6 affords Fe3(p3-q2-P,P-PPhC6H4PPh-2)(p3-q2,q6-CBu'CCH=CBu'Ph)(C0)4; this complex reaction involves PC(Ph) cleavage of a PPh2 and scavenging by hydrocarbyl ligands, and head-tohead coupling of the tert-butylalkynyl ligand~.~' The tri- and tetra-yne diyl complexes CP*(CO)~F~ { p-(C=C),) Fe(C0)2Cp* ( n = 3 , 4) react with Fe2(C0)9 to form bis(alky1idyne) clusters Fe3{p3CC=CFe(C0)2Cp*} (p3-C(C=C),-2Fe(C0)2Cp*}(C0)9. The presence of at least one iron at the poly-yne termini is critical for alkylidyne cluster formation; while Fe {(C-C)3SiMe3) (CO)2Cp* affords Fe3{p3-CC-CFe(CO)2Cp*}(p3-CCrCSiMe3)(CO)9,reaction with Me3Si(C~C)3SiMe3 does not give an alkylidyne product.72 Nucleophilic attack by the face-capping CO oxygen atoms in [Fe3(p3CO)2(CO)9]2- on the chloroborane BC12(NBufSiMe3)gives the boryloxycarbyne cluster complex Fe3{ p3-COBC1(NButSiMe3)}2(C0)9 following elimination of KCl.73The cluster dianion [Fe3(p3-CCO)(C0)9]2-is reduced with the McMurry reagent (a Ti(O)/Ti(II) solution generated from TiC13(dme)l.5and a Zn-Cu couple) to give excellent yields of the ethynyl-capped cluster anion [Fe3(p3-q2-C2H)(CO)g]-, accompanied by small amounts of Fe3(p3-q2-

11: Organo-Transition Metal Cluster Complexes

299

CCH2)(CO)lo.The former is not a precursor to the latter; the ethynyl cluster anion is protonated at the core rather than at the organic ligand. Omitting the Zn-Cu couple from the reaction results in formation of the 0-metallated cluster Fe3[p3-CC0(TiCl(thf)4]](CO)9, for which the oxidation state Ti(II1) is inferred.74 Group 15 Zigands. Diiron nonacarbonyl reacts with IG(3-methyl-2-thienylmethy1idene)aniline to give the imidoyl-containing cluster Fe3(p-H)(p3-q2PhNC-2-C4H2S-3-Me)(C0)9.75 A previously-developed route to bis(ary1phosphinidene)triiron clusters has been extended to 4-aryl functionalised examples, with reaction between [Fe2(C0)8l2- and PC12(4-C6H4X)affording Fe3(p3PC6H&-4)2(CO)9. Stable radical monoanions and diamagnetic dianions are obtained on successive one-electron reductions. Linear correlations of Hammett q,parameter with IR v(C0) (for neutral, monoanion and dianion), redox potentials and EPR g values (of the radical monoanion) are observed, confirming a systematic tuning of the electronic structure of the cluster by the X ~ubstituent.~~ Group 16 Zigands. Treating Fe(CO)5 with P(SBu‘)Ph2 affords Fe3(p3-S)(pPPh2)2(p-CO)(C0)6,whichundergoes clean P-ligand substitution to give Fe3(p3-S)(p-PPh2)2(p-CO)(CO)5(L)[L = P(OMe)3, P(OPh)3, PMe2Ph, PPh3].77 The sulfur cap in the cluster dianion [Fe3(p3-S)(CO)9]2-is further metallated on reaction with [Fe(thf)(C0)2Cp]+, the cluster anion [Fe3(p3-SFe(CO)2Cp](CO),]- being obtained. Chemical oxidation and thermolysi : of the product both proceed with loss of the capping iron fragment, affording i7e3(p3S)2(C0)9,[Fe3(p3-S)(CO)9]- and [Fe5(p3-S)2(CO)14]2-.78 The disulfido cluster Fe3(p3-S)2(C0)9is also obtained from reaction between diiron nonacarbonyl and 3,3-dithio-l-(4-~ubstituted phenyl)-2-propen-1-0nes.~~ The unique heterometal is lost from the tetrahedral cluster dianions [MFe3(CO)14]2-(M = Cr, Mo, W) on reaction with sulfur dioxide, [Fe3(p3-q2SO2)(C0)9l2- and [Fe3(p3-S)(p-S02)(CO)~]2-being obtained. The former reacts with further sulfur dioxide to afford the latter. Cluster fragmentation occurs on treating [Fe4(CO)l3]2- with sulfur dioxide, the bridged species [Fe2(p-SO~)2(CO),]2-being obtained. The carbido cluster dianions [MFe3(p4C)(CO)14]2-(M = Cr, W) react with one equivalent of sulfur dioxide with loss of the heterometal and formation of [Fe3(p3-CCO)(p-S02)(CO)8]2-,which on reaction with further SO2 gives the cluster dianion [Fe3(p3-CCO)(pS02)2(CO)7]2-,the latter being obtained direct from [MFe3(p4-C)(CO)14]2(M = Cr, W), [MnFe3(p4-C)(CO)13]-, or [Fe3Rh(p4-C)(CO)12]- and excess sulfur dioxide.80 The diphosphine diselenide Fe{I ~ - C ~ H ~ P ( S reacts ~ ) P ~with ~ ) ~M3’(C0),2 (M = Fe, Ru) to give Fe3(p3-Se)2(p-dppf)(C0)7and R~&~-Se)~(CO)~(dppf) [dppf = 1,l’-bis(diphenylphosphino)ferrocene];in the former, the dppf ligand bridges the two non-bonded iron atoms, whereas in the latter it chelates one of the two non-bonded ruthenium atoms, the first example of dppf chelating at a has also been carbonyl cluster. The related cluster R~~(p~-Se)~(p-dppe)(CO)~ prepared; it possesses the same geometry as Fe3(p3-Se)2(p-dppf)(C0)7.Fluxional processes in the dppf-containing clusters have been assigned, consisting

300

Organometallic Chemistry

of the bidentate bridging ligand rocking below the square basal Fe2Se2plane in the iron-containing example, and exchanging P atoms between axial and equatorial positions in the ruthenium-containing cluster. 10.2.2 Tetranuclear Clusters. Cyclopentadienyl functionalisation of King's complex has been reported. Reaction of Fe4(p3-C0)4Cp4with RLi (R = Me, Bun, Ph), followed by HBF4, affords Fe4(p3-C0)4Cp3(q-C5H4R),a procedure which has been repeated for R = Ph to give Fe4(p3-C0)4Cp2(q-C5H4Ph)2. King's complex reacts with lithium diisopropylamide followed by bromoferrocene to afford Fe4(p3-C0)4Cp3{ q-C5H4(C5&)FeCp}and (Fe&3-C0)4Cp3}2(p-q-C5H4-q-C51-LJ. The latter product is also obtained from reaction between King's complex, lithium diisopropylamide, and dibromoferrocene, { q-C5H4[(q-C5H4)Fe(q-C5H4Br)]} and being accompanied by Fe4(p3-C0)4Cp3 { [Fe4(p3-C0)4CP3(qGH4)l(q -C5H4)12Fe. The iron-sulfur cluster Fe4(p3-S)2(p3-q2-S2)2Cp4 acts as a ligand to a range of molybdenum(I1) and tungsten(I1) complexes.82 The heterocubane cluster Fe4(p3-NPEt3)4C14, formed by reaction of iron(I1) chloride and Me3SiNPEt3 in the presence of potassium fluoride, reacts with Li(C=CR) (R = But, SiMe3) to afford Fe4(p3-NPEt3)4(C-CR)4which retain the heterocubane str~cture.'~

10.3 Ruthenium. - The precursor to most ruthenium cluster chemistry, R U ~ ( C O )is~prepared ~, in 80% yield by low pressure (5-20 atm) carbonylation of Ru02.xH20 at 160 "C in t01uene.'~This cluster is also available in 93% yield from carbonylation (1 atm) of an ethylene glycol solution of {RuC12(C0)3)2at 95°C in the presence of Na2C03. Similar controlled reduction of MC13 or (M(C0)3C12}2 at atmospheric pressure affords M&-H)4(C0)12, M4(pH)3(C0)12]- (M = Ru, 0s) and [ R U ~ ( ~ & > ( C O ) ~the ~ ] ~effect - ; on reduction selectivity of the nature and quantity of alkali carbonate, solvent, gas phase composition, temperature and reaction time has been studied? Positive and negative ion UV laser desorption time-of-flight mass spectra (LD TOF MS) of Ru3(C0)12 using a 337 nm N2 laser have been recorded. The negative ion spectra show peaks corresponding to loss of CO ligands, but do not show a molecular ion. Peaks corresponding to clusters up to nuclearity 11 are also observed, of greater intensity than the Ru3 peaks; these LD TOF MSderived clusters correspond to those observed from thermal reaction in the osmium system. The positive ion spectra show peaks corresponding to [RU~(CO)~]+ (x = 10-13), as well as R u clusters. ~ ~ LD TOF MS of O S ~ ( C O ) ~ ~ contain peaks for Os3-8 clusters, whereas LD TOF MS of Fe3(C0)12 contain peaks of nuclearity extending to about Fe3545. The extent of clustering under LD TOF mass spectrometry conditions is related to M-M bond strength.86 Solvents diethyl ether, ethyl acetate and acetonitrile act as photofragmentation quenchers for photosubstitution of CO in M3(CO)12 (M = Ru, 0s). CO is photosubstituted by PPh3 [to give M3(C0)12-n(PPh3), (n = I-3)], MeCN [to give M3(C0)12-n(NCMe)n(n = 1, 2)], and PCy3 [to give Ru~(CO)~(PCY~)~],

11: Organo- Transition Metal Cluster Complexes

30 1

while RSH (R = Et, Ph) gives M3(p-H)(p-SR)(CO)lo and then M3(p3-S)( ~ 0 ) 10.3.1 Trinuclear Clusters, C-ligands. Heating R U ~ ( ~ - H ) ~ ( J L ~ - Swith )CP*~ alkanes affords alkylidyne-capped clusters Ru3(pL-H)2(p3-S)(P~-CR)CP*~ [R = (CH2),Me (n = 3-9, (CH2)3CHMe2 (23), Cy, Ph], with the selective primary C-H cleavage ascribed to steric factors.88 Other C-ligand chemistry has focussed on alkynes. R U ~ ( C O ) ~ ~ ( N C M ~ ) ~ reacts with 1-ethynylcyclopentanol to give Ru3(p3-q',q ',q2-HC2CsH8OH)(pC0)(C0)9,89and with ethyne to give Ru3(p3-q2-C2H2)(p-C0)(C0)9together with the butterfly cluster R U & ~ - ~ ~ - C ~ H ~ ) (and C Othe ) ~edge-bridged ~, tetrain hedral cluster Ru5(p4-CCH2)(CO)s. Heating Ru3(p3-q2-C2H2)(p-CO)(C0)9 hexane affords the Ru4 and Ru5 clusters together with Ru3(CO)12, 24,25, and 26.Hydrogenation of Ru3(p3-q2-C2H2)(p-CO)(C0)9 affords Ru3(p-H)2(p3-q2C2H2)(C0)9,the thermolysis of which gives small amounts of Ru3(C0)12 and R U ~ ( ~ ~ - C ~ M ~amidst ~ ) ( Cextensive O ) ~ ~ decomposition.g0On sequential treat-

\ IRu /

ment with K[BHBus3] and AuCl(PPh3), Ru3(p-H)(p3-q2-C2H)(C0)9 affords the hydroxyallyl cluster Ru3(p-H){ p3-q3-CHCHC(OH)}(CO)8(PPh3) in addition to the expected auration products Ru3Au(p-H)(p3-q2-C2H)(C0)g(PPh3) (existing in tetrahedral and butterfly forms) and square pyramidal R u ~ A up3~( v~-CCH~)(CO)~(PP~~)~.~~ The reaction of RU(CO)~with 1,6-bis(trimethylsilyI)-1,3,5-hexatriyne affords Ru3(p3-q2-C2(C-CSiMe3)2)(CO)lo and the butterfly cluster Ru4{p4q2-C2(C-CSiMe3)2}(CO)12, the yield of the former product being higher from reaction between the alkyne and RU~(CO)~,(NCM~)~; the former product is converted into the latter on reaction with R U ( C O ) ~The . ~ ~ diyne-cluster (two isomers) and Ru3(p3adducts Ru~(p3-q2,q3,q3-C2~H3403)(p-C0)(C0)7

Organometallic Chemistry

302

q2,q2,q4-C28H3202)(CO)s are obtained from reaction between Ru3(CO)12 and 1,4-bis(1-hydroxycyclopentyl)-1,3-butadiyne. The Cs chain in the isomers arises from coupling of two diyne molecules with formation of a ruthenacyclopentadienyl ring and a fury1 ring. Reaction of the same alkyne with Ru3(CO)lo(NCMe)2 gives R ~ ~ ( p 31-,qq1,q 2- C14H1s02)(p-CO)(CO)9.Thermolysis of ~ H ~further ~ O ~ alkyne )(~-CO)( one isomer of R u ~ ( ~ ~ - ~ ~ , ~ ~ , ~ ~ - C ~ with affords 27, while heating Ru3(p3-q2,q2,q4-C28H3202)(C0)8 with Ru3(C0)12 gives the chain cluster 28.93 R u ~ ( C O reacts ) ~ ~ with 9-ethynylfluoren-9-01 to 1 2 2 1 2 4 give Ru3(p-H){p3-q ,q ,q -CC(C13H19)}(C0)9, RU3{p3'T\ ,q ,q -(HOC13HS)'

CCHC(C 3HsOH)CH}(p-CO)(C0)7 (with a metallacyclopentadienyl unit 1 2 2 from coupling two alkynes), Ru4(p3-0H)(p3-q ,q ,q -C&&CH)(p1 2 2 6 ~ ~ ) ( ~ ~RU5(pL-H)(p5'T) ) l O ~ ,q ,q ,q ,q ~ 1 3 ~ 7 ~ ~ ~ ) ( ~ 3 - ~ ~ ) ( ~ - ~ ~ ) ( ~ and Ru6(p5-q ,q ,q2,q3,q6-CI3H7CHC)(CO) 5.94Ferrocenyl(formy1)acetylene 1 1 2reacts with Ru3(CO)lo(NCMe)z to give the expected Ru3 { p3-71 ,q ,q C2(CHO)(Fc)}.The same acetylene reacts with R U ~ ( C Oin) ~refluxing ~ cyclo(with a hexane to give Ru~{~~-~~,~~,~~-C(F~)C(CHO)C(F~)CCHO}(C metallacyclopentadiene ring from alkyne coupling) and the butterfly cluster Ru4{p4-C2(CHO)(Fc)}(C0)12, thermolysis of the latter affording the square pyramidal Rug(pH)(p5-C)(p-q ,q -CFc)(CO)13.95 Ru3(p-H)(~ ~ - q ~ - M e N p y ) ( c [MeNpy O)~ = 2-(methy1amino)pyridyll reacts with diphenylacetylene to give the alkenyl cluster Ru3(p3-q2-MeNpy)( p-q 2PhC=CHPh)(CO)s, which reacts with PPh3 to give Ru3(p3-q2-MeNpy)(p-q2O=CPhC=CHPh)(C0)7(PPh3) and Ru3(p3-q2-MeNpy)(p-q2-O=CPhC=CHPh)(C0)6(PPh3)2, in which incorporation of PPh3 has induced CO migratory insertion into the Ru-alkenyl bond. The latter adds two equivalents of CO with loss of one PPh3 to afford the V-shaped cluster Ru3(p3-q2MeNpy)(p-q2-O=CPhC=CHPh)(CO)s(PPh3) in which the propenoyl ligand spans the non-bonding Ru ...Ru vector. Treating the alkenyl cluster Ru3(p3-q2MeNpy)(p-q2-PhC=CHPh)(C0)8 with CO also results in migratory insertion, affording Ru3(p3-q2-MeNpy)(p-q2-O=CPhC=CHPh)(CO)9 in which the propenoyl group once again spans the non-bonding Ru ...Ru edge. This cluster is stable under a CO atmosphere, but reverts to the alkenyl cluster under an inert atmosphere; treating it with CO/H2 mixtures produces a-phenylcinnamalde-

'

'

11: Organo-Transition Metal Cluster Complexes

303

hyde with recovery of R~~(p-H)(p~-q~-MeNpy)(C0)~. This cycle of reactions corresponds to the stepwise hydroformylation of diphenylacetylene, but viable catalysis is limited by competitive CO insertion into the Ru-N bond of the methylamidopyridyl Labile MeCN is displaced from the capped clusters M3(pmH)2(p3X)(CO)8fNCMe) (M = Ru, x = NS02C6H4Me-4; M = Os, X = S) on reaction with alkynes. The ruthenium cluster reacts with Bu~CECHto afford the alkenyl-containing cluster Ru3(p-H)(p3-NS02C6H4Me-4)(p-q2-CHCHBut)(CO)7. Other alkynes react with the ruthenium cluster and sulfur-capped osmium cluster by reductive coupling to give p-q2,q2 or q4-1,3-dienecontaining clusters Ru3(p3-CO)(p3-NS02C6H4Me-4)(p-q2,q2-CHCRCHCR)(CO)7 (R = H, Ph) and Os3(p3-S)(C0)8(q4-CH2CPhCHCHPh), with the intermediacy of mono- and bisalkenyl clusters demonstrated in the latter case.97 B-Zigands. Heating Ru3(CO)12 and nido-[7-CBloH& gives [Ru3(CO)8(qs-71). The CBloH1I)]-, protonation of which affords RU~(~-H)(CO)~(~~-~-CB~OH~ cluster anion is cuprated [with CuC1(PPh3) in the presence of TlPF61 and argentated (with AgBF4 and PPh3) to give Ru3(p-H) {q5-lO-M(PPh3)-7CBloHlo}(C0)7(PPh3), whereas auration [with AuCl(PPh3)I gives Ru3(pH) { q5- 1O-M(PPh3)-7-CBloH~o} (CQ8; the gold-containing product lacks an exopolyhedral B-H-Au interaction as well as a ruthenium-ligated phosphine." Stirring a mixture of Co2(CO)8and nido-l,2-{RuCp*)2B3H9 affords low yields of comma-[ 1-{R U C ~ * } ( ~ - H ) B ~ H ~ together ] ~ R U , with Co4(CO)12 and 1{RuCp*)-2-{Ru(CO)C~*)-~-{CO(CO)~)(~~-CO)B~H~.~~ Group 15 Zigands. R U ~ ( C O reacts ) ~ ~ with thiomorpholine to give Ru3(pH)(p-q 1,q2-SCH2CH2NH2)(CO)9, the organic ligand being derived from thiomorpholine ring-opening followed by loss of a C2 fragment, with thiazolidine to afford a diruthenium product@ ,' ' and with benzothiazole to give Ru3(pH)(p-2,3-q2-NSC7H4)(CO)lo and R u ~ ( ~ - H ) ( ~ ~ - ~ , ~ , ~ - ~ ~ the -NSC~H benzothiazolide ligand in the former coordinates through the imino nitrogen and C2 carbon atoms, and in the latter through the sulfur, the imino nitrogen and the C2 carbon atoms, with the former converting to the latter on heating. Pyrimidine-2-thione and benzimidazole-2-thione react with Ru3(C0)12 to give R u ~ ( ~ - H ) ( ~ ~ - ~ ~ - Sand N ~RU~(~-H)(~~-~~-N~SC~H~)(CO) C~H~)(C~)~ respectively, with an X-ray study of the former showing the organic residue bridging two ruthenium atoms through the sulfur and bonding to the third ruthenium through a ring nitrogen atom. lo' The first 44-electron triruthenium cluster, 29, has been prepared from the reaction between [Ru~(~-H)(CO)I 11- and excess PCy3, with the additional hydride ligand originating from solvent methanol. Its electron deficiency is relieved on reaction with CO, affording the 48-electron cluster R u ~ ( C O ) ~ ( P C with Y ~ ) ~three equatorially-ligated PCy3 ligands. The electronic structure of 29 has been established by EH and DFT MO calculations of the model compounds R u ~ ( ~ ~ - H ) ~ ( C ~and ) ~ Ru3(p3-H)2(CO)9. (PH~)~ Reaction of [OS~(~-H)(CO)~ '1- with excess PCy3 affords OS~(~-H)~(CO)~(PCY&, the first tri-substituted derivative of Os3(p-H)2(CO)10;once again, solvent methanol is

304

Organometallic Chemistry

the source of the additional hydride ligand.Io2 The methoxynitrido cluster R u ~ ( ~ ~ - C O ) ( ~ ~ - N O M reacts ~)(CO with ) ~ PPh3 to afford the mono- and bissubstituted products, and with dppm to afford Ru3(p3-CO)(p33"OMe)(pdppm)(C0)7, in which the dppm bridges a Ru-Ru bond bis-equatorially. The bis-PPh3 and dppm clusters are stable to heat, but the mono-PPh3 product affords R U ~ ( ~ - N C O ) ~ ( C O ) ~on( Pheating, P ~ ~ ) ~in which the isocyanate ligands span the non-bonding Ru.. .Ru vector. lo3 Reactions with primary and secondary phosphines and arsines involve the expected E-H (E = P, As) activation(s). Thus, Ru3(C0)12 reacts with FcCH2PH2 to give Ru3(p-H)2(p3-PCH2Fc)(C0)9and R u ~ ( ~ ~ - P C H ~ F C ) ~ ( ~ CO)(CO)lo with capping phosphinidyne ligands,lWand with CF3EH2 to give RU3(1-1'H)2(p3-PCF3)(c0)9, RU4(pL-H)2(p4-ECF3)(C0)13 (30, E = p), RU4(pH)2(p3-ECF3)2(C0)12, RU4(p3'AsCF3)2(CO)13, RU5(p'H)2(p3'ECF3)3(c0)15 with ECF3-linked R u and ~ Ru3 units, and 31; R u ~ ( ~ - H ) ~ ( ~ ~ - A ~ is CF~)~(C also obtained from reaction between Ru4(p-H)2(p3-AsCF3)2(p-AsCF3)(C0)~2 and R U ~ ( C O )Reacting ~~. Ru3(p-H)2(p3-PCF3)(C0)gwith Ru3(C0)12 gives 30 which, on treatment with further R U ~ ( C O )affords ~ ~ , 31. Heating 30 with the cyclophosphine (PCF3)4 gives the linear cluster Ru~(~-H)~(~~-PCF~)~(CO) The hydrides in 30 and its arsenic analogue are fluxional. Hydrogenating lo5 The secR u ~ ( ~ ~ - A s C F ~ ) ~affords ( C O ) ~Ru~(~-H)~(~~-AsCF~)~(CO)~~. ~ ondary phosphine and arsine EH(CF3)2 react with Ru3(C0)12 to give the RU4 { pRU3(C1-H)2{ p-P(CF31212(co)89 { RU3(p-H)(CO)1012 { p-E(CF3)2 12, P(CF3)2)2(co)13, RU4(p-H)3{p'E(CF3)2>(CO)12,RU4{p-E(CF3)2}2(C0)14, and 106 RU5(p4-ECF3)(C0)15* Groups 16 and 1 7 Zigands. Reacting [ R u ( O H ~ ) ~ ( ~ - C ~ with H ~ ) ][Ru2(p~+ H)3( T) -c6Me6)2]+affords [RU3(CL-H)3(C13-O)(f7-CgH6)(f7-C6Me6) the 2]+Crystal , structure of which reveals a water molecule hydrogen-bonded to the capping 0x0 ligand. Protonation of this cluster with HBF4.OEt2 proceeds stepwise, the first proton attacking the water to give a hydrogen-bonded hydronium cation, and the second proton cleaving the hydrogen bond to afford [R~~(p-H)~(p3oH)(r\-CsH6)(r\-C6Me6)2~2+, with a capping hydroxo ligand. The cluster cation [Ru3(p-H)3(p3-O)(rl-C~H6)(q-c6Me6)~]+ catalyses the hydrogenation of arenes to give the corresponding substituted cyclohexanes.lo7 Heating Ru(SCH2CH=CH2)(PPh3)2Cpin refluxing toluene results in C-S

11: Organo-Transition Metal Cluster Complexes

305

bond cleavage, loss of PPh3 ligands, and aggregation, affording R u ~ ( ~ ~ - S ) ~ ( ~ SCH2CH=CH2)Cp3;the fate of the C3 fragments has not been ascertained.lo8 P-Se cleavage results when R u ~ ( C O )is~ ~reacted with CH2(PPh2(Se))2, affording RU3(p3'Se)2(p-dppm)(C0)7, RU4(p4'Se)2(pL-CO)(p-dPPm)(C0)8, and Ru4(p3-Se)4(p-dppm)(CO)10. Thermolysis of R u ~p3-Se)2( ( p-dppm)(C0)7 gives R~&~-Se)~(p-dppm)2(C0)~2. Fluxional studies of Ru3(p3-Se),(p-dppm)(C0)7 suggest reversible migration of a Ru-Ru bond and oscillation of the dppm methylene group. lo9 Lavigne has summarised his studies of ruthenium clusters containing halogen and related ligands.' lo 10.3.2 Tetranuclear Clusters. 1,6-Bis(trimethylsilyI)hexa- 1,3,5-triyne reacts 2 with R u ~ ( C O ) ~to~ give the butterfly cluster Ru4(p4-q1,q2 ,q1 ,q C2(C=CSiMe3)2}(C0)12;subsequent reaction with C O ~ ( C Oresults )~ in slippage of the butterfly along the hexatriyne chain, affording Ru4(p4-Me3SiC2C=CC2{Co2(C0)6}SiMe3)(CO)12.1 l 1 Thermolysis of Ru3(pL-H)2(p3-q *,q5dihydr~acenaphthylene)(CO)~~ in chloroform affords 32, in which the organic residue is a rare face-capping 9-electron donor ligand. l 2 Heating Ru4(p4-q2-C2H2)(C0)12 results in replacement of three wingtipligated CO ligands by a solvent toluene molecule, affording Ru4(p4-q2C2H2)(C0)9(q-C6HsMe);the temperature dependence of the crystal structure is suggested to be consistent with the initial stages of putative arene wingtip to hinge migration.' l 3 The reactivity of R Q ( ~ - H ) ~ ( ~ - E C F ~ ) ( (E CO = )P,~ As) ~ towards alkynes has been investigated. Thus, reaction with RC=CR (R = Ph, in which the acetylene H) affords Ru4(p4-ECF3)(p4-q2-C2R2)(p-C0)2(C0)9, interacts with the cluster core by a 2 0 + 4n: interaction, and with hexafluoro(CO)12, in which the acetylene but-2-yne gives Ru4(p4-PCF3){ p4-q2-C2(CF3)2> is coordinated via a 4 0 interaction. Ru4(pL-H)2(p4-ECF3)(CO)13 reacts with but-2-yne to afford 33 by P-C formation, and 34 by alkyne dimerisation. Reaction with diphenylbutadiyne affords Ru4(p4-PCF3)(p4-q4PhCCCHCHPh)(CO)I in which the 1,4-diphenylbut-3-en-1-yne fragment results from migration of both bridging hydrides of the precursor to the product cluster."4

Me

(33)

Me

(34) E = P, AS

306

Organometallic Chemistry

(37)R' = H

(39)R = Ph, SiMe,

Scheme 1

10.3.3 Pentunucleur Clusters. Ru5(p5-C2PPh2)( p-PPh2)(CO)13 reacts with dppm to give Ru5(p5-C2PPh2)(p-PPh2)(CO) 12(dppm)and Rug(p&PPh2)(p-dpprn)(p-PPh2)(CO)11;in the latter, the dppm bridges an outer Ru-Ru bond adjacent to that bridged by the PPh2 group."5 Further chemistry of Ru5(p5-C2)(p-SMe)2(p-PPh2)2(CO)llhas been described, the chemistry with terminal alkynes being summarised in Scheme 1. Reaction with terminal alkynes HC=CR (R=Ph, But, SiMe3) affords 35 (R = %Me3 only) together with the pentagon cluster 36. For R = Ph and SiMe3, 36 is carbonylated to afford 37, in which one ruthenium atom of the precursor has been extruded from the core (though retained by bridging ligand coordination), together with 38. Thermolysis of 37 gives the decarbonylation product 36 together with 39.'l 6 Reactions of Ru~(~~-C~)(~-SM~)~(~-PP~&(CO)~ 1 with internal alkynes have also been reported, and are sumrnarised in Schemes 1 and 2. Reaction with diphenylethyne gives 40 and 41 (R = Ph) (the former giving the latter on heating), whereas reaction with but-2-yne affords 41 (R = Me) only. Carbonylating 41 (R = Ph) gives 37 (R, R = Ph), which affords a mixture of 40 and 41 on heating.' l 7 The reaction of Ru~(p5-C2)(p-SMe)2(p-PPh2)2(CO)11 with C2(SiMe3)2 affords two isomers of 42 (R = SiMe3), together with 43, in which an SMe ligand has been lost from the precursor. Treating the isomers with

\

PhCdWPh

I

Me (43)

Scheme 2

(47) R, R' = Ph, M P h

I

(42, R = SiM4, H) R=H

co

(44)

t

I

308

Organometullic Chemistry

KOH results in desilylation and formation of 42 (R = H), the carbonylation of which affords 44; for 42 (R = H) and 44,the organic ligand is butatrienylidene, formed by end-to-end coupling of the C2 moiety with the vinylidene C=CH(SiMe3).' " The chemistry of R U & S - C ~ ) ( ~ - S M ~ ) ~ ( ~ - P P1~1 ~with ) ~ ( aC butadiyne O) is summarised in Scheme 2. Reaction with 1,4-diphenylbuta-1,3-diyne gives Rug jp5-CCC(C=CPh)CPh}(p3-SMe)(p-SMe)(pPPh2)2(CO)n [n = 11 (45), 9 (46)], 47 (two isomers), 48, and 49. Thermolysis of 49 also gives 46. Both 46 and 49 have 80 c.v.e., two more than expected for a pentanuclear cluster with six M-M bonds.'" Reaction of R U & ~ - C ~ ) ( ~ - S M ~ ) ~ ( ~ - P 1P1 ~with ~ ) ~buta( C O1,3-diene ) gives 50; this contains a p3-q',q ',q2-cyclohex-l-en-4-yne ligand formed by cycloaddition of the diene to the C2 unit.12* Ru3(p3-q2-C2H2>(p-CO)(C0)9 gives R~S(p4-q~Thermolysis of CHCHCCH2)(CO)15and Ru6(p-H)(p4-C)(p4-q2-C2Me)(p-CO)(CO)~6 in 6 8 % yields, the former product involving coupling of two ethyne molecules, the latter involving ethyne disproportionation to carbide and methylethynyl.12' Re-investigation of the reaction between Ru3(p-dppm)(CO)lo and { Ru122 (CO)2Cp)2(p-C-C) has afforded RuS(p4-CC)(p-dppm)(p-CO)(C0)9Cp2. 10.3.4 HexanucZear Clusters. The hexaruthenium cluster chemistry of NO, SO2 and SO has been reviewed.'23 The reduction of coordinated SO in Rug(p6C)(p3-SO)(CO)15proceeds under 10 atm H2 to afford 51 and Ru6(p-H)4(p5c)(p3-s)(co)16; the former can be converted into the latter upon further hydrogenation, removal of hydrogen pressure reversing the reaction. Carbonylation of the sulfur monoxide-containing cluster gives Rug(p5-c)(p3124 S)(CO)~~.

Further cyclophane chemistry has been reported. Heating Ru3(CO)12 with 4amino[2.2]paracyclophane or 4-bromo[2.2]paracyclophane in refluxing octane 1 2 2 2 2 2affords RU6@6'C)b3'q ,q ,r\ 'C16H15NH2)(C0)14 or RU6(p6'C)(p3'q ,q ,q ClgH15Br)(CO)14, respectively, with the paracyclophane ring in the former product coordinated via the aniline ring in the novel p3-q1,q 2,q 2 mode.125 Similar reactions with [2.2]ortho-, anti-[2.2]meta-, and [2.2.2lpara-cyclophanes afford Ru6(p6-C)(C0)14(q6-cyclophane) products; the [2.2]para-cyclophane adduct has been prepared by an alternative synthesis, namely reacting [Ru5(p5C)(CO)14]2-with [ R ~ ( N c M e ) ~ ( q16H ~ - c6)]2+.126

1I : Organo-Transition Metal Cluster Complexes

(55)

(56)

309

(53

Heating R U ~ ( C Owith ) ~ ~1-ethynylcycloalkanolsaffords two new products in low yields in each case. Reaction with 1-ethynylcyclopentanolgives 52 and 53, reaction with 1-ethynylcycloheptanolyields 54 and 55, and reaction with 1ethynylcyclooctanol affords 56 and 57; the metallacyclic p4-17 ,q ,q2,q4-coordinated five-membered ring in three of these products is derived from the C-C bond and C-H bond activation^.^^

' '

10.3.5 R u ~ ( C O as ) ~a~Synthetic Intermediate. The use of R u ~ ( C O )as~ ~ a convenient source of Ru(CO), fragments is illustrated in reactions which afford mono- or di-nuclear products. Thus, R U ~ ( C O reacts ) ~ ~ with tris(2pyridylmethy1)ammonium perchlorate (tpa.3HC1O4) in toluene in the presence of acetic acid to give [Ru(OAc)(CO)(tpa)]+,and reacts with 2-pyridylcarboxylic acid (pyC02H) to afford R u ( ~ ~ C O ~ ) ~ ( Reaction C O ) ~ . with benzoic acid and pyridine (Hpy) in toluene gives Ru2(02CPh)2(C0)4(Hpy)2.127 Heating Ru3(CO)12 and ethyne in refluxing thf affords four binuclear products Ru2(CO),(C2H& (m= 4, 5 , 7, n = 4; m = 7, n = 2).'28 Bis(hydrosily1)benzenes react 1 with Ru3(C0)12 to give polymeric (-S~RR'RU(CO)~RU(CO)~S~RRC~H~the absorption maxima of which are considerably red-shifted from that of the monomeric PhMe&Ru( C0)4Ru(C0)4SiMe2Ph.29 10.3.6. Ruthenium Clusters as Catalyst Precursors. The following reactions have been reported as being catalysed by Ru3(C0)12 without isolation of specific intermediates: decarbonylative cleavage of a C-C bond in aromatic ketones, assisted by N-chelation to Ru, 13* reductive carbonylation of nitrobenzene in aniline to produce N,Nr-dipheny1urea,84intermolecular hydroamination of terminal alkynes with anilines to give ketimines (in the presence of acid or an ammonium salt),13' regioselective hydroamination of terminal alkynes,

Organometallic Chemistry

310

or hydroarylation of styrene, with N-methylaniline,132 intramolecular hydroamination of a l k y n e ~ , sequential '~~ insertion of CO and ethylene into the C-H bonds of 1-azadienes to give y - l a ~ t a m s , and ' ~ ~ the cyclocarbonylation of 1,6and 1,7-yne-imines to afford bicyclic a$-unsaturated lactams.135 A revised chloride-catalysed carbomechanism for the R~~(CO)~~/tetraalkylammonium nylation of nitroarenes to carbamates has been developed; contrary to earlier reports, the catalysis is now believed to proceed by way of aniline, and the active catalyst is mononuclear rather than trinuclear. 36 R U ~ ( C O in ) ~ the ~ presence of added N-ligands catalyses the following processes: allylic amination of olefins by nitroarenes [in the presence of bis(arylimino)acenaphthene],137 and hydroformylation of styrene to give branched and linear aldehydes (in the presence of 1,10-phenanthroline),and of acrylic esters to give branched and linear 0x0-alcohols (in the presence of quinuclidine). 38 Ruthenium clusters in the presence of added phosphines, or preformed phosphine-substituted ruthenium clusters, catalyse the following transformations: cycloaddition of ketones (or aldehydes), olefins and CO, leading to functionalised y-butyrolactones,139 hydroformylation of methyl acrylate to hydroamidation and hydroestergive dimethyl 2-formyl-2-methylglutarate,'38 ification of alkenes with formamides and alkyl formates, 140 benzo[b]thiophene hydrodesulfurisation,14' hydrogenation of carboxylic acids,142 hydrogenation and hydroformylation of alkenes,143~144hydrogenation of diphenylacetylene,145 and isomerisation and hydrogenation of 1-hexene.1463147 Hydrogenation of arenes, employing [ H ~ R u ~ ( ~ \ - C ~ H ~ )as~ ]the ( BpreF~)~ catalyst, has been effected in the room-temperature ionic liquid 1-butyl-3methylimidazoliumtetrafluoroborate. 148

'

'

10.3.7 Ruthenium Cluster Carbonyls on Surfaces. M3(CO)12 (M = Ru, 0s) has been deposited inside the pores of Vycor glass and the absorbed species have been thermally decomposed. At low temperatures (Ru, 65°C; Os, llOOC), surface bound HM3(CO)lo(p-OSi-) is formed, followed by cluster breakdown at higher temperatures (Ru, 130 "C; Os, 200 "C) to give M(CO),(OSie)2 (n = 2, 3). Heating R~~(CO)~~-incorporated porous Vycor glass at 250 "C under air results in cluster decomposition and formation of Ru02 nanoparticles. Raising the temperature to 1200"C results in collapse of the glass pores and formation of a transparent silica glass/Ru02 nanocomposite.'41 Alumina-supported Ru3(C0)12 is a precursor for a catalyst active for hydrogen exchange and hydrogenation of propene.' 50 Carbon-supported potassium salts of ruthenium and osmium cluster carbonyl anions afford catalysts active for ammonia synthesis. 51 Magnesium fluoride-supported Ru3(C0)'2 is a precursor for a catalyst which is highly active for hydrodesulfurisation of thiophene, this system producing lower yields of hydrogenated products than ruthenium catalysts on other supports.152

'

10.4 Osmium. - The chemistry of triosmium clusters and benzoheterocycles has been summarised. 53

'

11: Organo- Transition Metal Cluster Complexes

31 1

While most chemistry of the 'lightly stabilised' Os3(C0)lo(NCMe)2proceeds with retention of cluster core nuclearity, reaction with (diphenylthiocarbazono)phenylmercury results in cluster fragmentation to give structural isomers of (OS(CO)~P~} 2 (p-q2-SC(NNPh)2> 2. 54

'

10.4.1 Trinuclear Clusters, C-ligands. O S ~ ( C O ) ~ ~ ( N Creacts M ~ ) ~with 1,6bis(trimethylsily1)hexa-1,3,5-triyne to give O ~ ~ ( p 3 -,qq ,q2-Me3SiC-CC2CeCSiMe3)(p-CO)(CO),, which, on treatment with Ru3(C0)12, undergoes core expansion to afford RuO~~(p4-q ,q2,q ,q2-Me3SiCrCC2CrCSiMe3)(C0)12. The free alkyne linkage in the cyclotetradeca-1,S-diyne cluster Os3(p3-q2-C14H~~)(CO)lo reacts with Co2(C0)8, affording Os3[p3-q2-C14H20{ ~ ~ ~ ( ~ ~ ) ~ } ] ( ~ ~ The ~ ~ )diynyl ( ~ ~complex ) ~ . 6 8W(C=CCrCPh)(0)2Cp* reacts with OS~(~-H)~(CO)~O to give 0s3(p-H){p-q3-C(=CHPh)CCW(O)2Cp*}(CO)lo, which consists of three interconverting isomers 58; thermolysis of this mixture affords Os3(p-H)(p-q ,q2-C=CCHCHPh)(CO)10 [by removal of the W(O)2Cp* group] and W o ~ ~ ( p - o ) ~',q2(p-~) C_CCHCHPh)(CO)&p* (by decarbonylation).155

'

'''

'

'

'

The Schiff base-containing clusters O S ~ ( ~ - H ) ~ ( ~ ~ - C N C ~ H ~ C H = N C6H4R)(C0)9 (R = H, NMe2, SMe, CMe3, NH2, Br, CI, OCnH2n+l,n = 1, 6, 7, 9) are obtained from reaction of O S ~ ( ~ - H ) ~ ( ~ ~ - C Cwith ~ ) ( one C O equivalent )~ of 1,8-diazabicyclo[5.4.O]undec-7-ene(dbu) in the presence of a large excess of the Schiff base ligands. The analogues OS~(~-H)~(~~-CN-C~H~Y)(CO)~ (Y = ECH=CH-4-C6H40Me,CH2-4-C6H4NO2)are prepared similarly.l 56 Reaction of CNBU' with Os3(p-H)(p-SbPh2)(CO)loproceeds by way of Os0 s cleavage to give OS~(H)(~-S~P~~)(CNB~~)(CO)~~; the isonitrile ligand ligates at one of the antimony-bridged osmium atoms, and the cluster exists as separable isomers, which differ in the location of the isonitrile ligand (equatorial or axial).l 57 Group 15 ligands. Os3(C0)lo(NCMe)2 reacts with 1-(2-thiazolylazo)-2naphthol to give Os3(p-H)(p-q2-NC3HSN=NC1~H&H-2)(CO)1~ and Os3(p H)(p-q3-NC3H2SN=NC10H60-2)(C0)9, the former with an orthometallated ligand, the latter with a five electron-donating azo ligand after 0-H cleavage. Reaction of the same cluster with 4-amino-4-nitroazobenzene gives Os3(pH)(p-NH-4-C6H4N=N-4-C6H4NOz)(CO)10, in which the amino nitrogen bridges an 0s-0s linkage, and with 2- (4-(diethy1amino)phenylazo)benzoic (in which acid affords Os3(p-H)(p-q2-O2CCgH4-2-N=NC6H4-4-NEt2)(Co)~~

312

Organometallic Chemistry

the carboxylate group bridges an 0s-0s bond) and Os3(p-Cl)(p-q2OC(0)C6H4-2-N=NHC6H4-4-NEt2} (C0)g (in which one of the chloro-bridged osmium atoms is ligated by a carboxylate oxygen atom and the other by an azo nitrogen atom).158 Addition of acetaldehyde to OS&-H)(H)(CO)~~(NH~) gives Os3(pH)(H)(CO)lo(HN=CHMe) with a terminal imine ligand, and an interaction between the axial hydrido and imine l i g a n d ~ . ' ~ ~ Reduction of Os3(C0)lo(N,N'-diimine) (diimine = pyridine-2-carbaldehydeN-isopropylimine) and 0s3(p-H)(p-diimine)(CO)9 [diimine= CSH3N-2C(H)=NPr', 6-CH2C5H3N-2-C(H)=NPr', 2,3-dipyrid-2'-ylbenzoquinoxaline14-ylI has been studied by cyclic voltammetry and spectroelectrochemistry;the greater stability of the radical anions of the latter three clusters has been rationalised by EH MO calculations on model compounds, and is attributable to localisation of the odd electron at the lowest x*-orbital of the orthometallated ligands. 160 The clusters O~~(CO)~~(N,N'-diimine) (diimine = 1,4-di-R-l,4diazabutadiene, pyridine-2-carbaldehydeN-R-imine), containing diimines with reactive imine bonds, photoisomerise to afford Os3(cr-N,p-N,q2-C=N-diimine)(CO)lo;the quantum yields for these isomerisations decrease with increasing steric bulk of the diimine. A mechanism has been proposed for the photoisomerisation. Irradiation of Os3(CO)lo(N,M-diimine)[diimine = pyridine-2carbaldehyde-M-R-imine, R = Me2N(CH2)2, Me2N(CH2)3, 2-~yridyl(CH~)~; diimine = 2-acetylpyridine-llr-R-imine, R = Me2N(CH2)2, 2-~yridyl(CH~)~] with visible light affords the CO-bridged photoproducts Os3{ p1KC:1K C : ~ KN',M'(R)-diimine-M-C(O)} ~N, (C0)9, the reaction proceeding via intermediacy of a zwitterion (either solvent-stabilised or intramolecularlystabilised);'62 the existence of the zwitterion has been confirmed by timeresolved microwave conductivity.163 Reacting (9-nicotine or (R)-l-(4-pyridyl)ethanol with O S ~ ( C O ) ~ ~ ( N C M ~ ) ~ affords diastereomeric orthometallated products Os3(p-H){p-(S)-NC5H3C4H7NMe}(CO)lo (four isomers) or Os3(p-H)(p-(R)-NC5H3CH(OH)Me4}(C0)10 (two isomers), respectively, which can be separated by HPLC; the CD spectra are characteristic of the relative configuration of the Os3CN unit. 164 Excess imidazo(1,Za)pyridine reacts with O S ~ ( C O ) ~ ~ ( N CtoMgive ~)~ the metallated products Os3(p-H)(p-1,2-q2-C7H5N2)(CO)lo and Os3(p-H)(p-l,7-q2-C7H5N2)(CO)10, and with O S ~ ( C Ol-(NCMe) )~ to afford the Ncoordinated O S ~ ( C O1(q ) ~ -C7H6N2), the latter undergoing double C-H activation on heating to give Os3(p-H)(p-1,2-q2-C7H5N2)(CO)lo and Os3(p-H)(p-l,7-q2-C7H5N2)(CO)10. The N-ligand in Os3(CO)1l(q1-C7H6N2)is displaced by PPh3, P(OMe)3 and C N B d Clusters Os3(p-H)(p-1,2-q2-C7H5N2)(CO)lo and Os3(p-H)(p-1,7-q2-C7H5N2)(CO)lo react with further imidazo(1,2-a)pyridine to give Os3(p-H)2(pL-l ,2-q2-C7H5N2)2(C0)8and Os3(p-H)2(p-1,7-q2C7H5N2)(p-1,2-q2-C7H5N-J(C0)8, respectively, by further C-H activation, and with PPh3 to afford mono-substituted products. 165 0s3(p-H)(p3-q:C13H8N)(C0)9 reacts with PPh3 to give the addition product Os3(p-H)(p-q C13H8N)(C0)9(PPh3),which is thermally or photochemically decarbonylated to afford the unexpected o-x-vinyl cluster Os3(p-H)(p3-q3-

11: Organo-Transition Metal Cluster Complexes

c13H&)(C0)8(PPh3).

313

Os3(p-H)(p3-q2-C13H8N)(C0)9 adds H - followed by H+ to give OS~(~-H)~(~~-~~-C~~H~N)(CO)~, labelling studies using D-/H+ showing that initial nucleophilic attack occurs at C9 of the 5,6-benzoquinoline ligand. Reaction of Os3(p-H)(p3-q2-C13H8N)(cowith )9 lithium isobutyryl nitrile, followed by protonation, proceeds by nucleophilic addition across the 3,4 double bond to afford Os3(p-H){p3-q2-C13H9(4-Me2CCN)N} (CO)9. In contrast, Os3(p-H)(p3-q2-Cl3H8N)(c0)9 reacts with n-BuLilH+ to give Os3(pH)2{~3-q2-C13H8(9-C4H9)N}(CO)9[by addition at C9], Os3(p-H){p3-q2c13H7(6’C4H9)N} (co)9 and OS3(p-H) { p3-q2-c13H7(5’C4H9)-N}(co)9, the latter two by nucleophilic substitution of Bun for H. 166 The diphosphines [M(4’-”phenylphosphin0-2,2’:6‘,2’’-terpyridine)2]~+ (M = Fe, Ru) react with Os3(CO)11(NCMe)to afford [(0~3(CO)11}~{p-M(4’diphenylpho~phino-2,2’:6‘,2”-terpyridine)2}]~+ in 3040% yield. 167 The kinetics for substitution reactions of Os3(p-q4-C4Pb)(CO)9with P-donor nucleophiles have been studied, the osmacyclopentadiene ring activating associative attack at the non-ring ligated osmium by a factor of lo9 compared to reactions at OS~(CO) 12. 68 Group 16 and I7 Zigands. Pyrimidine-2,4-dithiol or pyridine-2-thiol reacts with ‘lightly stabilised’ triosmium clusters O S ~ ( C O1(NCMe) )~ or Os3(CO)lO(NCMe)2 to give {OS3(p’H)(CO)lO) 2(p-S2C4H2N2) or OS3(P-H)(pSCsH4N)(CO)lo,respectively; the former loses CO on photolysis to afford {Os3(p-H)(CO)101(p-s,r,N‘S2C4H2N2) {OS3(C1’H)(C0)91 The thermal and photochemical transformations of 2-methylthiothiophene at triosmium clusters has been examined (Scheme 3). Reaction with Os3(CO)lo(NCMe)2at room temperature proceeds by S-coordination and oxidative addition of the C-H bond at the 3 position to give 59. Cluster 59 decarbonylates in refluxing octane to afford 60, and is photochemically isomerised to give 62,which is in turn decarbonylated to afford 63. Cluster 60 photochemically isomerises to 61, which undergoes further isomerisation to afford 63.l7O Other triosmium chemistry with S-ligands proceeds by ring opening. Reacting Os3(CO)lo(NCMe)2 with benzo[b]thiophene affords Os3(p-H)(pC8HSS)(CO)loand O S ~ ( ~ . - H ) ~ ( ~ ~ - C ~ by H ~oxidative S ) ( C ~ )addition ~ of one and two C-H bonds of the S-containing ring, respectively, together with the ring-opened product 64; thermolysis of the first-mentioned product affords the latter two, and photolysis of the first-mentioned product cleanly affords 64.17’ Reacting the bis-acetonitrile precursor with 2-vinyltetrahydrothiophene gives Os3(p-H)(p-SCH2CH2CH=CHCH=CH2)(CO)lo, with ring-opening proceeding exclusively at the vinyl-substituted carbon atom.172 The same triosmium precursor ring-opens the cyclic sulfone 1,3-dithietane-1,l-dioxide, to give Os3{ p-S, C,0-SCH2S(CH2)02}(CO)10, 173 and 3,ti-dihydro-1,2-dithiin, to afford isomeric Os3(p3-SCH2CH=CHCH2S)(CO) 10 and Os3(pSCH2CH=CHCH2S)(CO)10,the latter products containing bridging 2-butenedithiolato ligands formed by S-S cleavage of the dithiin. The butenedithiolato ligand in OS~(~~-SCH~CH=CHCH~S)(CO)~~ is fluxional. Heating OS~(~~-SCH~CH=CHCH~S)(CO)~~ affords OS~(~-SCH~CH=CHCH~S)-

314

Organometallic Chemistry

[Os(co)lo(NcMekl

(60)

hv

isomerisation

Scheme 3

(CO)lo, irradiation of which proceeds by way of double C-S cleavage, elimination of butadiene, and formation of 0s3(P ~ - S ) ~ ( C Oand ) ~ Os4(p3-~)2(~0)12. 74 Bromination of Os3(C0)10(EPh3)2(E = P, As) affords [Os3(p-Br)(CO)10(EPh3)2][O~Br3(C0)3], with the bromine attacking the most electron-rich bond (that linking the phosphine-ligated osmium atoms).175 10.4.2 Higher-nuclearity Clusters. The ‘lightly stabilised’ Os4(p-H)4(C0)11(NCMe) reacts with the mono-pyridyl ligands pyrido[2,3-b]pyrazine or 4pyridinecarboxaldehyde to afford nitrile substitution products in which the cluster is pyridine-ligated. Reactions of O S ~ ( ~ - H ) ~ ( C O ) ~ ~ (with N C bipyrM~)~ idyl or phenanthroline-related ligands give N,N’-chelated products for 2,2’bipyridine, 4,4-dipheny1-2,2’-bipyr idine, 1,10-phenanthr oline, 2,9-dimethyl4,7-diphenyl-1,10-phenanthroline, and dipyrido[3,2-a:2’,3’-c]phenazine, whereas reaction with diphenyl-2-pyridylphosphineaffords o ~ ~ ( p - H ) ~ ( pP-N, PPh2C5H4N-2)( CO) o. 76 Similar reactions with 2,2’-bipyrimidine, 2,3- bis(2pyridy1)pyrazine (dpp) and 2,3’-bis(2’-pyridyl)-5,6-dimethylquinoxaline afford N,N-chelated analogues. Protonation of 0~4(p-H)4(CO)lo(N,N‘-dpp) gives a water-soluble cationic cluster.177 Reaction of Os6(CO)16(NCMe)2 with di(2-pyridy1)disulfide gives a mixture of 65 and 66. Cyclic voltammetry studies on 65 reveal two metal-based oneelectron reductions, and an irreversible ligand-centred oxidation.17’ Reaction

11: Organo-TransitionMetal Cluster Complexes

315

heating the former with excess ligand in refluxing chloroform affords the latter. Reactions with cyclic dithioethers afford a ran e of bicapped tetrahedral products. Thus, the cyclic 1,3-dithioether (CH2)3S H2 gives Osg{pm H 2 } ( C O ) 1 6 , whereas reaction with the cyclic 1,4-dithioether 2 . Similar reaction $(CH2)2SCH2cH2affords O S ~ ( C O{ $(CH2)2SCH2&12} )~~ with the cyclic 1,3,5-trithioether SCH2SCH2SCH2 SCH2SCH2SCH2)(p-CO)(CO)14. The mixed-donor li and reacts to give isomeric clusters Os6{ (CH2)20CH2 H2}(CO)15{ S(CHZ)Z@H2CH2} and Osg{p- (CH2)20CH2 H2}(C0)15{ b(CH2)2SCH2cH2}; the former loses its mixed-donor ligands on carbonylation, affording Osg { pS(CH2)2OCH2&€2} (CO)16 and O S ~ ( C O )whereas ~~, hydrogenation proceeds with structural rearrangement to give Osg(p-H)2 { p-$(CH2)2OCH2(%2} (CO)15{$(CH2)20CH&H2), the core of which consists of two fused tetrahedra sharing a common edge.179 The planar raft cluster O S ~ ( C O ) ~ ~ ( N Creacts M ~ ) with P-donor ligands by initial rapid formation of the adducts O S ~ ( C ~ ) ~ ~ ( L ) ( Nin C Ma ~pre) equilibrium step, followed by slow dissociation of NCMe; the equilibrium and rate constants vary systematically with the electronic and steric properties of L.'~' The mixed-donor ligand $(CH2)20CH2cH2reacts with Os7(C0)19(NCMe)2 to give a mixture of 67--69; carbonylation of 68 gives 70, an isomer of 69.181

h

d 6-

10.5 Mixed-metal Clusters Containing Only Group 8 Metals. - Reacting Fez@with two equivalents of [R~(NcMe)~cp*]'affords the heterocubane cluster [Fe2R~2(p3-S)4Cp*4]2+, which exhibits four electrochemicallyreversible one-electron redox waves. In contrast, reacting Fe2(p-q2-S2)2(qC5H3(SiMe3)2-1,3} with the same ruthenium-containing precursor affords the + 182 q-C5H3(SiMe3)2-1,3)2Cp*] . V-shaped cluster [Fe2R~(p3-q2-S2)(p3-S)2{ piZeo-2,3-(RuCp*2B4Hs), which possesses a square pyramidal structure, undergoes core-expansion on reaction with Fe2(C0)9 to afford octahedral piZeo-6-Fe(C0)3-2,3-(RuCp*)2( p3-CO)B4H4.183

Organometa llic Chemistry

316

B 0

11

Group9

11.1 Cobalt. - The behaviour of cobalt carbonyl complexes under vacuum or near vacuum conditions has been studied, conditions for the formation of C O ~ ( ~ ~ - H ) ( ~ - C O )defined, ~ ( C O ) and ~ thermodynamic parameters for the decomposition of C O ~ ( C Oto) ~give Co4(C0)12~ a l c u l a t e d . ' ~ ~ 11.1.I TrinucZear Clusters. A range of tricobalt methylidyne clusters incorporating carbohydrate groups have been prepared by reaction of the acylium cation [Co3(p3-CCO)(C0)9lf with a carbohydrate, or reaction of C O ~ ( C O ) ~ with 1,l ,1-tribromomethyl sugar derivatives.185 The tricobalt methylidyne cluster unit is also a building block for a range of poly-cluster arrays. Thus, reacting C O ~ ( ~ ~ - C C O ~ H ) (with C O )metal ~ trifluoroacetates affords Cr2{p02CCCo3(CO)9}(~ - 0 ~ C C F ~ ) ~ ( t hand f ) ~ Sm2{ p-O2CCC03(C0)9}2(p-02CCF3)4{OC(OH)CCo3(CO)9}2(thf)2, cluster-substituted analogues of known organic carboxylates, and reaction with Pt(I1) acetate gives Copt { p02CCCo3(CO)9}3(p-02CMe){ OC(OH)CCO~(CO)~}. Reaction with Zn(OH), in thf gives Zn&-O) { ~ - O ~ C C C O ~ ( C O but ) ~ in ) ~ 2-methyltetrahydrofuran , gives CoZn{p-02CCCo3(CO)9} { CO(CO)~} (OC4H7Me-2).Reacting the same tricobalt precursor with Cr(I1) acetate gives Cr2Co(p3-0){ p-02CCCo3(co)9) 4(@2CMe)2 {oc(oH)cco3(co)9)2(OH2) and Cr3(p3'0) { p-02ccc03{ OC(OH)Me}2 , cluster analogues (C0)g)4(p-02CMe)2{OC(OH)CCO~(CO)~> of known organic carboxylate 0x0 metal trimers. Deprotonation of the

I I : Organo-Transition Metal Cluster Complexes

317

tricobalt precursor using a bulky base affords [ C O{ ~ p-O2CCCo3(CO)9}3{ 02CCC03(C0)9}21 - . 86 Reacting C O ~ ( C Owith ) ~ propargyl trichloroacetate affords Cog { p3-CC(0)OCH2(p-q2-C2H[Co2(C0)6])}(C0)9 and Co3(p3-CEt)(CO)9. 187 Co3(p3-CMe)(C0)9 reacts with diphenyl-2-thienylphosphineto afford the mono- and bis-substitution products, with thermolysis of the former resulting in partial conversion to the latter; the thienyl group is non-coordinating in these clusters.188 Oxidative and reductive behaviour of isomers of Co3(CO)3Cp3 has been studied. C03(p-C0)3Cp3 maintains its CO disposition in the 48 e and 49 e forms, but isomerises to [Co3(p-CO)2(CO)Cp3]+on one-electron oxidation. Cog(ll.3CO)(p-C0)2Cp3 and Co(p-C0)2(CO)Cp3 are present in a 1:l ratio at room temperature in the 48 e form, and are in rapid equilibrium; oxidation affords exclusively [Co3(p-CO)2(CO)Cp3]+, and reduction gives [Cog(pg-CO)(pCO)2Cp3]-. In contrast, C03(pg-Co)(p-CO)~(q-C~&Me)Cp*2retains its CO disposition in the 47 e, 48 e and 49 e forms, a result ascribed to steric f a ~ t 0 r s . l ~ ~ C H R Iby ) Creduction ~~ of Hydrogenation of C O ~ ( ~ ~ - ~ ~ - C ~ H ~ C R 'proceeds (R = Me, R' = H; the alkenyl group to afford Co3(p3-q6-C6H5CHRCH~R')cp3 R = H, R' = Ph; R = Ph, R' = H), a structural study of one example showing a small,but statisticallysignificant,Kekulbtype distortion of the p3-phenylring. 190 Reaction of C O ~ ( C O ) ~ with AsPh2(SPh) affords Co3(p3-S)(p-A~Ph2)(AsPh3)(C0)6by arsenic-sulfur bond cleavage.19' 11.1.2 Tetranuclear Clusters. C O ~ ( C Oreacts ) ~ with diprop-2-ynyl ether to give 71, in a reaction involving hydrogen migration and C-C bond formation,'92 and with diphenyl-2-pyridylphosphine to afford Co&P,N-PPh2py)(pC0)3(C0)7.'93

Co4(CO) 2 reacts with 4-diethynylbenzene or Co2(p-q 2-HC2C6H4C&H)(C0)6 to afford C04(CLq-q2-HC2C6H4CECH)(p-CO)2(CO)8 Or c O 4 {p4q2-HC2C&[( p-q2-c2H)c02(co)6]1(p-c0)2(c0)8, respectively.194 Dibenzothiophene (dbt) reacts with Co4(CO) to give C04(p-C0)3(C0)6(q 6dbt). This is desulfurised on treatment with Cr(C0)3(NCMe)3to give CO&C0)3(C0)6(q-C6H6), a product also obtained from reaction between C04(CO)12 and ben~0thiophene.l~~ 11.1.3 Higher Nuclearity Clusters. Reaction of CoC12 and ligand L with sodium sulfide affords [co6(p3-s)8(L)6]"+ [L = PMe2Ph, n = 1; L = P(OMe)3,

318

Organometallic Chemistry

n = 01, 196 and with lithium phenylimide gives [Co&4-NPh)(p-NPh)6(L>dZ(L = PEtPh,) and [co,(p3-NPh)6(p-NPh)3(L)2]-(L = PPh'). 197 11.2 Rhodium and Iridium. - Oro and co-workers have summarised studies of polynuclear mixed-valence rhodium and iridium 'blues'. 98 Oxidative coupling of the imido-capped cluster anion [Rh3(p3-NC6H4Me4)2(co)6]- affords the transoid bi-edge-bridged square cluster Rh6(p3NC6H4Me-4)4(Co)~2.199 Reaction of 20 different internal or terminal alkynes with Rh4(C0)12 give products proposed to be Rh2(p-r12-RC2R')(CO)6;this is the likely pathway for catalyst poisoning observed when alkynes are present in the rhodiumcatalysed hydroformylation of a1kenesb2O0Detailed study of the latter process with 20 different alkenes has revealed that differences in rates of hydroformylation are due to differences in conversion from cluster to mononuclear acyl intermediate,201studies employing cyclohexene have eliminated contributions to catalysis from monometallic binuclear elimination,202and studies employing styrene suggest CO-assisted polyhedron opening as the first step."' Rh4(C0)12 catalyses the reaction of 2-propynylamine, hydrosilane and CO to give 2-(dimethylphenylsilylmethyl)alkenal,204 and Rh6(C0)16 catalyses the carbonylation of 2-arylethynylbenzamides to afford spiro compounds and fur an one^.^'^ [Rh(C0)2(NCMe)2]BF4, prepared by chloride abstraction from Rh&Cl)2(CO)4 using AgBF4 in acetonitrile, is dark blue in the solid state, and consists of 1-D stacks due to Rh(1)-Rh(1) contacts.206 Decarbonylation of zeolite-supported Rh6(C0)16 or Ir4(CO)12 in H2 at 200 "C or 300 "C, and decarbonylation of alumina or magnesia-supported Ir4(CO)12,[Ir6(C0)15]2- and [IT~(~-H)(CO)~affords supported clusters with intact metal frameworks which are catalytically active for propene hydrogenation.2079208 Zeolite NaX-supported [Rh6(CO)16]2- has also been prepared, decarbonylation affording clusters and aggregates active for toluene hydr~genation.~'~Zeolite Nay-supported Ir4(CO)12, Ir6(CO)16 and Rh6(C0)16, and decarbonylated clusters derived therefrom, have been studied by '29Xe NMR spectroscopy; the largest chemical shift from that observed with the bare zeolite is seen with Ir4(CO)12,suggesting that Ir4(CO)12in the zeolite supercages is small enough to permit entry of the xenon.210 11.3 Mixed-metal Clusters Containing Only Group 9 Metals. - The dimetallaborane { R h c ~ * ) ~ B & ~reacts c l with Co2(CO)8 by B-H o-bond metathesis to afford { Co(CO)~)~(Co(CO)3}(RhCp*)2(p-CO)B3HC1.211 Reaction of Co2(CO), with Rh&-C1)2(C0)4 on Si02 affords Co3Rh(CO)12, chemistry which parallels that seen in solution. Thermal treatment of Co4(CO)12 and Rh2(p-C1)2(C0)4 on Si02 under a reducing atmosphere affords a bimetallic Co-Rh catalyst active for ethylene hydroformylation.21

11: Organo-Transition Metal Cluster Complexes

12

319

Group10

12.1 Nickel. - Nucleophilic attack of the CO oxygen atom in [Ni(CO)Cp]- at the boron atom in BC12(NR2) [NR2= NBut(SiMe3), N(SiMe3)2] or B2C12(NMe2)2,followed by salt elimination, affords Ni3{ p3-COBC1(NR2)}(p3CO)Cp3 or Ni3(p3-COB(BNMe2C1)(NMe2)}(p3-CO)Cp3,re~pectively.~~ Reaction of nickelocene with tert-butyl lithium affords NiButCp, which decomposes to give N & ( ~ . L ~ - C P $ ) CNi(PMe3)4 P ~ . ~ ~ ~ reduces a range of 2nitrophenols, to give firstly Ni(OAr)2(0PMe&, and then Ni3(p3-NC6H2-2-03-R-5-R’)2(PMe3)4(R = But, H; R’ = Me, But, OMe).214 12.2 Palladium. - Reaction of P ~ ( O A Cwith ) ~ excess 2,4,6-triphenylphosphinine, followed by PEt3, affords the triangular Pd3(p-PC5H2Ph3-2,4,6)3(PEt3)3, calculations on a model cluster suggesting that the phosphinines bond to the metal core using both CT and n; orbitals.215Bubbling COS gas through a solution of Pd2(p-S02)(p-dba)(PBz3)2(dba = dibenzylideneacetone) affords 72 by S-CO cleavage. [Pd4(p4-q3,q2,q2,q3-PhCHCHCHCH=CHCH=CHCHPh)2l2+ as its BF4salt has been prepared by reaction of [Pd(NCMe)4](BF4)2,1.5Pd2(dba)3and all-trans- 1$-diphenyl- 1,3,5,7-0ctatetraene, counter anion exchange affording the [B(3,5-(CF3)2C6H3}4]- salt; the Pd4 cluster chain is ‘sandwiched’ by the polyenes. Chain slippage to afford the q2,q2,q2,q2-complexoccurs with donor solvents such as pyridine, the solvent coordinating to the terminal Pd atoms. Reducing the amount of Pd(0) in the original synthesis from three equivalents affords the Pd3 sandwich chain, whereas increasing it to four equivalents and employing a hexa-ene affords the Pd5 sandwich chain.21 Reacting Pd2(dba)3.CHC13with an excess of dmb (dmb = 1,8-diisocyano-pmenthane) and PPh3 affords linear 73,Raman spectroscopy of which reveals v(PdPd) active modes at 165 and 86 cm-’. EHMO calculations suggest that the HOMO and LUMO are two do* orbitals arising from interacting Pd atoms. The polymeric { [Pd4(dmb)5](MeC02)2}nis formed from reaction of Pd2(dba)3.S (S = C6H6, CHC13) with excess dmb and Pd(02CMe)2. These complexes luminesce with microsecond lifetimes.

1*+ I

PBz3

320

Organometallic Chemistry

12.3 Platinum. - The reactions of Pt3(p-PPh2)3Ph(PPh3)2with silanes or siloxanes HSiR3 (R = Ph, Et, OSiMe3,OMe) afford Pt3(p-PPh2)3(SiR3)(PPh3)2, which contain a direct Pt-Si bond.334 In a similar manner to its palladium analogue above, [Pt4(dmb)4(PPh3)2I2' is formed from reaction between Pt2(dba)3.CHC13,two equivalents of dmb, and one equivalent of PPh3. Replacing PPh3 in this synthesis with 0.5 equivalents n, with of a bidentate phosphine gives the polymeric { [Pt4(dmb)4(diphos)]C12} molecular weights in the range 84000 to 307000 according to viscometry.218 Reaction between trans-PtH(c~CC5H~N-2)(PPh~)~ and ci~-Pt(C~F~)~(thf)2 proceeds by way of a binuclear intermediate to eventually afford 74, a zwitterion in which a cationic Pt3 cluster unit is attached to an anionic alkynylplatinate.21

(74)

The heterocubane Pt4(p3-F)4Me12is formed from the reaction of AgF on Pt4(p3-I)4Me12; the product is readily hydrolysed, forming successively Pt4(p3F)3(~3-OH)Me12,Pt4(~~3-F)2(~3-0H)2Mel 2, Pt4(~3-F)(CL3-OH)3Me12 and Pt4@3OH)4Me12,all of which retain the heterocubane core. NMR studies reveal that the methyl groups of the partially-hydrolysed clusters exchange intramolecularly with retention of core integrity.220 The platina-P-diketone Pt2H2(p-C1)2(COMe)4reacts with 2,2'-bipyridine to give [ { (bipy)Pt(p-COMe)2Pt(COMe)2H}2I2+,an organometallic analogue of a platinum blue complex; bond distances suggest that closed shell d 8 4 ' interactions in the Pt4 zigzag chains are strong.221 Platinum carbonyl cluster dianions [{Pt3(C0),},l2- (n = 4-6) are synthesised by reaction of H2PtC16with CO and H 2 0 in the mesoporous channels of FSM16 which have been modified by impregnation and hydrolysis of Ti or Zr alkoxides, and subsequent calcination. The supported clusters are decarbonylated to afford nanoparticles active for CO hydrogenation with C2-C3 alkane selectivity.222

13

Group11

Luminescent Group 11 cluster complexes,223and more specifically those incorporating alkynyl l i g a n ~ l s ; have ~ ~ been summarised.

13.1 Copper. - The photoluminescent properties of copper cluster complexes have been reviewed.225

32 1

1I : Organo-Transition Metal Cluster Complexes

Reaction of Cu(C6H3Mes2-2,6)(Mes= C6H2Me3-2,4,6)with Pb (Si(SiMe3)3)2 affords Cu3{ ~ - s i ( S i M e ~3,) with ~ ) Cu. ..Cu distances indicating weak attractive d'O-d'O interactions.226Combining CuC1, dppm and MesSeSiMe3gives Cu3(pdppm)(p-SeMes)3.39 Stirring [C~~(dppm)~(dmcn)~](BF~)~ (dmcn = dimethyl cyanamide) and sodium tungstate in 1:l CH2Cl21MeOH affords 75, in which the W042- is

F?,,:(]

Ph2

Ph2

CU'

Ph2P\

RCk \

p

h

/pph2

cu

cu

2

p

v

I

PPh2

located inside the cavity formed by the phenyl rings of the dppm l i g a n d ~ . ~ ~ ~ The same dicopper precursor affords monocapped [Cu&-OH)(pdppm)3](BF4)2 when stirred in hot CH2C12/MeOH. Dimeric [Cu,(pdppm)2(NCMe)4I2+ reacts with halide to give dicapped [Cu&3-X)2(pd ~ p m ) ~ ]Ab + . initio calculations on model compounds reproduce the experimental trend in Cu...Cu distances, which are modulated by variation in capping ligand.228 The UV-vis spectra the triangular clusters [Cu3(p3-q '-C=CR),(pdppm)3](3-")+ (R = 4-C6H4NOz74-C6H4Ph, 4-C6H&Me, 4-C6H4NH2, C6H13; n = 1, 2) and heterocubane clusters C U ~ ( C L ~ - T ) ' - C ~ C C ~ H ~ -(R ~ -=REt, )~(PP~~ OMe, Ph, N02) contain high-energy intraphosphine bands and low-energy metal-perturbed intraacetylide or metal-to-acetylide CT bands. These clusters produce long-lived intense luminescence when excited. The triangular clusters undergo metal-centred CuIIII oxidation.229 Copper(1) iodide, KI and PMe3 react to afford C U ~ ( ~ ~ - I ) ~ (which P M ~has ~)~, been shown to adopt a heterocubane geometry by solid-state 31PNMR, far-IR and Raman s p e c t r o s c ~ p i e s . ~ ~ ~ { P-PP~~(CH~)~O(CH~)~O(CH~)~PP 2 CU~(JA -CrCPh)z(p3-q2-C2Ph)2 -~ exhibits intense luminescence in solution and in the solid state; the cluster dispersed in polyvinylcarbazole can function as the emitting layer in an electroluminescentdevice.23 13.2 Silver. - Alkali metal acetylides react with silver iodide to form M[Ag(C2H)2],which on heating afford the ternary silver acetylides MAgC2.232 Silver acetylide combines with silver nitrate in various ratios to afford double salts in which the structural motifs Ag,(pn-C2) ( n = 6 - 8 ) are seen.233AgBF4 and {Ag(C2Buf)>, combine in a 1:2 ratio to give polymeric ([Ag3(C2B u ~ ) ~ ] ( B F ~ )Two ) , . ~equivalents ~~ of AgBF4 react with 6,6-bis(diphenylphosphin0)-2,2'-bipyridyl to give 76, which adds X- (X = Br, I) to afford 77 and 78 in non-coordinating solvent or 79 in coordinating solvent (L = MeCN, dmso);

Organometallic Chemistry

322

I

12+

4+

1 2+

1 2+

L

the photoluminescent properties of clusters in this system are sensitive to structural changes associated with ligand and solvent coordination.235 - with [Ag(NCMe)4]+ affords co-crystalline Ag8(p8Treating [Se2P(OPri)2] Se)(p4-q2-Se2P(OPri)2}6, with a cubic metal core and encapsulated selenium atom, and octahedral Ag6{ p3-q2-Se2P(OPri)2}6.236 13.3 Gold. - Reaction of diphenylphosphinous acid with AuCl(SMe2)affords ( A u C ~ ( P P ~ ~ Owhich, H ) } ~ when treated with an excess of BF3.OEt2, gives 80; the prismatic Au3C13Au3unit is remarkably robust, withstanding attack by HC1 and HBF4 which are by-products from the reaction.237 Addition of benzyl isocyanate to a suspension of AuCl(PPh3) in a methanolic KOH affords Au3{ p-q2-C,N-(MeO)C=NBz)}3, which is luminescent as a solid at room temperature.238The gold oxonium reagent [ ( P ~ ~ P A u ) ~ O ] B F ~ reacts with 1,2-diphenylhydrazine to give a mixture of [Au3(p3-NC6H4-4-

11: Organo-Transition Metal Cluster Complexes

323

NHPh)(PPh3)$ and [AU~(~~-NC~H~-~-NHP~)(PP~~)~]+, both clusters reacting with hydrazine to afford the dinitrogen complex [Au6(p6-q22+ 239 N2)(PPh3)61 * A ~ ~ ( p - d p p f ) ( S C ~reacts F ~ ) ~with four equivalents of Au(OC103)(PPh2R) (R = Ph, Me) to give {Au3(p3-SC6F5)(PR3)2}2(p-dppf), and with AgC104 to afford [Au2(p-dppf)(p-SC6F5)]C104, in which two cations are linked in the solid state through Au.. .Au interaction^.^^' The gold thiolate complex Au{S(CH2)2N=CHFc}(PPh3) reacts with two equivalents of Au(OTf)(PPh3) to give AU~(~~-~~-S,N-SCH~CH~N=CHFC)(PP~~)~]~+.~~ The reaction of Au2(p-Se)(PPh3)2 with two equivalents of [Au(PPh3)](CF3S03)affords [Au4(~-Se)(PPh3)4l2',with the selenium atom at the apex of a square pyramidal core; loose association of two cations in the crystal lattice through Se...Au interactions is observed.242 Decomposition of 2,4,6-((Bu'NC)AuS} 3C3N3 gives Au4{ p3-q3S2C3N3SAu(CNBut))2(CNB~t)2, the crystal structure of which reveals significant intermolecular Au. ..Au bonding resulting in an extended sheet-like structure.243Oxidation of Au(SC6H4Me-4)(PPh3)affords rectangular [Au4(p-

SC6H4Me-4)2(PPh3)4]2+.244

13.3 Mixed-metal Clusters Containing Only Group 11 Metals. - Short Au ...Ag interactions are observed in [A~Au~(~-N,C-~-CH~-~-RCSH~N)(P formed from reaction between Au(2-CH2-6-RC5H3N)(PPh3)(R = H, Me) and 0.5 equivalents of AgC104.245

14

Group12

The heterocubanes Zn4(p3-9-BBN-9-0)4Et4and Cd4(p3-9-BBN-9-O)Me4are formed on treating ZnEt2 or CdMe2 with (9-BBN),O; ZnBuf2is inert under these reaction conditions. The related complex z ~ ( p ~ - o B E t ~is) ~formed Et~ from reaction between ZnEt2 and (Et2B),0, but the synthesis of Cd4(p3OBEt2),Me4 requires reaction between CdMe2 and diethylborinic The triangular cluster cation [Hg3(p-d~prn)~]~+, formed from reaction between HgO, H2SiF6 or HPF6, dppm, and Hg, crystallises with anions inside the cavities formed by the dppm phenyl groups and the Hg3 triangle.247 Hg(CrCR)2 molecules aggregate in the solid state, th? phenyl example crystallising as a pentamer. The Hg...Hg distances (3.7-4.0 A) possibly indicate weak mercuriophilic interactions.248

15

Mixed-metal Clusters

As in previous accounts, the chemistry of clusters containing metals from more than one group of the Periodic Table is considered in this section, complexes being arranged in order of lowest Periodic group number.

324

Organometallic Chemistry

15.1 Group 4. - 15.1.1 Zr-Fe, Ru, Co. The chelating amido complex with [M(C0)2Cp]or ZrC12(thQ2[{ N(SiMe3)CH2}2CH2] reacts [CO(CO)~(PP~~)]to afford ZrM2(C0)4[{N(SiMe3)CH2}2CH2]Cp2 (M = Fe, Ru) or ZrCo2(CO)6[(PPh3)2 { N( SiMe3)CH2}2CH2],which contain unsupported Zr-M bonds.249

15.1.2 Ti-Ru, Rh, Ir, Cu. Treating T ~ R u ( ~ - S H ) ~ C I Cwith ~~C base ~ * affords the heterocubane Ti2R~2(p3-S)4Cp2Cp*2, EH MO calculations and a structural study suggesting dative Ru-+Ti bonds and a weak Ti...Ti interaction. Oxidation of this cluster by [FeCp2]+ affords the corresponding dication, whereas HCl oxidation gives the dichloride, species which can be interconverted by C1- or PF6-. Heating the dichloride results in Ti-Cp cleavage and formation of Ti2R~2(p3-S)4C13CpCp*2.250 Other heterocubanes are prepared on reacting [Ti2(p-S)2(S)2Cp2]2-with a range of halometal complexes, viz Ti2M2(p3-S)4(q4-~od)2Cp2 (M = Rh, Ir) and Ti2C~2(p3-S)4(PPh3)2Cp2.251 The same titanium reagent reacts with { M(p-Cl)(di~lefin)}~ to give TiM3(p3S)3(dioefin)3Cp[M = Rh; diolefin = cod, nbd, tfbb (tfbb = tetrafluorobenzobarrelene); M = Ir, diolefin = cod], carbonylation of which affords TiM3(p3s)3(co)6cp. The carbonyl-containing iridium derivative reacts with tertiary [L = PPh3, phosphines and phosphites to give TiIr3(p3-S)3(p-CO)(C0)3(L)3Cp PMe3, P(OMe)3,PMePh2](81). Labelling studies using 13C0 reveal that all CO ligands in these phosphine-containing clusters exchange rapidly, an equilibrium being established between T~IT~(~~-S)~(~-'~CO)(~~CO)~(PR~) and TiIr3(p3-S)3(p-13C0)( 13C0)4(PR3)2Cp and free phosphine. The PPh3-derivative can be protonated with HBF4, to afford [TiIR3(H)(p3-S)3(p-CO)(C0)3(PPh3)3Cp]BF4.252The diolefin clusters (M = Rh; diolefin = tfbb, cod) in the presence of P-donor ligands catalyse the hydroformylation of 1-hexene and styrene.253 TiMe3Cp* reacts with three equivalents of { Ir(p-OH)(~od)}~ to give * .254 TiIr3(p3-0)3(~~d)3Cp

15.2 Group 5. - 15.2.1 Ta-Rh, Ir. TaMe&p* reacts with four equivalents of

(M(p-OH)(cod)} (M = Rh, Ir) to afford TaM4(p3-0)4(~od)4-254 15.3 Group 6. - The chemistry of cuboidal Mo3MS4 (M = Co, Ni, Pd, Cu) and Mo3NiSe4clusters with CO has been reviewed.255 15.3.1 Mo, W-Fe. - The isomeric clusters cis- (82) and trans-Mo2Fe2(p3-S)(p3Se)(CO)8Cp2(83) are obtained from reaction between Fe2(j.~-SSe)(C0)~ and

Mo~(CO)~C~ or, , upon reacting Fe3(p3-S)(p3-Se)(C0)9with Mo2(C0)&p2. The tellurium-containing analogues cis- and trans-Mo2Fe2(p3-S)(p3Te)(C0)&p2 are formed on reacting Fe2(p-STe)(C0)6 with Mo2(C0)4Cp2, or from Fe3(p3-S)(p3-Te)(C0)9and M O ~ ( C O ) & P ~ . ~ ~ ~ Heating a mixture of Fe3(p3-E)2(C0)9 (E=S, Se, Te) with W(CrCPh)(C0)3Cp* affords 84, in which the alkynyl ligands have coupled in a novel tail-to-tail manner.257

I I : Organo-Transition Metal Cluster Complexes

325

'

\

(84) E = S, Se, Te

Metal exchange on W F ~ C O ( ~ ~ - S ) ( C Owith ) ~ C WCl(C0)3(q-C5H4R) ~ and on MFeCo(p3(R = H, Me) gives W2Fe(p3-S)(CO)7Cp(q-C5H4R),258 E)(C0)8(q-C5H4R) (M = Mo, W; E = S, Se; R = H, MeCO, Me02C) with [FeH(C0)4]- followed by acidic work-up affords MFe2H(p3-E)(CO>8(q1C5H4R).259In the latter system, derivatisation of WFe2H(p3-S)(C0)8{ qC5H4C(0)Me) employing 2,4-dinitrophenylhydrazinegives the corresponding hydrazone.259 A number of organometallic MoFe3S3 clusters have been prepared as synthetic analogues of the nitrogenase cofactor subunit,260and a number of tetrathiometallate clusters M2Fe2(p3-S)2(p-S)2(CO)&p*2 (M = Mo, W) have been prepared from Fe2(p-q2-S2)(p-q ,q '-S2)Cp*2 and M(C0)3(NCMe)3 or M(C0)6. 82 15.3.2 Mo, W-Ru, 0s. Metal exchange occurs on reacting Ru3(p3-NOMe)(p3CO)(CO), with MoH(CO)~C~,to afford MoRu2(p-H)(p3-NR)(C0)&p (R = H, OMe), the former product corresponding to conversion of rnethoxynitrido to nitrene.261 Alkyne-carbide coupling occurs on reacting W O S ~ ( ~ - H ) ( ~ ~ - C )lCp* (CO)~ with 4-ethynyltoluene, the alkylidyne-containing cluster W0s3(p3CCHCHC6bMe-4)(CO)11Cp* being obtained. The similar reaction with 3phenyl-1-propyne affords a further alkylidyne cluster 85, together with an

326

Organometallic Chemistry

alkenyl cluster 86. The 0x0 alkynyl complex W(CSPh)(0)2Cp* adds to RU~(~~-PN~R)(CO to ) ~afford ~ - ~ WRu4(p4-q2-C2Ph){ p3-q2-P(0)NR2}(p0)(p-CO)(CO)9Cp* and WRu4( p4-q2-C2Ph)( p3-PNR2)(p-O)2(CO)&p*, the former containing the first diisopropylaminophosphinidoxo ligand. Reaction of the latter with HBF4.0Et2 gives WRu4(p4-q2-C2Ph)(p3-0){p3-q2P(0)NR2}F(CO)&p* .262 Thermolysis of a mixture of Ru2(p-q2,q2-S2)(p-q‘,q ‘-S2)Cp*2 and two equivalents of W(C0)3(NCMe)3in toluene affords 87-90, whereas the similar reaction with one equivalent of the tungsten reagent gives 88 and Ru2W(pS)4(CO)2Cp*2, an isomer of 89. As 89 and its isomer react with W(C0)3(NCMe)3 and CO to afford 87 and 88, it is likely that the trinuclear clusters are reaction intermediates in the formation of the tertranuclear clusters.263

Mo, W-Co. Reacting Cp(C0)2M(p-C=CCrC)M’(C0)2Cp (M = M’ = Mo, W; M = Mo, M’ = W) with C O ~ ( C Ogives ) ~ the linked bis(carbyne) compound Cp(C0)8MCo2(p3,p3-q‘,q *- C C - C C ) M ’ C O ~ ( C O ) ~ C ~ . ~ ~ The C-C bond in MO~(~-HC~P~)(CO)~(~-C~H~C(O)R}~ (R = Me, OEt, Ph) also participates in cluster formation on reaction with CO~(CO)~, the butterfly clusters MO~CO~(~~-~~-HC~P~)(~-C~)~(CO)~{~-C~H~ 2 being formed.265A range of functionalised alkynyltungsten complexes have been reacted with C O ~ ( C Oto ) ~generate alkylidyne-WCo2 clusters with a reactive carbenoid as the P-carbon, the latter participating in a range of intramolecular cyclisations.266 The linear cluster MoCo2(p-q2,q2-S2C6H4-2)2(C0)2Cp2 is obtained from reaction of Co(q2-S2C6H4-2)Cp and M o ( C O ) ~ ( H ~ ~ ) ~ . ~ ~ ~ Metal exchange on Co3(p3-CC(0)OCH2(p-q2-C2H[Co2(C0)6])}(C0)9 with p(CO)3(q-CsH4R)]- [R = H, C(O)Me, C(O)C6H4-4-C02Me] or [(OC)3W{q~ ~ ~ ~ ~ ( ~ ) ~ ~ ~ ~ - ~ affords - ~ (W~C O)~ (-~ ~q- C-C ( ~ O)O ~ C~H ~~- > ~ (p-q 2-C2H[Co2(CO),])} (CO)8( q -CsH4R) or the expected linked cluster product.’87 15.3.3

327

11: Organo-Transition Metal Cluster Complexes

15.3.4 Mo, W-Rh,Ir. The 'triple-cubane' oxide cluster Mo4Rh4(p3-0)8( O ) & P * ~ . ~ H ~reacts O with MeSH with destruction of the cluster core, products with Mo-Mo bonds being formed.268 M2(p-S)2(S)2(q2-S2CNEt2)2(M = Mo, W) reacts with M'Cl(PPh3)3(M' = Rh, Ir) to give the triangular cluster products 91, and with (M'(p-Cl)(cod)>2 to afford the heterocubane clusters 92.269

(91) M = Mo, W M' = Rh, Ir

(92) M = Mo, W M' = Rh, Ir

Ligand substitution at mixed tungsten-iridium clusters has been the focus of further studies. The isomer distribution for the previously reported clusters WIr3(p-C0)3(C0)8-n(PR3),Cp (n = 1, 2; R = Ph, Me) has been assigned, with preference for a Wr2(p-CO)3 carbonyl distribution being observed. Carbonyl fluxionality processes are postulated from the results of 3C exchange spectroscopy (EXSY) studies.270WIr3(CO)I 1Cp reacts with 1,2-bis(diphenylphosphino)benzene (pdpp) to afford WIr3(p-C0)3(p-pdpp)(C0)&p, the rigid backbone of which restricts the cluster to one configuration in solution; in contrast, the related clusters WIr3(p-C0)3(p-L2)(C0)6Cp (L2= dppm, dppe) adopt two interconverting configurations in solution.271WIr3(CO)I1Cp reacts with isocyanides to give WIr3(CO)11- .(CNR),Cp (R = C6H3Me2-2,6, But; n = 1-3), a structural study of the bis-xylylisocyanide product revealing that the two incoming ligands are coordinated to the same iridium atom.272 W2Ir2(C0)&pz reacts with one or two equivalents of phosphine to give W21r2(p3-CO)(C0)7-n(L)nCp2 (L = PPh3, PMe3; n = 1, 2). The products have been resolved into their interconverting isomers at low temperature, structural assignment being aided by development and implementation of 2D triple resonance The ditungsten4iiridium cluster also reacts with P(OMe)3 to afford mono- and bisphosphite products W21r2(p-CO)3(CO)7-,(P(OMe)3)nCp2(n = 1,2), the latter decomposing on crystallisation to give WIr3(p-CO)3(CO)7{ P(OMe)3}Cp,274and with bidentate phosphines to afford W21r2(p'C0)3(pL'L)(c0)5cp2 (L = dppm, dppe).271 15.3.5 Mo-Pd. Pd2(p-dppam)2C12(dppam = (Ph2P)2NH]reacts with Na[Mo(functionalisation by KH CO)3Cp] to give M~Pd~(p~-CO)~(p-dpparn)~ClCp, followed by Me1 or EtI affording MoPd2(p3-C0)2(p-Ph2PNRPPh2)2C1Cp (R = Me, Et).2759276 15.3.6 Mo, W-Cu, Ag. Treating Mo(SB~')~(q~-drnsp)~ (dmsp = SCH2CH2PMe2)with CuBr affords { MoC~~(p~-S)(p-q~-dmsp)~Br}~(p-SB~~)2

328

Organometallic Chemistry

following C-S cleavage of a SBut ligand and ligand r e d i ~ t r i b u t i o nThe .~~~ sulfido ligands in wS3Cp*]- also act as assembling ligands, reaction with two equivalents of CuBr affording 93; in the presence of excess PPh3, though, the same reactants yield the trinuclear product WC~~(p~-s)(p-Br>(p-S)~s-w-s

lA\l

s-cu-s-cu-s I/\ I \I 'W-s s-wcp*

l\l

l/l

s -cu-s-cu-s I \ I01 s-w-s

(PPh3)2Cp*.278 In a similar vein, reaction of [wS3Cp*]- with AgCN has been * ~ }octanuclear essayed, a helical polymer { W2Ag3{~ ~ - S ) ~ ( ~ - S ) , ( C N ) C Pand cluster W4Ag4(p3-S)4(p-S)4(S)4Cp*4 being obtained.279Reacting [WS4l2- with Cu{S2P(OCHzPh)2) affords WCu&3-S)3 { p3-q2-S,S-S2P(OCH2Ph)2)(PPh3)3(S), which has an incomplete cubane-like structure, whereas the reaction of [W0S3l2- with Ag{ S2P(OPri)2) gives WAg3(p3-S)3{ p3-q2-S, S-S2P(OPri)2)(0)(PPh3)3,in which the dithiophosphate acts as a bidentate ligand. The thirdorder nonlinear optical properties of these clusters have been assessed by the Z-scan technique at 532 nm, with large nonlinearities observed, although the pulse lengths employed (of the order of ns) do not exclude thermal contributions.280WCu,(p3-S)(pL-S)2(0)(PPh3)3reacts with pyridine by addition and phosphine substitution, affording WC~,(p3-S)(p-S)2(Hpy)2(O)(PPh3)2.~~~ Combining equimolar MoHzCpz, WH2Cp2 and AgPF6 gives [M2Ag(pH)4Cp4]+ (M = Mo, W) together with [ M o W A ~ ( ~ - H ) ~ Cand ~ ~ ]reacting +, MoH2(q-C5H4Me)2with AgPF6 gives [Mo2Ag(p-H)4(q-C5H4Me)4]+.282 [MoS4I2-, CuI, cyanopyridine and pyridine react to form a cluster polymer {MoCU6(p4-S)4(p-I)2I2(HPY)4)n, and [CU(NCMekI+, dPPm and [WSe412combine to give the cationic cluster [WC~~(p~-Se)~(p-dppm)~]~+, both of which are effective optical limiters.2839284 [wS3Cp*]- reacts with three equivalents of [CU(NCM~)~]+ to give [W3Cu7(p3-S)9(NCMe)&p*3I4'+, which affords a 2D polymer on treatment with pyrazine/LiCl in MeCN.285 15.4 Group 7. - (ReCp*)2B4H8 reacts with C O ~ ( C O )to ~ afford (ReCP*)~{ C O ( C O ) ~ } ~ ( ~ - C O ) Bin~ H which ~ , a B4C02 ring, a new 'inorganic benzene', is sandwiched between the ReCp* fragments.286 Reaction of Ni(N03)2.6H20/NiC12 with ci~-[Mn(C0)4(SeR)~]- (R = Me, Ph) affords Mn2Ni(pL-SeR)4(CO)g,for which the Mn-Ni distance in the methylselenido example suggests little, if any, metal-metal bonding.287 A complete set of heterobimetallic hydroxy cubane clusters has been the n = 1 (from generated. In the series {Re3(C0)3)4--n{PtMe3)n(p3-OH)4,

11: Organo-Transition Metal Cluster Complexes

329

[Re3(CO)9(OH)4]-and ( p t ( ~ ~ - I ) M e ~n )=~2) (from , (Re(p3-OH)(CO),), and { P t ( ~ ~ - 1 ) M e as ~ ) ~a, minor product in a mixture) and n = 3 (from [ReBr3(C0),l2- and { Pt(p3-I)Me3}4) examples are now available, complementing the existing homometallic members of the series.288 Reaction of { AuCl}2(p-dppf) with [Re(C0)5]- affords 94.289[Re2Au(p-

PR2)C1(CO),(PR',)] - reacts with PHR"2 to give Re2Au(p-PR2)(C0),(PHR"2)(PR'3)(R = Cy, Ph; R' = Cy, Ph, Et; R" = Cy, Ph, Et; not all combinations), photochemically-induced deprotonation of which gives the doubly - . The latter products phosphido-bridged [Re2Au(p-PR2)(p-PR"2)(C0)6(PR'3)] react with MClPR'3 to afford R~~Au~(~-PR~)(cL-PR"~)(CO)~(PR'~)~ with a tetrahedral core geometry and phosphido groups bridging the Re-Re vector.290 The borole-containing carbonylrhenate [Re(CO),(q-C,H,BPh)]reacts with HgC12 to give Re2Hg(C0)6(q-C4H4BPh)2, with a linear Re2Hg array.291 15.5 Group 8. - 15.5.1Fe, Ru-Co. The C4 chains in Fe(CrCCrCH)(C0)2Cp* and Cp*(C0)2Fe(p-CrCCrC)Fe(CO)zCp* react with C O ~ ( C O to ) ~ afford adducts with tetrahedral Co2C2cores, subsequent rearrangements leading to a range of mixed iron-cobalt clusters: the identities of many of these products (95- 99) have been confirmed by structural studies.292 The coordinated C-S bond in the organothiocyanate complexes Fe(CO)2(PPh3)2(q2-SCNR) [R = Me, 4-C6H4NMe2,C(O)Me, C(O)C6&NMe2-4, C(O)Ph, C6H4Me-4, Ph, C6H4Cl-4]are cleaved on reaction with two equivalents of Co(PPh3)2Cp, clusters FeCo2(p3-S)(CNR)(CO)2(PPh3)Cp2 being formed. These clusters exist as isomers, differing in the nature of the second face-capping ligand (CO or CNR). Methylation with MeOS02CF3proceeds at the isonitrile N to afford the corresponding cluster cation in all cases except the CNC6H4NMe2-containingcluster, for which alkylation at the NMe2 group is observed.293 Oxidation of {FeCp*){Co(q-C5H3But2-l,3)I2(P4)(P) gives (FeCp*){Co(qC5H3But21,3)}3(P20)(PO)(P2),containing the first cluster-bound N20-analogue ~ ~ 0 . ~ ~ ~ A range of diynes reacts with RuCoz(CO)11 to give the linked cluster

Organometallic Chemistry

330 Cp*Fe

/I c‘

Nc \

Fe

‘I\

(95) CD*

cp7\

H

C

Nc

complexes [RUCO~(CO)~](~~-I~~-HC~R-~~-~~-C~H)[RUCO~ [R = (CH2)5, CH20CH2, C6H4-1,2-(C02CH2)2,C6H4-1,4-(OCH2)2].295 Metallo-site selectivity for substitution at HMCo3(C0)12 (M = Fe, Ru) clusters has been reported, with PCyH2 substituting at Co in the ironcontaining cluster, but at Ru in the ruthenium-containing example; subsequent substitution by NMe3 occurs at a non-ligated cobalt atom. The HMCo3(CO)l1(PCyH2)are converted to MCo2(p3-PCy)(C0)9in solution, the intermediacy of 100 being demonstrated in the ruthenium system.296

15.5.2 Ru, Os-Rh. Reacting R~(CO)~(thf)(q~-7,8-C2B9H11) with Rh&CO)2Cp*2 affords a mixture from which the triangular RuRh2(p3-CO)(pCO)Cp*(q5-7,8-C2B9H11) has been separated and identified.297 nido-1,2-(RuCp*)2(pL-H)2B3H7 reacts with C O ~ ( C Oto ) ~give nido-1-(RuCp*)2- (Ru(CO)Cp*}-3-Co(C0)2(p3-CO)B3H6, which on thermolysis loses hydrogen to afford ~Z~~~-~-CO(CO)~-~,~-(RUC~*)~(~~-CO)(~83 Reaction of [H4Os4(CO)I11- with [Rh(NCMe)3Cp*I2+affords 101- 103, the specific product distribution depending on reaction conditions. [Os3(p-

33 1

11: Organo-Transition Metal Cluster Complexes

(105) (hydride location arbitrarily assigned)

(106)

H)(CO)II]- reacts with the same rhodium reagent to give Os3Rh(p-H)2(pCO)(CO)9Cp*, Os3Rh(p-C0)2(C0)9Cp* and Os3Rh2(p-H)(p-C0)2(p-q ,q CH2CSMe4)(C0)&p*, vacuum pyrolysis of the second-mentioned product affording the first-mentioned cluster. Coupling [Os3(p-H)(CO) 13- to [RhCl(dppe)Cp*]+ affords Os3Rh(p3-H)(p-Cl)(p-CO)(CO)&p*,with the chloro ligand bridging the osmium wingtips of the butterfly cluster core.298 The same triosmium precursor reacts with [Rh(q4-cod)2]+to give Os3Rh(pH)(CO)~o(q4-cod)and 104; the former product is carbonylated to afford O S ~ R ~ ( ~ - H ) ~ ( Cand O ) ~reacts ~, with a further equivalent of [Os3(pH)(CO)l1]- to give 104. Hydrogenating 0~3Rh(p-H)(CO)~o(q~-cod) affords 105, while reaction with diphenylacetylene gives 106. The unsaturated cluster O S ~ ( ~ - H ) ~ ( reacts C O ) ~with ~ [Rh(dp~m)~]+ to give 107.299

' '-

332

Organometallic Chemistry

15.5.3 Ru, Us-Ir. The hydrogensulfido-bridged Cp*ClIR@-SH)2IRClCp* reacts with R u H ~ ( P P to ~ ~give ) ~ R u I ~ ~ ( ~ ~ - S ) ~ C ~ ~The ( PrutheniumP~~)C~*~. ligated phosphine and chloro ligands on the product are displaced by bidentate (L2 p *=~dppe, lf depe), subsequent phosphines, affording [ R ~ 1 r ~ ( p ~ - S ) ~ C l ( L ~ ) C ( L ~way ) C Pof* ~Ir-Ir reaction with BH4- affording R u I I - ~ ( ~ - H ) ~ ( ~ ~ - S ) ~ by bond cleavage. The ruthenium-ligated chloride is also displaced by CO and isocyanides, while thiolates afford R u I ~ ~ ( ~ ~ - S ) ~ ( S A The ~ )dppe-con~C~*~. taining cluster is alkylated at ruthenium on treatment with Me2CuLi, but at a Cp* ligand on reaction with CHCH2Li.300 [Ir(C0)4]- reacts with R u ~ ( ~ - C ~ ) ~ C ~to~ (afford C O ) ~Ru21r2(p-H)(pC1)(C0)12,a butterfly cluster with the chloro ligand spanning the ruthenium ~ing-tips.~'~ The tetrahedral [ R U ~ I ~ ( ~ - C O ) ~ ( C Oreacts ) ~ O ]with - acetylenes RC-CR' (R, R'=Me, Et, Ph; not all combinations) to give the butterfly cluster anions [Ru~I~(~~-~~-RC~R')(~-CO)(CO)~~] - , carbonylation of the latter proceeding with expulsion of ruthenium to afford [Ru21r(p3-q2-RC2R')(CO)9]-; the product can be protonated in some cases to the corresponding hydrido clusters Ru~(~-H)(~~-~~-RC~R')(CO)~.~'~ The cluster anions [M31r(CO)13] - (M = Ru, 0s) undergo cluster degradation on reaction with dppm, affording HM2Ir(CO)~(dppm)~, while [ R u ~ I ~ ( ~ - C O ) ~ ( C O gives ) ~ ~the ] - electron deficient (44 c.v.e.) cluster HRu2Ir(C0)6(PCy3)3 on reaction with PCy3 in methanol. [ O S ~ I ~ ( C O )has ~ ~ ]been prepared;303it reacts with PCy3 to give tetrahedral H20s2Irz(CO)lo(PCy3)2 and H ~ O S ~ I ~ ( C O ) ~ (the P Cformer ~ ~ ) ~corresponding to cluster vertex metal atom r e p l a ~ e m e n t . Ligand ~~ substitution at [H2Ru31r(CO)121- proceeds to afford the mono-substituted derivatives [H2R~31r(CO)1 1(L)]- (L = PPh3, PMe3, P(OPh)3, AsPh3, SbPh3), protonation of which gives the corresponding neutral trihydrido clusters.305Protonation of [Os3Ir(CO)13]- gives the corresponding mono-hydrido cluster, whereas hydrogenation affords [H20s3Ir(C0)12]-. Both [ O S ~ I ~ ( C O )and ~ ~ ][-R U ~ I ~ ( C O ) ~ ~ ] are catalytically active for the carbonylation of methanol. In the ruthenium system, cluster reaction with methanol proceeds by 0 - H activation to give [HR~31r(OMe)(C0)~2]-, and then loss of formaldehyde to afford [H2R~31r(C0)12] - .306 15.5.4 Fe, Ru, 0s-Pd, Pt. Reaction between MnPt(p-C=CHPh)(C0)2(dppm)Cp and Fe2(C0)9 affords Fe3Pt(l~q-q~-CCHPh)(CO)~(dppm),~'~ and that between [FeH(C0)2(q-C4H4BPh)]- and trar~s-PtBr~(4-Mepy)~ (4Mepy = 4-methylpyridine) affords the linear cluster Fe2Pt(P - H ) ~ ( C O ) ~ ( ~ Me~y)~( The stepwise build-up of mixed ruthenium-platinum clusters has been studied, [Pt(d~pm)~]~' reacting with [RuH(CO)~] - to afford firstly [RuPtH(pdppm)2(C0)3]+, and then R~~Pt(p-dppm)2(p-CO)(CO)~.~~~ [Pt3(p3-CO)(pdppm)3I2' undergoes core-expansion on reaction with [RuH(CO)~] - , giving [R~Pt~(p-H)(p-dppm)~(CO>~]+, the product rearranging in solution to afford 108.309

The square pyramidal Os&-C)(C0)14(PPh2py) reacts with PdC12(NCMe)2

I l : Organo-Transition Metal Cluster Complexes

-I+

\ /

-

P'

333

Ph,

to afford 109, the product slowly reacting in refluxing CHC13 to give 110 and 111. Cluster 109 reacts with I2 to give 109, a product corresponding to terminal chloro replacement, and 111, corresponding to global chloro repla~ement.~~'

15.5.5 Fe-Ag, Au. The synthetic chemistry and structural features of mixed iron-Group 1llGroup 12 clusters formed from anionic iron cluster precursors have been reviewed. Reaction of [Fe(C0)J2- with [M2(p-dppm)2I2+(M = Ag, Au) proceeds to afford [FeAg3(p-dppm)3(CO)4]+and [FeAu3(p-dppm>2(CO)4]+;in the former product, the Fe(C0)4 unit caps the Ag3 triangle, whereas in the latter product, Fe(C0)4 bridges an Au-Au edge of the Au3 triangle. The iron-silver mixedmetal cluster is also prepared on cluster degradation of [Fe8Ag13(C0)32j3 with d ~ p m . ~Similar ~' structural differences are seen in reactions of [Fe3(p3E)(C0)9l2- (E = 0, S) with AuCl(PPh3), the 0x0-capped cluster affording the tetrahedral cluster anion [Fe3Au(p3-o)(p-Co)3(co)6(PPh3)]and the sulfidocapped cluster giving the butterfly cluster anion [Fe3Au(p3-S)(C0)9(PPh3)]-. The higher-nuclearity precursor [Fes(p3-S)2(CO)14]2- does not add gold, instead yielding the bicluster salt [Aug(p3-S)2(PPh3)6][Fe5(p3-S)(cO) 1 4 1 . ~ ~ ~ Replacement of H by the isolobal Au(PPh3), on reaction of the chain cluster Ru~(~-H)~(~~-PCF~)~(CO)~~ with dbu/AuC1(PPh3), occurs to afford 112, in which the gold occupies the coordination site vacated by H; in contrast, Ru&H)2(p4-PCF3)(C0)13reacts with dbu/AuCl(PMe3) with structural rearrangement to give 113. [H40s4(CO)l1]2- is aurated by ClAu(p-PPh2CH2PPhz)AuCl to give H4Au20s4(p-dppm)(CO)11. 46 The dithiolate-bridged complexes Ru2(p-bdt)(C0)6- x(PPh3), (x = 0, 2)

Organometallic Chemistry

334

(bdt = benzene-l,2-dithiolate) reacts with [Au(PPh3)]' to give the triangular cluster cations [Ru2Au(pbdt)(C0)6 -,(PPh3) 1 +.314 A number of mixed iron-gold cluster-containing carbosilane dendrimers have been prepared by attachment of chlorogold units to the phosphineterminated periphery of carbosilane dendrimers, and then displacement of chloride by [Fe3(CO)11]2-3357316 or Fe2(p-Co)(p-PPh2)(C0)6]- anions; dendrimers as large as 114 have been n-

I

PPh2

1/ ' =\""/3

Au

(114) x = PPb, n = 0; X = Fe(C0)4,n= 8

15.5.6 Ru, os-Hg. R U ~ ( ~ - ~ ~ ~ ) ( C O ) ~ - (, x( = P 0, P ~2)' ~react ) ~ with HgC12 to give triangular R~~Hg(p-bdt)Cl~(CO)~ -,(PPri3)x.314 Organomercurials containing S-donor ligands have been used to assemble mixed rutheniudosmium-mercury clusters. O S ~ ( C O ) ~ ~ ( N Creacts M ~ ) with ~

I I : Organo-Transition Metal Cluster Complexes

335

HgPh(SCsH4N-2) to give 115 and 116, whereas R U ~ ( C O ) ~ ~ ( N Creacts M~)~ with the same organomercurial to give 117. Reaction of O S ~ ( C O ) ~ ~ ( N C M ~ ) ~ with HgPh(mbt) (Hmbt = 2-mercaptobenzothiazole) affords Os6Hg(pmbt)2(CO)20, an analogue of 116, and the butterfly cluster Os3Hg(pmbt)(mbt)(CO)lo in which an Os3 triangle is edge-bridged by mbt and Hg(mbt) units.

\ /

15.6 Group 9. - C O ~ N ~ ( C O reacts ) ~ C ~with cyclooctatetraene (cot) to give

Co2Ni(l.13-r12,r13,r13-CgH8)(C0)6, in which the cot ligand caps the hetero-

metallic triangle.318 A range of mixed cobalt-palladium clusters have been prepared containing the 'assembling' ligands (Ph2P)2NH (dppam), (Ph2P)2NMe (dppame) and (Ph2P)2N(CH2)3Si(OEt)3(dppaSi). Pd&-dppam)2Clz reacts with [Co(CO)4]to give spiked triangular Co2Pd2(p3-CO)3(p-dppam)2(CO)s, subsequent reaction with L=dppam, dppame or dppaSi proceeding by loss of the CO(CO)~ 'spike' to afford triangular [ C O P ~ ~ ( ~ - Cp -Od)~~p(a m )p-L)]+. ~( The tris-dppa product can be N-derivatised by sequential treatment with H- and Me1 to give [C~Pd~(p~-CO)~(p-dppame)~].+ Reaction of C~~Pd~(p~-CO)~(p-dppm)~(CO) with dppam, dppame, or dppaSi affords [CoPd2(p3-CO)2(p-dppm)2(cL-L)]+ (L = dppam, dppame, dppaSi). These clusters have been studied by cyclic voltammetry, with the dppm-containing clusters the most r e d ~ x - s t a b l e . ~ ~ ~ Other examples with Co2Pd and Co2Pt cores have also been reported.2753276 The reaction between Rh4(C0)12 and Pt(PPh& affords trigonal bipyramidal

336

Organometallic Chemistry

Rh2Pt3(p-CO)s(C0)4(PPh3)3,in which the rhodium atoms are located in the equatorial plane, and Rh2Pt2(p-C0)3(C0)4(PPh3)3, a butterfly cluster with platinum atoms in the wing-tip positions; carbonyl migration in the latter proceeds by way of localised exchange about the hinge rhodium atoms, and interchange of bridging and semi-bridging carbonyl on the Rh-Pt bonds.320 [RhSPt(CO)15]- has been used to prepare supported mixed rhodiumplatinum cluster catalysts, with mild decarbonylation conditions affording clusters of twenty atoms or less, and harsh conditions affording larger aggregates; the aggregated clusters are significantly more active for toluene hydrogenation.3143321 Reaction of [Pt(d~pm)~]+ with [Ir(C0)4]- and dppm (ratio 1:2:1) affords Ir2Pt(p-dppm)3(p-CO)(C0)2; the intermediacy of equilibrating IrPt(pdppm)2Cl(CO)2and [IrPt(p-dppm)2(CO)3]+has been established, and a cluster growth mechanism proposed.322 Ir2 { p-2,6-NCSH3(PPh2)2}2C12(C0)2 reacts with [Cu(NCMe)4]+to afford the linear cation [Ir2Cu{p-q2 -2,6-NCSH3(PPh2)2}2C12(CO)2]+,323AuCl(PPh3) with - to give the spiked trigonal bipyramid C O ~ A U ~ ( C O ) ~ ( and PP~~)~, [CO(CO)~] ClAu(p-cis-dpen)AuCl [dpen = 1,2-bis(diphenylphosphino)ethylene] with [CO(CO)~]-gives C02Au2(p-cis-dpen)(CO)8.~~~ 15.7 Group 10. - Pt2(dba)3 reacts with [ A u ( P P ~ ~ )in~ ]the + presence of dmb to give [Pt2A~&dmb)~(PPh~)~]~+, a planar butterfly cluster with gold atoms at the hinge positions; the cluster is luminescent at low temperature (solid and frozen glass), and at room temperature in the solid state, with the emission band at -875 nm assigned to a PtAu-m* (CNR) charge transfer process.324 Further silica-supported Pt-Au clusters have been reported; Pt2Au4(p-q2C2But)gis the precursor for bimetallic catalysts active for selective C-C bond , ~ ~[ p~t A ~ ~ ( P P h ~ )reversibly 7]~+ absorbs CO, in contrast scission of h e ~ y n eand to its solution behaviour in which the cluster framework is fragmented.326 Pd2(p-C1), (C6H4-2-PPh2CHC(0)CH2PPh3} reacts with Hg(OAc);! to give 118, in which the orthometallated ylide groups function as C,C,C-tridentate l i g a n d ~ . [pt(CrCPh)4]2~~~ reacts with CdCl2to give [Pt2Cd2(p-q C2Ph)8C12]2-;the low energy emission of this cluster is assigned to a n*(C2Ph) -+ Pt2Cd2core transition.328

'-

15.8 Clusters Containing Three Different Metals. - Reacting RuCo2(p3Se)(CO), with functionalised cyclopentadienyl-containing metal carbonyl

I I : Organo-Transition Metal Cluster Complexes

337

anions [M(CO)3{q-C5H3RC(0)R‘}]- [M = W, R = H, R’ = H, Me, Ph, C6H&(O)Me; M = Mo, W, R = Me, R’ = Me] affords the chiral clusters MRuCo(p3-Se)(C0)8{ q-CsH3RC(O)R’} by metal exchange protocols; 329y330 a linked example is obtained by treating the same cluster precursor with Na2[(OC)3W{ q-C5H4C(0)C6H4C(O)-q-C5H4)W(C0)3]. WuCo(p3-Se)(C0)8{q-C$&C(O)Me} is reduced by BH4-, to give WRuCo(p3-Se)(CO),{ qC5H&H(OH)Me}, and undergoes further metal exchange on reaction with [Fe(C0)4]2-/H+, to afford WF~RU(CL~-H)(~~-S~)(C~)~ { q-C5&C(O)Me) .329 Other metal exchange reactions afford M O W F ~ ( ~ ~ - S ) ( C O ) ~ C ~ ( ~ - C ~ H ~ R (R = H, Me),258and MFeCo(p3-S)(CO)7(PPh3)(q-C5H4R)(M = Mo,W; R = H, MeCO, Me02C).259 Thermal reaction of W R U ~ ( ~ - S ) ~ ( C O ) ~with C P *PtMe2(cod) ~ affords ‘Tshaped’ WRU~P~(~~-S)(~-S)~M~~(CO)~CP*~ and the ‘star’ cluster WRu2Pt2(p3S)~M~~(CO)~CP*~.~~ Deprotonation of WRu3(p-H)(p4-q2-BH)(C0)&p affords the corresponding cluster anion, which reacts with AuCl(PPh3) to give 119 and with ClAu(p-dppf)AuCl tp afford {WRU~AU(~-H)(~~-B)(CO)&~}~(~-~PP~) the latter reaction yields 119 as an unexpected by-product, the only source of PPh3 being the [N(PPh3)2]+ cation.332 MnPt(p-C=CHPh)(C0)2(dppm)Cp reacts with Fe2(C0)9 to give MnFePt(p3-q2-CCHPh)(p-dppm)(p-CO)(CO)4Cp.307 A mixture of the isomeric octahedral cluster anions cis- and trans[Ru4Rh2(p6-B)(c0)~6]-is aurated by ClAu(p-dppb)AuCl to give products the former proposed to be &and trans- { RU~R~~AU(~~-B)(CO)~~)~(~-~PP~), converting rapidly to the latter. The same cluster precursor reacts with ClAu(p-dppm)AuCl to give the linked cluster {RU~R~~AU(~~-B)(CO)~~)~ dppm), the mono-substitution product Ru~R~~Au(~~-B)(CO)~~(PP~~C PhZAuCl), R~Rh~Au(p6-B)(p-dppm)(CO)15 (a capped octahedral cluster with dppm spanning a Ru-Au vector) and 120, in which a square-based pyramidal Ru4Rh unit is capped on the square face by an A u group, ~ the boron adopting a p7-coordination mode.332 Ru~(~~-NOM~)(~~-CO)(CO)~ reacts with Mo2Hg(CO)&p2 to afford MoRu3Hg(p-NH2)(CO)13Cp,in which the molybdenum ‘spike’ is attached to the butterfly wing-tip mercury atom.261

Organometallic Chemistry

338

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.

P. Braunstein, L. A. Oro and P. R. Raithby, Eds., Metal Clusters in Chemistry, Wiley-VCH, Weinheim, 1999. H. Wadepohl, Coord. Chem. Rev., 1999,185-6,551. B. F. G. Johnson, Coord. Chem. Rev., 1999,190-2,1269. J. D. Aiken I11 and R. G. Finke, J. Molec. Catal. A A , 1999, 145, 1. S. F. A. Kettle, E. Diana, E. Boccaleri and P. L. Stanghellini, Eur. J. Inorg. Chem., 1999,1957. P. A. Brooksby, N. W. Duffy, A. J. McQuillan, B. H. Robinson and J. Simpson, J. Organornet. Chem., 1999,582, 183. T. Eguchi and B. T. Heaton, J. Chem. Soc., Dalton Trans., 1999,3523. B. T. Heaton, J. A. Iggo, I. S. Podkorytov, D. J. Smawfield, S. P. Tunik and R. Whyman, J. Chem. Soc., Dalton Trans., 1999, 1917. C. J. Sleigh, S. B. Duckett, R. J. Mawby and J. P. Lowe, Chem. Commun., 1999, 1223. J. S. McIndoe and B. K. Nicholson, J. Organornet. Chem., 1999,573,232. C . Decker, W. Henderson and B. K. Nicholson, J. Chem. Soc., Dalton Trans., 1999,3507. S . Takara, S. Ogo, Y. Watanabe, K. Nishikawa, I. Kinoshita and K. Isobe, Angew. Chern., Int. Ed., 1999,38,3051. T. Kurikawa, H. Takeda, M. Hirano, K. Judai, T. Arita, S. Nagao, A. Nakajima and K. Kaya, Organometallics, 1999,18, 1430. J. E. McGrady, J. Chem. Soc., Dalton Trans., 1999, 1393. R. Gautier, F. Ogliaro, J.-F. Halet, J.-Y. Saillard and E. J. Baerends, Eur. J. Inorg. Chem., 1999, 1161. M. Stener, K. Albert and N. Rosch, Inorg. Chim. Acta, 1999,286, 30. E. Hunstock, C. Mealli, M. J. Calhorda and J. Reinhold, Inorg. Chem., 1999,38, 5053. R. Gautier, J.-F. Halet and J.-Y. Saillard, Eur. J. Inorg. Chem., 1999, 673. M. T. Garland, K. Costuas, S. Kahlal and J.-Y. Saillard, New J. Chem., 1999,23, 509. P. Macchi, L. Garlaschelli, S. Martinengo and A. Sironi, J. Am. Chem. Soc., 1999,121,10428. J. Zachara and A. Zimniak, Acta Crystallogr., 1999, C55, 58. J. Liu, E. P. Boyd and S. G. Shore, Acta Crystallogr., 1999, C55,29. M. I. Bruce, 0. Kuhl, B. W. Skelton and A. H. White, Aust. J. Chem., 1999, 52, 705. W. K. Leong and Y. Liu, J. Organornet. Chem., 1999,584,174. A. Vega, E. Spodine, A. Arce, J. Manzur, A. M. Garcia and M. T. Garland, Acta Crystallogr., 1999, C55, 322. W. K. Leong and M. W. Lum, Acta Crystallogr., 1999, C55, 881. L. J. Farrugia, D. Braga and F. Grepioni, J. Organornet. Chem., 1999,573, 60. R. D. Pike, W. H. Starnes Jr. and G. B. Carpenter, Acta Crystallogr., 1999, C55, 162. L. G. Kuz’mina, A. A. Bagatur’yants, J. A. K. Howard, K. I. Grandberg, A. V. Karchava, E. S. Shubina, L. N. Saitkulova and E. V. Bakhmutova, J. Organornet. Chem., 1999,575,39. Q. Zhang, X. Xin, M. Hong, R. Cao, S. S. S. Raj and H.-K. Fun, Acta Crystallogr., 1999, C55,726.

11: Organo-Transition Metal Cluster Complexes

31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45.

46. 47. 48. 49. 50.

51. 52. 53. 54.

55. 56. 57. 58.

339

Q.-H. Jin, X.-L. Xin, Y.-H. Deng and K.-B. Yu, Acta Crystallogr., 1999, C55, 860. U. Florke and H.-J. Haupt, Acta Crystallogr., 1999, IUC9900103. K. Panneerselvam, T.-H. Lu, S.-F. Tung, A. K. Dash and P. Mathur, Acta Crystallogr., 1999, C55, 1250. R. Della Pergola, L. Garlaschelli, M. Manassero and M. Sansoni, J. Cluster Sci., 1999,10, 109. J. V. Barkley, T. Eguchi, R. A. Harding, B. T. Heaton, G. Longoni, L. Manzi, H. Nakayama, K. Miyagi, A. K. Smith and A. Steiner, J. Organomet. Chern., 1999,573,254. F. Calderoni, F. Demartin, F. Fabrizi de Biani, C. Femoni, M. C. Iapalucci, G. Longoni and P. Zanello, Eur. J. Inorg. Chem., 1999,663. A. Ceriotti, N. Masciocchi, P. Macchi and G. Longoni, Angew. Chem., Int, Ed., 1999,38,3724. S . L. Horswell, C. J. Kiely, I. A. O’Neil and D. J. Schiffrin, J. Am. Chem. SOC., 1999,121,5573. M. Bettenhausen, A. Eichhofer, D. Fenske and M. Semmelmann, 2. Anorg. Allg. Chem., 1999,625,593. N. Zhu and D. Fenske, J. Chem. SOC., Dalton Trans., 1999,1067. V. W.-W. Yam, E. C.-C. Cheng and K.-K. Cheung, Angew. Chem., Int. Ed., 1999,38, 197. G. Schmid, R. Pugin, T. Sawitowski, U. Simon and B. Marler, Chem. Cornmun., 1999,1303. G. Schmid, R. Pugin, W. Meyer-Zaika and U. Simon, Eur. J. Inorg. Chem., 1999, 205 1. L. 0.Brown and J. E. Hutchinson, J. Am. Chem. SOC., 1999,121,882. R. Raja, G. Sankar, S. Hermans, D. S. Shephard, S. Bromley, J. M. Thomas, B. F. G. Johnson and T. Maschmeyer, Chem. Commun., 1999,1571. A. J. Amoroso, M. A. Beswick, C.-K. Li, J. Lewis, P. R. Raithby and M. C. Ramirez de Arellano, J. Organomet. Chem., 1999,573,247. F. Fabrizi de Biani, C. Femoni, M. C. Iapalucci, G. Longoni, P. Zanello and A. Ceriotti, Inorg. Chem., 1999,38,3721. F. Demartin, C. Femoni, M. C. Iapalucci, G. Longoni and P. Macchi, Angew. Chem., Int, Ed., 1999,38, 531. V. W.-W. Yam,K.-L. Yu and K.-K. Cheung, J. Chem. SOC.,Dalton Trans., 1999, 2913. J. P. H. Charmant, J. ForniCs, J. Gbmez, E. Lalinde, R. I. Merino, M. T. Moreno and A. G. Orpen, Organometallics, 1999,18, 3353. N. T. Tran, M. Kawano, D. R. Powell, R. K. Hayashi, C. F. Campana and L. F. Dahl, J. Am. Chem. SOC.,1999,121,5945. S . Kleinhenz and K. Seppelt, Chem. Eur. J., 1999,5, 3573. F. A. Cotton, C. A. Murillo and M. A. Petrukhina, J. Organomet. Chem., 1999, 573,78. C. D. Abernethy, F. Bottomley, R. W. Day, A. Decken, D. A. Summers and R. C. Thompson, Organometallics, 1999,18,870. L. Y. Goh, W. Chen and R. C. S. Wong, Organometallics, 1999,18,306. K. V. Adams, N. Choi, G. Conole, J. E. Davies, J. D. King, M. J. Mays, M. McPartlin and P. R.Raithby, J. Chem. Soc., Dalton Trans., 1999,3679, B. Rink, M. Brorson and I. J. Scowen, Organometallics, 1999,18,2309. A. S . Weller, M. Shang and T. P. Fehlner, Organometallics, 1999, 18, ‘ 3 3 .

340

Organometallic Chemistry

59. 60.

M. Scheer, P. Kramkowski and K. Schuster, Organometallics, 1999, 18,2874. M. Shieh, H.-S. Chen, H.-Y. Yang and C.-H. Ueng, Angew. Chem., Int. Ed., 1999,38,1252. T. Saito, J. Chem. SOC.,Dalton Trans., 1999,97. R. Sewel, T.-W. Tseng and K.-L. Lu, J. Organomet. Chem., 1999,582,160. A. C. Hillier, A. Sella and M. R. J. Elsegood, J. Organomet. Chem., 1999, 588, 200. M. Bergamo, T. Beringhelli, G. D’Alfonso, P. Mercandelli, M. Moret and A. Sironi, Angew. Chem., Int. Ed., 1999,38, 3486. T. Beringhelli, G. D’Alfonso, M. Bergamo, M. Panigati, F. Porta, R. Mercandelli, M. Moret and A. Sironi, J. Am. Chem. Soc., 1999,121,2307. L. J. Farrugia, A. L. Gillon, D. Braga and F. Grepioni, Organometallics, 1999, 18, 5022. E. Sappa, J. Organomet. Chem., 1999,573,139. M.-A. Hsu, W.-Y. Yeh, G.-H. Lee and S.-M. Peng, J. Organomet. Chem., 1999, 588, 32. M. Shieh, J. Cluster Sci., 1999,10, 3. W.-Y. Yeh, M.-A. Hsu, S.-M. Peng and G.-H. Lee, Organometallics, 1999, 18, 880. A. J. Carty, G. Hogarth, G. D. Enright, J. W. Steed and D. Georganopoulou, Chem. Commun., 1999, 1499. M. Akita, A. Sakurai and Y. Moro-oka, Chem. Commun., 1999,101. H. Braunschweig, C. Kollann, M. Koster, U. Englert and M. Muller, Eur. J. Inorg. Chem., 1999,2277. R. W. Eveland, C. C. Raymond and D. F. Shriver, Organometallics,1999,18,534. D.-L. Wang, W.-S. Hwang, L. Lee and M. Y. Chiang, J. Organomet. Chem., 1999,579,211. J. L. Perkinson, M.-H. Baik, G. E. Trullinger, C. K. Schauer and P. S. White, Inorg. Chim. Acta, 1999,294, 140. N. Choi, G. Conole, M. Kessler, J. D. King, M. J. Mays, M. McPartlin, G. E. Pateman and G. A. Solan, J. Chem. SOC.,Dalton Trans., 1999,3941. H.-J. Jeon, N. Prokopuk, C. Stern and D. F. Shriver, Inorg. Chim. Acta, 1999, 286,142. C. Alvarez-Toledano, J. Enriquez, R. A. Toscano, M. Martinez-Garcia, E. Cortes-Cortks, Y. M. Osornio, 0. Garcia-Mellado and R. GutiCrrez-Perez,J. Organomet. Chem., 1999,577, 38. R. W. Eveland, C. C. Raymond, T. E. Albrecht-Schmitt and D. F. Shriver, Inorg. Chem., 1999,38, 1282. W.-Y. Yeh, C.-Y. Wu and L. W. Chiou, Organometallics, 1999,18, 3547. P. K. Baker, J. E. Barclay, A. I. Clark, D. J. Evans, K. Mitchell and R. L. Richards, J. Organomet. Chem., 1999,572,265. U. Riese, K. Harms, J. Pebler and K. Dehnicke, 2. Anorg. Allg. Chem., 1999, 625, 746. I. Shimoyama, T. Hachiya, M. Mizuguchi, T. Nakamura, M. Kaihara and T. Ikariya, J. Organomet. Chem., 1999,584, 197. C. Roveda, E. Cariati, E. Lucenti and D. Roberto, J. Organomet. Chem., 1999, 580, 117. G. Critchley, P. J. Dyson, B. F. G. Johnson, J. S. McIndoe, R. K. O’Reilly and P. R. R. Langridge-Smith, Organometallics, 1999, 18,4090. N. E. Leadbeater, J. Organomet. Chem., 1999,573, 211.

61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77.

78. 79.

80. 81. 82. 83. 84. 85. 86. 87.

11: Organo-Transition Metal Cluster Complexes

88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113.

114. 115. 116. 117.

341

K. Matsubara, A. Inagaki, M. Tanaka and H. Suzuki, J. Am. Chem. SOC.,1999, 121,7421. C . S.-W. Lau and W.-T. Wong, J. Organomet. Chem., 1999,589,198. M. I. Bruce, B. W. Skelton, A. H. White and N. N. Zaitseva, J. Chem. SOC., Dalton Trans., 1999, 1445. M. I. Bruce, N. N. Zaitseva, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton Trans., 1999,2777. R. D. Adams, U. H. F. Bunz, W. Fu and G. Roidl, J. Organomet. Chem., 1999, 578, 55. C. S.-W. Lau and W.-T. Wong, J. Chem. SOC., Dalton Trans., 1999,251 1 . C . S.-W. Lau and W.-T. Wong, J. Chem. SOC.,Dalton Trans., 1999,607. C. S.-W. Lau and W.-T. Wong, J. Organomet. Chem., 1999,588, 113. P. Nombel, N. Lugan, B. Donnadieu and G. Lavigne, Organometallics, 1999, 18, 187. S. Ali, A. J. Deeming, G. Hogarth, N. A. Mehta and J. W. Steed, Chem. Commun., 1999,2541. D. D. Ellis, A. Franken and F. G. A. Stone, Organometallics, 1999, 18, 2362. X. Lei, M. Shang and T. P. Fehlner, Angew. Chem. Int. Ed., 1999,38, 1986. K. M. Hanif, M. B. Hursthouse, S. E. Kabir, K. M. A. Malik and E. Rosenberg, J. Organomet. Chem., 1999,580,60. R. Dilshad, K. M. Hanif, M. B. Hursthouse, S. E. Kabir, K. M. A. Malik and E. Rosenberg, J. Organomet. Chem., 1999,585, 100. G. Suss-Fink, I. Godefroy, V. Ferrand, A. Neels, H. Stoeckli-Evans, S. Kahlal, J.-Y. Saillard and M. T. Garland, J. Organomet. Chem., 1999,579,285. K. K.-H. Lee and W.-T. Wong, J. Organomet. Chem., 1999,575,200. N. J. Goodwin, W. Henderson, B. K. Nicholson, J. Fawcett and D. R. Russell, J. Chem. SOC.,Dalton Trans., 1999, 1785. H. G. Ang, S. G. Ang, S. Du, B. H. Sow and X. Wu, J. Chem. SOC.,Dalton Trans., 1999,2799. H.-G. Ang, S.-G.Ang and S. Du, J. Organomet. Chem., 1999,590,l. M. Faure, M. Jahncke, A. Neels, H. Stoeckli-Evans and G. Suss-Fink, Polyhedron, 1999,18,2679. A. Shaver, M. El-Khateeb and A.-M. Lebuis, Inorg. Chem., 1999,38,5913. D. Cauzzi, C. GraifT, G. Predieri, A. Tiripicchio and C. Vignali, J. Chem. Soc., Dalton Trans., 1999,237. G. Lavigne, Eur. J. Inorg, Chem., 1999,917. P. J. Low, K. A. Udachin, G. D. Enright and A. J. Carty, J. Organomet. Chem., 1999,578,103. H. Nagashima, A. Suzuki, H. Kondo, M. Nobata, K. Aoki and K. Itoh, J. Organomet. Chem., 1999,580,239. M. I. Bruce, B. W. Skelton, A. H. White and N. N. Zaitseva, Aust. J. Chem., 1999,52, 68 1. H. G. Ang, S. G. Ang and S. Du, J. Chem. SOC.,Dalton Trans., 1999,2963-70. C. J. Adams, M. I. Bruce, B. W. Skelton and A. H. White, Aust. J. Chem., 1999, 52,409. C. J. Adams, M. I. Bruce, B. W. Skelton and A. H. White, J. Chem. SOC.,Dalton Trans., 1999,2451. C . J. Adams, M. I. Bruce, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton Trans., 1999, 1283.

342

Organometallic Chemistry

118. C. J. Adams, M. I. Bruce, B. W. Skelton and A. H. White, J. Organomet. Chem., 1999,584,254. 119. C. J. Adams, M. I. Bruce, B. W. Skelton and A. H. White, J. Organomet. Chem., 1999,589,213. 120. C. J. Adams, M. I. Bruce, B. W. Skelton and A. H. White, J. Organomet. Chem., 1999,573,134. 121. M. I. Bruce, B. W. Skelton, A. H. White and N. N. Zaitseva, J. Chem. Soc., Dalton Trans., 1999, 13. 122. L. T. Byrne, J. P. Hos, G. A. Koutsantonis, B. W. Skelton and A. H. White, J. Organomet. Chem., 1999,592,95. 123. Y. Wakatsuki and T. Chihara, Bull. Chem. SOC. Jpn., 1999,72,2357. 124. T. Chihara, T. Tase, H. Ogawa and Y. Wakatsuki, Chem. Commun., 1999,279. 125. P. Schooler, B. F. G. Johnson and S. Parsons, J. Chem. Soc., Dalton Trans., 1999,559. 126. P. Schooler, B. F. G. Johnson, L. Scaccianoceand R. Tregonning, J. Chem. Soc., Dalton Trans., 1999,2743. 127. L. Xu and Y. Sasaki, J. Organomet. Chem., 1999,585,246. 128. M. I. Bruce, B. W. Skelton, A. H. White and N. N. Zaitseva, Aust. J. Chem., 1999,52,413. 129. P. Nombel, Y. Hatanaka, S. Shimada and M. Tanaka, Chem. Lett., 1999,159, 130. N. Chatani, Y. Ie, F. Kakiuchi and S. Murai, J. Am. Chem. SOC.,1999,121,8645. 131. M. Tokunaga, M. Eckert and Y. Wakatsuki, Angew. Chem. Int. Ed., 1999, 38, 3222. 132. Y. Uchimaru, Chem. Commun., 1999,1133. 133. T. E. Miiller and A.-K. Pleier, J. Chem. SOC., Dalton Trans., 1999, 583. 134. D. Berger and W. Imhof, Chem. Commun., 1999,1457. 135. N. Chatani, T. Morimoto, A. Kamitani, Y. Fukumoto and S. Murai, J. Organomet. Chem., 1999,579,177. 136. F. Ragaini, A. Ghitti and S. Cenini, Organometallics, 1999,18,4925. 137. F. Ragaini, S. Cenini, S. Tollari, G. Tummolillo and R. Beltrami, Organometallics, 1999, 18,928. 138. T. Mitsudo, N. Suzuki, T. Kobayashi and T. Kondo, J. Molec. Catal. A , 1999, 137,253. 139. N. Chatani, M. Tobisu, T. Asaumi, Y. Fukumoto and S. Murai, J. Am. Chem. SOC., 1999,121, 7160. 140. T. Kondo, T. Okada and T. Mitsudo, Organometallics, 1999,18,4123. 141. P. Frediani, A. Salvini and S. Finocchiaro, J. Organomet. Chem., 1999,584,265. 142. A. Salvini, P. Frediani, M. Bianchi, F. Piacenti, L. Pistolesi and L. Rosi, J. Organomet. Chem., 1999,582,218. 143. J.-X. Gao, P.-P. Xu, X.-D. Yi, H.-L. Wan and K.-R. Tsai, J. Molec. Catal. A, 1999, 147,99. 144. D. J. Ellis, P. J. Dyson, D. G. Parker and T. Welton, J. Molec. Catal. A, 1999, 150,71. 145. G. Gervasio, R. Giordano, D. Marabello and E. Sappa, J. Organomet. Chem., 1999,588,83. 146. B. Fontal, M. Reyes, T. Suarez, F. Bellandi and J. C. Diaz, J. Molec. Catal. A , 1999,149,75. 147. B. Fontal, M. Reyes, T. Suarez, F. Bellandi and N. Ruiz, J. Molec. Catal. A , 1999,149, 87. 148. P. J. Dyson, D. J. Ellis, D. G. Parker and T. Welton, Chem. Commun., 1999,25.

I I : Organo-Transition Metal Cluster Complexes

343

149. A. J. G. Zarbin, M. D. Vargas and 0. L. Alves, J. Mater. Chem., 1999,9, 519. 150. S . Naito and M. Tanimoto, J. Mol. Catal. A, 1999,141,205. 151. S . M. Yunusov, E. S. Kalyuzhnaya, H. Mahapatra, V. K. Puri, V. A. Likholobov and V. B. Shur, J. Mol. Catal. A , 1999,139,219. 152. M. Wojciechowska,M. Pietrowski and S. Lomnicki, Chem. Commun., 1999,463. 153. M. J. Abedin, B. Bergman, R. Holmquist, R. Smith, E. Rosenberg, J. Ciurash, K. Hardcastle, J. Roe, V. Vazquez, C. Roe, S. Kabir, B. Roy, S. Alam and K. A. Azam, Coord Chem. Rev,, 1999,190-2,975. 154. FA. Kong and W.-T. Wong, J. Organomet. Chem., 1999,589,191. 155. T.-K. Huang, Y. Chi, S.-M. Peng and G.-H. Lee, Organometallics, 1999, 18, 1657. 156. W.-Y. Wong and W.-T. Wong, J. Organomet. Chem., 1999,584,48. 157. G. Chen and W. K. Leong, J. Organomet. Chem., 1999,574,276. 158. F.-S. Kong and W.-T. Wong, J. Organomet. Chem., 1999,589,180. 159. S . Aime, M. Ferriz, R. Gobetto and E. Valls, Organometallics, 1999,18,2030. 160. J. Nijhoff, F. Hartl, J. W. M. van Outersterp, D. J. Stufkens, M. J. Calhorda and L. F. Veiros, J. Organomet. Chem., 1999,573,121. 161. J. Nijhoff, M. J. Bakker, F. Hartl and D. J. Stufkens, J. Organomet. Chem., 1999, 572, 27 1. 162. J. Nijhoff, F. Hartl, D. J. Stufkens and J. Fraanje, Organometallics, 1999, 18, 4380. 163. J. Nijhoff, F. Hartl, D. J. Stufkens, J. J. Piet and J. M. Warman, Chem. Commun., 1999,991. 164. A. J. Deeming, M. J. Stchedroff, C. Whittaker, A. J. Arce, Y. De Sanctis and J. W. Steed, J. Chem. Soc., Dalton Trans., 1999,3289. 165. J. Akther, K. A. Azam, A. R. Das, M. B. Hursthouse, S. E. Kabir, K. M. A. Malik, E. Rosenberg, M. Tesmer and H. Vahrenkamp, J. Organomet. Chem., 1999,588,211-21. 166. R. Smith, E. Rosenberg, K. I. Hardcastle, V. Vazquez and J. Roh, Organometallics, 1999,18, 3519. 167. E. C. Constable, C. E. Housecroft and A. G. Schneider, J. Organomet. Chem., 1999,573,101. 168. A. J. Poe and C. Moreno, Organometallics, 1999,18,5518. 169. E. W. Ainscough, A. M. Brodie, R. K. Coll and J. M. Waters, Aust. J. Chem., 1999,52,801. 170. A. J. Arce, A. J. Deeming, Y. De Sanctis, D. M. Speel and A. Di Trapani, J. Organomet. Chem., 1999,580,370. 171. A. J. Arce, A. Karam, Y. De Sanctis, M. V. Capparelli and A. J. Deeming, Inorg. Chim. Acta, 1999,285,277. 172. R. D. Adams, 0.-S. Kwon and J. L. Perrin, J. Organomet. Chem., 1999,584,223. 173. R. D. Adams and W. Huang, J. Organomet. Chem., 1999,573,14. 174. R. D. Adams and J. L. Perrin, J. Organomet. Chem., 1999,582,9. 175. W. K. Leong and Y. Liu, Organometallics, 1999,18,800. 176. Y.-Y. Choi and W.-T. Wong, J. Organomet. Chem., 1999,573,189. 177. Y.-Y. Choi and W.-T. Wong, J. Chem. Soc., Dalton Trans., 1999, 331. 178. K. S.-Y. Leung and W.-T. Wong, J. Chem. Soc., Dalton Trans., 1999,2521. 179. K. S.-Y. Leung and W.-T. Wong, J. Chem. Soc., Dalton Trans., 1999,2077. 180. D. H. Farrar, A. J. Poe and R. Ramachandran, J. Organomet. Chem., 1999, 573, 217. 181. K. S.-Y. Leung and W. T. Wong, Eur. J. Inorg. Chem., 1999,1757.

344

Organometallic Chemistry

182. M. Yuki, K. Kuge, M. Okazaki, T. Mitsui, S. Inomata, H. Tobita and H. Ogino, Inorg. Chim. Acta, 1999,291,395. 183. X. Lei, M. Shang and T. P. Fehlner, J. Am. Chem. Soc., 1999,121,1275. 184. R. Tannenbaum and G. Bor, J. Organomet. Chem., 1999,586,18. 185. J. L. Kerr, B. H. Robinson and J. Simpson, J. Chem. SOC.,Dalton Trans., 1999, 4165. 186. V. Calvo-Perez, M. Shang, G. P. A. Yap, A. L. Rheingold and T. P. Fehlner, Polyhedron, 1999,18, 1869. 187. J. Zhang, X.-N. Chen, Y.-Q. Yin, W.-L. Wang and X.-Y. Huang, J. Organomet. Chem., 1999,582,252. 188. J. D. King, M. Monari and E. Norlander, J. Organomet. Chem., 1999,573,272. 189. M. P. Robben, P. H. Reiger and W. E. Geiger, J. Am. Chem. Soc., 1999,121,367. 190. H. Wadepohl, K. Buchner, M. Hernnann and H. Pritzkow, J. Organomet. Chem., 1999,573,22. 191. G. Conole, J. E. Davies, J. D. King, M. J. Mays, M. McPartlin, H. R. Powell and P. R. Raithby, J. Organomet. Chem., 1999,585, 141. 192. X.-N. Chen, J. Zhang, S.-L. Wu, Y.-Q. Yin, W.-L. Wang and J. Sun, J. Chem. SOC.,Dalton Trans., 1999, 1987. 193. F.-E. Hong, Y.-C. Chang, R.-E. Chang, C.-C. Lin, S.-L. Wang and F.-L. Liao, J. Organomet. Chem., 1999,588,160. 194. S . M. Draper, M. Delamesiere, E. Champeil, B. Twamley, J. J. Byrne and C. Long, J. Organomet. Chem., 1999,589,157. 195. J . Chen and R. J. Angelici, Organometallics, 1999,18, 5721. 196. B.-S. Kang, T.-B. Wen, X.-Y. Yu, H.-X. Zhang, Y.-X. Tong, C.-Y. Su, Z.-N. Chen and H.-Q. Liu, J. Cluster Sci., 1999,10,429. 197. H. Link and D. Fenske, 2. Anorg. Allg. Chem., 1999,625,1878. 198. C. Tejel, M. A. Ciriano and L. A. Oro, Chem. Eur. J., 1999,5,1131. 199. C. Tejel, M. Bordonaba, M. A. Ciriano, F. J. Lahoz and L. A. Oro, Chem. Commun., 1999,2387. 200. G. Liu and M. Garland, Organometallics, 1999,18, 3457. 201. G. Liu, R. Volken and M. Garland, Organometallics, 1999,18,3429. 202. J. Feng and M. Garland, Organometallics, 1999,18, 1542. 203. J. Feng and M. Garland, Organometallics, 1999,18,417. 204. I. Matsuda, Y. Fukuta and K. Itoh, Inorg. Chim. Acta, 1999,296,72. 205. S.-W. Zhang, T. Kaneko, E. Yoneda, T. Sugioka and S. Takahashi, Inorg. Chim. Acta, 1999,296, 195. 206. M. E. Prater, L. E. Pence, R. CICrac, G. M. Finniss, C. Campana, P. AubanSenzier, D. JCrome, E. Canadell and K. R. Dunbar, J. Am. Chem. Soc., 1999, 121,8005. 207. W. A. Weber, A. Zhao and B. C. Gates, J. Catal., 1999,182, 13. 208. G. Panjabi, A. M. Argo and B. C. Gates, Chem. Eur. J., 1999,5,2417. 209. W. A. Weber, B. L. Phillips and B. C. Gates, Chem. Eur. J., 1999,5,2899. 210. A. Labouriau, G. Panjabi, B. Enderle, T. Pietrass, B. C. Gates, W. L. Earl and K. C. Ott, J. Am. Chem. SOC.,1999,121,7674. 211. X. Lei, M. ShangandT. P. Fehlner, Chem. Commun., 1999,933. 212. L. Huang and Y. Xu, Bull. Chem. Soc. Jpn., 1999,72,199. 213. S . Pasynkiewicz, A. Pietrzykowski, L. Bukowska and L. Jezykiewicz, J. Organomet. Chem., 1999,585,308. 214. H.-F. Klein, A. Dal, S. Hartmann, U. Florke and H.-J. Haupt, Inorg. Chim. Acta, 1999,287, 199.

I I : Organo- Transition Metal Cluster Complexes

345

215. M. T. Reetz, E. Bohres, R. Goddard, M. C. Holthausen and W. Thiel, Chem. Eur. J., 1999,5,2101. 216. S. V. Tarlton, N. Choi, M. McPartlin, D. M. P. Mingos and R. Vilar, J. Chem. SOC.,Dalton Trans., 1999, 653. 217. T. Murahashi, E. Mochizuki, Y. Kai and H. Kurosawa, J. Am. Chem. Soc., 1999, 121,10660. 218. T. Zhang, M. Drouin and P. D. Harvey, Inorg. Chem., 1999,38,957. 219. J. R. Berenguer, E. Egukibal, L. R. Falvello, J. ForniCs, E. Lalinde and A. Marta, Organometallics, 1999,18, 1653. 220. R. J. Cross, M. Haupt, D. S. Rycroft and J. M. Winfield, J. Organomet. Chem., 1999,587, 195. 221. M. Gerisch, C. Bruhn and D. Steinborn, Polyhedron, 1999,18,1953. 222. A. Fukuoka, M. Osada, T. Shido, S. Inagaki, Y. Fukushima and M. Ichikawa, Inorg. Chim. Acta, 1999,294,281. 223. V. W.-W. Yam and K. K.-W. Lo,Chem. SOC.Rev., 1999,28,323. 224. V. W.-W. Yam, K. K.-W. Lo and K. M.-C. Wong, J. Organomet. Chem., 1999, 578, 3. 225. P. C. Ford, E. Cariati and J. Bourassa, Chem. Rev., 1999,99,3625. 226. J. Klett, K. W. Klinkhammer and M. Niemeyer, Chem. Eur. J., 1999,5,2531. 227. J. K. Bera, M. Nethaji and A. G. Samuelson, Inorg. Chem., 1999,38, 1725. 228. J. K. Bera, M. Nethaji and A. G. Samuelson, Inorg. Chem., 1999,38,218. 229. V. W.-W. Yam, W. K.-M. Fung and K.-K. Cheung, J. Cluster Sci., 1999,10, 37. 230. G. A. Bowmaker, E. N. de Silva, P. C. Healy, B. W. Skelton and A. H. White, J. Chem. SOC.,Dalton Trans., 1999,901. 231. Y. Ma, C.-M. Che, H.-Y. Chao, X. Zhou, W.-H. Chan and J. Shen, Adv. Mater., 1999,11,852. 232. W. Kockelmann and U. Ruschewitz, Angew. Chem., Int. Ed., 1999,38,3492. 233. G.-C. Guo, G.-D. Zhou and T. C. W. Mak, J. Am. Chem. SOC.,1999,121,3136. 234. IS. A. Al-Farhan, M. H. Ja’far and 0. M. Abu-Salah, J. Organomet. Chem., 1999,579, 59. 235. V. J. Catalano, H. M. Kar and J. Garnas, Angew. Chem. Int. Ed., 1999,38, 1979. 236. C. W. Liu, I.-J. Shang, J.-C. Wang and T.-C. Keng, Chem. Commun., 1999,995. 237. C. Hollatz, A. Schier, J. Riede and H. Schmidbaur, J. Chem. Soc., Dalton Trans., 1999,111. 238. A. L. Balch, M. M. Olmstead and J. C. Vickery, Inorg. Chem., 1999,38,3494. 239. A. Xia, A. J. James and P. R. Sharp, Organometallics, 1999,18,451. 240. 0. Crespo, F. Canales, M. C. Gimeno, P. G. Jones and A. Laguna, Organometallies, 1999,18, 3142. 241. E. M. Barranco, M. C. Gimeno, P. G. Jones, A. Laguna and M. D. Villacampa, Inorg. Chem., 1999,38, 702. 242. S . Canales, 0. Crespo, M. C. Gimeno, P. G. Jones and A. Laguna, Chem. Commun., 1999,679. 243. W. J. Hunks, M. C. Jennings and R. J. Puddephatt, Inorg. Chem., 1999, 38, 5930. 244. J. Chen, T. Jiang, G. Wei, A. A. Mohamed, C. Homrighausen, J. A. Krause Bauer, A. E. Bruce and M. R. M. Bruce, J. Am. Chem. SOC., 1999,121,9225. 245. J. E. Casas, M. C. Gimeno, P. G. Jones, A. Laguna and M. Laguna, J. Chem. Soc., Dalton Trans., 1999,2819. 246. S . Lulinski, I. Madura, J. Serwatowski and J. Zachara, Inorg. Chem., 1999, 38, 4937.

346

Organometallic Chemistry

247. A. Knoepfler-Muhlecker,B. Scheffter, H. Kopacka, K. Wurst and P. Peringer, J. Chem. SOC.,Dalton Trans., 1999,2525. 248. S. J. Faville, W. Henderson, T. J. Mathieson and B. K. Nicholson, J. Organomet. Chem., 1999,580,363. 249. L. H. Gade, S. Friedrich, D. J. M. Trosch, I. J. Scowen and M. McPartlin, Inorg. Chem., 1999,38,5295. 250. S. Kabashima, S. Kuwata and M. Hidai, J. Am. Chem. SOC.,1999,121,7837. 251. T. Amemiya, S. Kuwata and M. Hidai, Chem. Commun., 1999,711. 252. M. A. Casado, M. A. Ciriano, A. J. Edwards, F. J. Lahoz, L. A. Oro and J. J. PCrez-Torrente, Organometallics,1999,18, 3025. 253. M. A. Casado, J. J. PCrez-Torrente, M. A. Ciriano, L. A. Oro, A. Orej6n and C. Claver, Organometallics, 1999,18, 3035. 254. R. Fandos, C. Hernandez, A. Otero, A. Rodriguez, M. J. Ruiz, J. L. Garcia Fierro and P. Terreros, Organometallics,1999,18,2718. 255. R. Hernandez-Molina and A. G. Sykes, Coord. Chem. Rev., 1999,187,291. 256. P. Mathur, S. Chatterjee, S . Ghose and M. F. Mahon, J. Organomet. Chem., 1999,587,93. 257. P. Mathur, M. 0. Ahmed, A. K. Dash and M. G. Walawalkar, J. Chem. Soc., Dalton Trans., 1999, 1795. 258. F. Xu, S. Y. Yang, W. H. Sun, J. Y. Yu and K. B. Yu, Polyhedron, 1999, 18, 1541. 259. L.-C. Song, Y.-B. Dong, Q.-M. Hu, W.-Q. Gao, D.-S. Guo, P.-C. Liu, X.-Y. Huang and J. Sun, Organometallics, 1999,18,2168. 260. J. Han, K . Beck, N. Ockwig and D. Coucouvanis, J. Am. Chem. SOC.,1999,121, 10448. 261. K. K.-H. Lee and W.-T. Wong, J. Organomet. Chem., 1999,577,323. 262. J. H. Yamamoto, G. D. Enright and A. J. Carty, J. Organomet. Chem., 1999, 577, 126. 263. M. Yuki, M. Okazaki, S. Inomata and H. Ogino, Organometallics, 1999, 18, 3728. 264. M. I. Bruce, J.-F. Halet, S. Kahlal, P. J. Low, B. W. Skelton and A. H. White, J. Organomet. Chem., 1999,578,155. 265. J. Zhang, X.-N. Chen, Y.-Q. Yin and X.-Y. Huang, J. Organomet. Chem., 1999, 579, 304. 266. Y.-T. Shiu, R. J. Madhushaw, W.-T. Li, Y.-C. Lin, G.-H. Lee, S.-M. Peng, F.-L. Liao, S.-L. Wang and R.-S. Liu, J. Am. Chem. SOC.,1999,121,4066. 267. M. Nihei, T. Nankawa, M. Kurihara and H. Nishihara, Angew. Chem., Int. Ed., 1999,38,1098. 268. R. Xi, B. Wang, M. Abe, Y. Ozawa, I. Kinoshita and K. Isobe, Bull. Chem. Sac. Jpn., 1999,72, 1985. 269. T. Ikada, S. Kuwata, Y. Mizobe and M. Hidai, Inorg. Chem., 1999,38,64. 270. S. M. Waterman and M. G. Humphrey, Organometallics, 1999,18, 3116. 271. S. M. Waterman, M. G. Humphrey and J. Lee, J. Organomet. Chem., 1999,589, 226. 272. S. M. Waterman, M. G. Humphrey and D. C. R. Hockless, J. Organomet. Chem., 1999,579,75. 273. S. M. Waterman, M. G. Humphrey, J. Lee, G. E. Ball and D. C. R. Hockless, Organometallics, 1999,18,2440. 274. S. M. Waterman, M. G. Humphrey and D. C. R.Hockless, J. Organomet. Chem., 1999,582,310.

11: Organo-Transition Metal Cluster Complexes

347

275. I. Bachert, I. Bartusseck, P. Braunstein, E. Guillon, J. RosC and G. Kickelbick, J. Organomet. Chem., 1999,580,257. 276. I. Bachert, I. Bartusseck, P. Braunstein, E. Guillon, J. RosC and G. Kickelbick, J. Organornet. Chem., 1999,588,144. 277. Y. Arikawa, H. Kawaguchi, K. Kashiwabara and K. Tatsumi, Inorg. Chem., 1999,38,4549. 278. J.-P. Lang and K. Tatsumi, J. Organomet. Chem., 1999,579,332. 279. J.-P. Lang and K. Tatsumi, Inorg. Chem., 1999,38,1364. 280. H. Zheng, W. Tan, M. K. L. Low, W. Ji, D. Long, W.-T. Wong, K. Yu and X. Xin, Polyhedron, 1999,18, 31 15. 281. Y. Liu, Y.-H. Mei, X.-Q. Xin and W.-T. Wong, Transition Met. Chem., 1999,24, 81. 282. H. Brunner, D. Mijolovic, B. Wrackmeyer and B. Nuber, J. Organomet. Chem., 1999,579,298. 283. H. Hou, Y. Fan, C. Du, Y. Zhu, W. Wang, X. Xin, M. K. M. Low, W. Ji and H. G. Ang, Chem. Commun., 1999,647. 284. Q.-F. Zhang, S. S. Sundara Raj, H.-K. Fun and X.-Q. Xin, Chem. Lett., 1999,619. 285. J.-P. Lang, H. Kawaguchi and K. Tatsumi, Chem. Commun., 1999,2315. 286. S . Ghosh, M. Shang and T. P.Fehlner, J. Am. Chem. SOC., 1999, 121, 7451. 287. W.-F. Liaw, S.-Y. Chou, S.-J. Jung, G.-H. Lee and S.-M. Peng, Inorg. Chim. Acta, 1999,286, 155-9. 288. U. Brand, C. A. Wright and J. R. Shapley, Inorg. Chem., 1999,38,5910. 289. Y. Katsukawa, S. Onaka, Y. Yamada and M. Yamashita, Inorg. Chim. Acta, 1999,294,255. 290. H.-J. Haupt, D. Petters and U. Florke, Z. Anorg. Allg. Chem., 1999,625, 1652. 291. P. Braunstein, U. Englert, G. E. Herberich, M. Neuschiitz and M. U. Schmidt, J. Chem. Soc., Dalton Trans., 1999,2807. 292. M.-C. Chung, A. Sakurai, M. Akita and Y. Moro-oka, Organometallics, 1999, 18,4684. 293. A. R. Manning, L. O’Dwyer, P. A. McArdle and D. Cunningham, J. Organomet. Chem., 1999,573,109. 294. 0.J. Scherer, S. Weigel and G. Wolmershauser, Angew. Chem., Int. Ed., 1999, 38, 3688. 295. X.-N. Chen, J. Zhang, Y.-Q. Yin and W.-L. Wang, Chem. Lett., 1999,583. 296. S . Bouherour, P. Braunstein, J. Rose and L. Toupet, Organometallics, 1999, 18, 4908. 297. J. C. Jeffery, P. A. Jelliss, G. E. A. Rudd, S. Sakanishi, F. G. A. Stone and J. Whitehead, J. Organomet. Chem., 1999,582,90. 298. S . Y.-W. Hung and W.-T. Wong, J. Organomet. Chem., 1999,580,48. 299. W.-T. Wong, Organometallics, 1999,18,3474. 300. T. Kochi, Y. Nomura, Y. Ishii, Y. Mizobe and M. Hidai, J. Chem. Soc., Dalton Trans., 1999,2575. 301. A. U. Harkonen, M. AhlgrCn, T. A. Pakkanen and J. Pursiainen, J. Organomet. Chem., 1999,573,225. 302. V. Ferrand, G. Suss-Fink, A. Neels and H. Stoeckli-Evans, Eur. J. Inorg. Chem., 1999,853. 303. G. Suss-Fink, S. Haak, V. Ferrand and H. Stoeckli-Evans, J. Mol. Catal. A , 1999,143,163. 304. S . Haak, G. Suss-Fink, A. Neels and H. Stoeckli-Evans, Polyhedron, 1999, 18, 1675.

348

Organometallic Chemistry

305. G. Suss-Fink, S. Haak, V. Ferrand, A. Neels and H. Stoeckli-Evans, J. Organomet. Chem., 1999,580,225. 306. S. Haak, A. Neels, H. Stoeckli-Evans, G. Suss-Fink and C. M. Thomas, Chem. Commun., 1999, 1959. 307 A. B. Antonova, A. A. Johansson, N. A. Deykhina, D. A. Pogrebnyakov, N. I. Pavlenko, A. I. Rubaylo, F. M. Dolgushin, P. V. Petrovskii and A. G. Ginzburg, J. Organomet. Chem., 1999,577,238. 308. B. T. Sterenberg, M. C. Jennings and R. J. Puddephatt, Organometallics, 1999, 18,2162. 309. B. T. Sterenberg, M. C. Jennings and R. J. Puddephatt, Organometallics, 1999, 18, 3737. 310. J. W.-S. Hui and W.-T. Wong, J. Cluster Sci., 1999,10,91. 311. M. Ferrer, R. Reina, 0. Rossell and M. Seco, Coord. Chem. Rev., 1999, 193-5, 619. 312. V. G. Albano, C. Castellari, M. C. Iapalucci, G. Longoni, M. Monari, A. Paselli and S. Zacchini, J. Organomet. Chem., 1999,573,261. 313. V. G. Albano, C. Castellari, C. Femoni, M. C. Iapalucci, G. Longoni, M. Monari, M. Rauccio and S. Zacchini, Inorg. Chim. Acta, 1999,291,372. 314. J. A. Cabeza, M. A. Martinez-Garcia, V. Riera, D. Ardura, S. Garcia-Granda and J. F. Van der Maelen, Eur. J. Inorg. Chem., 1999, 1133. 315. M. Benito, 0. Rossell, M. Seco and G. SegalCs, Organometallics, 1999,18, 5191. 316. M. Benito, 0. Rossell, M. Seco and G. Segales, Inorg. Chim. Acta, 1999,291,247. 317. F.-S. Kong and W.-T. Wong, J. Chem. SOC.,Dalton Trans., 1999,2497. 318. H. Wadepohl, S. Gebert, R. Merkel and H. Pritzkow, Chem. Commun., 1999, 389. 319. I. Bachert, P. Braunstein, M. K. McCart, F. Fabrizi de Biani, F. Laschi, P. Zanello, G. Kickelbick and U. Schubert, J. Organomet. Chem., 1999,573,47. 320. F. M. Dolgushin, E. V. Grachova, B. T. Heaton, J. A. Iggo, I. 0. Koshevoy, I. S. Podkorytov, D. J. Smawfleld, S. P. Tunik, R. Whyman and A. I. Yanovskii, J. Chem. SOC.,Dalton Trans., 1999, 1609. 321. M. Shirai, 0.-B. Yang, W. A. Weber and B. C. Gates, J. Catal., 1999,182,274. 322. B. T. Sterenberg, H. A. Jenkins and R. J. Puddephatt, Organometallics, 1999, 18, 219. 323. S.-M. Kuang, Z.-Z. Zhang, Q.-G. Wang and T. C. W. Mak, Polyhedron, 1999, 18,493. 324. T. Zhang, M. Drouin and P. D. Harvey, Inorg. Chem., 1999,38,4928. 325. B. D. Chandler, A. B. Schabel, C. F. Blanford and L. H. Pignolet, J. Catal., 1999, 187, 367. 326. Y. Yuan, K. Asakura, H. Wan, K. Tsai and Y . Iwasawa, Bull. Chem. SOC.Jpn., 1999,72,2643. 327 L. R. Falvello, S. Fernandez, R. Navarro and E. P. Urriolabeitia, Inorg. Chem., 1999,38,2455. 328. J. P. H. Charmant, L. R. Falvello, J. Fornies, J. Gomez, E. Ialinde, M. T. Moreno, A. G. Orpen and A. Rueda, Chem. Commun., 1999,2045. 329. J. Zhang, E.-R. Ding, X.-N. Chen, Y.-H. Zhang, C.-P. Song, Y.-Q. Yin and J. Sun, Synth. React. Inorg. Met.-Org. Chem., 1999,29, 1315. 330. E.-R. Ding, S.-L. Wu, Q . 4 . Li, Y.-Q. Yin and J. Sun, Synth. React. Inorg. Met.Org. Chem., 1999,29,565. 331. M. Yuki, M. Okazaki and H. Ogino, Chem. Lett., 1999,649. 332. C. E. Housecroft, D. M. Nixon and A. L. Rheingold, Polyhedron, 1999, 18,2415.

I I : Organo-Transition Metal Cluster Complexes

349

333. A. D. Hattersley, C. E. Housecroft and A. L. Rheingold, Inorg. Chim. Acta, 1999,289,149. 334. R. Bender, P. Braunstein, S.-E. Bouaoud, M. Merabet, D. Rouag, P. Zanello and M. Fontani, New J. Chem., 1999,23,1045.

12 Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel, including Carbenes and Carbynes BY MICHAEL K. WHllTLESEY

1

Reviews and Articles of General Interest

Review articles relating to the applications of late transition metal organometalllic complexes for the activation of C-C bonds' and the activation of C-H bonds2 (as a route to making new C-C bonds) have appeared. The applications of early-late heterobimetallic complexes have been discussed3, as has the role of alkynyl complexes as building blocks for organometallic polymer^.^ The luminescent properties of metal alkynyl complexes has also been re~iewed.~ A number of shorter reviews of relevance to the current chapter have appeared. The activity of palladacycles in Heck type reactions has been described6,while the function of calix[4]arene complexes as models for catalytic activity of 0x0 surfaces has been disc~ssed.~ An overview of the coordinationlactivation of organic substrates by carbonylhalo ruthenium complexes has appeared.8 The cycloisomerisation of alkynols by transition metal complexes, including Group 8 and 9 compounds, has been reviewed.' A detailed description of the synthesis, characterisation and reactivity of ruthenium and osmium vinylidenes has appeared" and there has also been a review of the reactivity of Group 8 metal indenyl complexes, including alkenyl, alkynyl, carbene and allenylidene complexes. * The synthesis, reactivity and catalytic applications of Group 10 metallacycles has been described12, while the role of palladium complexes with nitrogen ligands (typically N-N ligands) in stoichiometric and catalytic C-C bond formation has been re~iewed.'~ Ultrafast infrared studies of C-H bond activation by half-sandwich rhodium complexes have been described.l4

2

Metal-Carbon o-Bonds Involving Group 8,9 and 10 Metals

2.1 The Iron Triad. - Density functional theory (DFT) and a combined DFT/molecular mechanics approach has been used' to investigate the polymerisation of ethene by [(2,6-((R)N=C(R)),-C5H3N) FeC3H7]+,with a model ligand set (R = R' = H) and also the substituents on the actual catalyst (R = 2,6Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001

350

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 351

C6H4(iPr)2,R' = CH3). The rate-determining step for propagation and termination involves capture of ethene by the complex. The calculations indicate that the presence of bulky arms on the diimine leads to suppression of the termination step and an increase in the rate of ethene insertion, fuelling polymerisation. Ab initio calculations have been used to study16 the catalytic polymerisation of ethene by 1. The barrier for alkene insertion into the Fe-

qfw -N 'Ar

1 Ar = 2,6-diisopropylphenyI

CH3 bond is remarkably low (10.3 kJ mol-'), much lower than found in the related iron diimine complexes reported previously by Brookhart and coworkers. Theoretical studies17 (hybrid DFTmartree-Fock) studies, in collaboration with FT ion cyclotron resonance mass spectrometry, have been used to probe the energetics of interconversion of Fe(CHCH2)+, HFe(CHCH)+, (H)2Fe(CCH)f and HFe(CCH2)+. Density functional studies have been used to model the hydrogen exchange between the hydride and methyl groups in [(q-C5Me5)Os(dmpm)(CH3)H]'.l 8 Time-resolved infra red spectroscopy (TRIR) has allowed detection of (qC5H5)(CO)FeC(0)Meand has been used to elucidate the kinetics and activation parameters for re-formation of the precursor compound, (q-C5H5)(C0)2FeCOMe, and the methyl migration product (q-C5H5)(CO)2FeMe. l9 Oxidative hydroboration of (q-C5R5)(CO)2Fe((CH2)n- 1CH=CH2)(R = H, Me; n=2-5, 7) provides a route to the w-hydroxyalkyl complexes, (qC5R5)(C0)2Fe{ (CH2),CH20H}.20 The 16-electron species Ru(PCy&(C0)HCl has been shown to catalyse the hydrogenation of terminal and cyclic alkenes. The reaction with ethene has led to the observation21 of two key intermediates, R u ( P C ~ ~ ) ~ ( C O ) ( C ~ H and ~ ) CR~u ( P C ~ ~ ) ~ ( C O ) ( C H ~ C H ~ ) C ~ , which have been characterised by NMR spectroscopy. The reaction of the transient hydride complex [Ru(C0)2C12H]- with alkenes and alkynes has been reported.22It reacts with dimethylacetamide at high temperature to give [ R u ~ ( ~ - C ~ ) ~ ( C-O, )which ~C~~ ] activates terminal alkynes to afford Ru alkyl complexes. The reaction of TpiprFeCl(Tpipr= tris(3,5-diisopropylpyrazolyl)borate) with EtMgBr in thf leads to the iron ethyl complex TpiRFeCH2CH3, which does not undergo P-hydride elimination even upon heating at 110°C for five to ci~-Ru(dmpe)~Me~ hours.23Addition of [(3,5-(CF3)2C6H3)4B]-[H(OEt2)2]+ in the presence of ethene gave trans-[Ru(dmpe)2Me(C2H4)]+,which has been characterised by X-ray ~rystallography.~~ A range of osmium alkyl cornp l e ~ e scontaining ~~ a core (q-C5Me5)Os(q3-C3H5)unit have been prepared, including (q -C5Me5)Os(q 3-C3H5)(CH3)2 and [(q-C5Me5)0s(q3-C3H5)with PPh3 (H20)CH3]+. Treatment of [(q-C5H5)Os(NCH3)(CH2SiMe3)2]+

352

Organometallic Chemistry

produces (q -C5H5)Os(NCH2)(CH2SiMe3)2and the osmium(1V) hydride complex 2, which results from a-H elimination and orthometallation.26 C-X bond activation reactions have been utilised to prepare compounds containing Ru-C bonds. R u ( P P ~ ~ )reacts ~ C ~with ~ the chelating phosphine 1,3,5-(CH3)3-2,6-CPr2PCH2)2c6H under 2 atm H2 to give ClRu(PPh3)2(2,6(1Pr2PCH2)2-3,5-(CH3)2c6H) as a result of C-C activation, while reaction in the absence of H2 with NaOtBu gives the C-H activation product 3.27Similar

reaction of Ru(PPh3)3HCl with the same phosphine has been used to demonstrate that the kinetic product in the reaction resulting from C-H activation is irreversibly converted to the product of C-C activation in the presence of dihydrogen. C-S bond activation in 3-acetyllformylthiophene or 2-acetyV formylthiophene has been observed2*in the presence of Ru(cod)(cot) and 1,2bis(diethy1)phosphinoethane (depe) to afford the thiaruthenacycles, ~ U ( S C R = C H C R ' = C H ) ((R ~ ~=~H, ~ )R' ~ = CHO, COMe; R = CHO, COMe, R' = H). In the case of iron chemistry, Fe(N2)(depe)2 has been shown to cleave C-S and C-H bonds in a range of sulfur heterocycles. For example, the thiaferracycle l?e(SC6H4CH=&I)(depe)2has been formed29and characterised using X-ray diffraction. Addition of Me1 to this species cleaves the Fe-S bond to afford trans-[FeI{(E)-CH=CHC6H4-2-SMe)( d e ~ e ) ~ ] The . dinitrogen complex breaks only C-H bonds, and not C-0 bonds, in furans. Addition of BF3.0Et, or MeSiOTf to (q-C5Hs)(CO)Ru(R){PN(Me)CH2CH2&Me(OMe))(R = Me, CH2SiMe3) yields the corresponding phosphenium complexes, which undergo spontaneous reaction with triphenylphosphine resulting in migratory insertion of the phosphenium ligand into the RuC bond to give 4.30 A series of osmametallocenophanes [ ( T ~ - C ~ H ~ ( C H ~ ) ~ O S (C0)4(CH2),(q-C5H5)]M (n = 3, 4, 6; M = Fe, Ru) have been prepared3' and the electrochemical properties of the metallocene centre investigated. The rare osmium aryl boryl complexes, cis- and trans-[Os(Bcat)(o-CH3C6H5)(C0)2(PPh3)2], have been synthesised and characterised in the solid state using X-ray ~rystallography.~~ The &-complex undergoes slow reductive elimination +

4 R = Me, Cl+SiMe,

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 353

of o-tolylBcat at room temperature and oxidative addition of HBcat, allowing the direct observation of two fundamental steps in the proposed mechanism of hydroboration. The osmium(I1) phenyl hydride complex OsH(C6H&CO)L2 (L=PtBu2Me) reacts with D2 to give reductive elimination of benzene. The reaction with C6D6 yields OsD(C6D5)(CO)L2exclusively (there is no H/D exchange), but not via an q2-arene complex. The phenyl hydride complex reacts with fluoroarenes ArF-H to give osH(Ar~)(cO)L2and benzene with attack occurring preferentially at the arene C-H bond ortho to fluorine. Both the C-H bond cleavage of H-ArF and the C-H bond formation of C6H6 take place via initial dissociation of one of the bulky PtBu2Mephosphine l i g a n d ~ . ~ ~ The water soluble hydride complex fac-[RuH(CO)2(H20)3]+ inserts ethene in water to form ~~c-[Ru(C~H~)(CO),(H~O)~]+.~~ This exists as the dimer [Ru~(C~H~)~(CO)~(H~O)~]~+ in the solid state, as shown by X-ray crystallography. The solution monomer reacts with CO to give an acyl complex which eliminates C2H5C02Hto regenerate the hydride starting material. Thermolysis of Ru(dppp)(PPh3)(CO)H2at 110"C in the presence of styrene results yields a cyclometallation product as a result of intramolecular C-H activation of one of the dppp phenyl rings.35Cycloruthenated complexes36of the form [(q-c6H,>RU(c-N)(cH,cN)I+ (c-N = CsH4-2-CH2NMe2,C&-3,4(OCH3)2-2-CH2NMe2and (R)-(+)-C6H4-2-CH(Me)NMe2)are formed by intramolecular C-H activation of c-N by [(T~-C~H~)RUC&. Isomerisation was observed upon treating [Fe2(C0)6(p-PPh2){ p-q1:q2HC=C=CH2}]with acid to give [Fe2(C0)6(p-PPh2){p-q1:q2-C(CCH3}].37 The (R = Me, related species [Fe2(CO),(p-PPh2)(p-q ':r11-HC=C(P(NR2)3)CH2)] Et, "Pr) decarbonylate in solution over days to give the q3-vinylcarbene complexes [Fe2(CO)&-PPh2)(p-q1:q3-C(H)C{P(NR2)3}CH2)]. In addition for R = Et, a second competing isomerisation reaction occurs to yield [Fe2(CO),(pPPh2)(p-q ':q2-{ P(NEt2)3}C(O)CHC=CH2)] via phosphine-carbonyl-allenyl coupling. Thermolysis of [Fe2(CO)6(p-PPh2) { p-C(C'Bu}] at 140 "C for 30 hours led to isolation of the bridged phosphido alkenyl complex, [Fe2(CO)&PPh2) (p-o-Ph2PC6H4C=CHtBu}],in 35% yield.38 The product formed upon addition of dppm to [Fe2(CO)6(p-PPh2){ p-RC=CHR}] is found to be substitution dependent. For R = R =H; R=EtO, R'=H; R = H , R = P h , simple substitution occurs to give trans-[Fe2(CO)4(p-PPh2)(p-alkenyl)(p-dppm)]. With R = Ph; R' = H and R = R = Ph, migratory insertion is observed to form trans[Fe2(C0)4(p-PPh2) { p-O=CC(Ph)=CHR}(p-dppm)]. P-C bond formation and a 1,4-proton shift occur for R = CMe=CH2, R' = H to give the p-alkylidene [ F ~ z ( C O{ p-HCC(Me)=C(MePPh2} )~ (p-d~prn)].~' Reaction of one equivalent of HC=C(CH2)4CrCH with two equivalents of RU(P'P~~)~(CO)HCI leads to the binuclear complex (PiPr3)2(CO)ClRu{ (A)CH=CH(CH2)4CH=CH-(E)}RuCl(CO)(P'Pr3)2. A mixed RuOs bisalkenyl (A)derivative can be prepared by reaction of (PiPr3)2(CO)ClRu{ CH=CH(CH2)4CrCH} with Os(P'Pr3)2(CO)HCl. Addition of HCl to the bisalkenyl complex selectively affords (PiPr3)2(CO)ClRu{ CHZCH(CH~)~CH-} OSC~~(CO)(P'P due ~ ~to ) ~ the greater nucleophilicity of the osmium alkenyl unit.@ Addition of PMe3 to OS(CO),(~~-HC(CH) pro-

(a-

Organometallic Chemistry

354

duces a range of products which undergo reactions leading to new 0s-C bonds.41 O S ( P M ~ ~ ) ~ ( C O ) ~ ( ~ ~ - H C isomerises = C H ) at room temperature to OS(PM~~)~(CO)~(C=CH)H, while O S ( P M ~ ~ ) ( C O ) ~ ( ~ ~ - H Cforms - C H ) the :q :q '-H2C2C(0)C2H2)]. The mixed dimeric species [0~2(PMe3)~(CO)~(p-q metal alkenyl complexes [RhM~(R)(Co)~(dppm)~] (R = CH=CH2, CH2CH=CH2), [RhMo(C(R')=CHR)(CO)4(dppm)2] (R = R = C(O)OMe, CF3; R = H, R' = C(0)Me) and [RhW(CH=CH2)(CO)4(dppm)2] have been reported. Both the RWMo and R h N vinyl complexes [RhM(CH=CH2)(C0)4(dppm)2]can be protonated at -80°C by HBF4 to give the ethylidene species [RhM(=C(H)CH3)(CO)4(dppm)2]'-,which rearrange to ethene complexes upon warming.42 The silyl migrated product [Ru(CH=C(SiMe3)Ph)(CO)L2][BAri] (L = PtBu2Me, Ar' = 3,5-C,@3(CF3)2) is formed upon addition of Me3SiC-CH to [RuH(CO)L2][BAri]. The reaction can be reversed by addition of C0.43 Photolysis of (q-C5H5)2R~2(p-CH2)2(C0)2 in thf with excess norbornadiene gave the C-C coupling product 5.44Isotopic labelling experiments suggest that there is a bridging methylidene intermediate. Further to this, photolysis of (qC5H5)2Ru2(p-CH2) (p-13CD2)(13C0)2in C6D6 in the absence of the diene

' '

5

6

resulted in an equilibrium mixture of (~-CSH~)~RU~(~-CHD)(~-'~CH (13CO)2and (q-C5H&Ru2( p-CD2)(p-' 3CH2)(1 3C0)2. Two fluxional processes have been detected in (q-C5Me5)2R~2(p-CH2)(SiR3)(p-Cl) (SiR3= SiMe3, SiEt3, SiMe2Et, SiMe2Ph).45At low temperature, the silyl group moves between ruthenium atoms, while at high temperature, interchange of the two CH2 protons occurs via reversible formation of a C-Si bond between CH2 and SiR3. [Rho~(CO)~(p-CH~)(dppm)]+ reacts with excess diazomethane at -40 "C to give 6, through the condensation of four methylene units46 The terminal methylene group displays an agostic interaction with the rhodium centre. When the reaction is performed at room temperature, [RhOs(q CH2CH=CH2)(CH,)(CO)3(dpprn)2]+ is formed, with the q '-ally1 group bonded at rhodium and the methyl to osmium. This species is not interconvertible with 6. The vinylidene complex47 TP(PP~~)~RU(=C=C(P~)CH~CN) (Tp = hydridotris(pyrazolyl)borate), which is formed in the reaction of Tp(PPh3)zRuC-CPh with ICHZCN, reacts with NaOMe to give the cyclopropenyl complex, TP(PP~~)~RU-HCN). Treatment of [Fe3(CO)9(CCO)]2- with TiC13(DME)1.5 and Zn-Cu couple leads to formation of [Fe3(C0),(CrCH)]- in 70% yield, providing a new

'-

12: Complexes Containing Meral-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 355

approach48 to introducing C2 units into clusters. Racemic [(qs-C9H7)(CO)(P(OMe)3)Fe-C=CR] (R = Ph, Me, SiMe3, C-C"Bu, p-MeC6H4) is formed upon treating (q 5-C9H,)(C0)2Fe-CzCR with a slight excess of P(OMe)3 in refluxing dibutyl ether. Reflux in neat trimethyl phosphite, however, gives [(CO)(P(OMe)3)3Fe(=C=C(inden-1-yl)R)], via indenyl migration to Cp of the alkynyl group. The reaction is independent of the nucleophilicity of the substituent on Cp, but is slower for P(OEt)3 compared with P(OMe)3. The proposed reaction mechanism49involves the formation of a C7H9 radical. The room temperature reaction of (q-C5Me5)(C0)2Fe-(CrC),-Fe(C0)2(q-C5MeS) (n = 3, 4) with Fe2(C0)9 yields [(q-C5Me5)(C0)2Fe-C(C-p3-C-Fe3(C0)9-p3-C(CrC),-2-Fe(C0)2(q-C5Me5)] as a result of C r C cleavage?' The reaction of [(q-C5H5)(PPh3)2Ru(C(CCaH4-p-Me)] with [(q-C5Me5)Ru(p3-C1)]4 in a ratio of 4: 1 in refluxing thf gives [(q-C5H~)(PPh3)2Ru(q':q~-p~-CrCC~H~-pMe)Ru(q-C5Me5)]+. This can be protonated with HOTf to give [(q-

C5H5)(PPh3)2R~(q1:q6-p2-C=CHCgH4-p-Me)Ru(q-C5Me5)]2+.5' The coordinatively unsaturated ruthenium and osmium precursors R u ( P P ~ ~ ) ~ H(X X = C1, 02CMe) and MHCl(CO)(PPh& react with HC-CCPh20H giving access to alkenyl, alkynyl, propenylidene and acetoxyallenyl complexes.52 A one-pot route to [(p-cymene)(PCy3)ClRu(=C=C=CPh2)]+has been reported. The complex shows anion dependent catalytic activity (ring-closing metathesis, cyclisation) towards organic subs t r a t e ~ .Phenylacetylene ~~ reacts with [L2Os(CO)(NO)]' (L = P'BuMe) to afford the alkynyl hydride product and then [L2(CO)(NO)Os(=C=C=CPh2)]+. A mixture of these products is deprotonated with NEt3 to give neutral L2(CO)(NO)OsC=CPh. If the alkyne used is Me$iCrCSiMe3, [L2(C0)(NO)Os(=C=C(SiMe3)2)]' is formed54, which can be doubl h drol sed to [L2(CO)(NO)Os(=C=CH2)]+. Treatment of [Rul-k +$-C(Ph)C( NPh) ([Ru] = [(q-C5H5)(dppe)Ru)with ICH2CN yields the air-stable S-alkylation product [[Ru]=C=C(Ph)C(=NPh)SCH2CN]+, which may be deprotonated by "BmNOH in acetone to give the 5-membered heterocyclic species [Rulk=C(Ph)C(=NPh)SkHCN, which isomerises to [Rulk=C(CN)SC(NHPh)=ePh. If [Rul-k=C(Ph)C(=NPh)$ is reacted with BrCH2R (R = C02Me,p-C6H4CN, C6H5), an S-alkylation product and the Nalkylation product, [[Ru]=C=C(Ph)C(=S)NPhCH2R]+,are formed in a ratio depending upon R.55 Treatment of [(q-C5H5)(PPh3)20s]' or [(q-C5H5)(dppe)Fe]+with 0.5 equivalents of HC(CHC(OH)C(CH followed by Al2O3 gave [(q-C5H5)(PPh3)2OS=C=C=CHC=C-OS(PP~~)~(~-C~H~)]+ and [(q-C5H5)(dppe)Fe=C=C=CHC~C-Fe(dppe)(q-CSHs)]+ re~pectively.~~ Addition of HCrCC(0H)RR' (R = R' = H; R = R' = Me; R = Me, R = Ph) to (q-C5Me5)(PEt3)2R~Clin MeOH at 0 "C in the presence of NaBH4 gives [(q-C5Me5)(PEt&Ru(C-CC(OH)RR')H]+, which rearranges both in solution and the solid state to the hydroxyvinylidene complexes, [(q-C5Me5)(PEt3)2R~=C=C(H)C(OH)RR]+.57 In a later report, the same authors58report the formation of hydroxyvinylidene complexes with a wider range of substituents and show that these can be dehydrated by alumina to give alkenylvinylidenes [(q-C5H5)(PEt3)2-

356

Organometallic Chemistry

Ru=C=C(H)C(R)=CH2]+,or allenylidenes [ ( ~ - C ~ H ~ ) ( P E ~ ~ ) ~ R U ( = C = C = C ( R ) Ph)]+,for complexes with bulkier R/R’ groups (R =H, R’ = Ph; R = R’ = Ph). Copper(1) catalysed coupling of a range of metal substrates M including (qC5H5)(C0)3WCl,(dppe)PtC12and (PPh3)AuCl with [Ru]-C&-C~H~-~-C(CR ([Ru] = ( T - ~ - C ~ H ~ ) ( P PR ~~ = )H, ~R SiMe3) U ; leads to [RU]-CEC-C&-~-C=CM moieties.59 Treatment of (q-C5H5)(PPh3)2RuClwith RCcCSiMe3 (R = Ph, -C(CPh, -C-CC-Ph, SiMe3)in the presence of KF/MeOH results in desilylation of the alkyne and produces molecules containing unsaturated chains of up to six carbon atoms. These can be further derivitised by (NC)2C=C(CN)2or C O ~ ( C O )Bimetallic ~.~~ complexes have been formed6’ by reaction of (qC5Me5)(dppe)Fe-CrCL (L = 4-pyridyl, 3-pyridyl, 2-pyridyl) with W(CO),(thf) and (PhCN)2MC12 (M=Pd, Pt), with the W, Pd and Pt centres bonded through the pyridyl nitrogen. A range of unsymmetrical bisalkynyl complexes, trans-[(dppm)ZM(C=CR)(C=CR’)] (M = Ru, 0 s ; R =p-N02C61i4,R’ = Ph; R =p-MeC6&, Ph, R’ =p-MeC6&), have been prepared.62 A series of oligothienylalkynyl ruthenium(I1) complexes including trans-(dppm)2C1Ru(C=CR) and trans(dppm)2Ru(CrCR)2 (R = 2-thienyl etc.) have been reported63and their structures, electrochemistry and visible spectroscopy studied. Similarly, structural, spectroscopic and electrochemical measurements of ruthenium bisarylalkynyl complexes based around macrocyclic amine ligands have been reported? Crystallography, spectroscopy, electrochemistry and computational methods have been used to probe6’ electronic interactions between the two halves of the alkynyl linked complexes [CO~(~-M~~S~C=CC~CEC[RU(PP~~)~(~(C0)4(dppm)] and [CO~(~-M~~S~C~C~CC~C[RU(PP~~)~(~-CSH (dppm)]. The first third order NLO measurements on an organometallic dendrimer have been reported following studies on 1,3,5-C6H3(pCrC-C6H4C-C-trans-[R~(dppe)~]-C~c-3,5-C&I3(p-C=C-C6H4-c-C- trans[Ru(C=CPh)(dppe)21)2>3.66 Addition of (NC)2C=CHPh to (q-CSHS)LL‘RuC=CPh leads to a [2+2] cyclisation to form (q-C5H5)LL’Ru(&C(Ph)CH(Ph)c(CN)2} (L = PPh3, L = P(OMe)3; L = PPh3, L’ = CNtBu; L = L = dppe). However, addition of (NC)2C=C(C1)Phin the case of L = PPh3, L’ = P(OMe)3, results in electrophilic addition and demetallation to give the phosphonate vinylidene complex, (qC5H5)(PPh3)Ru[P(0)(OMe)2{ =C=C(Ph)C(Ph)C(CN)2}].67 The NLO properties of a series of o-arylalkynyl, o-enynyl and o-dienynyl ruthenium(I1) and bimetallic Ru(I1)-M (M = Cr(O), W(O), Fe(II), Ru(I1)) complexes have been studied, and the largest hyperpolarisibility (Po) value reported so far for a bimetallic complex has been found.68 The chiral cyclopentadienyl iron complexes (9-and (R){ q5-[1-Ph2(0H)C-2-Me-4-PhC5H2]} Fe(C0)2R (R = Me, C-CPh) have been prepared.69 Addition of HCl to the osmium alkenyl-alkynyl complex [bs(C(CC02CH3)(CH=CHC(d)OCH3)(CO)(PiPr3)2]leads to C-C coupling7’ to give the butadienyl derivative [bs{C(CH=CHC02CH+CHC(b)OCH3)C1(CO)(PiPr3)2]. A series of butatrienylidene complexes including (q-C~Me~)(dippe)Fe(C=CC-C)Fe(C0)2(q -C5Me5)], (q-C5Me5)(P2)Fe{ =C=C=C=C(H)-

12: Complexes Containing Metal-Carbon a-Bonds of the Groups Iron, Cobalt and Nickel 357

Fe(CO)2(q-C5Me5)}]+and (q-C5Me5)(P2)Fe{=C=C=C=C(CH3)Fe(C0)2(qC5Me5)}]’ (P2= dppe, dippe) have been prepared and their electronic structure described7’ on the basis of spectroscopic measurements. Neutral alkynyl complexes (q-C5H5)(PPh3)2RuC=_CPh2Nu have been s ~ n t h e s i s e dby ~ ~addition of 0-, N- and C-based nucleophiles (Nu) to [(q-C5H5)(PPh3)2Ru(=C=C=CPh2)]+. The reaction of [(q-C5H5)(PiPr3)(CO)Ru(C=C=CPh2)]+ with (C6H1l)N=C=N(C6H1 followed by NaOMe gives the iminoazetidin lidenemeth 1 [(q-C5H5)(PPr3)(CO)Ru{ (2)-CH=d = N M g ] . Addition of HBF4 results in rearrangement to the thermodynamically more stable hexahydroquinolinylidenemethyl species 7.73 The reaction of [[Ru](C=C=CPh2)]’ ([Ru] = (qC5H5)(PiPr3)(CORu)with diethylamine or piperidine gives the azoniabutadienyl complexes [[Ru]{ C(CH=CPh+NEt,}]+ and [[Ru]{ C(CHzCPh2)-

I+ =NCH2(CH2)3CH2]]+respectively. The former is deprotonated upon addition of NaOMe to produce the aminoallenyl species [[Ru](C(NEt2)=C=CPh2)].The corresponding azoniabutadienyl complexes produced with primary amines are deprotonated at the nitrogen atom to give the azabutadienyl complexes [[Ru](C(CH=CPh2)=NHR}]+(R = “Pr, Ph).74 The substitution chemistry of T P ( P P ~ ~ ) ~ Rwith u C ~ alkynes has been shown75 to be solvent dependent. Addition of HC-CR (R =p-MeCsH4, CPh20H) in thf gave Tp(PPh3)2Ru=C=CH(p-MeC6H4) and Tp(PPh3)zRu(=C=C=CPh2) respectively. In thf/MeOH, HCrCC6H4-p-Me affords T P ( P P ~ ~ ) ~ R U C = C C ~ H ~Related - ~ - M ~complexes . have also been prepared starting from Tp(dppf)RuCl. Regioselective C=C bond cleavage has been observed76 upon treatment of fac,cis-(PNP)C12Ru(=C=C=CPh2)or fac,cis(PNP)C12Ru(=C=C(H)C(R)=CH2)(R = Me, Ph) in CH2C12or thf with water. The dinitrogen bridged dimer [(RuC12(q2-N”N)>2(p-N2)] (NN” = 2,6-bis{(dimethy1amino)methyl)pyridine) reacts with PhCECH to form mer,cis[Ru(=C=CHPh)C12(NN”)]. The related compound mer-[Ru(=C=CHPh)(OTf)(NN”)(PPh3)] can be made from mer,trans-[RuC12(NN”)(PPh3)] and HCECPh in the presence of AgOTf.77 Addition of two equivalents of PCy3 and HC=C(OH)Ph2 to [(p-cymene)RuCl2I2 or Ru(PPh3)4C12 yields ( P C Y ~ ) ~ C ~=C=C=CPh2), ~RU( which readily reacts with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene(IMes) to give (PCy3)(IMes)C12Ru(=C=C=CPh2).78 The same allenylidene species

358

Organometallic Chemistry

(PCy3)2C12Ru(=C=C=CPh2) (and the related compound (PCy3)(qMeC6H4'Pr-4)Cl4Ru2(=c=C=cPh2)) have been shown to act as effective precursors for ring closing metathesis (RCM) of a,o-dienes and dienyes at room t e m ~ e r a t u r e .The ~ ~ first coordinatively unsaturated allenylidene complexes of Group 8 have been synthesised." Treatment of 16-electon 0s) with HCrC(OH)Ph2 produces M(PPh3)3C12 (M = Ru, (PPh3)2C12M(=C=C=CPh2). The triphenylphosphine ligands are easily replaced to give a range of complexes including (PCy3)2C12RuC=C=CPh2, (PPh3)(CO)C12Ru(=C=C=CPh2) and [(PPh3)([9]aneS3)C1M(C=C=CPh2)]'. The reaction of (q-C9H7)(PPh3)2R~C1 with excess 1-ethynyl-1-cyclohexanol and NaPF6 in refluxing methanol results in coupling of two molecules of in 55% yield.81The alkyne to give [(q-C9H7)(PPh3)2R~(=C=C=C(C13H20))]+ allenylidene group is replaced upon refluxing in the presence of other alkynes to give [(q-C9H7)(PPh3)2Ru(=C=C(H)R)]+(R = 1-cyclopentenyl, 1-cycloheptenyl, 1-cyclooctenyl) or (q-C9H7)(PPh3)2Ru(=C=C=CPh2). Alternatively, the allenylidene complex can be converted to the alkynyl complex of (qC9H7)(PPh3)2Ru(C-CC(C13H20)R) upon addition of NaR (R = OMe, CN) at -20 "C. The reaction of [(q-C5H,)(PR3)2Ru(=C=C=C=CH2)]+(R = Ph, OMe) with arylimines ArN=CH(C6H4X) (Ar = CH3C6H4, x = H; Ar = C6H5, X =p-N02; Ar =p-MeOC6H4, x =p-NO2; Ar = C6H5, x = C02Me; Ar =p-MeOC6H4, X =p-NO2) yields either (q-C5H5)(PPh3)2R~(CSC9H4X(N)Ar), following initial attack of the butatrienylidene ligand art the imine carbon, or l-azabuta1,3-dienyl complexes, (q -C5H5)(PPh3)2R~(C-CC( =NAr)CH=C(H)C6H&), by cycloaddition of the N=CH group to C"-Cp and ring opening.82 R ~ ( d p p m ) ~ reacts C l ~ with HCECC-CH and a range of tertiary amines to give trans-[(dppm)2ClRuC=CC(=CH2)(NR2R')If, via the intermediate butatrienylThe iron diphenylbutenidene complex, [(dppm)2C1Ru(=C=C=C=CH2)]+.s3 ynyl complex 8 is formed in the reaction of FeLC12, FeL(H)Cl or [FeLH(H2)]+

(L = P(CH2CH2PMe2)3)with phenylacetylene in alcohol ~olution.'~ The solid state structure shows that the n-bound alkyne group is cis to the apical phosphorus L, whereas in solution, the compound exists as a pair of equilibrating isomers with the n-alkyne cis or trans to apical P. Addition of 'BuNC to [Fe2(C0)6(p-PPh2){ p-q':r12a,p-(H)C,=Cp=C,Hz)l is believed to initially form the unstable zwitterionic allene bridged complex [Fe2(C0)6(p-PPh~){ p-q :q'-('BuNC)HC=C=CH}], which undergoes facile 1,3-H migration to give [Fe2(C0)6(p-PPh2)(p-q1:q '-(tBuNC)C=C=CH3}] or hydrolysis to [Fe2(C0)6(p-PPh2){ p-q ':~2-('BuNHC(0)CH2)C=CH3tI.85The

'

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 359

phosphanioalkynyl complexes [(q -CgH7)(PPh3)2Ru(C=CC(R ')H(PR3))]' (R' = Ph, PR3 = PMe3; R' = H, PR3= PPh3) can be deprotonated by BuLi at -20 "C to afford the ylide alkynyl species [(q-C9H7)(PPh&Ru{C=CC(R')=PR3}]. These react with aldehydes and ketones in situ to give (qC9H7)(PPh3)2Ru(C&C(R')=CR2R3)] (R2R3= CH2(CH2)3CH2,R1= Ph, H; R2 = H, R3= Me, R' = Ph, H; R2= R3= R' = Ph). Protonation with HBF4 affords the vinylidene complexes [(q 'C9H7)(PPh3)2RU' (=C=C(H)C(R')=CR2R3)]+.Alternatively, reaction of the ylide alkynyl complexes with unsaturated aldehydes forms the o-polyenynyl complexes (qC9H7)(PPh3)2R~(C=CC(R1)=CH(CH=CH)nR2) (n = 1: R2 = Ph, R' = Ph, H; R2 = nPr, R' = Ph, H; n=2: R2 = Me, R' =Ph, H), which can be protonated with tetrafluoroboric acid to form the highly unsaturated vinylidene complexes

[(~-C~H~)(PP~~)~RU{=C=C(H)C(R~)=CH(CH=CH),R~}]+.~~ 2.2 The Cobalt Triad. - Density functional calculations have been useds7 to examine the activation of C-H bonds in propane and cyclopropane by (qCSHS)M(PH3) (M = Rh, Ir). These studies show that the rhodium complex is more selective than the iridium analogue and that the selectivity arises from the singlet-triplet energy gap of the 16-electron fragment and the o(C-H) + o*(C-H) triplet excitation energy of the hydrocarbon. The same technique has also been used to probe the reaction of Ir(PH3)2Clwith CX, (X=F, Cl, Br, I).88 Theoretical studies have elucidated8' that the very short C=C bond found in the X-ray crystal structure of (q-CSMeS)Ir(PMe3)(CH=CH2)Harises from disorder originating from the co-crystallisation of two or more isoenergetic conformations originating from rotation about the Ir-C" axis. An ab initio investigation" of the transformation of ethyne to vinylidene (HC-CH + :C=CH2) promoted by [ C O P ( C H ~ C H ~ P P ~has ~ ) ~found ] + that the alkynyl hydride product formed upon oxidative addition is a key intermediate on the reaction pathway. TRIR measurements in liquid Kr and liquid Xe have been used to probe'' the kinetics of reaction of (q-CSMe5)Rh(C0)2with linear and cyclic alkanes. Stronger Rh o-alkane interactions are observed with larger alkanes (cyclic RH binds more favourably than linear RH), but the rates of oxidative addition to form (q-CSMes)Rh(CO)R(H)are faster for smaller alkanes. Thermolysis of [(ttp)RhCH2CH2X](ttp = 5,10,15,20-tetratolylporphyrinate; X = Me, Ph) at 120 "C in C6D6 results in a reversible 1,2-alkyl rearrangement. The rate of the reaction and the position of the equilibrium is found to be dependent on the group X.92 The reaction of RhC13 with a series of 6substituted 2,2'-bipyridines HL(N2CloH7R) (R = CH2Ph, CMe2Ph, CMe2H, CMe3, CH2CMe3)in refluxing water/acetonitrile gave either cyclometallated species, neutral Rh(L)(CH3CN)C12 and/or [Rh(L)(CH3CN),Cl]'. In the case of R=CMe2Ph, activation of the methyl group occurs in preference to the phenyl g r o ~ p . 'A ~ new high yield route to RhC12(PPh3)2(C6Hs) has been de~cribed'~ using RhC12(SbPh3)2(C6Hs) (formed from RhC13 and SbPh3) and PPh3. The molecular structure of the rhodium phenyl complex shows two RhC1.e-H-C interactions, but gives no evidence for agostic Rh.. .H-C bonding.

360

Organometallic Chemistry

The presence of pyridine or 4-tert-butylpyridine in the reaction of [Rh(C8H14)2C1]2 with chlorinated solvents leads to formation of the oxidative addition products, rner-RhL3RC12 (L = py, 4-tBupy; R = CH2C1, CHC12, CH2Ph)." Upon heating [RhL2C1]2 (L = C2H4, CgH14) with { l-CF3-2,6(CH2PtBu2)2c6H3)at 160 "C, C-C bond cleavage of the aryl-CF3link occursg6 to give [Rh(CF3)(2,6-(CH2PtBu2)2-CsH3)C1]. Reaction of TpMe2Rh(C2H4)2 (TpMe2= tris(3,S-dimethylpyrazol-1-yl)hydroborate) with nitrogen donor ligands L, including CH3CN and pyridine, at room temperature gives the rhodium(II1) derivatives TpMe2Rh(C2H~)(CH=CH2)L as the kinetic prod u c t ~ .Thermolysis ~~ of TpMe2Rh(C2Hs)(CH=CH2)(NCCH3) at 60 "C in benzene produced TpMe2Rh(C2H5)(C6Hs)(NcCH3),via an intermediate q2arene complex, TpMe2Rh(CH2=CH2)(q2-C6H6).Thermolysis of a benzene solution of TpMe2Rh(C2H4)(PMe3) at 110 "C gave the C-H activation product TpMe2Rh(PMe3)(C6H5)H, while heating in the presence of thiophene gave products of C-H and C-S bond activation in a ratio of 85:15. Heating the iridium analogue, T P ~ " ~ I ~ ( Cin~ the H ~presence ) ~ , of thiopheneg8afforded the C-H activation product TpMe21r(2-SC6H3)2(SC6H4). In contrast, starting with the iridium(II1) dihydride complex TpMe21r(C2b)H2 gave the thiophenyl hydride complex, TpMe21rH(2-SC6H3)(sC4b),which readily loses the coordinated SC4H4 group in the presence of good donors such as PMe3 or acetonitrile. Ethene inserts into the Ir-H bond in DrHCl(PiPr3)(NCCH3),Ifto which has been usedg9to form the stable give [Ir(C2HS)Cl(PiPr3)(NCCH3)3]+, iridium(II1) ethyl complexes, [Ir(C2H~)Cl(PiPr3)(CSHSN>2(NCCH,)1' and

[Ir(q2-OCCH3)(C2H5)Cl(PPr3)(NCCH3)3]+. Cyclometallation of [Ir(dp~f)~]+ (dppf = 1,1'-bis(dipheny1phosphino)ferrocene) is observedlWin solution. Chiral ortho-lithiated amine derivatives, such as those from (R)- or (3-1-(dimethylamino)-1-phenylethane,react with [(qC5H5)CoI2I2 to form a mixture of the two diastereoisomers (Rc, &,)-la,(Rc, 27,-,)-lb and (Sc, &,)-2",(Sc, &,)-2b shown in 9.The isomers 1" and 2bare favoured with de of 90%. The reaction with PR3, in most cases, yields cationic

I+ 9

10

products with retention of the configuration.lo' Intramolecular C-H bond activation is observed upon reaction of o-Ph2PC6H&H20C(0)Et with [Rh(nbd)(PPh&]+ or vR(cod)C1]2 leading to cleavage on the benzylic C-H bond of the phosphine.lo2 The same behaviour is foundlo3 using 0Ph2PC6H4CH2N(Me)C(0)Et. In a related processLo4,the cationic iridium

12: Complexes ContainingMetal-Carbon o-Bon& of the Groups Iron, Cobalt andNicke1 361

complex [Ir(cod)(o-Ph2PC6H4CH20CH2C&14N-2)]+dissolves in CDC13 at room temperature to afford an equilibrium mixture of the starting material and the C-H activation product 10. Reaction of [RhIr(CH3)(CO)3(dppm)2]+ with PR2R' (R = R = Me; R = R'= OPh; R = Me, R' = Ph; R = OMe, R' = Ph) gave the iridium-phosphine bound species, [RhIr(CH3)(PR2R')(CO)(dppm)2]+, although an intermediate Rh bound phosphine complex could be observed at 80 "C. Addition of H- to [RhIr(CH3)(CO)3(dppm)2]+ gave the rhodium hydride complex, [RhIr(CH3)H(CO)3(dppm)z]+, which readily eliminates methane at room temperat~re."~ The dimer (dfe~e)~Ir&H)~H (dfepe = ( C ~ F ~ ) ~ P C H ~ C H ~ P ( reacts C~FS)~) with ethene (1 atm) to give trans- and cis-2-butenes and (dfepe)21r2(p-q3:q1C&)(p-H)H. '06 The reaction of (3,5-Me2-2,6-(CH2PtBu2)2C6H> with [Rh(~oe)~(solvent),]+ results in C-C bond activation in thf, but C-H bond activation in acetonitrile. This latter product can be converted to an analogue of the C-C cleavage product upon dissolving in thf.lo7 Thermolysis of [Rh(L)(2,6-(CHzPtBu2)2C6H3}cl] (L = Et, "Pr) yields [HRh(L)(2,6(CH2PtBu2)2C6H3}CI] and ethene or propene respectively via P-hydride elimination. 13C NMR labelling experiments demonstrate that this reaction is irreversible, while deuterium isotope experiments suggest'08 that it is also rate determining. Oxidative addition of Me1 to Rh(PNP)R (PNP = 2,6-bis(diphenylphosphanylmethy1)pyridine; R = Me, Ph) yields Rh(PNP)(Me)RI. Addition of T1BF4 to these rhodium(II1) complexes in acetone results in loss of MeR.'@ The reaction of TlBF4 with Rh(PNP)Me(Ph)I in CH$N/thf gives the stable cationic alkyl aryl species [Rh(PNP)Me(Ph)(CH3CN)]+,which has been characterised by X-ray crystallography. Hydrogenolysis of iridum alkyl groups has been observed' lo upon treatment of [(q-CsMe5)IR(PMe3)(H20)(CRF)]+ (RF=(CF3)2F, CF3, CF2CF3) with one atmosphere of hydrogen at room temperature. Protonation of (q-CSMe5)IrMe4with HCl or HOTF in low temperature dichloromethane solution yields (q-CSMe5)IrMe3C1and (q-CSMeS)IrMe30Tf respectively. Addition of ER3 (E=P, As, Sb; R=Me, Et, Ph) gives the substitution products [(q-CsMe5)Ir(ER3)Me3]+. The PMe3 complex, [(qC5Me5)Ir(ER3)Me3]+, reacts with excess phosphine over two days at room temperature to give [(PMe3)41rMe2]+upon elimination of Me(CSMe5). Lithium iridate, [(q-C5Me5)Ir(PMe3)(H)Li],reacts with 3,3-dimethylbutanetriflate-1,2-syn-d2 followed by chlorination to give [(q-C5Mes)Ir(PMe3)(CHDCHDCMe3)C1-anti-d2]. l2 The predominant inversion of configuration at carbon unambiguously demonstrates that the reaction occurs via an SN2mechanism. The iridate complex has been observed to react with CX bonds in C6F6, CH2=CH(CF3) and CF2=CF(CF3) to give [Ir](C6F5)H, [Ir](CH2CH=CF2)H and [Ir](CF=CF(CF3))H respectively ([Ir] = [(qCSMe5)Ir(PMe3)).The observations' that (i) Tp'RhL(CH3)D (Tp' = hydridotris(3,5-dimethylpyrazolyl)borate,L = CNCH2CMe3) yields Tp'RhL(CH2D)H prior to loss of CH3D, (ii) Tp'RhL(CD3)H gives Tp'Rh(CD2H)D prior to loss of CD3H and (iii) the rate of reductive elimination of CH4 from Tp'RhL(CH3)H in C6HdC6H5F is dependent on [C&] provide indirect

'''

'

'

362

Organometallic Chemistry

evidence for a o-alkane complex along the reaction pathway to alkane loss. The 16-electron fragment Tp'Rh(CNCH2CMe3) reacts with H2C=C(H)R (R = H, Me) to form Tp'Rh(CNCH2CMe3)(CH=CH2)H and Tp'Rh(CNCH2CMe3)(CH2CH=CH2)Hrespectively. Both compounds readily form q2-alkene complexes. However, neither Tp'Rh(CNCH2CMe3)(CH2CMe=CH2)H nor Tp'Rh(CNCH2CMe3)(CH=C(H)Me)Hrearranges to alkene complexes, but they both reductively eliminate alkene in the presence of ben~ene."~Thus, competition experiments of this kind have allowed the kinetic and thermodynamic selectivity of the metal fragment for different types of C-H bonds to be established. The iridabenzene complex 11 is formed by direct reaction of a 3-vinyl-lcyclopropane with Vaska's complex. The synthesis, characterisation and reactivity of the related iridathiabenzene complex 12 has also been reported. l6 The reaction of (R'c=CR2)Co2(C0)6 with equimolar amounts of the alkynes R3C=CR4 provides a general route' l 7 to binuclear cobaltacyclopentadienes. Electrochemical reduction of the cobaltafluorene complex (qX5H5)(PPh3)CoC1& yields the cobalt(I1) mono-anion 13 via loss of phosphine. Further reduction gives the dianion, which is stable in solution and can be characterised by 'H NMR spectroscopy.' l8 A range of trimetallic cyclopropenium cations have been prepared' including [ { (q-CsHs)(CO),M}3(p3-C3)]+ (M = Fe, Ru), although they have, perhaps surprisingly, proved to be remarkably unreactive. The first example of two-step amidation of coordinated ethene has been reported12' with the formation of 14 upon treatment of [tpaRh(C2H4)]' (tpa = N'N'N-tri(2-pyridylmethy1)amine) with H202 and H+/ CH3CN.

''

'

'',

o"'...

khrp::Pph3

,r'.

Wmy,, G

,

IP r 3j P 4 +

'co

Ph

11

PEb 12

2+

15

16

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 363

The dimeric hydride complex [(q-C5Me5)IrH3I2yields C-S and C-H activation products with N and S heterocycles in the presence of tert-butylethene as a hydrogen acceptor. Thus, reaction with 2-methylthiophene affords 15. With N-methylpyrrole, a dinuclear product arising from C-H activation a to nitrogen is formed, along with the zwitterionic product 16 containing an Ir-Ir triple bond. 12' Diphenyl vinylcyclopropene reacts'22with Rh(PMe3)3Clto give two isomeric q 3;q - 1,3-pentadienediyl complexes. Hydrogen peroxide oxidation of [(Metacn)Rh(cod)]+ (Metacn = K ~ 1,4,7-trimethyl-l,4,'7-triazacyclononane) affords [(9-oxabicyclo[4.2.l]nona-2,5-diyl)(Metacn)Rh]+. The related species, [(9-oxabicyclo[4.2.l]nona-2,5-diyl)-{rc3-fac-N,N-di(2-pyridylmethylamine)rhodium]+ converts both in solution and the solid state to the hydroxycyclooctadienyl complex, [1,4,5,6-q4-(2-hydroxycycloocta-4-enel,&diyl){ ~c~-fac-N, N-di(2-pyridylmethylamine)rhodium]+.123 Addition of aqueous HC1 results in intrato [Ir(CH3)(CH=CHNEt3)(CrCC6H4-p-Me)(CO)(PPh3)2]+ moleular coupling of the methyl and alkynyl groups to produce [Ir { C(CH3) =CH(C6H4-p-Me) }(CH=CHNEt3)C1(CO)(PPh3)2]f.24 This reacts further to form [Ir(CH=CHNEt3)Cl2(Co)(PPh,),1+ and cis-CH3CH=CH(C6H4-p-Me). The alkenyl phosphonium species [Rh(acac)(q2-(E)-CH(PCy3) =CHR) PCy3]+ is formed upon refluxing [Rh(acac){(E)-CH=CHR)(PCy3)2]+ (R= C6H11, C6H5,H) in di~hloromethane.'~~ Addition of MeOTf to [Ir2(C0)3(dppm)2] affords [Ir2H(C0)3(pCH2)(dppm)2], which shows'26 H/p-CH2 scrambling at room temperature. Removal of one CO group gives [Ir2Me(C0)2(dppm)2],in which the methyl readily transfers between the two metal centres. Addition of CO, PR3, CNtBu or SO2 results in C-H cleavage to give [Ir2H(CO)2L(pCH2)(dppm)2]+(L = CO, PR3, CN'BU) or [Ir2H(CO)2(p-CH2)(p-S02)(dppm)2]+. The novel mixedvalence Rh(0)-Rh(I1) complex 17 has been prepared.'21 Phenylacetylene under-

'

17 L = (Cog,PiPr3

goes oxidative addition to [Ir2(p 1,8-(NH)2naphth)H(CO)2(PiPr3)2]+ to give [Ir2(p-1,8-(NH)2naphth)(p-CrCPh)H2(CO)2(PiPr3)2]+ as the kinetic product. This isomerises in acetone solution to [Ir2(p-1,8-(NH)2naphth)(pH)H(C(CPh>(CO),(PiPr,),1+. In comparison, the diiridium species [Ir2(p-1,8(NH)2naphth)(OTf),(C0)2(PPr&]+ reacts with PhCECH in CH2C12 to give 12, which isomerises on [Ir2(p-l,8-(NH)2naphth)H(CrCPh)(C0)2(PiPr3)2][OTf heating to [Ir2(~-1,8-(NH)2naphth)(p-C=CHPh)(OTf)2(C0)2(PiPr3)2].'28 If the reaction with PhCrCH is performed in acetone, then [Ir2(p-1,8-

364

Organometallic Chemistry

(NH)2naphth)(C=CPh)(C0)2(PiPr3)2]+ is formed, which reacts with excess alkyne to give [Ir2(p-1,8-(NH)2naphth)(C(CPh)2(C0)2(P'Pr3)2]. Protonation of [RhIr(C0)2(p2-q':q2-CrCPh)(dppm)2]+w]- (X = BF4, 0Tf)with HBF4 or HOTf provides a route'29 to [RhIr(X)(CO)&-H)(pC=CPh)(dppm)2]+, which under CO forms the vinylidene bridged species [RhIr(CO)4(p-CCHPh)(dppm)2]2+. The allyl vinylidene complex [RhIr(Y)(CO)(p-CO)(p-CC(Ph)CH2CH=CH2)(dppm)2]+w]is formed upon reaction of [RhIr(X)(C0)2(p-H)(p-C-CPh)(dppm)2]+ with CH2=CHCH2Y (Y = Cl, Br). NMR studies from - 80 "C to - 50 "C show that the oxidative addition intermediate [RhIr(C0)2(p-Y)(q -CH2CH=CH2)(p-C=CPh)( d ~ p m ) ~ can ] + be detected on the way to the allyl vinylidene. The dinuclear reacts with propyne and iridium alkyl complex [Ir2(CH3)(CO)(p-CO)(dppm)2]+ phenylacetylene at low temperature to give [Ir2H(CH3)(C0)2(pC2R)(dppm)2]+,which rearrange below room temperature to the vinylidene bridged species [Ir2(CH3)(CO)2(p-C=CHR)(dppm)2]f. At room temperature, elimination of CH4 occurs to give [Ir2(CO)2(p-C=CR)(dppm)2]+.The starting alkyl complex reacts with HC-CH at low temperature to give analogous low temperature products, but warming of the vinylidene species in the presence of CO leads to vinylidene hydrogedmethyl exchange to form [Ir2(H)(C0)3(pC=CHCH3)(dppm)2]+. The vinyl carbene complexes 18 are formed if

P-P 18

[Ir2(CH3)(CO)2(dppm)2]+is treated with RCrCR' (R = R' = Me, Et, "Pr; R = Me, R' = Et; R = Me, R' = Ph), via double C-H bond activation of the CH3

Addition of Bu4NF.xH20 or KF to ~~~~S-[(P'P~,>~R~(OT~)(=C=CH (R = Ph, tBu) gives ~~~~S-[(P'P~~)~R~F(=C=CHR)I. Reaction of this with HOTf reforms the starting material, while the reaction with PhCICH gives ~~~~S-[(P'P~~)~R~(C=CP~)(=C=CHR)].'~~ The solvent complex cis-[(P'Pr&_ Rh(a~etone)~]+ reacts with HCECR (R = C6H4-p-Me, C(OH)Ph2) to form (PiPr3)2Rh(acetone)(=C=CHR).For this complex with R = C(OH)Ph2, elimination of water occurs at ambient temperature to give the cationic [(P'Pr3)2Rh(acetone)(=C =C=CPh2)]'. Neutral allenylidene complex complexes are formed upon reaction of this with NaOAc or I c O H . ' ~ ~ The iridium allenylidene complex (P'Pr3)21r(OH)(=C=C=CPh2) reacts with excess RC-CH (R = Ph, C02Me) to form trans-(PiPr3)21r(C=CR)2{ CH=CRCH=C=CPh2).133

(a-

12: Complexes Containing Metal-Curbon o-Bonds of the Groups Iron, Cobalt and Nickel 365

2.3 The Nickel Triad. - Density functional (DF) calculations have been used to probe the polymerisation of ethene and propene by Pd(I1) diimine complexes (N-N)PdR2 (modelled using N-N = -NHCHCHNH-). Individual steps are discussed in including the pathways for 2,l- and 1,2-insertionsfor propene as well as the strength of P-agostic interactions. DF theory has been used to probe the energetics and mechanism of imine insertion into Pd-Me and PdCOMe bonds to probe the possibility of performing imine/CO co-polymerisation. Insertion into the latter is over 80 kJ mol-' lower in energy.135 A theoretical study of the reaction mechanism of platinum catalysed hydrosilylation of ethene has been reported.136 Theoretical studies'37 show that C-C reductive elimination from (PH3)2Pd(q3-C3HS)(CH3) is highly exothermic (1 14 kJ mol- '), but that there is a large activation barrier for the process (96 kJ mol-'). Theoretical studies have been used to explain the very short C=C bond found in the solid state structure of [(PPh3),Pt(CMe=C(H)Me)]+(see Section 2.2 for a related Ir case).89 High-pressure NMR studies have been used to probe the kinetics of reductive elimination of methane from cis- and tran~-[Pt(BPMA)(cH3)~Hl+ (BPMA = bis(pyridylmethy1)amine). Measurements of activation parameters together with deuterium isotope incorporation studies point to the involvement of a five-coordinate platinum species as a steady-state intermediate. 38 Spectroscopic observations at low temperature of the chain growth steps in the polymerisation of ethene by [(cc-diimine)NiMe(solvent)]+[BAr'4]- (Ar' = 3 3 C ~ H ~ ( C F ~indicate'39 )Z) that the barriers to insertion for Ni are 16-20 kJ mol-' less than for the Pd analogue. This translates to higher turnover frequencies of 103-104 h- at room temperature. I9F NMR magnetisation transfer experiments have revealed14' that interconversion of the syn and anti rotational isomers of cis-Pd(2-C6BrF4)2(tht)2 (tht = tetrahydrothiophene) occurs by two competitive pathways, namely (i) aryl group rotation in the four-coordinate starting complex and (ii) aryl group rotation in a threecoordinate complex resulting from dissociation of a tht ligand. Thermolysis of the platinum(1V) complex (dppe)PtMe30Ac in non-polar solvents (benzene, thf) gives (dppe)PtMe2 and MeOAc as a result of C - 0 reductive elimination. In competition with this is C-C reductive elimination, which yields (dppe)PtMe(OAc) and C2H6. This latter process dominates in more polar solvent^.'^' Mechanistic evidence points to the importance of fivecoordinate [(dppe)PtMe3]+ as a common intermediate in both processes. Kinetic measurements on the reaction of [Ni(triphos)Me]+ with anhydrous HCl in acetontrile that CH4 loss only occurs after two protonation steps: formation of [HNi(triphos)Me]+,followed by direct protonation of the methyl group. The rates of CO insertion into a Pd-Me bond have been studied for (P-N)Pd(CH3)X (P-N = R2P-o-C6H4CH2NMe2,M ~ ~ N - o - C ~ H ~ C H ~ P R ~ ; R = C6H5, C6HI1;X = C1, OTf) and found to be fastest with the most basic p h ~ s p h i n e s . 'A ~ ~series of cis-(PR3)2PtMe2 (R = Me, Et, 'Pr, pyrrole, cyclohexyl) complexes have been probed'@ using solution calorimetry and it is observed that the larger the cone angle of the phosphine, the lower the thermodynamic stability of the complex.

'

'

366

Organometallic Chemistry

Treatment of tran~-NiF(2-c~F~N)(PEt~)~ with PhLi and ZnMe yields transNiR(2-C5F4N)(PEt3)2] (R = Ph, Me) respectively.145 The dimeric arene complex, [(d'bpe)Ni]2(p-q2:q2-C6H6),is formed upon thermolysis of (dtbpe)NiMe2 in benzene. Protonation of the dimethyl complex with triflic acid affords (d'bpe)NiMe(OTf), which reacts slowly with two equivalents of ethene to form [(d'bpe)NiEt]+[OTf]- and propene in equal amounts.146 Upon refluxing a benzene solution of trans-[(PPh3)2PtMe(OEt2)]+[BAr] - , anion decompostion takes place to yield 19. The reaction is highly dependent on the

weakly bound ligand: [(PPh&PtMe(MeOH)]+ and [(PPh3)2PtMe(MeCN)]fdo not give analogous reactions. Similarly replacing PPh3 by either PEt, or PiPr3 shuts down this most unusual reaction.147 Protonation of (tacn)PtMe2 (tacn = 1,4,7-triazacyclononane)with triflic acid affords [(tacn)Pt (Me)2H]+,which is stable up to ca. 200 "C in the solid state.14* Both starting material and product can be oxidised with peroxide to give [(tacn)Pt(Me)zOH]', which is readily protonated to give [(tacn)Pt(Me)2(H20)]2'. Reaction of TpPtMe(C0) with water yields the unexpected hydride complex, TpPtMeH,, which has been characterised by multinuclear NMR spectroscopy and elemental analysis. The proposed'49 mechanism of formation involves nucleophilic attack by water on the coordinated CO, release of C02 followed by protonation at the Pt centre. The X-ray crystal structure of (cod)Pt(OH)Me has been reported15* and the reaction of this compound with acidic C-H bonds described. For example, reaction with 1,3butadiyne gives [(cod)PtMeJ2(p-CrC-C-C) and (cod)PtMe(C-C-C-CH). The tetramethylplatinum(1V) complexes (LL)PtMe4 (LL = 4,4-di-tert-butyl2,2'-bipyridyl { buzbpy}, tmeda, bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene (Ar2NN}) react with fac-(L'L')PtMeOTf (L'L' = LL) to afford an equilibrium mixture containing the starting species, fac-(LL)PtMeOTf and (L'L)PtMe4. The proposed mechanism of the rea~tion'~' involves initial loss of triflate from fac-(L'L)PtMeOTf and attack of the resulting electrophilic platinum cation on one of the trans-methyl ligands in (LL)PtMe4. Elemental sulfur reacts with (dcpe)PtH(R) (R=Me, C H ~ ~ BPh) U , to give the sulfhydryl complexes, (dcpe)Pt(SH)R. These are stable to reductive elimination of alkylor arylthiols up to 130"C.152Sulfur dioxide reacts with (dcpe)PtMe2 to form (dcpe)Pt(S02Me)Me, which eliminates both CH4 and methylsulfinic acid upon treatment with concentrated HCl. Addition of Mg{ CH(SiMe&} C1 to (cod)PdC12 in the presence of PMe3 gives the dimer [Pd{CH(SiMe&}(pCl)(PMe3)]2,which is t r a n ~ f o r m e d in ' ~ ~the presence of additional PMe3 to a mixture of cis- and trans-Pd{CH(SiMe3)2)Cl(PMe3)2. The reaction of excess N2CH2SiMe3with (diop)Pt(CH,)Cl (diop = (4R,SR)-4,5-bis(diphenylphosphi-

12: Complexes Containing Metal-Carbon cr-Bonds of the Groups Iron, Cobalt and Nickel 367

nomethyl)-2,2-dimethyl-1,3-dioxolane) produces (diop)Pt(CH2SiMe3)C1, whereas addition to (skewphos)Pt(CH3)Cl (skewphos = (2S,4$)-2,4-bis(dipheny1phosphino)pentane)yields (skewphos)Pt(CH2CH2SiMe3)C1. 154 The cationic diimine complex 20 cleaves both aromatic and aliphatic C-H bonds at room temperature in trifluoroacetic acid solution.155 [LiCH2N(Me)]2CH2 reacts with (PMe3)2NiC12 to give the solvent-free dinickelate mi( { CH2N(Me))2CH2)Li2]2in 84% yield. The X-ray crystal structure shows'56 that the four lithium atoms 'glue' together the two dianionic nickelate species. The diplatinum compounds trans- and cis-l,2[C6H10{N=CH-2-C5H4N(PtMe2))2] undergo substitution with [H]+[HOB(C6F&]- in CH3CN or with HBF4 in the presence of CO to give trans- and cis-1,2-[C6Hlo{N=CH-2-C5H4H(PtMeL)}2]fi]2.157 Oxidative addition of 8-(bromomethyl)quinoline to diorganometal Pd(I1) and Pt(I1) complexes yields M(1V) species including 21, which is the first structurally characterised example of an aryl Pd(1V) complex.lS8

I+

20

21

Catalytic dimerisation of ethene by (dfepe)MMe(02CCF3) (M = Pd, Pt) occurs in trifluoroacetic acid at 80 "C to give 2-(trifluoroacetato)butane as the only organic product.' 59 Ring-opening polymerisation of heterocycles has been observed'60 using [bpyPd(CH3)L]' (L =p-MeC6H4C(H)=NR, R = Ph, Me, 'Bu; L=CH3CN). Thus reaction in thf under a CO atmosphere at 70°C affords the ring-opened polymer of thf; dioxolanes and lactones undergo similar chemistry. The cationic hemi-labile system [(P-N)Pd(CH3)CH3CN]+ (P-N = o-(dipheny1phosphino)-N-benzaldimine)reacts with CO to give [(P-N)Pd(C(0)CH3)CH3CN]+, which inserts ethene, substituted alkenes and alkynes. The isolation'62 and X-ray characterisation of (dppp)Pd(C6F5)(PPh2.BH3)has been achieved; such a species has been postulated to be important on the pathway of palladium catalysed coupling of secondary phosphines and boranes. The nature of the bisphosphine P2, the counterion X and the solvent have all been shown to influence the regioselectivity of addition of R'PdP2X to CH2=CHMe and CH2=CHPh. For example, for P2 = dppe, X = OTf and a solvent mixture of 9:l CH2C12/DMF, there is 98% selectivity for addition of R' to the P-carbon of styrene. Stoichiometric experiments at low temperature have allowed NMR detection'63 of two intermediate species, [p2PdCH(Ph)CH2Ph]' and [P2PdCH(Ph)CH$. Nickel tetracarbonyl reacts with carbodiphosphorane Ph3P=C=PPh3 to form (C0)3NiC(PPh3)2 and (C0)2NiC(PPh3)2, both of which have been

368

Organometallic Chemistry

structurally characterised. Density functional theory yields a Ni-C(PH3)2 bond strength of 139 kJ mol-’ for the model system (C0)2NiC(PH3)2. The coordination of Mn(C0)3f to benzofuran leads to activation of the C-0 bond to insertion by Pt(PPh&. 165 [(q6-biphenylene)Mn(CO)3]+ reacts with (PPh3)2Pt(C2H4)to give 22 resulting from Pt insertion into a C-C bond? [4+ I] cycloaddition of [(PM~~)~N~(T~~-P~C(NM~S)N=C(CF~)~)] is observed upon low temperature addition of two equivalents of t B ~ N Cwhich gives 23.

Ph’ 22

23

The reaction is analogous to a Diels-Alder reaction and is unprecedented for Ni(0) c~rnplexes.’~~ The first example of a Pt(1V) octahedral liquid crystalline species has been observed16* as a result of the oxidative addition of Me1 to (L)Pt(acac) (L = 4,4’-bis(a1koxyazobenzene)). Further work has been reported on the catalytic hydrophosphination of acrylonitrile. Pt(P-P)(CH2CHCN) (P-P = dppe, dcpe) acts as a catalytic precursor for this process. Reaction with P-H bonds yields Pt(P-P)(PRR’)H, which inserts acrylonitrile to afford Pt (P-P)(CH(CN)CHZPRR’)H, and then subsequently reductively eliminates to reform the precursor species. 69 Pt(bu2bpy)Me2 reacts with (R2SnE)3 (R=Me, Ph; E=Se, Te) to make P t ( b ~ ~ b p y ) M e ~ ( R ~ SThe n E )tin ~ . compounds undergo exchange of R2Sn or E groups with (R2’SnE)3 and (R2SnE’)3 respectively to produce Pt(bu2bpy)Me2(R2SnE-RiSnE) and Pt(bu2bpy)Me2(R2SnE-R2SnE). 170 Photolysis of (2,9-Me2-phen)Pt(alkene)X2 (alkene = C2H4, CH2=CHMe, CH,=CHEt; X=C1, Br) in the presence of C12 or Br2 affords of @,%Me2phen)PtX3(CH2CHRX). The mechanism of f~rmation’~’ is proposed to involve attack of an X radical on the coordinated alkene by cross oxidation that also involves the metal centre. Addition of (acac)AuPPh3 to [Pd(pC1)(C6H4-2-PPh2C(H)COCH2PPh3)122’ (ratio 1:2) yields [Pd(C6H4-2PPh2C(H)COCH2PPh3)(acac-0,0‘)]+ by transmetallation of the acac group.172 Further addition of the gold reagent results in formation of [Pd(C&-2PPh2C(H)COCH(AuPPh3)(PPh3))(acac-O,O’)], in which the orthometallated ylide fragment acts as a C,C,C-tridentate ligand. The redox chemistry of [(T~-C~H~)F~(C~H~CH=CH-~~-M(P (th = 2,5-substituted thiophene; M = Pd, X = Br, I; M = Pt, X = Br) has been shown’73 to depend on the substituents on the thiophene spacer unit. These compounds have also been studied by UV-visible spectroscopy. Imidoyl complexes of palladium have been found174to behave in solution as an equilibrium mixture of isomers in the form of imines ([Pd(C(=NR’)-

’

12: Complexes ContainingMetal-Carbon 0-Bonds of the Groups Iron, Cobalt and Nickel 369

CH2C6H4Y} (X)(PR3)2]and enamines ([Pd(C{ NHR')=CHC6H4Y}(X)(PR3)2]. Electron acceptor groups at Y favour the latter form. Pyridylphenyl isocyanides and pyridylethynyl isocyanides have been used to prepare assemblies of Pd and Pt complexe~.'~~ Thus, tran~-MI~(C"~H~-(%r)~-2,6-(C~H~N-4)-4)~ (M=Pd, Pt) react with Pd(dppp)(OTf), to form the molecular squares, [Pd(dppp)(trans-[MI2(CNC6H2-(iPr)2-2,6-(c5~N-4)-4)2]4(OTf)8.

The phospha-palladacycle 24 has been shown'76 to be an effective catalyst for the Heck coupling of aryl bromides and chlorides with styrene in ionic liquids. Similarly, 25 and related Pd(I1) cyclometallated imine catalysts have proved to be effective for both Heck and Suzuki coupling in conventional organic solvents.1773178 The reaction of 1,3-di(2-pyridyl)benzene with K2PtC1, results in cycloplatination at C-2 of the benzene ring. In contrast, reaction with Pd(OAc)2 yields the dimeric dipalladated complex 26. 179 The cyclometallated complex 27 reacts with stoichiometric amounts of HX (X=Cl, OAc, OTf) to give tran~-Pd(CH2CMe2Ph)X(PMe&],which itself reacts with 2 equivalents of triflic acid to yield the x,q'-coordinated Ic-arene corn lex 28.'80 Three membered phosphapalladacycles Mes*(Me) @ - & CH(3 R Ar) dC1 have been

1

Me

2

25

prepared18' upon reaction of (cod)Pd(CH3)Cl with 1-[(E)-Mes*P=C(H)]-3-Rbenzene (Mes* = 2,4,6-tri-tert-butylphenyl;R = 2-pyridyl, N-phenylcarbaldimino).

Organometallic Chemistry

370

Treatment of (PhCN)2PdC12with equimolar [py(SCH2C(O)R)-2] (R = Ph, Me, OMe) gives the cyclometallated species [ m H C ( O ) R ) - 2 }(pC1)2Pd(py(SCH2C(0)R)-2)Cl]. Two equivalents of ligand produces trans[PdC12(py(SCH2C(0)R)}2], which can be subse uently reacted with base to give the doubly cyclometallated species cis- Pd(py(S HC(OR)-2}2)].182 The palladalactone complex (PMe3)2Pd(OCOCH2 =CH2) is formed'83 in the reaction of (PMe3)2Pd(q2-CH2=CHPh)and diketene. It reacts with Me1 to afford trans-(PMe3)2Pd(I)(C(=CH2)CH2C(0)OMe). The three palladacycles, (bpy)Pd(C6H4NH2-2)I,tran~-(PR3)~Pd(C6H4NH2-2)1 (R = Ph, p-tolyl, Me, Cy) and trans-(PPh&Pd(C6H4(N=CHPh)-2}1 all insert C0.'84 A range of binuclear doubly cyclometallated Pt(I1) and Pt(1V) complexes have been prepared. 85 Their structures and reactivities towards phosphines have been investigated by NMR, EPR, cyclic voltammetry and WNISINIR absorption spectroscopy. Oxidative addition of diiodomethane at Pt(I1) has been observed'86 with the formation of the triply bridged Pt(1V) complex, di-p-iododiiodo-p-methylene-bis[3,4,5-tris(methoxy)2-([(4-hexylphenyl)imino]methyl}phenyl-C,N]diplatinum. Structural and dynamic NMR spectroscopy has been used to inve~tigate'~~ the influence of counterion X on the activity of [(bpy)Pd(q' ,q2C8H120Me)]'[X] - to copolymerise styrene and CO. Phenylacetylene inserts into both the Pt-Si and Pt-Sn in cis-L2Pt(SiR3)(SnMe3) (L = PMe2Ph; SiR3 = SiMe3, SiMezPh, SiMePh2, SiPh3), although the ratio of products is highly dependent on the silyl group.'88 For the SiMe3 derivative, only insertion into the Pt-Si bond is seen, even at -70 "C. For SiR3 = SiMe2Ph,a 2: 1 ratio of products from insertion into Pt-Si and Pt-Sn is observed at -5 "C, but this all converts to the former at room temperature. Terminal alkynes HC-CR (R = Ph, p-Me2NC6H4, p-N02C&, n-CgH19) react with Pd(dppm)C12 under conditions of reflux to give the alkenyl phosphphorus ylide compounds 29 resulting from alkyne insertion into a Pd-P

+-

'

bond. 18' A mixture of the q I-propargyl and -allenyl complexes, trans[(PPh3)2Pt( -CH2C=CPh)CNRlf and trans-[(PPh&Pt( q -CPh=C=CH2)CNR]+, are formed in a ratio of 6:l upon reaction of [(PPh3)2Pt(q3CH2CCPh)]'[X]- (X = OTf, BF4, PF6) with RNC (R = CMe3, CH2Ph).lg0In solution, trans-[(PPh&Pt(q '-CH2C=CPh)CNCMe3]+ rearranges to the indenyl complex, tr~ns-[(PPh3)~Pt(q1H-inden-2-yl)CNCMe3]', which can be isolated in the case of the triflate salt. The reaction of trans(PPh3)2(CO)Ir(C=CPh) with HC=CPh and H2 gives cis,~is-[Ir(H)(C-CPh)~(CO)(PPh3)2] and cis,cis-[IrH2(C=CPh)(CO)(PPh3)21 initially. These then

'

'

'-

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 371

isomerise to tran~,trans-[IrH(CrCPh)~(CO)(PPh~)2]and cis,trans[IrH2(C=CPh)(CO)(PPh3)2].19' The 16-electron nickel ethene complexes, Ni(PR3)2(C2H4)(R=Me, Et, Pr, Bu, Ph) and Ni(dcpe)(CzH4), react with ClCrCCl to produce NiP2(C=CCl)Cl, [NiP2(C-CPR3)Cl]+ or NiPC12(C6Cl4PR3) depending on R and the reaction conditions.192 The bis(phosphinoalkynyl) complexes, [NiP2(C&PR3)2][SbF6]2, have subsequently been synthesised. The indenyl complexes (1-Me-C9H6)(PR3)NiC~CPh(R = C6H5, C6H11) have been shown to be effective catalyst precursors for polymerisation of PhC(CH upon addition of MAO. The reaction is to involve a species like (1-Me-C9H6)(PR3)Ni(p-R)(p-Me)AlX2 as an intermediate. The dinuclear and trinuclear complexes, cis-[Pt(C6F5)(p-l~C":q~-c=CR)2M(cod)]- and cis-[{ Pt(C6F5)2(p-l~C":rl~-C~CR)~) {Rh2(p-Cl)(cod)2}]-, are produced'94 upon reaction of CiS-[Pf(C6F5)2(C-cR)2]2- (R = SiMe3,'Bu) with [M(c0d)C1]~(M = Rh, Ir) or [Rh(cod)(~olvent)~]+. In related chemistry, trans[(PPhzH)zPt(C&)( C-CR)] (R = Ph, 'Bu) or cis-[(PPh2H)2Pt(C=CR)2] react with [Rh(acac)L2] (L = cod, CO) in acetone to give the alkynyl/diphenylphosphido-bridged species, trans,cis-[(C6F~)(PPh2H)Pt(p-~C~:rl~-C~CR)(pPPh2)RhL2] and C~~,C~~-[(C~CR)(PP~H)P~(~-KC":~~~-C-CR)(~ The mixed alkynyl/phosphinites [{ (PPh20)2H1Pt(p - ~ c "q: 2-C=CR)(p - ~ P , ( o PPh20)ML2] (ML2 = Rh(cod), Rh(C0)2, Ir(cod)) have also been reported.Ig5 An equimolar mixture of trans,cis-[(PPh3)2(C6F5)Pt (p-1KC":~KN-C(C-C~H~N2)Pt(H)(PPh3)2]+and the tetranuclear alkynyl cluster [(cis-Pt(C6F5)2(PPh3)()131K C ~ : ~ K C ~ : ~ K N - C ~{ PC~~~H(~CN~-F~~) ) ~ ( ~ ~ - ~ K C ~ ; ~ ~ " , P : ~ ( N 2)(PPh3)2}] is formed upon rearrangement of trans,cis-[(PPh3)2(H)Pt(p1Kca:q20,,p:2KN-C~c-c5H4N-2)Pt(c6F5)2] in solution.'96 Addition of a three-fold excess of PPh2H to Li2[Pt(C=CtBu)4] gives trans[P~(C=C'BU)~(PP~~H)~] and a low yield of [Pt(C=C'Bu)2 -x(PPh20)2+xLi2Sn]2 (x = 0, S, = (H2O)3; x = 1, S, = (H20)2). If Li2[Pt(C(CPh)4] is used as the starting material, analogues of the two compounds above are formed along 197 The C12 complex, trans,trans-(pwith [Pt(C=CPh)2(PPh2CHPhCH2PPh2)]. tol)(P(p-tol)3)2Pf(C~c)6Pt(P(tol)3)2(p'tol)has been prepared'98 using (P@t~l)~)~Pt(p-tol)Cl and HC~CC~CH/cat.CuI/HC~CSiEt~/O~/cat.CuCl/tmeda followed by wet "Bu4NF and a Hay coupling step (02/cat.CuCl/tmeda) in 83% yield. The Pt-Pt distance is 17.856 A (X-ray crystallography). Large platinum alkynyl dendrimers of up to 45 Pt atoms have been re~0rted.l~' 3

Carbene and Carbyne Complexes of Group 8,9 and 10

MP2 ab initio calculations have been used2*' to study differences in the geometries of L2(CO)(X)C10s=CHR (L = PPr3; X = H, C1; R = SiMe3, Ph) by calculations on the model system (PH3)2(CO)XC10s=CH2. These studies reveal that the 16-electron species that would result from carbene insertion into 0s-H is more thermodynamically stable than the 18-electron precursor complex, but that there is a high kinetic barrier that exists for site exhange in

372

OrganometaIlic Chemistry

d6 hexacoordinate complexes. Density functional theory has been used to investigate the tautomeric alkylidyne and bisalkylidene species (CH3)2M(=CH)Xand CH3M(=CH2)2X(M = Ru, 0s; X = Cl, CH3, CF3, SiH3, SiF3).201The bis-alkylidene form is found to be the more stable of the two no matter what the substituents. There has been a range of papers produced reporting new N-heterocyclic carbene (NHC) complexes of the late transition metals. The bidentate carbene complex of palladium(I1) 30 has been prepared202and characterised by X-ray crystallography. A range of cationic nickel(I1) complexes incorporating NHC ligands have been synthesised203,including 31. Stable zero-valent nickel, as

CHR

'But

30

But' 31

32

well as palladium and platinum, NHC complexes have been prepared using the metal vapour synthesis technique.2wHomoleptic and heteroleptic NHC complexes of Pd and Pt have been prepared and characterised by X-ray crystal10graphy.~'~ The Pd(0) NHC alkene complexes Pd(tmiy)z(alkene) (tmiy = 1,3,4,5-tetramethylimidazol-2-ylidene; a1kene = tetracyan oethene, maleic anhydride) react with aryl halides to afford Pd(I1) species such as Pd(HNC)2(C6H5)I and Pd(NHC)2(C6H4-p-N02)I. The latter reacts with nbutylacrylate through halide abstraction to give (E)-4-nitrocinnamate in a Heck coupling reaction.206EthenelCO co-polymerisation is cata1ysed2O7by cis[CH2{fi(H>C=C(H)N(R)&Pd(HCCH3)2l2+ (R = Me, 2,4,6-C6H2) at low pressures to give strictly alternating poly(C2H4-alt-CO). The palladium(I1) complex trans- { 1,3-di(1'-(R)-phenylethylimidazolin-2-ylidene)(triphenylphosphine)palladium}diiodide proves to be an effective catalyst precursor for Suzuki and Stille couplings.208 Addition of two equivalents of silver trifluoroacetate to (PCy3)2C12Ru(=CHPh) gives [RU~(=CHP~)~(CF~C~~)~(~-CF~CO~)~(PC~~ which catalyses the metathesis of internal alkenes. The preparation of 32 represents the first attempt210to prepare cis-phosphine Grubbs-like metathesis catalysts. Although this system shows only moderate catalytic activity, addition of Me3SiOTf yields the dinuclear species [(dtbpm)(p-Cl)R~=CHR]2~+ (dtbpm = tBu2PCH2PtBu2,R = CH=CMe2, CHMe2) which are the most active homogeneous Ru(I1) ROMP catalysts described so far.21* 1,6-Heptadiyne and HC-CR' (R' = Ph, C6H9, nBu, H) react with [(~-CSH~)RU(CH~CN)~(PR~)]+ (R=Me, Ph, Cy) to give the ruthenium ally1 carbene complexes [(qC5H5)Ru(=CH-q3-C(CH2)3CCHPR3)]+ and [(q -C5H5)Ru(=C(R')-q 3CHC(R')CHPMe3)]' respectively.212The mixed phosphine-antimony carbene

12: Complexes Containing Metal-Carbon a-Bonds of the Groups Iron, Cobalt and Nickel 313

complex C1(PiPr3)(SbiPr3)Ir=CR2is formed in the reaction of C1(PiPr3)(Sb" Pr3)Ir(C2H4)with N2CR2 (R = C6H5,p-MeC6H4).It reacts with NaCp to give (q-C5H5)(PiPr3)Ir=CR2or PiPr3 to form trans-[C1(PiPr3)21r=CR2]. This latter carbene complex (R = Ph) may be treated with aqueous HBF4 yielding [C1(PiPr3)2(H)Ir=CPh2]+,which forms [Cl2(P'Pr3)2(H)IR=CPh2]upon adding NaC1.213 A range of (q-C5Me5)(L)RuC1complexes have been synthesised (L = 1,3bis(R)imidazol-2-ylidene, R = C6H11, p-MeC6H4, p-ClC6H4, adamantyl; L = 4,5-dichloro-1,3-bis(2,4,6-trimethylphenyl)imidazol-Z-ylidene). Solution calorimetry sudies have provided measures of the electron donor properties of these carbenes; in all cases, except R = adamantyl, they are better donors than PCy3.214 A structural and calorimetric study of (q-C5Me5)(IMes)RuCl (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene)indicates that the carbene ligand is both bigger and also a better o-donor than PCy3. On the (PCy3)(IMes)C12Ru=C(H)Phhas been prepared and basis of these its activity for alkene metathesis investigated. It proves to be a better catalyst than ( P C Y ~ ) ~ C ~ ~ R U = C A ( H range ) P ~ . of mixed phosphine-NHC carbene complexes have been investigated216as ROMP and RCM catalysts. A combination of experimental work and density functional theory has been used to show that Grubb's ROMP catalysts are more active using a combination of NHC and phosphine ligands. Incorporation of a second metal yields even more active ~ y t e m s This . ~ ~ has ~ also been shown in a second, closely related paper.218The reaction of Ru(PPh&C12 with I ,2-c6H&Me)(CHN2) and PCy3 affords 33, which is a catalyst for alkene RCM.219Remarkably, the compound can be recovered after reaction by chromatography on a silica gel column. Remarkably high thermal stability has been shown220for ruthenium imidazolylidene complexes such as 34, which show no decomposition after 10 days at 80 "C. These compounds are catalytic precursors for RCM of dienes.

33

34

The cationic osmium methylidene complex, [(q-C5Me~)(dpprn)Os=CH2)]+, is produced221upon addition of MeOTf to (q-C5Me5)(dppm)OsH.One of the products formed in the reaction of L2(CO)RuHCl (L = PiPr2Ph)with CO and RCHN2 (R = Ph, H) is the carbene complex L2(CO)Ru(=CHR)HC1.222The reaction of excess CH2=CH(OMe) with LZRuH(C1) (L = PtBu2Me) and [L2RuH(CO)]' yields L2Ru(=C(OMe)Me)HCl and [L2Ru(CH2CH20Me)(CO)]+ respectively. The P-alkoxy ligand shows a R u t OMe interaction. Density functional calculations indicate223that in both cases the thermody-

374

Organometallic Chemistry

namic products are being formed. The &hydrogen dihydride complex L2R~(H2)2H2(L=PCy3) reacts with CHRC12 ( R = H , Ph) to form L2C12Ru=CHR and hydrogen gas. In the reaction with C12C=CH2, L2C12Ru=C(Me)H is formed through hydrogenation of the presumed vinylidene primary product. The role of H2 can be overcome by using L ~ R u ( N ~ ) ~ H ~ as the precursor complex. Thus, reaction of this with CHEtCl2 yields L2C12R~=C(Et)H.224 Addition of excess HC-CR (R = C6H5, C6H9, C02Me) and ally1 alcohol to TpRu(DMS0)2Cl provides225a route to the allyloxy carbene complexes, T~RU(=C(CH~R)OCH~CH=CH~)C~. Ruthenium carbene complexes of the type (q-C5H5)(PPh3)Ru(=C(H)C02Et)Clhave been shown226 to be key intermediates in the formation of diethyl maleate from ethyl diazoacetate catalysed by (q-CsH~)(PPh3)2RuCl. Low temperature addition of MeC(0)Cl to [(q-C5Hs)M(SnPh3)(CO)(C(0)CH2R)]- (M = Fe, Ru; R = H, Me, Pr, Ph) yields227 the acyl(oxy) carbene complexes [(q-C5H5)(SnPh3)(CO)M{ =C(OCOMe)CH2R}], which rapidly eliminate MeC02H to give the vinylidene complexes (q-C5HS)(SnPh3)(CO)M(=C=CHR). The reaction of TpMe21R(CH2=C(Me)C(Me)=CH2) with three equivalents of p-MeOC6H4C(0)H at 135 "C gives TpMe21R(CO)(C6H4-pOMe)(CH2C(Me)=CMe2)via intermediate aldehyde and hydroxycarbene complexes. With additional p-MeOC6H4C(0)H, the aldehyde complex reacts further to afford the metallabicyclic carbene complex 35, which has been structurally characterised.228Excess NH2R (R = MeCH2CH2, C6H5, C6H11, -)-CH(Me)( 1-naphthyl), H) reacts with fac,cis(R)-CH(Me)(Et), (9-( [(PNP)C12Ru(=C=CHPh)] (PNP = MeCH2CH2N{ CH2CH2PPh2}2) in thf to form fac,cis-[(PNP)C12Ru=C(NHR)CH2Ph]via fac,cis-[(PNP)ClRu(C-CPh)(NH2R)].229Addition of Me2NCH2NMe2 to a chloroform solution of (cod)Pt(CH2C1)C1 containing excess ligand L = ER3 (E = P: R = C6H5, p MeOC6H4,p-FC6H4, C2H5; E = As, R = C6H5) yields the (dimethy1amino)carbene complexes, cis-[LPt(CHNMe2)C12],along with significant amounts of the ylide complexes cis-[LPt(CH2NMe3)C12].230 With L = AsPh3, a second carbene complex, trans(As, CH2)-[(AsPh3)Pt(CHNMe2)(CH2NHMe2)C1]+, is also formed. The preparation of the alkoxy carbenes [(q-C5H5)(CO)Fe{q2C(OCH2CH=CHPh)C6H4-o-X}]+(X = OMe, Cl) has been described.231Consecutive nucleophilic attack by alcohol and then amine on trans-[Pt(RNC)212] gives the biscarbene complexes 36.232Addition of [ClCH=NMe2]+to a range H

I

35

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 375

of (N-N)Pt(q2-alkene) complexes (N-N = 2,9-Me2-I , 10-phenanthroline, 6,6'Me2-2,2'-bipyridyl; alkene = (Z)-Me02CCH=CHC02Me, (E)-RCH=CHR (R = C02Me, CN)) gives cationic Pt(I1) carbene complexes with the general structure [PtC1(CHNMe2)(N-N)(alkene)]+.233 Attempts to prepare similar non-heteroatom stabilised carbene complexes have resulted in the isolation of [Pt(R)(N-N)(q',q2-CH(Y)02CCH=CHC02Me)] (R = Me, Ph; Y = CO,Et, C02NMe2,CN). Addition of Li2Cu(CN)R2 (R = Me, n B ~Ph, , C-CC6H4-p-Me) to [Fez&C(X)SMe2)(p-CO)(CO)2(q-C5H5)2]+ leads234 to the neutral p-alkylidenes [Fe2(p-C(X)R)(p-C0)(C0)2(q-C5H5)2]resulting from nucleophilic attack at the bridging carbon and loss of Me2S. Terminal alkynes RC(CH react with [(PiPr3)2(H20)0~H2(~2-OCOCH3)]+ to give products dependent upon R.235 For R = P h and C(OH)Ph2, the metallacyclopro ene com lexes and [ SH(K-0COCH3)sH(K'-OCOCH~){ C(Ph)CH2)(PiPr3)2]+ {C[C(OH)Ph2] H2)(PiPr3)2]+are formed. In the cases of R=CMe3 and R = SiMe3, the carbyne compounds [(P'Pr&OsH( - C C H ~ C M ~ ~ ) ( K ~ are formed. Density OCOCH3)]+ and [(PiPr3)20sH(~CCH3)(~2-OCOCH3)]+ functional calculations have been used to explain this product distribution. Addition of HBF4 to the osmium vinylidene complex [OsH(pz)(=C=CHPh)(Hpz)(PiPr3)2] (pz = pyrazole) gives [ O S H F ( X ! C H ~ P ~ ) ( H ~ Z ) ( P ' PThe ~ ~ X-ray ) ~ ] + .crystal ~ ~ ~ structure shows extensive intra- and intermolecular hydrogen bonding between 0s-F and the pyrazole N-H. L20sH2C12 (L = PCy3) reacts with HCrCR (R = C6H5, %Me3) to give the carbyne hydride product L20sHC12(-CCH2R). The product with R = SiMe3 reacts with water to give L20sHC12((CCMe).Addition of NaOMe to L20sHC12(rCCH2Ph)gives L20sHCl(=C=CHPh), which can be protonated to form [L20sHCl(rCCH2Ph)]+.237The trihydride L20sH3Cl reacts with HCECC(CH~)~CI to give a mixture of L20sHC12(rCCH=C(CH3)2)and L20sH2C12(=CHCH=C(CH3)2). The latter complex is labile and converts to the former upon warming to just above room temperature. Carbon-hydrogen bond bond activation of hexane at 170 "C by [{ (q-C5Me5)Ru)3(p-S)3(p-H)3] affords the p3-hexylidyne [{(q-C5Me5)Ru)3(p3-S)(p-H)2{p3-C(CH2)4CH3)]. The reactions with pentane and heptane similarly yield p3-alkylidyne complexes. Cleavage of the benzylic C-H bond is observed with toluene to give [{(r\-C5Me5)Ru)3(P3-S)(P-H)2{ P3-CC6H5)

+

+

References 1. 2. 3. 4. 5.

B. Rybtchinski and D. Milstein, Angew. Chem., Int. Ed. Engl. 1999,38, 870. Y. Guari, S. Sabo-Etienne and B. Chaudret, Eur. J. Inorg. Chem. 1999,1047. N. Wheatley and P. Kalck, Chem. Rev. 1999,99, 3379. P. Nguyen, P. Gbmez-Elipe and I. Manners, Chem. Rev. 1999,99, 1515. V. W.-W. Yam, K. Kam-Wing Lo and K. M.-C. Lo, J. Organornet. Chem. 1999, 578,3.

376

Organometallic Chemistry

6.

W. A. Herrmann, V. P. W. Bohm and C.-P. Reisinger, J. Organomet. Chem. 1999,576,23. C. Floriani, Chem. Eur. J. 1999,5, 19. G. Lavigne, Eur. J. Inorg. Chem. 1999,917. B. Weyershausen and K.-H. Dotz, Eur. J. Inorg. Chem. 1999, 1057. M. C. Puerta and P. Valerga, Coord. Chem. Rev. 1999,193-195,977. V. Cadierno, J. Diez, M. Pilar Gamasa, J. Gimeno and E. Lastra, Coord. Chem. Rev. 1999,193-195,147. J. Campora, P. Palma and E. Carmona, Coord. Chem. Rev. 1999,193-195,207. C. J. Elsevier, Coord. Chem. Rev. 1999,185-136,809. H. Yang, K. T. Kotz, M. C. Asplund, M. J. Wilkens and C. B. Harris, Acc. Chem. Res. 1999,32,551. E. A. H. Griffiths, G. J. P. Britovsek, V. C. Gibson and I. R. Gould, Chem. Commun. 1999,2223. L. Deng, P. Margl and T. Ziegler, J. Am. Chem. SOC.1999,121,6479. H. Chen, D. B. Jacobson and B.S. Freiser, Organometallics 1999,18,5460. R. L. Martin, J. Am. Chem. SOC.1999,121,9459. S. M. Massick and P. C. Ford, Organometallics 1999,13,4362. G. Joorst, P. Karlie and S. Mapolie, Polyhedron, 1999,18,3377. N. Shirawasa, M. Akita, S. Hikichi and Y. Moro-okay Chem. Commun. 1999, 417. M. Faure, L. Maurette, B. Donnadieu and G. Lavigne, Angew. Chem., Int. Ed. Engl. 1999,38,518. C. S . Yi and D. W. Lee, Organometallics 1999,18,5152. K. Umezawa-Vizzini and T. R. Lee, J. Organomet. Chem. 1999,579,122. H. D. Mui, J. L. Brumaghim, C. L. Gross and G. S. Girolami, Organometallics 1999,18,3264. J. L. Koch and P. A. Shapley, Organometallics 1999,18,814. M. E. van der Boom, H.-B. Kraatz, L. Hassner, Y. Ben-David and D. Milstein, Organometallics 1999,18, 3873. J. G. Planas, M. Hirano and S. Komiya, Chem. Cornmun. 1999,1793. T. Morikita, M. Hirano, A. Sasaki and S. Komiya, Inorg. Chim. Acta 1999, 291, 341. K. Kawamura, H. Nakazawa and K. Miyoshi, Organometallics 1999,18,4785. E. Lindner, I. Krebs, R. Fawzi, M. Steimann and B. Speiser, Organometallics 1999,18,480. C. E. F. Rickard, W. R. Roper, A. Williamson and L. J. Wright, Angew. Chem., Int. Ed Engl. 1999,38, 1110. K. B. Renkema, R. Bosque, W. E. Streib, F. Maseras, 0. Eisenstein and K. G. Caulton, J. Am. Chem. Soc. 1999,121,10895. T. Funaioli, C. Cavazza, F. Marchetti and G. Fachinetti, Inorg. Chem. 1999, 38, 3361. H. Kawano, R. Tanaka, T. Fujikawa, H. Hiraki and M. Onishi, Chem. Lett. 1999,5,401. S . Fernandez, M. Pfeffer, V. Ritleng and C. Sirlin, Organometallics 1999, 18, 2390. S. Doherty, M. Waugh, T. H. Scanlan, M. R. J. Elsegood and W. Clegg, Organometallics 1999,18,679. A. J. Carty, G. Hogarth, G. D. Enright, J. W. Steed and D. Georganopoulou, Chem. Commun. 1999,1499.

7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38.

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 377

39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68.

G. Hogarth, K. Shukri, S. Doherty, A. J. Carty and G. D. Enright, Inorg. Chim. Acta 1999,291, 178. M. L. Buil and M. A. Esteruelas, Organometallics 1999,18, 1798. T. Mao, Z. Zhang, J. Washington, J. Takats and R. B. Jordan, Organometallics 1999,18,2331. T. W. Graham, F. Van Gastel, R. McDonald and M. Cowie, Organometallics 1999,18,2177. D. Huang, K. Folting and K. G. Caulton, J. Am. Chem. SOC.1999,121,10318. M. Akita, S. Nakanishi, H. Musashi and Y. Moro-oka, Chem. Commun. 1999, 145. Q. D. Shelby, W. Lin and G. S. Girolami, Organometallics 1999,18, 1904. S. J. Trepanier, B. T. Sterenberg, R. McDonald and M. Cowie, J. Am. Chem. SOC. 1999,121,2613. Y.-H. Lo, Y.-C. Lin, G.-H. Lee and Y. Wang, Organometallics 1999,18,982. R. W. Eveland, C. C. Raymond and D. F. Shriver, Organometallics 1999,18,534. H. Fischer and P. A. Scheck, Chem. Commun. 1999,1031. M. Akita, A. Sakurai and Y. Moro-oka, Chem. Commun. 1999, 101. H. Matsuzaka, Y. Sato, H. Okimura, T. Ishii, M. Yamashita, S. Kitagawa, M. Kondo, M. Shiro and M. Yamasaki, Chem. Lett. 1999,5,865. K. J. Harlow, A. F. Hill and T. Welton, J. Chem. Soc., Dalton Trans. 1999, 191 1. M. Picquet, D. Touchard, C. Bruneau and P. H. Dixneuf, New. J. Chem. 1999, 23, 141. K. B. Renkema and K. G. Caulton, New. J. Chem. 1999,23,1027. C.-W. Chang, Y.-C. Lin, G.-H. Lee and Y. Wang, Organometallics 1999, 18, 3445. H. P. Xia, W. S. Ng, J. S. Ye, X.-Y. Li, W. T. Wong, Z. Lin, C. Yang and G. Lia, Organometallics 1999,18,4552. E. Bustello, M. JimCnez-Tenorio, M. C. Puerta and P. Valerga, Organometallics 1999,18, 950. E. Bustello, M. JimCnez-Tenorio, M. C. Puerta and P. Valerga, Organometallics 1999,18,4563. M. I. Bruce, B. C. Hall, P. J. Low, B. W. Skelton and A. H. White, J. Organornet. Chem. 1999,592,74. M. I. Bruce, B. C. Hall, B. D. Kelly, P. J. Low, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton Trans. 1999, 3719. S . Le Stang, F. Paul and C. Lapinte, Inorg. Chim. Acta 1999,291,403. M. Younus, N. J. Long, P. R. Raithby, J. Lewis, N. A. Page, A. J. P. White, D. J. Williams, M. C. B. Colbert, A. J. Hodge, M. S. Khan and D. G. Parker, J. Organornet. Chem. 1999,578,198. Y. Zhu, D. B. Millet, M. 0. Wolf and S. J. Rettig, Organometallics 1999, 18, 1930. M.-Y. Choi, M. C.-W. Chan, S. Zhang, K.-K. Cheung, C.-M. Che and K.-Y. Wong, Organometallics 1999,18,2074. P. J. Low, R. Rousseau, P. Lam, K. A. Udachin, G. D. Enright, J. S. Tse, D. D. M. Wayner and A. J. Carty, Organometallics 1999,18, 3885. A. M. McDonagh, M. G. Humphrey, M. Samoc and B. Luther-Davies, Organometallics 1999,18, 5195. C.-W. Chang, Y.-C. Lin, G.-H. Lee and Y. Wang, J. Chem. Soc,, Dalton Trans. 1999,4223. V. Cadierno, S. Conejero, M. P. Gamasa, J. Gimeno, I. Asselberghs,

378

69. 70. 71.

72. 73. 74. 75. 76. 77. 78. 79. 80.

81. 82. 83. 84.

85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95.

Organometallic Chemistry S. Houbrechts, K. Clays, A. Persoons, J. Borge and S. Garcia-Granda, Organometallics 1999, 18, 582. T. Katayama, Y. Morimoto, M. Yuge, M. Uno and S. Takahashi, Organometallics 1999,18, 3087. C. Bohanna, M. L. Buil, M. A. Esteruelas, E. Oiiate and C. Valero, Organometallics 1999, 18, 5176. F. Coat, M. Guillemot, F. Paul and C. Lapinte, J. Organomet. Chem. 1999, 578, 76. M. I. Bruce, P. J. Low and E. R. T. Tiekink, J. Organomet. Chem. 1999,572,3. M. A. Esteruelas, A. V. Gomez, A. M. Lopez, E. Oiiate and N. Ruiz, Organometallics 1999, 18, 1606. D. J. Bernad, M. A. Esteruelas, A. M. Lbpez, J. Modrego, M. C. Puerta and P. Valerga, Organometallics 1999,18,4995. B. Buriez, I. D. Burns, A. F. Hill, A. J. P. White, D. J. Williams and J. D. E. T. Wilton-Ely, Organometallics 1999,18, 1504, C. Bianchini, M. Peruzzini, F. Zanobini, C. Lopez, I. de 10s Rios and A. Romerosa, Chem. Commun. 1999,443. I. del Rio, R. A. Gossage, M. S. Hannu, M. Lutz, A. L. Spek and G. van Koten, Organometallics 1999,18, 1097. H.-J. Schanz, L. Jafarpour, E. D. Stevens and S. P. Nolan, Organometallics 1999, 18, 5187. A. Furstner, A. F. Hill, M. Liebl and J. D. E. T. Wilton-Ely, Chem. Commun. 1999,601. K. J. Harlow, A. F. Hill and J. D. E. T. Wilton-Ely, J. Chem. Soc., Dalton Trans. 1999,285. V. Cadierno, M. Pilar Gamasa, J. Gimeno and E. Lastra, J. Chem. Suc., Dalton Trans. 1999,3235. M. I. Bruce, M. Ke, B. D. Kelly, P. J. Low, M. E. Smith, B. W. Skelton and A. H. White, J. Organomet. Chem. 1999,590,184. R. F. Winter and F. M. Hornung, Organometallics 1999,18,4005. L. D. Field, B. A. Messerle, R. J. Smernik, T. W. Hambley and P. Turner, J. Chem. SOC.,Dalton Trans. 1999,2557. S. Doherty, G. Hogarth, M. Waugh, T. H. Scanlan, W. Clegg and M. R. J. Elsegood, Organometallics 1999,18, 3 178. V. Cadierno, M. Pilar Gamasa and J. Gimeno, J. Chem. Soc., Dalton Trans. 1999,1857. M.-D. Su and S.-Y.Chu, Chem. Eur. J. 1999,5,198. M.-D. Su and S.-Y.Chu, J. Am. Chem. SOC.1999,121,1045. M. B. Hall, S. Niu and J. H. Reibenspies, Polyhedron, 1999,18, 1717. E. Perkz-Carreiio, P. Paoli, A. Ienco and C. Mealli, Eur. J. Inorg. Chem. 1999, 1315. B. K. McNamara, J. S. Yeston, R. G. Bergman and C. B. Moore, J. Am. Chem. SOC. 1999,121,6437. K. W. Mak, F. Xue, T. C. W. Mak and K. S. Chan, J. Chem. SOC.,Dalton Trans. 1999,3333. A. Zucca, S. Stoccoro, M. A. Cinellu, G . Minghetti and M. Manassero, J. Chem. SOC.,Dalton Trans. 1999, 3431. R. Cini and A. Cavaglioni, Inorg. Chem. 1999,38, 3751. K. J. Bradd, B. T. Heaton, C. Jacob, J. T. Sampanthar and A. Steiner, J. Chem. Soc., Dalton Trans. 1999, 1109.

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 379

96. M. E. van der Boom, Y. Ben-David and D. Milstein, J. Am. Chew. SOC.1999, 121,6652. 97. M. Paneque, P. J. PCrez, A. Pizzano, M. L. Poveda, S. Taboada, M. Trujillo and E. Carmona, Organometallics 1999,18,4304. 98. M. Paneque, M. L. Poveda, V. Salazar, S. Taboada, E. Carmona, E. GutiCrrezPuebla, A. Monge and C. Ruiz, Organometallics 1999,18, 139. 99. E. Sola, J. Navarro, J. A. Lopez, F. J. Lahoz, L. A. Oro and H. Werner, Organometallics 1999,18,3534. 100. B. Longato, L. Riello, G. Bandoli and G. Pilloni, Inorg. Chem. 1999,38,2818. 101. M. R. Meneghetti, M. Grellier, M. Pfeffer, J. Dupont and J. Fischer, Organomet a l k s 1999, 18, 5560. 102. S. Sjovall, M. Johansson and C. Andersson, Organometallics 1999,18,2198. 103. S. Sjovall, P. H. Svensson and C. Andersson, OrganometaZlics 1999,18, 5412. 104. Y. Kataoka, M. Imanishi, T. Yamagata and K. Tani, Organometallics 1999, 18, 3563. 105. 0.Oke, R. McDonald and M. Cowie, Organometallics 1999,18, 1629. 106. J. M. Hoerter, R. C. Schnabel, P. A. Goodson and D. M. Roddick, Organometallics 1999,18, 5717. 107. B. Rybtchinski and D. Milstein, J. Am. Chem. SOC. 1999,121,4528. 108. M. E. van der Boom, C. L. Higgit and D. Milstein, Organometallics 1999, 18, 2413. 109. C. Hahn, M. Spiegler, E. Herdtweck and R. Taube, Eur. J. Inorg. Chem. 1999, 435. 110. R. P. Hughes and J. M. Smith, J. Am. Chem. SOC. 1999,121,6084. 111. P. J. Alaimo and R. G. Bergman, Organometallics 1999,18,2707. 112. T. H. Peterson, J. T. Golden and R. G. Bergman, Organometallics 1999,18,2005. 113. D. D. Wick, K. A. Reynolds and W. D. Jones, J. Am. Chem. SOC.1999, 121, 3974. 114. D. D. Wick and W. D. Jones, Organometallics 1999,18,495. 115. R. D. Gilbertson, T. J. R. Weakley and M. M. Haley, J. Am. Chem. SOC.1999, 121,2597. 116. J. R. Bleeke, P. V. Hinkle and N. P. Rath, J. Am. Chem. SOC.1999,121,595. 117. R. J. Baxter, G. R. Knox, P. L. Pauson and M. D. Spicer, Organometallics 1999, 18, 197. 118. B. T. Donovan-Merkert, P. H. Rieger and W. E. Geiger, Organometallics 1999, 18,3194. 119. M. S . Morton and J. P. Selegue, J. Organomet. Chem. 1999,578,133. 120. B. de Bruin, M. J. Boerakker, R de Gelder, J. M. M. Smits and A. W. Gal, Angew. Chem., In?. Ed. Engl. 1999,38,219. 121. D. A. Vicic and W. D. Jones, Organometallics 1999,18, 134. 122. R. P. Hughes, H. A. Trujillo, J. W. Egan Jr. and A. L. Rheingold, Organometallics 1999,18,2766. 123. B de Bruin, J. A. Brands, J. J. J. M. Donners, M. P.J. Donners, R. de Gelder, J. M. M. Smits, A. W. Gal and A. L. Spek, Chem. Eur. J. 1999,5,2921. 124. C. S. Chin, H. Cho, G. Won, M. Oh and K. M. Ok, Organometallics 1999, 18, 48 10. 125. M. A. Esteruelas, F. J. Lahoz, M. Martin, A. Martinez, L. A. Oro, M. C. Puerta and P. Valerga, J. Organomet. Chem. 1999,577,265. 126. J. R. Torkelson, F. H. Atwi-Nsiah, R. McDonald, M. Cowie, J. G. Pruis, K. J. JalkanenandR. L. DeKock, J. Am. Chem. Soc. 1999,121,3666.

380

Organometallic Chemistry

127. U. Herber, B. Weberndorfer and H. Werner, Angew. Chem., Int. Ed. Engl. 1999, 38, 1609. 128. M. V. Jimenez, E. Sola, A. P. Martinez, F. J. Lahoz and L. A. Oro, Organometallics 1999,18, 1125. 129. D. S. A. George, R. W. Hilts, R. McDonald and M. Cowie, Organometallics 1999,18,5330. 130. J. R. Torkelson, R. McDonald and M. Cowie, Organometallics 1999,18,4134. 131. J. Gil-Rubio, B. Weberndorfer and H. Werner, Eur. J. Inorg. Chem. 1999,613. 132. B. Windmiiller, 0. Nurnberg, J. Wolf and H. Werner, J. Chem. SOC.,Dalton Trans. 1999, 1437. 133. K. Ilg and H. Werner, Organometallics 1999,18,5426. 134. A. Michalak and T. Ziegler, Organometallics 1999,18, 3998. 1999,121,4238. 135. L. Cavallo, J. Am. Chem. SOC. 136. S. Sakaki, N. Mizoe, M. Sugimoto and Y. Musashi, Coord. Chem. Rev. 1999, 190-192,933. 137. B. Biswas, M. Sugimoto and S. Sakai, Organometallics 1999,18,4015. 138. U. Fekl, A. Zahl and R.van Eldik, Organometallics 1999,18,4156. 139. S. A. Svejda, L. K. Johnson and M. Brookhart, J. Am. Chem. SOC.1999, 121, 10634. 140. A. C. Albeniz, A. L. Casado and P. Espinet, Inorg. Chem. 1999,38,2510. 141. B. S. Williams, A. W. Holland and K. I. Goldberg, J. Am. Chem. SOC.1999,121, 252. 142. R. A. Henderson and K. E. Oglieve, Chem. Commun. 1999,2271. 143. P. H. P. Brinkman and G. A. Lunistra, J. Organomet. Chem. 1999,572,192. 144. C. M. Haar, S. P. Nolan, W. J. Marshall, K. G. Moloy, A. Prock and W. P. Giering, Organometallics 1999,18,474. 145. T. Braun, S. Parsons, R. N. Perutz and M. Voith, Organometallics 1999, 18, 1710. 146. I. Bach, R. Goddard, C. Kopiske, K. Seevogel and K.-R. Porschke, Organometallics 1999,18, 10. 147. W. V. Konze, B. L. Scott and G. J. Kubas, Chem. Commun. 1999,1807. 148. E. M. Prokopchuk, H. A. Jenkins and R. J. Puddephatt, Organometallics 1999, 18,2861. 149. A. Haskel and E. Keinan, Organometallics 1999,18,4677. 150. A. Klein, K.-W. Klinkhammer and T. Scheiring, J. Organomet. Chem. 1999, 592,128. 151. G. S. Hill, G. P. A. Yap and R. J. Puddephatt, Organometallics 1999,18, 1408. 152. M. S. Morton, R. J. Lachicotte, D. A. Vicic and W. D. Jones, Organometallics 1999,18,227. 153. F. M. Alias, T. R. Belderrain, E. Carmona, C. Graiff, M. Paneque and A. Tiripicchio, J. Organomet. Chem. 1999,577, 316. 154. P. Bergamini, E. Costa, C. Ganter, A. G. Orpen and P. G. Pringle, J. Chem. SOC., Dalton Trans. 1999, 861. 155. L. Johansson, 0.B. Ryan and M. Tilstet, J. Am. Chem. SOC.1999,121,1974. 156. H. H. Karsch, K.-A. Schreiber and M. Reisky, Organometallics 1999,18, 3944. 157. C. R. Baar, M. C. Jennings, R. J. Puddephatt and K. W. Muir, Organometallics 1999,18,4373. 158. A. J. Canty, J. L. Hoare, J. Patel, M. Pfeffer, B. W. Skelton and A. H. White, Organometallics 1999,18,2660. 159. S. White, B. L. Bennett and D. M. Roddick, OrganometalZics 1999,18,2536.

12: Complexes Containing Metal-Carbon 0-Bonds of the Groups Iron, Cobalt and Nickel 381

160. N. K. Lim, K. J. Yaccato, R. D. Dghaym and B. A. Arndtsen, Organometallics 1999,18,3953. 161. K. R. Reddy, C.-L. Chen, Y.-H. Liu, S.-M. Peng, J.-T. Chen and S.-T. Liu, Organometallics 1999,18,2574. 162. A. C. Gaumont, M. B. Hursthouse, S. J. Coles and J. M. Brown, Chem. Commun. 1999,63. 163. M. Ludwig, S. Stromberg, M. Svensson and B. Akermark, Organometallics 1999, 18, 970. 164. W. Petz, F. Weller, J. Uddin and G. Frenking, Organometallics 1999,18,619. 165. X. Zhang, E. J. Watson, C. A. Dullaghan, S. M. Gorun and D. A. Sweigart, Angew. Chem., Int. Ed. Engl. 1999,38,2206. 166. X. Zhang, G. B. Carpenter and D. A. Sweigart, Organometallics 1999, 18, 4887. 167. H. H. Karsch, A. W. Leithe, M. Reisky and E. Witt, Organometallics 1999, 18, 90. 168. M. Ghedini, D. hcci, A. Crispini and G. Barberio, Organometallics 1999, 18, 21 16. 169. D. K. Wicht, I. V. Kourkine, I. Kovacik, D. S, Glueck, T. E. Concolino, G. P. A. Yap, C. D. Incarvito and A. L. Rheingold, Organometallics 1999,18,5381. 170. M. C. Janzen, H. A. Jenkins, L. M. Rendina, J. J. Vittal and R. J. Puddephatt, Inorg. Chem. 1999,38,2123. 171. F. P. Fanizzi, L. Maresca, C. Pacifico, G. Natile, M. Lanfranchi and A. Tiripicchio, Eur. J. Inorg. Chem. 1999, 1351. 172. L. R. Falvello, S. Femandez, R. Navarra and E. P. Urriolabeitia, Inorg. Chem. 1999,38,2455. 173. K. R. J. Thomas, J. T. Lin and K.-J. Lin, Organometallics 1999,18, 5285. 174. J. C h p o r a , S. A. Hudson, P. Massiot, C. M. Maya, P. Palma, E. Carmona, L. A. Martinez-Cruz and A. Vegas, Organometallics 1999,18,5225. 175. A. Mayr and J. Guo, Inorg. Chem. 1999,38,921. 176. W. A. Herrmann and V. P. W. Bohm, J. Organomet. Chem. 1999,572,141. 177. M. Ohff, A. OhfTand D. Milstein, Chem. Commun. 1999,357. 178. M. Weissman and D. Milstein, Chem. Cornmun. 1999, 1901. 179. D. J. Cardenas, A. M. Echavarren and M. C. Ramirez de Arellano, Organometallics 1999,18,3337. 180. J. Campora, J. A, Lbpez, P. Palma, P. Valerga, E. Spillner and E. Carmona, Angew. Chem., Int. Ed. Engl. 1999,38, 147. 181. M. van der Sluis, V. Beverwijk, A. Termaten, F. Bickelhaupt, H. Kooijman and A. L. Spek, Organometallics 1999,18, 1402. 182. J. Vicente, M.-T. Chicote, C. Rubio, M. C. R adr e z de Arellano and P. G. Jones, Organometallics 1999, 18, 2750. 183. R. Kakino, K. Nagayama, Y. Kayaki, I. Shimizu and A. Yamamoto, Chem. Lett. 1999,5,685. 184. J. Vicente, J.-A. Abad, A. D. Frankland and M. C. Ramirez de Arellano, Chem. Eur. J. 1999, 5, 3066. 185. M. Crespo, C. Grande and A. Klein, J. Chem. Soc., Dalton Trans. 1999, 1629. 186. K. Praefcke, B. Bilgin, J. Pickardt and M. Borowski, J. Organomet. Chem. 1999, 592, 155. 187. A. Macchioni, G. Bellachioma, G. Cardaci, M. Travaglia, C. Zuccaccia, B. Milani, G. Corso, E. Zangrando, G. Mestroni, C. Carfagna and M. Formica, Organometallics 1999, 18,3061.

382

Organometallic Chemistry

188. F. Ozawa, Y. Sakamoto, T. Sagawa, R. Tanaka and H. Katayama, Chem. Lett. 1999,5, 1307. 189. A. Allen Jr. and W. Lin, Organometallics 1999,18, 2922. 190. M. N. Ackermann, R. K. Ajmera, H. E. Barnes, J. C. Gallucci and A. Wojcicki, Organometallics 1999,18,787. 191. C. S . Chin, M. Oh, G. Won, H. Cho and D. Shin, Polyhedron, 1999,18,811. 192. K. Siinkel and U. Birk, Polyhedron, 1999,18,3187. 193. R. Wang, F. BClanger-GariCpy and D. Zargarian, Organometallics 1999, 18, 5548. 194. I. Ara, J. R. Berenguer, E. Eguizabal, J. ForniCs, E. Lalinde and F. Martinez, Organometallics 1999,18,4344. 195. L. R. Favello, J. ForniCs, A. Martn, J. Gomez, E. Lalinde, M. T. Moreno and J. Sacristan, Inorg. Chem. 1999,38,3116. 196. J. R. Berenguer, E. Eguizabal, L. R. Falvello, J. ForniCs, E. Lalinde and A. Martin, Organometallics 1999,18, 1653. 197. L. R. Favello, J. ForniCs, J. Gomez, E. Lalinde, A. Martin, M. T. Moreno and J. Sacristan, Chem. Eur. J. 1999,5474. 198. T. B. Peters, J. C. Bohling, A. M. Arif and J. A. Gladysz, Organometallics 1999, 18, 3261. 199. K. Onitsuka, M. Fujimoto, N. Ohshiro and S. Takahashi, Angew. Chem., Int. Ed. Engl. 1999,38,689. 200. H. Gerard, E. Clot and 0. Eisenstein, New. J. Chem. 1999,23,495. 201. S.H. Choi, Z. Lin and Z. Xue, Organometallics 1999,18, 5488. 202. F. E. Hahn and M. Foth, J. Organomet. Chem. 1999,585,241. 203. R. E. Douthwaite, D. Haussinger, M. L. H. Green, P. J. Sicock, P. T. Gomes, A. H. Martins and A. A. Danopoulos, Organometallics 1999,18,4584. 204. P. L. Arnold, F. G. N. Cloke, T. Geldbach and P. B. Hitchcock, Organometallics 1999,18,3228. 205. W. A. Herrmann, J. Scwartz, M. G. Gardiner and M. Spiegler, J. Organomet. Chem. 1999,575,80. 206. D. S . McGuiness, K. J. Cavell, B. W. Skelton and A. H. White, Organometallics 1999,18, 1596. 207. M. G. Gardiner, W. A. Herrmann, C.-P. Reisinger, J. Schwarz and M. Spiegler, J. Organomet. Chem. 1999,572,239. 208. T. Weskamp, V. P. W. Bohm and W. A. Herrmann, J. Organomet. Chem. 1999, 585, 348. 209. W. Buchowicz, J. C. Mol, M. Lutz and A. L. Spek, J. Organomet. Chem. 1999, 588, 205. 210. S. M. Hansen, F. Rominger, H. Metz and P. Hofmann, Chem. Eur. J. 1999, 5, 557. 21 1. S. M. Hansen, M. A. 0. Volland, F. Rominger, F. Eisentrager and P. Hofmann, Angew. Chem., Int. Ed. Engl. 1999,38, 1273. 212. K. Mauthner, K. M. Soldovzi, K. Mereiter, R. Schmid and K. Kirchner, Organometallics 1999,18,468 1. 213. D. A. Ortmann, B. Weberndorfer, J. Schoneboom and H. Werner, Organometallics 1999, 18, 952. 214. J. Huang, H.-J. Schanz, E. D. Stevens and S. P. Nolan, Organometallics 1999, 18, 2370. 215. J. Huang, E. D. Stevens, S. P. Nolan and J. L. Petersen, J. Am. Chem. Soc. 1999, 121,2674.

12: Complexes Containing Metal-Carbon o-Bonds of the Groups Iron, Cobalt and Nickel 383

216. J. Huang, H.-J. Schanz, E. D. Stevens and S. P. Nolan, Organometallics 1999,18, 5375. 217. T. Weskamp, F. J. Kohl, W. Hieringer, D. Gleich and W. A. Herrmann, Angew. Chem., Int. Ed. Engl. 1999,38,2416. 218. U. Frenzel, T. Wekamp, F. J. Kohl, W. C. Schattenmann, 0. Nuyken and W. A. Herrmann, J. Organomet. Chem. 1999,586,263. 219. J. S . Kingsbury, J. P. A. Harrity, P. J. Bonitatebus Jr. and A. H. Hoveyda, J. Am. Chem. SOC.1999,121,791. 220. L. Jafarpour, H.-J. Schanz, E. D. Stevens and S. P. Nolan, Organometallics 1999, 18, 5416. 221. J. L. Brumaghim and G. S. Girolami, Chem. Commun. 1999,953. 222. H. Werner, W. Stuer, B. Weberndorfer and J. Wolf, Eur. J. Inorg. Chem. 1999, 1707. 223. D. Huang, H. GCrard, E. Clot, V. Young Jr., W. E. Streib, 0. Eisenstein and K. G. Caulton, Organometallics 1999, 18,5441. 224. M. Olivan and K. G. Caulton, Inorg. Chem. 1999,38,566. 225. E. Ruba, C. Gemel, C. Slugovc, K. Mereiter, R. Schmid and K. Kirchner, Organometallics 1999,18,2275. 226. W. Baratta, A. Del Zotto and P. Rigo, Organometallics 1999,18,5091. 227. H. Adams, S. G. Broughton, S. J. Walters and M. J. Winter, Chem. Commun. 1999,1231. 228. E. GutiCrrez-Puebla, A. Monge, M. Paneque, M. L. Poveda, V. Salazar and E. Carmona, J. Am. Chem. SOC. 1999,121,248. 229. C. Bianchini, D. Masi, A. Romerosa, F. Zanobini and M. Peruzzini, Organometallics 1999,18,2376. 230. G. Ferguson, Y. Li, A. J. McAlees, R. McCrindle and K. Xiang, Organometallics 1999,18,2428. 231. C. S . Schulz, M. Tohier, S. Sinbandhit and V. Guerchais, Inorg. Chim. Acta 1999, 291,449. 232. S.-W. Zhang, F. Motoori and S. Takahashi, J. Organomet. Chem. 1999,574,163. 233. M. E. Cucciolito, A. Panunzi, F. Ruffo, V. G. Albano and M. Monari, Organometallics 1999,18, 3482. 234. S . Bordoni, L. Busetto, M. C. Cassani, A. Palazzi and V. Zanotti, Inorg. Chim. Acta 1999,291,333. 235. M. L. Buil, 0. Eisenstein, M. A. Esteruelas, C. Garca-Yebra, E. GutikrrezPuebla, M. Olivan, E. Oiiate, N. Ruiz and M. A. Tajada, Organometallics 1999, 18,4949. 236. M. A. Esteruelas, M. Olivan, E. Oiiate, N. Ruiz and M. A. Tajada, Organometallics 1999,18,2953. 237. H. Werner, S. Jung, B. Weberndorfer and J. Wolf, Eur. J. Inorg. Chem. 1999, 951. 238. K. Matsubara, A. Inagaki, M. Tanaka and H. Suzuki, J. Am. Chem. SOC.1999, 121,7421.

13 Hydrocarbon Transition Metal domplexes other than q-C5H5and q-Arene Complexes BY KEVIN R. FLOWER

1

Introduction

This survey of the 1999 literature relating to n- hydrocarbon complexes of the transition elements other than q-C5H5 and q-arene complexes is similar in nature to previous reports.' This chapter is sub-divided into the following sections dealing with: reviews; complexes containing allyls or monoalkenes; unconjugated alkenes; conjugated alkenes; acyclic alkenes; alkynes and polymetallic complexes.

2

Reviews

The chemistry of complexes containing carborane ligands has been described and contains examples of ancillary n-hydrocarbon fragmenk2 A theoretical overview of Pd and Pt dimers that contain bridging phosphido ligands has appeared: some of the compounds discussed contain n-hydrocarbon m~ieties.~ The use of bent metallocenes for stabilising unusual coordination geometries at carbon has been r e p ~ r t e d ;as~ has planar tetracoordination of the carbon atom in Group 4 and 5 complexe~.~ The structures of early-late transition metal heterobimetallic complexes have been reviewed,6 as has the stuctures of the pentagonal bipyramidal complexes CZOS~-[M~(CO)~(RC~R)~], nido[M2(CO)6(RC2R)2](M = Fe, Ru, 0 s ) along with related compound^.^ The chemistry of: ortho-arene-cyclynes;8 n-complexes containing annulated cyclobutene rings;gpolyethynylated cyclic n-systems and their utility in building two and three dimensional networks;" vinylketenes;'' and the use of metal vinylidene complexes in catalysis'* have all been reviewed and contain material of interest. The use of 7r-hydrocarbon complexes in organic transformations continues to be an area of high activity and many reviews on different aspects of the subject have appeared and include: the use of stoichiometric transition metal organometallics in organic synthesis;l 3 chromium(0) promoted higher order cycloaddition reactions;l5 chelation assisted hydroacylation reactions;l4 recent developments in the scope and selectivity of chromium-carbene annulation reactions;l6 the use of organomanganese reagents;' transformations facilitated by [Fe(CO)3(q4-diene)] complexes; organoiron complexes;l 9 [co2(co)8] induced transformations of alkynyl and pentadienyl-cyclopro-

*'

Organometallic Chemistry, Volume 29 0The Royal Society of Chemistry, 2001

3 84

13: Hydrocarbon Transition Metal n-Complexes other than q-C5H5and 11-Arene Complexes 385

panes;20cycloisomerisation of alkynols;21activation of electrophiles by electrophiles through dimeric association;22an entire issue of Journal of Organomet a l k Chemistry was dedicated to Pd catalysed chemistry and contains many articles of interest;23 Pd catalysed pronucleophile addition to unactivated carbon<arbon multiple bonds;% carbon+arbon bond formation again catalysed by Pd;25the factors that influence the activation of carbon-carbon bond formation and outlooks for future development.26 Inorganic and organometallic chemistry in supercritical fluids has been des~ribed?~ as have the developments of new polymerisation catalysts that are not based upon the metallocenes.28

3

Complexes Containing Allyls or Monoalkenes

3.1 Cr, Mo, W. - The preparation and characterisation of fac[Cr(CO)3(dppe)(q2-Cm)]and a mixture of fac/mer-[Cr(CO)3(dppe)(q2-C60)] was reported.29 Preparation of the ylidine complexes [M(C0)5(N-allyl-2,3dihydrobenzoxazol-2-ylidine)] (M = Cr or W) was described and they were shown to lose CO on warming allowing q2-complexation of the pendant ally1 moiety to give 1.30 Treatment of cis-exo-2-phenyl-3-(2-E-phenylethenyl)norbornane with [Cr(C0)6] afforded 2 which on exposure to visible light gave 3.31

2

1

3

A collection of the carbene tethered alkenelallyl complexes 4, 5, and 6 have been prepared and ~haracterised.~~ A computational study on the benzannulation reaction of heteroatom-stabilised chromium carbene complexes (Dotz reaction) has been carried out and the results suggest rejection of the Casey

HO' 4

5

6

pathway in favour of a lower energy route that goes through a chromahexatriene intermediate.33In a mechanistic study on the reaction of Fischer carbene complexes with alkynes (benzannulation reaction), evidence was presented for equilibration between several vinyl-carbene intermediates.34 The synthesis of [Mo(C0)2( 1,lO-phen)(dibutylmaleate)(q2-C~)] has been described and its electrochemistry investigated. The first three one-electron reductions were found

386

Organometallic Chemistry

to occur at 0.15 v more negative potential than for free c60 and this was explained in terms of the effect of dn-back donation from the metal; the fourth one-electron reduction causes dissociation of the f ~ l l e r i d e Treatment .~~ of [Mo(C0)6] with potentially chelating sulfur- and nitrogen-containing ally1 acetates in the presence of sodium-P-diketonates afforded sulfur or nitrogen tethered q3-allylcomplexes with ancillary P-diketonate l i g a n d ~The . ~ ~reaction between [M(CO),j] (M = Cr or Mo) with 2,2-bis(cyclopentadienyl)propane afforded 7, amongst other products. For both Cr and Mo the complexes were structurally characterised and their photochemistry in~estigated.~~ The exocyclic fluorenyl containing complex 8 has been prepared and structurally

7

characterised. The compound has been the subject of a density functional theory calculation which, in line with experimental results, predicted the exocyclic nature of the fluorenyl c ~ o r d i n a t i o nA . ~general ~ route for the preparation of [ C ~ M O ( C O > ~ ( ~(L ~ -=L2-alkylidenecyclobutanoyl )] carrying various functional groups) was described.39 The synthesis and fluxional properties of the structurally characterised complex [Mo(C0)2{q2-S2P(OEt),>(q3-C3H5)] were described in detail.40The redox induced ring slippage (q5 q3) of the indenyl moiety in a large range of complexes of the type [(q5-Ind)CpMoL2] (L = phosphines, nitrogen donors, isonitriles etc.) was studied.41 A single crystal X-ray diffraction study was used to determine the absolute configuration of exo-syn-syn-dicarbonyl(q5-cyclopentadienyl)(q3-1,2,3-1R,2S,3S-1-phenylbut-2-en-1-yl)M0(11).~~ The reactivity of 9 towards Grignard reagents was investigated and poor lateral stereocontrol observed when a methyl group was in the 2-position of the ally1 moiety; however, reaction of 10 towards Os04 showed good diastereomeric control (25:1). When the methyl group was in the 1-position, no conformational control and poor lateral- and stereocontrol was observed.43The allyl-containing complex [Mo(NCMe),(THF)(CO)2(q3-2-MeC3H4)] was prepared and structurally characterised. On treatment with oxonucleophiles the THF ligand was displaced; loss of NCMe was also observed to occur leading to the formation of aggregates and oligomeric complexes, several of which were structurally characterised? Enantio-controlled [5+2] cycloaddition reactions to the q 3-pyrany1-containing complexes of type 11

13: Hydrocarbon Transition Metal n-Complexes other than q-CJHjand q-Arene Complexes 387

have been described. Resulting from this methodology a collection of substituted oxabicyclo[3.2.1] octenes of high enantiopurity have been synthe~ i s e d The . ~ ~preparation and fluxional nature of 12 has been described. The inequivalent alkene ligands were shown to exchange. The W-H was also shown not to undergo hydrogen exchange with the alkene l i g a n d ~ The .~~ crystal and molecular structure of trans-[w(CO)4(q2-C2H4)2]was reported. The C=C bonds of the trans-alkenes are staggered relative to each other and eclipse the w(CO)4] fragment. The preparation and reactivity of the compounds w(CO),(q2-C2H4)6-n] (n = 3-5) were also described. In an associated paper analogous prop- 1-ene and but- 1-ene containing compounds were reported along with the spectroscopic characteristics of unstable mono-alkene and cis-bis-alkene complexes obtained at low temperature!* The photochewas mical conversion of w(co)6] into trans-~(~0)4(q~-(~-cyclooctene)21 studied and it was suggested that the reaction proceeds via a cis isomer which is dficult to isolate. The two diasteroisomers produced were isolated and separated by fractional cry~tallisation?~Warming of [Cp*W(NO)(q2-PhCH=CH2)] in pentane, hexane, 2,2-dimethylbutane or diethyl ether induces a double solvent C-H activation, leading to a series of crystallographically characterised benzallyl containing complexes.50Treatment of [CpW(CO)3(q CH2(CH,),Ar}] (n = 0, 1) with triflic acid in CH2C12 effected a cyclocarbonylation reaction yielding [CpW(CO)2(q3-cyclopentenoyl)] (n= 0) or [CpW(C0)2(q3-cyclohexenoyl)] (n = l).51 The complexes [CpW(C02)(q2:q CH2CHCHR-Y-CO-)] were obtained on treatment of [CpW(CO)3(q CH2C(CR)] (R=Me, Ph) with triflic acid followed by either water or a A collection of complexes of the type [C~w(CO)~(q~-n-yprimary a~nine.'~ lactonyl)] that contain aldehyde functionalised lactonyl ligands were prepared and characterised. Reaction of these compounds with NO[PF6] and NaI in NCMe effected an intramolecular allylation of the tethered aldehyde leading to a-methylene butyrola~tones.~~

'-

''-

3.2 Fe, Ru, 0s. - The dehydrogenation of ethane by the fragments [Cp*M+] (M = Fe, Co, Ni) in the gas phase was studied by FT-ICR-MS. The Co and Ni fragments were found to effect the dehydrogenation reaction, whereas Fe did not.54 The molecular structure of [Fe(C0)4(q2-CH2=CH2)]has been determined using microwave spectroscopy. Density functional theory calculations were also carried out in an attempt to predict the experimental data. The predictions were found to be in excellent agreement with the experimental results.55Density functional theory, along with molecular mechanics, has been applied to aspects of ethene polymerisation effected by Fe(I1) bis(imine)pyridine systems,56and in a related study ab initio calculations were carried out on the ethene polymerisation capabilities of iron-based catalysts with 2,6-bis(imino)pyridyl ligandd7 A collection of [Fe(II)(q3-but-1-en-3-yn-2-yl)] complexes containing tetradentate tripodal-phosphine ligands have been prepared and characterised. One of the compounds synthesised was found to catalyse the stereospecific head-to-tail dimerisation of phenyla~etylene.~~ Compound 13 has been prepared from [Fe(q4-C6H5Me)(q6-C6H~Me)] on reaction with: (i)

388

Organometallic Chemistry

ethene at - 78 "C, (ii) bulky stannylenes and their reactivity towards CO was also described.59Treatment of 14 with PhCH=CH20Na yielded the chelating alkene-alkoxycarbene complex E 6 0 Fe substituted enals have been shown to

13

14

15

undergo cascade reactions to give a,P-butenolides and y-butyrolactones via hydrido-alkene intermediates,61 and some five-membered-ring heterocycles have also been prepared: with associated mechanistic studies suggesting the intermediacy of hydrido-alkene species.62 Treatment of [(PdBr(q3-allyl)}21 with [Fe(C0)3(NO)] afforded good yields of the allyl-transferred complexes [Fe(CO)2(NO)(q3-allyl)].631,7-1nduction in the Mukaiyama aldol reaction of silylenolether-substituted [(n-allyl)Fe(CO)3] lactam and lactone complexes with aldehydes and the Lewis acid BF3.0Et2was described. The diastereocontrol was shown to be dependent upon the nature of the endo-substituent on the seventh carbon atom from the metal centre reaction site.64The total synthesis of 16 was reported and utilised [Fe(CO)3(q3-allyl)]methodology in several of the steps.65A collection of ferracyclic q3- ally1 and q3-pentadienyl complexes were prepared and characterised on treatment of [Fe2(CO)g] with a range of unsaturated diols and examples include 17, 18 and 19.66Racemic mixtures of

17

18

19

[Fe(C0)3(q ':q3-C(0)XCH2CHCMeCH2}](X = 0, NMe2) were resolved using HPLC on cellulose tris-(3,5-dimethyl-phenyl)carbonate/silicagel RP8. The absolute configuration of one isomer was determined by X-ray crystallograph^.^^ The synthesis and molecular structure of [Ru(Me)(dmpe)(q2CH2=CH2)]has been described? The compound [Ru(acac)2(q2-C,H&] has been prepared and spectroscopically characterised. The reactivity of the complex has been investigated and is centred around substitution of the q2cyclooctene ligand.69 Compound 20 has been prepared and shown by VTwith NMR spectroscopy to be fluxi~nal.~' Treatment of [RuHCI(CO)(PP~~)~] 2-methyl-2-propen-1-01has been investigated and shown to yield a variety of

13: Hydrocarbon Transition Metal n-Complexes other than q-C5H5and q-Arene Complexes 389 Me,

*Me

20

21

products including structurally characterised 21.71 Treatment of [{RuC12(q3L)}2(p-N2)] { L = 2,6-bis(dimethylamino)methylpyridine} with a variety of alkenes afforded the monomeric alkene-containing complexes [RuC12(q2alkene)(q3-L)]. Ally1 bromide was shown to coordinate as an q2-alkene too, with no propensity to oxidatively add to the metal centre; terminal alkynes afforded vinylidiene-containing complexes and internal alkynes were unreact i ~ e The . ~ ~reaction of [R~(q~-dimethylfurnarate)~(~f-COT)] with bipy and 1,lO-phen was described. Displacement of one dimethylfumarate and one double bond of the q6-COT ligand was found to occur: analogous COD complexes were also prepared.73Treatment of [Ru(q4-COD)(q6-COT)]with either phenylvinylsulfide or oxide in the presence of 1,2-bis(diethylphosphino)ethane yielded [Ru(q ‘-CzH3EPh)(q4-COD)(depe)](E = 0, S): selective ligand exchange with PMe3 was described.74Reaction of 22 with internal and terminal alkynes has been investigated in the presence of base and found to yield 23; in the absence of base 24 was obtained. For both internal and

24

terminal alkynes coupling was found to go through a metallacylopentene; for terminal alkynes alternative routes via vinylidene and metallacyclobutane intermediates were also observed.75Treatment of the compounds [CpRu(NCMe)2(PR3)][PF6](R = Me, Ph, Cy) with hepta-1,6-diyne and HC=CR has been investigated and found to yield complexes of type 25. The reactivity of these compounds was also d e ~ c r i b e d .Selective ~~ coupling between alkenes and terminal alkynes in the coordination sphere of tris(pyrazoly1)borate-containing Ru complexes was described. A selection of q3-butadienyl and q2-butadiene-

25

26

390

Organometallic Chemistry

containing complexes resulted and were structurally ~haracterised.~~ [(cp*R~Cl)~] was shown to react with a variety of enamines to afford complex mixtures which included: [Cp*Ru(q5-azadienyl)]; [Cp*RuC12(q3-azadienyl)] and [Cp*Ru(q4-amino-1,3-diene)]. Some of the complexes prepared were structurally ~haracterised.~~ Treatment, at low temperature, of [Ru(q3-2-MeC3H4)(q4-COD)]with a range of bidentate phosphorus ligands containing cyclohexyl groups led to some interesting q3-allyl containing complexes resulting from: cyclohexyl C-H activation, reductive-elimination of the 2methallyl ligand and COD hydrogenation, i. e. 26.79Treatment of [Ru3(CO)12] with a- and P-styrylpentamethyldisilane has been described and the q3-allyl complexes [Ru(C0)3(R)(q3-TMS-C3H3-3-Ph)] (R = H, TMS, D) were isolated and characterised.80 The reactions of [CpRu(L)(L)(C=CPh)] (L, L = phosphines) with HPhC=C(CN)2 has been investigated and found to yield: cyclobutenyl, butadienyl and n-ally1 complexes." The complex [Os(NH3)5(q2selenophane)]was prepared and its reactivity was investigated and found to be essentially the same as that of its sulfur analogue.82 A collection of q2thiophene complexes of the type [ O S ( N H ~ ) ~ ( ~ ~ - L ) ](L [ O=Tvariety ~] of thiophenes) were prepared and characterised. Their reactivity towards electrophiles was reported and, depending upon the thiophene substitution pattern, reaction occurred at either sulfur, C(2) or C(3).83 The reactivity of [Cp*2Os2Br2] towards 3-bromo-2-methylpropene or cycloocta-l,3-diene was investigated and in both cases allyl-containing complexes of the type [Cp*OsBr2(q3-L)] (L = 2-Me-C3H4,C8H13)were obtained. The reactivity of the two complexes towards alkylating agents was also described.84 3.3 Co, Rh, Ir. - The alkene-containing complexes [(Tp-L)Co(q2-C2H3R)] (R = Me, H; L = Me, tBu) have been prepared and characterised. The complexes were found to be not very reactive, even though they are electron deficient and sterically ~rowded.'~Compound 27, which contains a bulky stannylene, has been prepared and characterised.86Spectroscopic evidence has been presented for the preparation of 28, in which the phenyl group is q2bound to the Co centre. The complex's reactivity was briefly de~cribed.'~ During the [co2(co)8] catalysed silylation of ct,P-unsaturated- and aromatic

27

Me Ind

29

28

Ind

Ph

30

13: Hydrocarbon Transition Metal 7c-Complexesother than q-CSHj and q-Arene Complexes 391

carbonyl compounds a series of [Co(q3-allyl)] complexes were observed.88 Linkage isomerisation in the ketene complexes 29 and 30 was described. Carbonylation causes displacement of the ketene ligand in 29 but not in 30, which is contrary to what might be expected from HSAB theory.89A selection of fluoro-containing Rh(1) complexes have been prepared that contain alkenes and internal alkynes as ancillary ligands. Complexes that contain terminal alkynes tend to isomerise to vinylidene complexes.90The complex [RhH(q2C,) { (PPh2CH2)3CMe}]has been prepared and structurally chara~terised.~' The synthesis, characterisation and reactivity of [TpRh(NCMe)(q2-COE)] have been reported. The complex's reactivity centres around displacement of the cyclooctene ligand?2 The reaction between [RhCl(PPh3)3] and methylene cyclopropenes at 0°C and 50°C has been investigated. At 0°C simple ncoordination of the methylene cyclopropene is observed, whereas at 50 "C ring opening and isomerisation to an q4-butadiene is observed affording complexes of the type [RhCl(PPh3)2{q4-H2C=C(R)CH=CH2)].93The compound [(q5-lMe-Ind)Rh(PCy3)(q2-H2C=CH2)]was prepared by reaction of [(q5-l -MeInd)Rh(~l~-H~c=CH2)~] with PCy3 and fully characterised. VT 31P('H}-NMR spectroscopy was used to calculate the barrier to indenyl ring rotation.94 A collection of methylarenium complexes of type 31 have been prepared and characterised. Deprotonation readily gave complexes of type 32.95A series of

cyBu'

@rt2

--NEb

+M-CI

PBut2

+M-CI

-

HOTf

31

I

PBu:

32

complexes of the type [ C P * R ~ ( ~ ~ - H ~ C = C H [RR=) SiMe3, ~] SiMe2OEt, Si(OiPr)3,SiMe(OSiMe&, SiPh20'PrI were prepared and fully characterised. e ~deuterated )~l solvents led Heating the complex [ C ~ * R h ( q ~ - H ~ c = c H S i Min to H/D exchange of the alkene protons. The ability of these complexes to convert alkoxysilanes to silylenolates was also described.96 The reaction between [RhC1(PPh3)3]and a variety of vinylallenes afforded fully characterised complexes, such as 33, 34, and 35. The coordination mode found was TMS

Cl-Rh-7I P h 3 ( 4 p h

-

pbp TMS Rh

PPh3

33

34

/

&eM Ph

Me Ph3P/RhXC, 35

determined by the steric requirements of the n-hydrocarbon fragment. Further, the catalytic properties of these complexes were described.97Treatment of r]rphle2Rh(q2-H2C=H&] with Lewis bases afforded the Rh(III) compounds ~ P M ~ ~ R ~ ( ~ - C H ~ C H ~ ) ( ~ ~(L -H = py, ~C= NCMe, H ~ ) (PR3). L)] These complexes were found to activate C-H bonds in py, thiophene, and

392

Organometallic Chemistry

ben~ene.~' [RhCl(PMe3)2]effects ring opening of 3-vinylcyclopropene yielding two isomeric products of [RhC1(PMe3)2(q3:q'-pentadienyl)]?' Density functional theory has been used to study the Ir(II1) catalysed dehydrogenation of alkanes. The process was shown to take place in four steps: (i) oxidative addition of the alkane, (ii) dihydride reductive elimination, (iii) P-hydride transfer from a metal alkyl, (iv) dissociation of the alkene.lW The alkene has been prepared and evidence complex [Ir(PiPr3)(q2-H2C=CH~)(q6-C6H6)] for C-H activation was presented. lo' The reaction of [Ir(H)2(PiPr3)(NCMe)3][BF4]with ethene and propene was described. Reaction with ethene afforded free ethane (metal-catalysed hydrogenation) and an ethene complex, whereas propene afforded an q3-allyl complex via a C-H activation process and an q2-alkene complex.lo2 The compound [Cp*Ir(NCMe)(q3-C3H4-1-Ph)] reacts with terminal alkynes in the presence of base to give the mixed oacetylide-n-ally1complexes [Cp*Ir(C=CR)(q3-C3€&-1-Ph)]. Reaction of these compounds with HCl, Me1 causes coupling of the allyl and acetylide fragments to give compounds of type 36;treatment with excess HC1 leads to a pentadiene containing complex.lo3

Me0 R

CI

36

O

37

3.4 Ni, Pd, Pt. - A collection of indenyl-Ni complexes that contained imidato ancillary ligands were prepared and characterised. The indenyl ring was shown to have ring-slipped to the q3-coordination mode. A solid-state structure suggested partial localisation of the bonds for the allyl fragment and that the indenyl ring is best described as: q2:q bound. Density functional theory has been used to study the polymerisation of propene by [Pd(II)(diimine)] systems.'05 A spectroscopic FTIR and FT-Raman study of the anions [PdC13(q2-H2C=CH2)]- and [PdC13(q2-HC=CH)]- was reported. Density functional theory was used to calculate the 'expected' spectra and these were found to be in good agreement with the experimentally observed. The calculations also showed that the Pd complexes are less stable than the analogous Zeise's salt,Io6 Molecular mechanics parameters have been developed for Pdalkene complexes that contain ancillary phosphine ligands using crystal structure and quantum chemical data. Reasonably accurate structures can be predicted using the force-field; further, useful data for allylic-alkylation reactions can also be obtained.lo7 The tetra-alkene complex 37 has been isolated and fully structurally characterised. Isolation of this complex led the authors to comment on the mechanism of the Saegusa oxidation."' The compound [Pd(PPh3)2(q 2-C70)] has been prepared and crystallographically

'-

13: Hydrocarbon Transition Metal 71-Complexesother than q-CSHj and q-Arene Complexes 393

characterised. C70 was shown to bond through the (a-b) bond at a highly pyramidalised 6:6 ring junction at the pole of the fullerene; further, the molecule was shown to be fluxional by VT NMR.lW A collection of Pd complexes containing an q2-dibenzylideneacetonemoiety with bulky ancillary phosphine ligands have been prepared and characterised. Their reactivity was also described.'" A series of [Pd(q2-alkene)] complexes with chiral P-N (oxazoline) ligands, based around a naphthalene backbone, have been reported. The dynamic behaviour and utility of these compounds in asymmetric was also investigated."' A series of allylation reactions (ee upto [Pd(NN)(q2-alkene)]have been prepared (where the N-N backbone is carbohydrate based). l2 Nucleophilic attack by the carbonyl stabilised ylides R3P=CHCOR' (R = Ph, p-tolyl; R' = OEt, OMe, NMe2) on the coordinated diene in [MC12(q4-COD)]afforded exo-cyclic-cyclohexenyl-containingcomplexes. Ligand substitution reactions centred around the Cl- moiety were also described. Low temperature spectroscopic techniques were used to follow the chain growth in a-diimine complexes. l4 A theoretical study using MP2MP4(SDQ) and CCSD(T) methods was carried out to interpret the structure, bonding and propensity for reductive elimination in the compounds [Pd(XH3)(PH3)(q3-C3H5)](X= C, Si, Ge, Sn).' Density functional theory has been used to analyse the electronic effects in the regiospecificity of the TsujiTrost reaction. The shortest Pd-ally1 bond in unsymmetric allyl moieties was found closest to the most electron-withdrawing group and that nucleophilic attack occurs remote to the stongest EWG; this is in excellent agreement with experiment.' l 6 Ab initio calculations have been carried out to investigate the mechanism of PdRt nucleophilic attack on 2-propenylcarbonate. Three steps were identified in the process: (i) n-ally1 formation; (ii) conversion to a metallacycle; (iii) reformation of the n-allyl.' l 7 The solvated transition state for nucleophilic attack in cationic q3-allyl complexes was studied computationally. The gas-phase transition-state in most cases did not model that obtained using continuum solvation models. Predictions in Pd assisted allylic alkylations was discussed. A new molecular mechanics force field MM3* for calculations relating to Pd-n-ally1 complexes containing ancillary P- and N-donor ligands was developed using crystal structure and quantum chemical data.' l9 Three 8silyl substituted [(q3-allyl)Pd] compounds were synthesised and a density functional theory study of their structure and reactivity was carried out using simplified model compounds. The results obtained suggested hyperconjugated interactions between the Pd-ally1 system and the C-Si o-bond: the magnitude of the interaction is affected by the ancillary ligands.12* Reaction kinetics and mechanisms of nucleophilic attack on the n-ally1 ligand in cationic Pdcomplexes has been investigated and the data presented strongly suggested that attack occurs directly at the ligand rather than at the rnetal.l2' The oxidative addition of allylacetates to Pd(0) complexes has been studied. Mechanistic evidence presented suggests that there are several equilibria attained and that they are solvent dependent. Further the acetate ion has been shown to be non-innocent by aiding in racimisation.122 [PdC14I2- catalysed exchange and isomerisation reactions of chiral allyl alcohols effected by OH-,

'

''*

394

Organometallic Chemistry

MeO-, and PhO- at high [Cl-] were described in terms of the stereochemical outcome of the Wacker process.123 Amphiphilic supported Pd-n-ally1 complexes were reported and their ability to catalyse the cross coupling of aryl halides with aryl-boron reagents in aqueous conditions was de~cribed.'~~ A Pd(0) catalysed non-standard Cope rearrangement that proceeded through a bis(x-allyl)Pd(II) intermediate was described. The Pd(I1)-ally1 intermediate was proposed to be formed through a non-strained C-C bond oxidative addition to Pd(0).'25 Treatment of terminal alkenes with PdC12 in refluxing 1,2-dichloroethane afforded [ { (q3-2,3,4-allyl)Pd(p-C1)}23 instead of the expected (q3-1,2,3-allyl) containing complexes.'26 A collection of p-silyl substituted x-ally1 complexes of Pd were prepared and characterised. Isolation of these intermediate allyl complexes allowed discussion of the regioselective catalytic pathways to allyl silanes formed via nucleophilic attack by nucleophiles such as malonates and en01ates.l~~ A series of Pd(I1) x-allyl-containing complexes with aminooxyl-radical substituted triphenylphosphine ligands were prepared and characterised. The EPR spectrum for the mono-ligand containing complex is essentially that of the free ligand. Incorporation of the free radical-containing ligands into the complex also had the effect of broadening the NMR spectra of the compounds.'28A collection of aryloxy-bridged Pd(I1) n-allyl-containing complexes were prepared and characterised. Reaction of these compounds with PPh3 caused bridge cleavage.129 Benzylcyclohexylphenylphosphine was resolved and the x-ally1 containing complex [PdCI(PPhCyBn)(q3-2-MeC3H4)]prepared from it. Treatment of this complex with Ag[BF4] in CH2C12 generated a catalyst that was used in asymmetric hydrovinylation reactions: ee values of between 45-85 were obtained.130 Some new chiral-at-phosphorus tetradentate oxazolinylphosphine ligands have been prepared and their coordination chemistry towards Ni and Pd investigated. Both mono- and binuclear complexes were obtained depending upon the reaction conditions and the use of these complexes in allylic-allylation reactions was reported (ee z 90%). The molecular structure of one of the allylcontaining complexes was obtained by single crystal X-ray diffraction study.l3 The complexes [ P ~ ( P P ~ ~ - P ~ ) ~ ( C O ~ R ) (have OAC been ) ] prepared and reacted with propadiene and alkynes. The isolation and molecular structure of [Pd(PPhz-Py)a{ q3-C3H4-2-C(Me)CH2)]was also described.132 Unusual P-C, coordination of 2-dimethylamino-2'-diphenylphosphino1,l'-binaphthyl to Pd has been described. Preparation of x-allyl-containing complexes was also described and reported to give a mixture of diastereoisomers. The activity of the complexes in amination and Suzuki coupling reactions was also reported. 133 A selection of new enantio-pure phosphinoamine ligands that contain a trans-2,5-diallylpyrrolidinyl unit were prepared and coordinated to Pd. The Pd complexes were then used in allylic-allylation reactions and found to give ee < 34%. 134 Some Pd-n-ally1 complexes containing phosphinoimine ligands were prepared and characterised. The complexes were found to display the following fluxional characteristics: (i) conformational change of the chelate ring; (ii) q3 -+ q 1 q3-interconversion of the allyl ligand; (iii) rotation of the allyl fragment about its bond axis.'35 A collection of Pd-n-ally1 complexes -+

13: Hydrocarbon TransitionMetal n-Complexes other than q-C5H5and q-Arene Complexes 395

containing potentially terdentate ligand centres built around P, N, and S donor atoms have been prepared and characterised. The use of these complexes for catalytic organic transformations was also described.136 Compounds 38 and 39 have been prepared and structurally characterised; significant bond length differences between the two structures was observed . They are also

38

39

40

found to rapidly interconvert on the addition or removal of a proton.'37 The complexes [Pd(bipy)(q1:q2-C8H120Me)][An](An = PF6, SbPF6, OTf, BPb, BF4, BARF) have been synthesised and fully characterised. Their ability to copolymerise CO and styrene was also studied. The complex's activity was found to be dependent upon the counter-anion.138 N21 and N22 etheno-bridged porphyrin Pd(I1) (q3-n-allyl) complexes have been prepared and the apparent x-ally1 rotation described.139 The reactivity of [Pd(q3-2-Me-C3H4)(p-P02F2)]3 towards P and S donor ligands has been reported to afford the bridge cleaved products [Pd(q3-2-Me-C3H4)(L)(P02F2)]and these compounds have been shown to be fluxional by VT NMR spetroscopy. The P02F2 moiety can be transferred to metallocenes on reaction with Cp2MC12 yielding [{Pd(p-Cl)(q32] with 2-Me-C3H4))2].14* Treatment of [{Pd(p-C1)(q3-2-Me-C3H4)} Ag[CF3S03] followed by a selection of thionate based ligands (pyridine-2and pyrimidine-4,6-dimethyl-2-thiothionate, imidazol-3-methyl-2-thionate nate) afforded the polymeric ally1 containing complexes [Pd(SR)(q3-2-MeC3H4)In.14' The origins of enantioselectivity in allylic-allylation reactions catalysed by Pd complexes containing chiral chelating N-S donor ligands was discussed. The data presented was interpreted and showed that the trans-effect has minimal influence on enantioselectivity, rather that selectivity arises from the steric asymmetry of the ligand.'42 A set of [Pd(P-ketiminato)(q3-allyl)] complexes have been prepared and characterised, one by a single crystal X-ray diffraction study. Their utility for the preparation of thin Pd films via CVD was also described.'43 A selection of q3-propargyl complexes of Pd were preparec. and their possible presence in catalytic cycles discussed.'41Evidence obtained from carbon kinetic isotope effects was shown to support a concerted mechanism for cycloaddition reactions at coordinated trimethylenemethane l i g a n d ~ . Density '~~ functional theory has been used to study complexes of the type [Pt(PH3)(q2-alkene)] (alkene = CllH16, C10H14, CgH12, C8Hlo). Pt to alkene backbonding was found to increase as the alkene became more pyramidal which is in agreement with experimental obsevations.146 Ab initio (HF, MP2) and density functional theory calculations have been carried out on the model systems pt(PR3)H(q2-propene)] in order to study alkene insertion into the Pd-H bond and barriers to P-hydrogen elimination. The results

396

Organometallic Chemistry

obtained were consistent with experimental observations.147 The synthesis and crystal structure of 40 has been reported. It was found that coordination of the alkene fragment brings one aromatic ring into proximity of the metal centre and that this sets up an q2-bonding i n t e r a ~ t i o n . 'A ~ ~set of [K(18-crown6)][PtC13(q2-alkene)]complexes have been prepared and characterised, several by ~rystallography.'~~ A selection of five-coordinate Pt(I1) alkene complexes have been prepared and some structurally characterised. Some of the compounds reported contained carbenes as ancillary ligands. Oxidative addition of GeMe,C4-, to the strongly nucleophilic [Pt(2,9-Me2-1,10-phen)(q2H2C=CH2)] afforded [PtCl(GeMe,C13-,)(2,9-Me*- 1,l0-phen)(q2-H2C=CH2)] which have trigonal bipyramidal geometry at Pt.151 The mechanism of alkene exchange in chloro/ethene complexes of Pt(I1) was studied using UV-vis, 'H-, and 19'Pt NMR spectro~copy.'~~ The relative position of the cation and anion in a series of complexes of the type [PtMe(q2-alkene)(diimine)][BF4]in CH2C12 has been investigated using 19F{'H}-HOESY NMR, which detects specific interionic dipolar interations. The data obtained allowed an interpretation of the substituent effects of the ligands on the accessibility of the metal centre by the counter-ani~n."~ Reaction of 41 with [Pt(PPh3)2(q2-H2C=CH2)]afforded spectroscopically characterised 42 which slowly rearranges to 43. 54 Linkage isomerisation between 44 and 45 has been studied by NMR spectroscopy. The

"'

'

solid state stucture shows the preference for 0-0 chelation over alkene coordination. 155 The addition of nucleophiles to [Pt(N,N,N,'N-Me4en)(q2H2C=CHR)] has been shown to give a mixture of anti- and Markovnikov products which isomerise to give purely Markovnikov isomers in the solid state. 56 The structure, bonding and reactivity of the q3-propargyl-containing complex Ipt(PPh3)(q3-CH2C=CPh)]has been studied using density functional theory. 157

3.5 Other Metals. - The fluxional nature of q3-allyl ligands in ansa-bridged scandocenes and yttrocenes has been studied by VT NMR spectroscopy. An q3+q1 coordination mode change as well as 180" rotation of the ally1 group was observed. It was also reported that donor solvents had little effect on alkene dissociation. 58 Density functional theory calculations have been carried out on the alkene metatheis effected by dicyclopentadienyl Ti(1V).

13: Hydrocarbon Transition Metal z-Complexes other than q-CSHS and q-Arene Complexes 397

Contrary to experimental mechanistic studies, no evidence for an alkenealkylidene intermediate was found.159 Density functional theory has also been used to study the factors that influence the insertion of alkenes during polymerisation by Ti based catalysts with 0, S, Se and Te based ancillary ligand sets. It was found that the greater the donor power the ligand the lower the barrier for alkene coordination and insertion. Treatment of [Ti(q5C5Me4TMS)2], which has a sandwich structure, with ethene afforded the crystallographically characterised ethene adduct [Ti(q2-H2C=CH2)(q5C5Me4TMS)2]. The preparation and crystal structure of [Cp2Ti(q2-C6,)]was described. The coordinated C-C bond of the fullerene was elongated from 1.38 The ansa-bridged fulvalene complex 46 was prepared via to 1.507(6) reductive elimination from a thermally unstable dialkyl precursor. 63 Thermolysis of 47 at 130" afforded 48 in which two C-H bonds of adjacent CH3

'

A

'

But

\

46

47

48

groups of a Cp* ring have added across the alkyne triple bond? The reactivity of permethylzirconocene and permethyltitanocene towards buta-l,3dienes was described. Both q4- and q2-coordination modes were observed along with coupling reactions, and the factors that influence these observations were discussed.165 Density functional theory has been used to study the formation of stereoerrors in the 'stereoselective' polymerisation of propene using zirconocene based catalysts.166 The preparation and reactivity of [Zr(=CHR)(q':q l-P-q '-P-C5H3-1,4-SiMe2CH2PPri)] was reported and it was shown to readily form alkene-, ketene- and ketimine-containing complexes.' 67 Compound 49 has been prepared and structurally characterised; it was also shown to dimerise dec-5-yne to 6,7-dibutyldodeca-5,7-dienein 95% yield. 16* Rac- and rneso-ethylene-bisindenylzirconocenealkene-phosphine containing complexes were prepared and characterised spectroscopically and in some cases crystallographically. Treatment of the compounds with B(C6F5)3 afforded the expected zwitterionic compounds.169 Reaction of [Cp2Zr(CH2TMS)(THF)][BPb]with [Cp2Zr(C=CMe)2] afforded [(C~2Zr)~pq2:q2-MeC(CMe)(p-[[kappa]l2-C-CH2TMs)][BPh4] which contains a planar four-coordinate carbon atom.I7' Compound 50 was obtained from rac[(Me2Si(l-indenyl)2ZrC12]by reaction with butadiene magnesium followed by B(C6F5). Reaction of 50 with propene in d8 toluene led to the observation of a regiospecific and stereoselective mono-insertion into the Zr-CH2 bond. It was also reported that 50 is an effective single component catalyst that polymerises by the relay mechanism. 17' A wide variety of organometallic complexes (mono- and dialkyl, allyl, butadiene) of Ta supported by a calix[4]arene-oxo

Organometallic Chemistry

398

50

49

51

matrix have been synthesised. The reactivity of these complexes has also been investigated; for example migratory insertion reactions were described.172 The reactivity of [Cp2Ta(q4-s-trans-C4Hs)]+with alkylisocyanides was described. Addition of a stoichiometric amount led to displacement of one double bond: addition of an excess led to complete displacement of the butadiene fragment.’73 The tuck-in complex 51 has been prepared and structurally characterised. The long Ta-C bond lengths to C(3) and C(4) mean that the bonding to the Cp ring is best described as q3. Treatment of the alkoxycarbene containing complex [Mn{ =C(OEt)Me)(CO)2(q5-C5H4Me)]with a,p-unsaturated aldehydes followed by water afforded complex 52, from which the aldehyde can be liberated by reaction with NCMe.’75 Treatment of [M][Mn(CO)5](M = PPN, Na) with c60 afforded [M][Mn(CO)s(q2-C60)]which was structually characterised.17‘ The allene complexes [ C P M ~ ( C O ) ~ ( ~ ~ R2C=C=CR’2)](R = R = H, F; R = H, R’ = F), e.g. 53, have been synthesised and fully characterised. Spectroscopic data suggest that the q2-perfluoroallene is a better n-acceptor than C0.177Treatment of [(qs-CloH9)Mn(CO)3]with L (L=CO or PMe3) afforded the ring slipped products [(q3-CIoH9)Mn(C0)3(L)]. Warming of these complexes led to loss of one CO ligand and reformation of the q5-coordination of the 1-H-hydronaphthalene ligand. The compound [(q5-CloH9)Mn(CO)3]unlike the indenyl analogue was shown to

52

53

54

catalyse the hydrosilation of ketones by Ph2SiH2.178 Reduction of trans[ReBr(terpy)(PPh3)2][OTflwith activated magnesium in the presence of excess t B ~ N Cor PMe3 and alkenes afforded the complexes [Re(L)2(terpy)(q2-a1kene)][OTfl where the alkene is found to coordinate in the same plane as the terpy ligand: ketones and aldehydes were also shown to form analogous ncomplexes.179 The complex [TpRe(CO)(PMe3)(q2-cycZo-C6H10)] was synthesised and shown to complex to naphthalene, thiophene and furan when refluxed in DME. Only one diastereoisomer is observed for the naphthalenecontaining complex, whereas for furan and thiophene mixtures are obtained. The reactivity of the ally1 complex [Cp*ReH(CO)(q3-C3Hs)] towards the electrophiles: CF3C02H, CF3C02D, CF3S03H, NO[BF4] and [p-

13: Hydrocarbon Transition Metal z-Complexes other than q-C5H5andy-Arene Complexes 399

C6H40Me][BF4]was investigated. Reactions with the acids afforded hydridopropene containing complexes. The use of CF3C02D led to a mixture of D at metal and D on the propene ligand suggesting initial attack by the electrophile is at the metal centre followed by either H or D migration to the allyl ligand.'" Complex 54 has been shown to be the active species in the [ C P R ~ ( H ) ~ ( P P ~ ~ ) ~ ] catalysed H/Dexchange between C6D6 and other arenes and alkenes. No evidence for phosphine dissociation during the exchange process was observed.182 Density functional theory calculations (B3LYP) were used to study the ground state of the norbornene bound photosensitiser [Cu(8-oxoquinilato)]. The q2-bonding interaction reduces the n-n* band gap; with the implication of this being that light with h 100 nm longer can be used to photoactivate the complexed norbornene.183 A theoretical study on the coordination geometry and a molecular orbital analysis of the dimethylcuprate anion was carried out. The interaction with ethyne and ethene was described and a Dewar-Chatt-Duncanson interaction suggested.184 The Cu(1) complex 55 that contains an q2-naphthalene ligand tethered to an aza-thia-macrocycle has been synthesised and crystallographically characterised. 85 The Cu(1) alkene-containing complex 56 has been prepared and structurally characterised.186 The formation of q3-allyl on Cu( 100) was reported and its cryogenic coupling with allyl bromide investigated.'87 Reaction of AgC104 with C214in benzene afforded structurally characterised 57. If the reaction is carried out in toluene no q2-arene interaction is observed.188

'

w 55

4

56

57

Complexes Containing Unconjugated Alkenes

FTIR was used to quantitatively investigate the reaction kinetics of ligand substitution reactions in [M(CO)4(q4-COD)](M = Cr, Mo, W).'*' In a related paper the displacement of NBD by bis(diphenylphosphino)alkanes, also studied by FTIR spectroscopy, showed the reaction to have first order dependence on complex.1g0A diverse range of six- and seven- coordinate halocarbonyl complexes of molybdenum(I1) and tungsten(I1) that contained diene ancillary ligands were synthesised and fully characterised. The zero valent ruthenium complexes [RuL(q2-dmfm)(q6-COT)] (dmfm = dimethyl fumarate; L = benzylamine, propylamine, dimethylamine, morpholine, pyridine) have been prepared and fully characterised.192 Hemilabile coordination of one of the hydroxyl groups of 58 in complexes of the type [Rh(q4-diene){ dppb(OH)2f][BF4] (diene = NBD, COD) was suggested to

"'

Organometallic Chemistry

400

" O Ho'

XPPh2 ph2 58

59

explain their temperature dependent 31P and lo3Rh NMR spectra. Density functional theory was used to compute changes in isomer energies and hence the lo3Rh shifts with good correlation between the experimentally observed data and that calculated.193 In a related study, the effect of steric and electronic effects on lo3Rh 6 values was studied for a selection of complexes of the type [RhL2(q4-COD)] (L = oxygen, nitogen donors). Again density functional theory calculations were carried out and the results compared to the experimentally obtained data: good correlation was obtained.194 NMR spectroscopy was used to study the exchange of the pendant and coordinated amino groups in 59. The process proceeds with retention of ring conformation and the mechanism was discussed in terms of: the induction of chirality; the principle of microscopic revesibility; the effect of rate differences of simultaneous processes.195 NMR exchange measurements on the cationic complexes [Rh(L2)(q4-COD][BF4](L2 = chiral bisphosphines; bidentate: P-N, P-S, N-N) were described along with crystal structures of two of the c ~ m p l e x e s . Cyclic '~~ voltammetry was used to study the reaction: [Rh(q4-COD)2]++ 2 soh

+ COD

+ [Rh(q4-COD)(solv)2]+

This methodology was shown to be as effective at studying the true composition of solutions of labile organometallics as spectroscopy.197 A collection of m3Rh(q4-COD)]' o\T3 = chelating nitrogen ligand system) have been prepared and their oxidation studied by electrochemical techniques, 0 2 and H202. For example, the complexes are selectively oxygenated by H202 to give Rh(II1)-oxabicyclononadienyl-containing complexes which rearrange to Rh(II1)-hydroxycyclooctadienyl containing systems.19* Treatment of [1ndRh(q2-H2C=CH2)2] with a range of quinones led to the expected bisethene substituted products. The crystal and molecular structure of [IndRh(q42,3,5,6-Me4-C6O2)]was r e ~ 0 r t e d . The l ~ ~ photochemistry of [(Me2Tp)Rh(q4COD)] has been investigated. It was found that rearrangement of the q4-1,5COD to the conjugated q4-1,3-COD form via a 1,3-hydrogen shift had occurred.200A wide selection of [Rh(q4-COD)]+complexes containing S-N donor ligands have been prepared and characterised.201 The complex [Rh(CrCPh)(PPh3)(q4-NBD)] has been prepared, along with a series of other phosphine containing analogues, and shown to polymerise phenylacetylene and rn-, p-substituted phenylacetylenes. It was found that 4-dimethylaminopyridine is required as an addative to give good polydispersities and to prevent the formation of crystallographically characterised Treatment of [Rh(NCMe)2(q4-COD)][BF4]with 100 molar equivalents of 'BuC2H yielded a

13: Hydrocarbon TransitionMetal n-Complexesother than q-CJH5and q-Arene Complexes 401

small amount of an open-chain tetramer and 61 which was stucturally characterised. A mechanism by which this complex formed was proposed.203 The electronic effects influencing Rh(1) catalysed hydrogenation was studied using crystal structure data from precatalysts and 31PNMRdata.204The chiral water soluble complex 62 was found to hydrogenate functionalised alkenes in

kh(C0D)

60

61

62

water with up to 99.6 ee.205Other complexes containing chiral p h ~ s p h i n e , ~ ~ ~ non-C2-symmetric mixed phosphine phosphinite;208 bicyclic ph~sphinite~'~ ligand systems were prepared and characterised and their utility in asymmetric hydrogenation investigated. A collection of [Rh(q4-COD)] containing complexes with chiral macrocyclic phosphine ligands,210phosphinoamine ligands with pendant N-bound ethylhydroxy or ethylmethoxy side-chains,*l' diphenylphosphnite functionalised cyclodextriny2'2and chiral bidentate thioether ligands2I3 were prepared and characterised. Their use as hydroformylation catalysts was also described. For the cyclodextrin-containing complexes their utility in hydroboration was also reported. [Rh(q4-COD)] complexes containing 1 1-(2-diarylphosphino-1-naphthyl)isoquinones have been prepared and characterised and their use in asymmetric hydroboration and oxidation reactions investigated: the best ee obtained was 97%. Mechanistic aspects of the catalytic reaction were also discussed.214Some chiral [Rh(LL)(q4-COD)]' precatalysts have been incorporated into a protein cavity and used in asymmetric hydrogenation reactions with ee from 3 to 48%.215Heterogenisation of [Rh{03S(C6H4)(CH2C(CH2PPh2)3) (q4-COD)] by hydrogen bond interaction between the SO3- group and silanol groups on partially dehydroxylated silica was described. Hydrogenation and hydroformylation reactions in a biphasic system were investigated using the catalyst in supported and unsupported form. The supported form was found more chemoselective and re-cyclable.216 [Rh(q4-COD)]tethered to heterogeneous Pd-Si02 was found to de-fluorinate 1,2-difluorobenzene and fluorobenzene under the mild conditions: of H2 (4 atm), 70 "C, N ~ O A C . The ~ ' ~ utility of heterogenised (USY-zeolite) chiral diphosphinite-containing [Rh(q4-COD)] complexes in hydroformylation was investigated. The heterogenised system was more active than the non-supported analogue and was shown to be capable of being recycled without any significant loss of activity.218Complexes of [M(q4-COD)] (M = Rh, Ir) with chelating nitrogen ligands based upon pyridine-amine-pyrrole or pyridineamine-pyrrolate systems have been prepared and characterised. The potential of these comlexes to polymerise phenylacetylene was also de~cribed.2'~A collection of chiral C1-dithioether ligands were prepared and the complexes y

402

Organometallic Chemistry

[Ir(SS)(q4-COD)][BF4]synthesised from them. These complexes were shown to undergo selective oxidative addition reactions with H2 and subsequent investigation of their utility as asymmetric hydrogenation catalysts reported (ee up to 62Y0).~~' [M(q4-diene)](M = Rh, Ir; diene = COD, NBD)-containing hemilabile phosphine-oxygen ligand sets based around benzylic systems were prepared and characterised. The benzylic-CH2 group was found to oxidatively add to the metal centre affording Rh(II1) and Ir(II1) complexes respectively.22' Other examples of benzylic-C-H activation include: addition of the hemilabile ligand Ph2PC6H40CH2NMeC(0)Etto [Ir(q4-C0D),1[BF4] afforded 63;222and the reversible C-H activation in 64 and 65: both 64 and 65 have been structurally

63

64

65

~ h a r a c t e r i s e d .The ~ ~ ~coordination of ortho- and para-quinones to trimethylphosphine-containing complexes of Co and Ni was investigated. 0-0 cordination was generally observed for Co(II1) and Ni(I1); however, for Ni(0) 66 was obtained.224 Ligand exchange reactions in [Ni(q4-COD)2] with bidentate pyridine based ligands were shown to occur with pseudo first order kinetics. The proposed mechanism invokes a 20e intermediate.225The complexes [PdR2(q4-COD)]{ R = CH(SiMe3)2,CH2SiMe2Ph}were prepared and found to be useful precursors for the preparation of [PdR2(L)2](L=N, P donor ligands) by displacement of the COD ligand.226 The triflate containing complex 67 was prepared and evidence for triflate ionisation obtained. Reaction with sterically demanding 2,g-diaryl substituted 1,lO-phenanthroline afforded the cationic penta-coordinate complex 68.227Reaction of [Pd(OAc)&

68

with dibenzylamine afforded the dimeric complex [Pd{ C6b-2(CH2NHCH2Ph))( ~ O A C ) which ]~ was converted to the bromide 69 on reaction with NaBr. Treatment of 69 with alkynes led to double insertion products 70 and 71: the reactivity of 71 was further investigated.228The organosiloxy containing complexes [MR(OSiR,)(q4-COD)] (M = Pd, Pt; R=Me, Et, Ph) have been prepared and characterised. Reduction of the complexes with H2 was also described.229Oxidative addition of SnR& - x )

13: Hydrocarbon Transition Metal z-Complexes other than q-C5H5and q-Arene Complexes 403

(R = Me, Ph; x = 4-0) to [Pt(q4-C0D),1 afforded the oxidative elimination products [Pt(SnRcx- l~C1~4-x~R)(q4-COD)]. The COD ligand in these complexes was readily displaced by phosphine ligands affording analogous phosphine containing complexes.230Complexes of the type [PtMe(L)(q4-COD)] {L=Cl, I, OH, Me, CH2C(0)Me, C2Ph, Py] have been prepared and characterised. The OH-containing complex was shown to react with acidic CH substrates to form new Pt-C bonds.231 Solution calorimetry was used to measure the reaction enthalpies on treatment of [pt(Me)2(q4-COD)]with a range of monodentate phosphines. It was found, in correlation with 31P-NMR data, that the Pt-P interaction is strongest with electron withdrawing substituents, at phosphorus, and that this interaction is not influenced by the size of the p h ~ s p h i n e . ~ ’ ~

Ph&C” L

’H

2

69

R 71

5

ComplexesContaining Cyclic Conjugated Alkenes

Cr, Mo, W. - Cycloheptatriene-containing [Cr(CO),] complexes have been used to construct a 6-aza-bicyclo[3.2.1] octane ring utilising higher order cycloaddition reactions. This methodology allowed a total synthesis of (+)peduncularine to be achieved.233Compound 72 was prepared and used in a benzannulation sequence featuring a [6n;+ 4x1 cycloaddition as part of a synthetic strategy for the preparation of (+)-estradi01.~~~ Cyclopropylcarbinyl ring-opening competition experiments showed that transition states bearing anionic, cationic or radical character at the benzylic position are stabilised to a greater extent than by being q6-coordinated to the [Cr(CO),] moiety than in the free system: this was also found by calculation.235Some tricarbonyl(dihydroazepinyl-chromiumcomplexes have been synthesised via alkyne inser5.1

24

m e & h Me’w N - 4

CrO,

72

73

-

oc-_N”: 1 -co 74

R

404

Organometallic Chemistry

tion into a Cr-alkylidene bond and compound 73 was structurally characterised. Reaction of these complexes with pyridine induces a rearrangement and subsequent isolation of (isob~tyry1methylene)pyrrolidines.~~~ Nucleophilic attack by the deprotonated thiobarbituric acid 1,3,5-trimethyl2-thiobarbituric acid on [Cr(CO)3(q7-C7H7)]+, [M(CO)3(q6-C7H,)]' (M= Fe, Ru) led to em-addition. A selection of multimetallic complexes were subsequently prepared and characterised from the neutral products.237 A 4: 1 thermal equilibrium mixture of 1,3,5,10-tetramethylheptalenewas reacted with [Cr(C0)3(NH3)3]yielding all four possible isomeric monometallic products as well as two bimetallic species. All of the complexes were fully characterised, including structurally. Thermal rearrangement between the isomers was observed and this was explained in terms of haptotropic shifts.238The electronic spectrum of the 'ion-pair' [Mo(C0)3(q7-C7H7)][BPb] has been recorded in CH2C12and shown to have an outer sphere charge transfer band at 370 nM A collection of cycloheptatrienyl complexes of the type [MoX(dppe)(q7-C7H7)]'+ ( z = 0, X = NCO, NCS, CN, 13CN;z = 1, X = CNMe, 3CNMe, oxacyclopentylidene) have been prepared. Cyclic voltammetry showed that all of the compounds undergo a reversible le oxidation, which was also achieved chemically. EPR and ENDOR studies suggest that the unpaired electron resides in an essentially a metal centred orbital.240 A collection of cycloheptatrienyl containing complexes containing o-bound polyacetylene ancillary ligands such as 74 have been prepared and characterised, A collection of N-(2-pyranyl)- and Ntheir reactivity was also in~estigated.~~' cyclohexylindole derivatives have been prepared by nucleophilic attack, of indole based nuclephiles, on cationic x-bound pyran and cyclohexadiene molybdenum carbonyl complexes: the organic fragment was obtained by oxidative cleavage.242Bromotriphenylmethane was shown to abstract hydride ion from [CpM~(CO)~(q~-cycZo-allyl)] in the presence of hexafluoroisopropanol affording [CpM~(CO)~(q~-cycZo-diene)l[Br].~~~ The complexes [M12(L)(q7-C7H7)] (M = Mo, W; L = NCMe, PPh3) were shown to efficiently ROMP norbornene.244 5.2 Fe, Ru, 0s. - The use of [Fe(C0)3(q4-cyclobutadienyl)]stabilised carbonium ions that were subsequently used for the formation of new C-C bonds was described.245 Reaction of the cationic complexes [CpFe(C0)2(PPh2C=CR)] (R = H, Me, tBu, Ph, Tol) with NaBH4 at - 78 "C afforded the complexes[(q4-C5H6)Fe(C0)2neutral cyclopentadiene containing ( P P ~ ~ C E C Rin ) ] good yield.246Irradiation of 75 in the presence of PPh3 yielded 76 which was structurally ~ h a r a c t e r i s e dCompound .~~~ 77 was obtained by a [2 + 2 +1] cycloaddition reaction . The organic fragment 78 was readily decomplexed on photolysis in NCMe followed by exposure to air.248Treatment of [Fe(C0)3(q4-cyclopentadienone)]complexes with NaOH followed by NaH afforded the anionic species [Na][FeH(C0)3(q4-cyclopentadieneone)], whereas reaction with H3P04 afforded [FeH(C0)2(q5-C5H40H)].The reactivity of these complexes was described along with a simple method for the decomplexation of the organic fragments.249Treatment of 79 with [Fe(CO)5]

13: Hydrocarbon TransitionMetal n-Complexes other than q-CsHs and q-Arene Complexes 405

75

* m o

76

TMS i, NCMelhv ii, air * -0

TMS

TMS

78

77

79

80

afforded structurally characterised 80 which was then converted, in a series of A selection of Fe-aryl complexes and aryl-cyclohexasteps, to ~orannulene.~~' dienyl-containing complexes have been prepared by nucleophilic addition of aryl lithium reagents to [(q5-1,4-dimethoxy-cyclohexadienyl)Fe(C0)3].251Flavones have been reacted with [Fe(C0)3(qS-cyclohexadienyl)]+ to give compounds of type 81. These complexes were then used as probes for molecular recognition events during induction of nodulation genes in Rhizobium Zegumin o s a r ~ r nThe . ~ ~nucleophilic ~ attack of anilines on [(q5-1-R-4-MeO-cyclohexadien~l)Fe(CO)~] has been investigated. Where the side-chain bears a leaving group the reaction was shown to proceed by initial elimination of the leaving group from the side-chain to give a vinyl group, rather than direct attack at the ring.253Complexation of a selection of nitroarenes to the [CpFe+] fragment was described and nucleophilic attack by CN- in DMF yielding cyclohexadienyl containing complexes was reported. Decomplexation of the organic fragment using DDQ afforded a wide range of nitro-containing aromatic nit rile^.^^^ Treatment of a range of complexes of type 82 with T1(02CCF3) afforded compounds of type 83 in reasonable yield.2s5The use of camphor derived aza-dienes enabled high ee (86%) complexation of prochiral cyclohexa1,3-dienes to the [Fe(C0)3] moiety under photochemical conditions.256By

81

82

83

406

Organometallic Chemistry

contrast low ee values were reported for the asymmetric complexation of 1methoxycyclohexa-1,3-diene to the [Fe(C0)3]moiety when amino acid-derived 1-azabutadienes were used as the chiral a ~ x i l l a r yThe . ~ ~preparation ~ of the marine alkaloid hyellazole and the non-natural regioisomer iso-hyellazole were prepared from [Fe(C0)3(q5-cyclohexadienyl)]+: a crystal structure of an (q4diene) intermediate was also reported.258The antibiotic alkaloids carbazomycin A and B were also prepared in several steps starting from [Fe(C0),(q5cy~lohexadienyl)]+.~~~ Compounds of type [Fe(C0)3(q4-cyclic-diene)](where the diene contains carboxylic acid groups) were converted to the cationic nitrosyl analogues on treatment with NO[BF4]. In the presence of NEt3 and a or 6 lactones containing a,j3-unsaturated aldehydes, insertion reactions were observed.260The reactions of [Fe(C0)2L(q6-C,H,)] (L = CO, PPh3, P(OPh)3) with carbomethoxymaleic anhydride have been studied kinetically and the data suggests that a previously suggested [4 + 21 Diels Alder adduct is the thermodynamic rather than the kinetic product.261The relative electrophilicities of free and [Fe(C0)3] complexed tropilium have been investigated using uncharged nucleophiles. The kinetic data suggest that the C-C bond forming step is rate determining with complexation of the [Fe(C0)3]fragment shown to have only a marginal effect on the relative electrophilicity. Density functional theory was used to rationalise these results in terms of thermodynamic effects and frontier orbital interactions.262[Ru(C0)3(PPh&] promoted coupling of alkynes under a CO2 atmosphere yielding the cyclobutadiene-containing complexes [Ru(C0)2(PPh3)(q4-C4R4)] and cyclopentadienone-containingcompounds [ R u ( C O ) ~ ( P P(q4-C4R&(0)}]. ~~) When asymmetrically functionalised alkynes were used a mixture of regioisomers were obtained.263 [Ru(q4in the COD)(q6COT)] was shown to dimerise bicyclo-[2.2.l]-hepta-2,5-diene presence of electron deficient alkenes such as N,N-dimethylacrylamide, dimethyfmarate, diethylmaleate. The molecular structure of the dimer was determined by a single crystal X-ray diffraction study of the [Ag(OTf)(q2dimer)], polymer. The solid state structure of [Ru(q2-dimethylf~marate)~( q6COT)] was also reported.264Treatment of [Ru(p-C1)Cl(q5-Me5-thiophene)12 with 1,4,7-trithiacyclononaneafforded the bridge opened complex [Ru(K~[9]aneS3)(q5-Me5-thiophene)I2+.Nucleophilic attack by the ethoxide ion was also investigated and shown to attack exo to the sulfur which was confirmed ~rystallographically.~~~ The reactivity of [CpRu(q4-C5&O)], anchored to native silicon (SUSi02) by a nitrile linker, towards phosphines has been described. The data obtained from in situ ellipsometry were comparable to those obtained when PR3 nucleophilically attacks [CpRu(q4-C5H40)L] (L = nitrile, py) to give the cyclopentenoyl complexes [CpRu(q3C5H40PR3)(L)].266 5.3 Other Metals. - Cyclohexadienyl containing complexes of type 84 have been prepared and ~ h a r a c t e r i s e d .The ~ ~ ~reaction between Li2[1,4-bisTMSCOT] afford a mixture of 85, 86 and 87. Compounds 86 and 87 were structurally characterised and their EPR spectra recorded.268Photochemical and ligand induced facile hapticity changes in 1-hydronaphthalene manganese

13: Hydrocarbon Transition Metal z-Complexes other than q-CSHj and q-Arene Complexes 407

Mepsi

84

85

06

87

carbonyl complexes were described.269Photolysis of [Mn(C0),(q5-C6H7)]in THF afforded [Mn(C0)2(THF)(q5-C6H7)].The reactivity of this complex towards a variety of allenes was described and a selection of complexes containing cycloaddition products were obtained and ~haracterised.~~' Reaction of [Mn(C0),(q6-arene)] with secondary a-cyano or a-sulfonyl carbanions was described and yielded neutral mono- and dinuclear cyclohexadienylcontaining complexes. Heterobinuclear MdCr complexes were prepared when analogous nucleophilic attack by carbanions of the type [Cr(C0)3(q6-areneLi)] occurred.271A collection of mono- and bimetallic complexes of Mn/Rh were prepared that contain the COT ligand and the COT was shown to bind in a variety of ways to the metal centres: many of the compounds were found to be The pervinylated cyclobutadiene-containing complex 88 has been prepared and structurally ~ h a r a c t e r i s e d .Bistrimethylsilylpropargylic ~~~ alcohol was dimerised by [C~CO(CO)~] to give a structurally characterised (q4cyc1obutadiene)-containing complex. This complex was then transformed to 1,8-diheterocyclo[CpCo(q4-1,2-diethynyl-3,4-bisTMS-cyclobutadiene)] .274 octatetradeca-4,ll -diynes were reacted with [CpCo(q4-COD)] and found to give the intramolecular [2 + 21 cycloaddition products 89.275The pentafulvalene complex 90 was prepared and fully characterised. This compound was readily protonated to give the cobaltocenium cation. Crystal structure data

suggests that the fulvalene is q4-coordinated with a short exo-double bond. Reversible one electron reduction was observed using cyclic voltammetry and EHMO calculations were carried out to model electrochemical and EPR properties.276The diastereoselectivity of [2 + 2 + 21 cycloaddition reactions of linear enediynes to give q4-cyclohexadienylcontaining complexes was reported to be improved by functionalising the triple or double bonds with ester, phosphine oxide or sulfoxide moieties.277 Stereoselective induction of [CpCo(CO)2] mediated [2 + 2 + 21 cycloaddition reactions of chiral phosphine oxide functionalised linear enediynes has been further described.278A collection of electrophilic Co complexes of type 91 have been prepared and shown to undergo [3 + 2 + 21 allyl/alkyne cycloaddition reactions yielding cyclohepta-

Organometallic Chemistry

408

dienyl-containing products like 92. A mechanism that involved a Co(II1) activation of a C-C bond was proposed.279

\Me

Me' 92

91

6

Complexes Containing Acyclic Alkenes

Reaction of the titanocene source [Cp2Ti(q2-TMSC(CTMS)]with 1,4-disubstituted-l,3-butadiynes has been described and for R = But compound 93 was obtained and found to be stable. When R = Ph the complex was unstable to dimerisation.280In a related study C P * ~ Z and ~ C P * ~ Twere ~ reacted with 1,4disubstituted-1,3-butadiynes and the preparation of several n-bound hydrocarbon-containing complexes described. As for the titanocene based systems, the stability of the complexes formed was dependent upon the 1,4-substituents.281 Reaction of the boratabenzene containing complex [(q6-cycZoRBCsH5)2Zr(PMe3)2] with 1,4-Ph2-buta-1,3-diyne affoded [(q6-cycZoRBC5H5)2Zr(q4-2,5-Ph2-buta1,2,3-triene)] (where R = NMe2 the complex was structurally characterised).282Treatment of the ansu-metallocene rac[{ Me2Si(C5H3Me)2}ZrC12] with butadiene magnesium afforded a mixture of

0

/'~ Y'pEb

*Cp-Ta

Pt

93

94

95

96

s-trans and s-cis-butadiene-containing complexes. A single crystal X-ray diffraction study of one of the s-trans diene complexes was described.283 Reaction of [MC1(q4-diene)(q5-1,3-TMS-C5H3)2](M = Zr or Hf) with benzylmagnesium bromide afforded [M(Bn)(q4-diene)(q5-1,3-TMS-CSH3)2]. The reactivity of these complexes towards B(C6F5)3 was investigated.284Compound 94 has been prepared, isolated and structurally characterised in a procedure used to generate vanadium based catalysts.285A selection of half sandwich Nb and Ta complexes containing 1,4-diazabutadiene ligands were prepared and a diverse range of bonding modes of the DAB ligands observed.286 [Cp*CpTa(q4-s-trans-C4H6)][MeB(C6F&] was prepared from [C~*TaClz(~~-s-trans-C4H6)] and structurally characterised. Its reactivity towards ketones was investigated and insertion into the Ta-C bond was

13: Hydrocarbon Transition Metal n-Complexes other than q-CSH5 and q-Arene Complexes 409

observed to yield seven-membered tantalatetrahydrooxepine cations; similar insertion reactions were observed on reaction with nit rile^.^^^ Treatment of [CpTaC12(q4-diene)] (diene= butadiene, 2,3-dimethylbutadiene, isoprene) with [Li2(COT)] afforded [CpTa(q,-COT)( q4-diene)]. The q’-coordination of the COT ligand was confirmed by single crystal X-ray diffraction study. When the complex [Cp*Ta(q3-C0T)(q4-C4H6)]is reacted with B(C6F5)3 the expected betaine complex 95 is obtained.288Compound 96, which has been crystallographically characterised, contains both q5-S and q5-U shaped pentadienyl coordination modes.289Density functional theory has been used to study the energy profiles for several complexes of the type [Fe(C0),(q4butadiene)] to calculate the energy differences between s-cis and s-transisomers. Excellent correlation with experimentally observed coordination modes was obtained.290In a related study quantum chemical methods have been used to structurally and energetically characterise isomers of [Fe(CO)3(q4-methylbutadiene)].The data was discussed and compared to that obtained experimentally.291 A collection of [Fe(CO)3(q4-azabutadiene)] complexes have been prepared and characterised. The solid state structures revealed a large number of hydrogen-bond interactions. EHMO calculations were also carried out on some of the complexes.292 The stereochemical factors influencing the rearrangement of [Fe(C0)3(q4-2-ethyl-1-azabuta1,3diene)] complexes to the endo-amino-buta-1,3-diene isomers were discussed. At no point was evidence obtained for the e ~ o - i s o m e r .Acyl ~ ~ ~ halides adjacent to an q4-diene in [Fe(C0),(q4-diene)] containing complexes were shown to readily react with allylsilanes, vinylsilanes and enamines to yield the corresponding ally1 ketones, vinyl ketones and 1,3-diketones. The vinyla-

tion reaction, unlike the others, required Lewis acid catalysis.294Complexes of type 97 were shown to undergo cyclisation and fluorination on treatment with BF30Et2 yielding optically active fluorinated cyclohexane derivative^.^'^ The use of [Fe(C0),(q4-diene)] as a mobili chiral auxiliary has been described. Good regio- as well as stereoselectivity was reported.2g6A chiral phosphinoacetate was used to discriminate between enantiotopic [Fe(C0),(q4-diene)] complexes allowing the preparation of optically active alkenes containing planar chirality with high ee and in good yield.297 [Fe(C0)2(PPh3)(q5-1,2-Me2-C5H3)][PF6]has been prepared and characterised and its reactivity towards hydride and C-based nucleophiles described. .~~~ Regiospecific addition was observed yielding 2E-42 diene l i g a n d ~ Diastereoselectivity of chiral l aabutadiene ligands where the diazabutadiene is part of a steroid has been described. The selectivity was found to be dependent upon the steric nature of the steroid s ~ b s t i t u e n t sStarting . ~ ~ ~ from a [Fe(C0)3(q4-dienal)] complex the stereoselective synthesis of substituted

Organometallic Chemistry

410

piperidines was achieved and included the total synthesis of of (+)- and (-)dienomycin C.300Using similar methodology the total synthesis of mycosamine was described.301 A collection of dioxaborolanylbutadienes have been prepared and coordinated to the [Fe(C0)3] fragment .302 The molecular structure of [Fe(CO)3(q4-2,3-6,7-dimethylene-dihydrofuran)]has been redetermined at 120 K 3 0 3 The synthesis, characterisation and reactivity of a wide range of diene and heterodiene complexes of the type [R~(CO)~(q~-diene)] have been reported. Several of the all-carbon-containing diene complexes have also been crystallographically characterised. The heterodiene complexes were found to be particularly reactive (unstable) and were not isolated in a M

e

98

-

99

pure Compound 98 has been reacted with alkynes and found to give compounds of type 99 where addition has occurred at the central carbon of the ally1 ether. Several exceptions to this pattern of reactivity were described along with the regioselectivity of the addition of asymmetric a l k y n e ~ . ~The ’~ crystal and molecular structure of [Cp*Ru(NCMe)(exo-q4-2-Me-C4H5)] was reported.306Reation of [( C p * R ~ c l ) with ~ ] 2-siloxy-4-methyl-l,3-pentadiene led initially to the diene complex [Cp*RuCl(q4-2-(ButMeSiO)-4-Me-penta1,3-diene)] which readily lost HC1 to give the pentadienyl complex [Cp*Ru(q5-2-(ButMeSiO)-4-Me-penta-1 ,3-dien~l)].~’~ Loss of PR3 from 100

100

101

caused the ketene to bind to the metal centre in an q4-fashion, 101, utilising a double bond in one of the phenyl rings. The fluxional nature of 101 was studied by VT-NMR spectroscopy.308A collection of mono- and dibutadiene-containing Rh(1) complexes were prepared and characterised. For some of the complexes on reaction with phosphines nucleophilic attack occurred on the butadiene ligand affording q3-allyl containing complexes: one of these products was structurally ~haracterised.~”Density functional theory has been used to study the Ni catalysed polymerisation of butadiene via the n-ally1 insertion mechanism.310It has also been used to study the synanti- isomerisation of the butenyl ligand in neutral and cationic complexes of the type [NiL(q4-butadiene)(q3-butenyl)] and related to Ni catalysed butadiene p~lymerisation.~~

13: Hydrocarbon TransitionMetal .n-Complexesother than q-CjHs and q-Arene Complexes 41 1

7

Complexes Containing Alkynes

Treatment of [ c ~ * ~ T i Cwith l ~ ] equimolar quantities of Mg and TMSC-CCrCTMS afforded 102, which is believed to be an intermediate in early transition metal catalysed oligomerisation of a l k y n e ~ Enyne-containing .~~~ complexes of type 103 have been prepared, characterised and their reactivity investigated.313Compound 104 has been prepared and structurally charac-

R-

ms+M

Ti Cp’p

\ W5W4Rk

/\

ph)pcp2 Ph-2,4,6-Me

Ph 102

103

104

terised.31 A collection of Nb isocyanide-containing complexes have been prepared and, in the presence of water, isocyanide coupling was observed to give q2-amino-alkyneligands via a protonatiodreductive coupling pathway.315 A collection of enyne or diyne-containing complexes of type 105 have been prepared and ~haracterised.~’‘The synthesis of a mixed 3e-nitrile 3e-alkynecontaining complex pp*Nb(C0)(q2-NCMe)(q2-PhC=CMe)] has been described. The vinylidene-containing complexes [M(C0)2(=C=CTMSz)(q C6H3-Me3)](M=Cr, Mo) have been prepared. For M = M o the complex is found to be in equilibrium with the alkyne isomer [M(C0)2(q2TMSC-CTMS)(q6-C6H3-Me3)]. Rapid isomerisation of the vinylidene complexes can be effected on le oxidation: le reduction of the resulting complexes affords the neutral alkyne complexes which only slowly isomerise back to the vinylidene isomers.321The reaction of [MoCl(GeC13)(CO)3(NCMe)2] with a collection of alkynes was r e p ~ r t e d . ~The ” reaction between [CpM(SR)(q2F3CCrCCF3)2](M = Mo, R = C6F5; M = W, R = 4-Me-C&) and alkynes has been described. A range of alkyne coupling reactions were observed leading to complexes containing butadienyl and flyover ligands. The type of coupling observed was alkyne dependent.320A collection of cationic alkyne complexes containing phosphite ancillary ligands were prepared and characterised. One of the complexes was shown to trimerise M e c ~ C P h . ~ Similar ~ l complexes containing linear triphos have also been described.322Electrochemical reduction of [M(L)(q2-alkyne)2(q5-C5R5)] ( M = Mo, W; L = NCMe, CO; R = H, Me) has been carried out and the radical intermediates formed during the coupling of the bound alkynes ~ h a r a c t e r i s e d .X-ray ~ ~ ~ crystallography and EPR spectroscopy has been used to study the redox pairs [Me2TpWX(CO)(q2MeCrCMe)]”+ (X = F, C1, Br, I). The data obtained is consistent with the HOMO being n-bonding with respect to the W-CO bond and wantibonding with respect to the W-X bond and &bonding to the alkyne bond.324Treatment of [Tp’W(O)I(CO)] with alkynes in the presence of TMNO afforded the complexes pp’WI(CO)(q 2-RC=CR)] in which unsymmetrical-alkyne rotomerisomers (where possible) were observed. Terminal alkyne-containing com-

’’

‘-

412

Organomet a l k Chemistry

plexes could also be converted into vinylidene complexes.325The 4e donor alkyne in [{WC14(q2-PhC=CPh)>2]was converted into a 2e donor on introduction of an imido ligand: attempts to convert the alkyne back to a 4e donor were unsuccessful.326Compounds of type 106 have been prepared and the chlorides found to be particularly labile.327An q4-bound alkyne has been prepared by carbyne and isocyanide coupling at a d4-W metal centre.328 Compound 107 has been generated and its reactivity towards simple alkenes and alkynes investigated using FTICR mass spectrometry. Adduct formation

TMS-cp' -b ;c\l Cp-TMS

Q0

'R' 105

106

107

and oligomerisations were observed and the results tested using density functional theory.329 These techniques have also been used to study the interconversion of [FeH(q2-HC-CH)] to [F~(G-CH=CH~)].~~' The preparation of [ O S ( C O ) ~ ( P M ~ ~ ) ( ~ ~ - H C =and C Hits ) ] reactivity towards phosphines has been described.331The coordinatively unsaturated complex [OsCl(NO)(CO)(PBU'~M~)~] forms an q2- adduct with PhC-CH which on warming rearranges to a vinylidene containing complex.332 Ab initio and density functional theory have been used to study the [CpCo(L)(L')] (L = L = CO; L = PR3, L' = C2H4) catalysed trimerisation of a l k y n e ~A. ~theoretical ~~ study into the rearrangement of acetylenes to vinylidene ligands promoted by [Co((P(CH2CH2PPh3))I was also carried out .334 Treatment of [Rh(OCMe2)(PPri3)2]+with internal alkynes affords simple q2-adducts, whereas reaction with terminal alkynes affords vinylidene complexes.335[Rb(CO) 121 was reacted with a variety of alkynes and approximately 20 alkyne-containing Rh complexes identified by in situ spectroscopy. Many of the complexes were found to be stable under hydroformylation conditions and this observation led the authors to comment as to why trace amount of alkynes irreversibly poison hydroformylation catalysts.336 The reaction of [Ir(CO)(PPh3)(PPh2C6H4NMe2)] with alkynes has been investigated and found to yield oacetylides as well as q2-alkyne-containing complexes.337Density functional theory has been used to study the bonding in Ni-alkyne complexes.338Alkyne complexes of the type mi(&-(diisopropy1phosphino)ethane) (q2-alkyne)] (alkyne = M e C S T M S , 'BuC-CTMS) have been prepared and characterised. Heating with biphenylene and excess alkynes led to the isolation of a range of novel organic products.339Dichloroacetylene has been shown to displace the coordinated alkene in [Ni(PR3)2(q2-H2C=CH2)]to give the analogous alkynecontaining complex. Competitive oxidative addition of the C-C1 bond was also described along with alkyne trimeri~ation.~~' A series of Pt(0) complexes

13: Hydrocarbon Transition Metal n-Complexesother than q-CSH5and q-Arene Complexes 41 3

containing alkynylphenylsilanes have been described and structurally characterised.341 8

Polymetallic Complexes

8.1 Bimetallic Complexes. - Reduction of [{q8-1,4-TMS-C8H6Ti(p-C1))2(THF)] with Mg in the presence of TMSCrCTMS afforded 108 which has been structurally characterised and has a particularly strong Ti-Ti interaction (2.326A).342Treatment of [Cp2Vjwith TMSCrCCSC-CTMS afforded the crystallographically characterised complex [(Cp2V)2(q3:q4-triyne)].The magnetic properties of this complex were measured between 2 and 300 K and evidence for a weak antiferromagnetic J exchange coupling of - 3.7 cm-' was indicated.343 Compound 109 has been prepared and characterised. EPR suggests interaction between the two metal centres and magnetic susceptibility measurements indicated weak antiferromagnetic He(1) and He(I1)

108

109

110

PES were reported for [Moz(q8-C8H4-1,4-SiPri&] and compared to that obtained from density functional theory calculations: good agreement was with CF3C2H gave obtained.345Reaction of [Cp2M02(p-SMe)3(NCMe)2][BF4] 110, whereas reaction with 4-Me-PhC2H afforded a flyover complex.346The synthesis and utility of [W2(0CH2Buf)6(q-diene)(py)](diene = butadiene, isoprene) in 1,3 selective hydrogenation was described.347Compound 111 was obtained on photolysis of [IndRe(C0)3].348The reactivity of [Fe2(C0)6(pPPh2)( p-q :q2-CH=C=CH2)] towards tris(dialkylamin~)phosphines~~~ and tB~NC350 has been investigated and nucleophilic attack on the bridging nr.

111

112

ph

Ph,

113

hydrocarbyl fragment observed. Thermolysis of [Fe2(Co)6(p-PPh2)(p-C2tBU)I led to two new structurally charcterised compounds [Fe2(C0)2(p-PPh2)(pLOPPh2C6H4C=CHBut)] and [Fe3(C0)4((p3-OPPh2C6H4CPPh2)(p3-cBut)(-CCH=CBut-q6-Ph)]: mechanisms for the rearrangements were presented.351 The reaction of [Fe(p3-s)(p-PPh2)2(p-co)(co)6] with alkynes has been de-

414

Organometallic Chemistry

scribed. A collection of compounds containing new P-C and S-C bonds were reported.352Treatment of 112 with [Fe3(CO)12]afforded 113.353The reaction between [{ Fe(C0)3}3(p-C7HS)2]and aryl-lithium reagents was found to cause coupling of the two cycloheptatrienyl rings. Further reactivity of the coupled rings was also presented.354Compound 114 has been prepared and structurally characterised. It is the first compound to display Pierls distortion.355Treatment of [ R u ~ ( C O ) ~with ~ ] ethyne afforded four spectroscopically characterised compounds one of which, 115, was structurally characterised and contains a

114

115

C8H8 fragment.356Cyclooctatetraene has been shown to display four different synfacial coordination modes in bimetallic Ru containing complexes and changes in hapticity were induced by le transfer reactions.357The compound [0s2(C0)8(p2-q :q -propene)] has been studied by FTIR spectroscopy: spectra for d3 and d6 isotopologues were also measured and used to interpret data relating to low temperature studies of chemisorbtion on Pt( 11 1) and Ni( 1 11). This led to comments being made about alkene orientation.358Treatment of [ O S ~ ( C O ) & J C M with ~ ) ~ ]2-vinyl-tetrahydrothiopheneled to two products: { p-q4-S(CH2)3CH=CH-CH2)(p-H)] and [os3(Co>10{ p[OS~(CO)~ S(CH2)2CH=CH-CH=CH2)], where ring opening of the thiophene ring occurrs exclusively at the carbon bearing the vinyl A one pot synthesis of cyclophanes such as 116 was d e s ~ r i b e d .The ~ ~ crystal and molecular structure of [(9-ethyny~-9-hydro~y-fluorene)Co~(~~)~] was described.361Other [Co2(CO),] fluorenyl, indenyl and cyclopentadienyl-containing complexes were obtained from dehydration of alkynol precursors.362 with a second equivalent of alkyne Treatment of [CO(C0)6(p-r\2:q2-Rc~cR] afforded 117, which then on reaction with another equivalent afforded 118 and alkyne t r i m e r ~It. ~was ~ ~later reported that the flyover complex 118 is not an intermediate in the trimerisation process.364A collection of related homodi-

’

R

R / n

W P

oc’ ‘co 117

116

0.

119

R

R 118

13: Hydrocarbon Transition Metal n-Complexes other than q-CSHj and q-Arene Complexes 415

nuclear [Co2(CO),] complexes containing flyover bridges or cyclopentadienone ligands have been prepared and ~ h a r a c t e r i s e d Hubels . ~ ~ ~ complex 119 has been structurally characterised and shown to have a semi-bridging CO ligand.366A collection of [Co(CO)6(p-q2:q2-alkyne)]complexes have been prepared and structurally characterised. Substitution of one of the carbonyl ligands leads to a variety of diastereoisomeric m i x t ~ r e s . ~ ~A~ -large ~ ~ ' selection of [C02(C0)6-,L,(p-q2:q2-propargylic)]complexes have been prepared and characterised and their reactivity i n v e ~ t i g a t e d . ~ The ~ l - ~photochemistry ~~ of [Co2(CO)6 -nLn(p-q2:q2-RC2H)](R = Ph, H) has been investigated using timeresolved and steady-state techniques.377A large number of [Co2(CO),- .L,(pq2:q2-alkyne)]complexes have been prepared, isolated and their utility in the Pauson-Khand reaction under a variety of different conditions investigated.378-389A collection of [C~~(CO)~(p-q~:q~-alkyne)] complexes have been prepared and a new mild carbonylative decomplexation method using primary and secondary amines was reported to give hydrocarbamoylation of the alkyne.390 A selection of [C~~(CO)~(p-q~:q~-alkyne)l complexes have been shown to react with triethylsilane to give triethylvinyl~ilanes.~~' [CO~(CO)~(~q2:q2-alkyne)]-containingcomplexes have been used in the synthesis of the ABC ring fragment of ciguatoxin (5R).392 A collection of [co2(co)6] containing enyne complexes have been synthesised and used to prepare optically active bicyclo[4.3.O]nonenone derivative^.^'^ Reaction of 120 with a nucleophile in the presence of a Lewis acid afforded 121 or 122 depending upon the R

Nu

122

group: primary alkyl substituents follow path a; secondary and tertiary follow path b. the influence of the [co(co)6] complexed alkyne was probed through reaction of 123 with AlMe3 which gave 124. The reaction followed path a, rather than the expected path b when the cyclopropyl group had replaced a [co(co)6] tethered alkyne 394 Compound 125 undergoes a Pd catalysed

123

124

"

Organometallic Chemistry

416

0

0 125

126

127

carbonylatiodcyclisation reaction to give 126 which on treatment with I2 gave 127 in reasonable overall yield.395BF30Et2 mediated [4 + 31 and fluorinative [4 + 31 cycloaddition reactions on [C0~(C0)~(q~-alkynyldiether)] afforded, in the presence of stannyl or silyl reagents, [co,(co)6] tethered fluoro- or nonfluorocycloheptyne-containing complexes.396A solution and solid-state NMR study of allylcobalt intermediates formed in the cobalt carbonyl catalysed polymerisation of 3-methyl-buta-1,3-diene was reported.397 The use of polymer-supported cobalt carbonyl via coordination to PPh3 (attached to the polymer) was used as a traceless linker for alkynes in solid phase synthesis.398 A collection of Rh(1) complexes containing vinyl-silanes and siloxanes have been prepared and characterised. Their fluxional properties have been studied by VT-NMR spectroscopy.399 The solid-state structure of [Rh2(02CCF3)4].C&k6 has been determined and shows a polymeric one dimensional structure with the Rh units bridged by the C6Me6 units in a [pq2:q2-]fa~hion.~"Some dimeric compounds and one dimensional polymers containing [Rh(q4-COD)] moieties based upon 1,4-bis(2-pyridyl)butadiyne, 1,4-bis(4-pyridyl)butadiyne,trans-1,2-bis(4-pyridyl)ethene have been prepared with and characterised.401Treatment of [Cp2Rh2(p-CO)(p-q2:q2-CF3CCCF3)] cyclic thio- and telluroethers has been investigated. Decomposition of the chalcogenide ether often occurred; however, for simple telluroethers compounds of the general type [Cp2Rh2(CO)(p-q:q'-CF3CCCF3)L] were obtained?02 Heating of [M(q4-COD)(q5-C5Me4-C(CH)](M = Rh, Ir) in the afforded the butatriene presence of a catalytic amount of [Ru(H)~(CO)(PP~~)~] complex 128. For M = Rh hydrogenation to a (crystallographically charac-

'

128

129

terised) butadiene bridged species by [Ru(H)2(CO)(PPh3)3] was observed.403 Reaction of [Ir2(dfepe)H(p-H)3](dfepe = bis(periluoroethylphosphino)ethane} with ethene afforded a mixture of cis- and trans- but-2-enes and 129.404The dinuclear complexes [(Ir(p-L)(q4-COD))2] (L = 2-aminopyridinato, 2-anilinopyridinato) were prepared and characterised. The electrochemicalproperties of the complexes were also probed using cyclic voltammetry and this allowed the EPR spectrum of the stable radical cation [{Ir(p-L)(q4-COD)>2]+to be with ~ b t a i n e d .The ~ ~ reaction of [Ir2(CH3)(CO)(p-CO)(dppm)2][CF3S03] alkynes has been reported. C-H bond activation of the methyl group was

13: Hydrocarbon Transition Metal n-Complexesother than q-CSH5 and q-Arene Complexes 417

cri'

,CP*

Ni-Ni

Bu'cp,

,CPBu'

+ Ni-Ni

\

But 131

130

observed and led to the formation of a wide range of new C-C bonds.406The synthesis and structural characterisation of 130 was reported and the Ni-Ni bond length of 2.496 is long.407Compound 131 was obtained on reaction of [CpzNi] with t-butyl radical. The Ni-Ni bond length is 2.432(1) The enolate complex 132 has been prepared and protonation affords 133. The enolate bonding in 132 resonates between being 0 or C bound? A collection of dimeric allyl-containing complexes have been prepared from (PdClIF] (X = BF4, OTf) and ally1 alcohols?' Reaction of PdHBr] with chiral terpenes was described and shown to yield enantiomerically pure q3-allyl-containing complexes and their reactivity was investigated? Compound 134 has been

A

132

134

133

135

prepared and structurally characterised. It was shown to have a memory effect in allylic-allylation reactions?l2 EXAFS, SAXS and UV-vis spectroscopy was used to study hydrosilylation using 135: no evidence was found for the formation of a colloidal catalytic system.413A collection of dimeric Cu(1) complexes of 3,3,6,6-tetramethyl-l-thia4cycloheptyne- 1,l-dioxide have been prepared and characterised. The crystal and molecular structures of some known thioether analogues were also p r e ~ e n t e d . ~Density '~ functional theory has been used to study the bonding and geometrical parameters for the tweezer like molecules [M(R){q2:q2-Cp2Ti(o-C(CR)2}](M = Cu, Au, Au). Significant metal-to-acetylide charge donation was observed which induces a strong coulombic attraction between the metal and acetylide l i g a n d ~ . ~A' ~large number of different titanocene based tweezer compounds have been prepared and their complexation to Cu, Ag and Au i n ~ e s t i g a t e d . ~ The ' ~ ' ~ oxide bridged heterobimetallic complex 136 was prepared on reaction of [{ I r ( p OH)(q4-COD)>2]with [Cp*TiMe3]. A range of similar complexes were also described?20 Other early-late transition metal heterobimetallic complexes such

Organometallic Chemistry

418

L

I

0 I

137

136

138

as 137421and 138422(L = Ind, Cp, Cp*) have been prepared and characterised. The Rh containing complex 138 was found to polymerise a-alkenes more effectively than its non-Rh complexed analogue. The electrochemicalreduction has been described. The differof anti- and syn-[Cr(CO)3(p-Ind)Rh(q4-COD)] ences in the reduction potential were explained and the electron transfer mechanism el~cidated.4~~ A collection of cationic alkyne complexes containing linear bridging triphos ligands have been prepared and ~ h a r a c t e r i s e dThe .~~~ complexes [{ (RS)PPh2)(C0)2Co{ p-C2(C02Me)}M(C0)2(q5-L)](L = Cp, Cp*; M = Mo, W; R = hydrocarbyl) have been prepared and their rearrangement under mild thermolysis investigated. The formation of several new bridged metallacycles was described.425 The reactivity of this compound with Ph2PC=CBut was also reported.426The crystal and molecular structures of acetylenedicarboxylate and [(C0)3Co(p.-L)Mn(C0)4] (L = dimethyl methylacetylene terolate) have been described.427A collection of compounds of type 139 have been prepared and characterised including electrochemically and by cry~tallography.~~~ A collection of bimetallic RdRh bimetallacarborane complexes containing ancillary COD or NBD ligands have been

139

140

141

de~cribed.4~' Reaction of [{ IR(p-OMe)(q4-COD))2] with [RhH2(CO)(PPh2H)(PPri3)2] afforded the heterobimetallic compound [(PPri3),(GO)HRh(p-H)(p-OMe)IR(q4-COD)]with a Rh-IR bond length of 2.8635(5) A.430 A collection of compounds of the type [{M(q4-diene))2(p-SS)](M= Rh, IR; SS = dithiolate derived carbohydrates) have been prepared and charact e r i ~ e d . 4 ~The ~ reactivity of [RhIR(CO)2(p2-q1 :q2-C-CPh)(dppm)2][BF4] towards protic acids and ally1 halides has been investigated. Ally1 to alkynyl migration reactions were described and compared to the migratory insertion reaction that involves transfer of a hydride or alkyl group to a coordinated a l k ~ n e . 4A~collection ~ of Pt/Rh or Pt/Ir bimetallics with bridging phosphido or alkynyl ligands have been prepared and ~ h a r a c t e r i s e d .A ~ ~series ~ of complexes of type 140 (R=C&15, C6F5) have been prepared and characterised, including cry~tallographically.~~~ Treatment of cis-[Pt(O-C6F&-

13: Hydrocarbon Transition Metal L'omplexes other than q-C5H5and q-Arene Complexes 419

(THF),] with cis-[Pt(o-C6F5)2(PPh2C-cPh)2] did not afford the expected simple THF displace dimer, but gave 141 where the alkyne has inserted into a Pt-C,F, bond. Other simple ligand substitution reactions were described.435 Reaction of [Pd(o-CrCPh)(bipy)] with CuX (X = C1, Br) afforded the expected tweezer complexes.436Similar reactions of [Pd(c~-C=CPh)(bipy-~Buz)lwith CuSCN and AgSCN were also described and the products structurally characterised. Electrochemical studies on the copper-containing tweezer compound showed a reversible le reduction for the bipy ligand and one irreversible CU(I) + CU(II) ~ a v e . 4 ~ ~ Multimetallic Complexes. - Reaction of [Cp2Ti(SH)2] with[M(acac)(q4diene)] (M = Rh, Ir; diene = COD, tetrafluorobarrelene) afforded the trinuclear complexes [Cp2(p3-S)2(acac){ M(q4-diene)}21 and the reactivity at the Rh and Ir centres has been investigated.438Titanocene and zirconocene sources have been reated with butadienylbenzene to yield a range of multimetallic m0tifs.4~~ Compounds of type 142 have been prepared by a series of substitution reactions.440Cyclotetradeca-l,8-ynehas been used as a bridging agent for a range of Mo, Co, Fe, Ru, Os, containing cluster compounds.441-442Treatment of [C~M(CGCC=CR)(CO)~]{M = Mo, W; R = H, Fe(COkCp, M(C0)3Cp} with [co2(co)8] have been described and adducts were formed at 8.2

142

143

the least hindered alkyne triple bond in each case. Where R = [M(C0)3Cp] a bisadduct was formed. Extended Huckel and density functional theory calculations were carried out to aid in structural rationali~ation.~~ A collection of triphos or halobridged multimetallic WlMo alkyne and allyl-containing complexes have been described.444Reaction of [Cp(CO)2Mn(p-C=CHPh)Pt(L)] (L = dppm, dppe, dppp) ~ i t h [ F e ~ ( C Oyielded )~] three clusters, of which one was structurally characterised Treatment of [Re(CO),( p-C( C)Re(CO),] with Cu(I), Ag(I), and Au(1) led to a range of complexes where the bridging acetylide coordinates in and q2-fashion to the Group 11 metal? Compounds of type 143 (NN = bipy, M = Cu, Ag) have been prepared and their luminescence behaviour i n v e ~ t i g a t e d .A~ ~new polymorph of [Fe3(C0)8(p3-q2:02diphenylallenylidene)] has been structurally characterised.448 Reaction of [PPN]2[Fe3(C0)9(CCO)] with [TiC13(DME)1.5] in the presence of a ZdCu couple afforded [PPNJ[Fe3(CO),(p3-o:q2:q2-CCH)][Fe3(C0)9(p3-o: q 2:q 2CCOTi(THF)4Cl] which was structurally chara~terised.~'Treatment of afforded the [Fe2(p-S)2(C0)6] with [Fe2(p-Co)(p2-q2-cH=cHPh)(co)6]which was anionic cluster [{Fe2(CO)6}2(~-S)(~-S)(p2-q2-CH=CHPh)(CO)6]reacted with a range of alkyl, acyl and organometallic halides?' [M3(pH)2(p3-X)(C0)8(NCMe)](M = Ru; X = NSO2C6H4-4-Me;M = 0 s ; X = s) was

Organometallic Chemistry

420

obtained on NCMe substitution of one CO ligand in the respective nonacarbony1 precursor. On reaction of these complexes with RC2H ( R = H , Ph) reductive coupling occurred affording the regioselective 1,3-diene containing clusters [M3(p3-X)(C0)8(L)](M = Ru; L = p-q2:q2-C4H4; M = 0 s ; L = q4C4H4R).451Compound [Ru3(p-H)(p3-PPhCH2PPh2)(p3-PhC2But)(CO)6] has been prepared and structutrally characterised. The unusual alkyne coordination mode was probed using density functional theory and the data obtained suggests the coordination mode results from the stereoelectronic asymmetry of was investigated as a the metallic fragment.452[R~~(p-H)(p-MeNpy)(C0)~] hydroformylation catalyst. PhC2Ph was converted to cinnamaldeyde; however, this reaction is in competition with alkyne insertion into the Ru-N bond, which has the effect of terminating catalytic activity.453Several papers dealing with the reactions of [Ru(CO)S], [Ru3(CO)12], [ R u ~ ( C O ) ~ ~ ( N C M and ~)~] alkynes has appeared and a diverse range of products The has received some attention. Its chemistry of [Ru5(p5-C2PPh2)(p-PPh2)(CO)13] reaction with dppm, alkynes, butadiene, TMSCSTMS, and 1,4diphenylbutadiyne have been A large scale reinvestigation of the reaction between [(CpRu(C0)2) 2(p-C2)] and [Ru3(CO)lo(p-dppm)] allowed isolation of the additional compound [R~&-C2)(p-CO)(C0)9(dppm)Cp] which was structurally c h a r a c t e r i ~ e dThe . ~ ~ crystallographically ~ characterised compounds [Ru&~-CHCHC=CH~)(CO)~~] and [Ru6(p-H)(p4-c)(p4cCMe)(p-CO)(CO)6] were obtained on thermal rearrangement of [Ru3(p3C2H2)(p-CO)(CO)9]at 50 0C.467A collection of RuIr2-sufido-bridged clusters containing unconjugated dienes have been synthesised and ~ h a r a c t e r i s e d . ~ ~ ~ Reaction of [ R U ~ I ~ ( C O ) with ~ ~ ] -internal alkynes gives the butterfly core clusters [ R U ~ I ~ ( CI O ( ~) ~ - ~ ~ - R C-C; carbonylation R)] caused cluster fragmentation and protonation led to neutral hydrido-alkyne-containingclusters.469 The reaction kinetics of the reaction between [ O S ~ ( C O ) ~ ( ~ - Cand ~ Pphos~)] phines has been reported and the rate of carbonyl substitution is generally lo9 times faster than in [ O S ~ ( C O ) ~ The ~ ] reaction . ~ ~ ~ of [0s(C0)10(NCMe)~]with cyclotetradeca-1 , 8 - d i ~ n e ~ and ~ l 1,6-bisTMS-hexa-1 , 3 , 5 - t r i ~ n ehas ~ ~been ~ described. Alkyne-carbide coupling was observed when [Cp*WOs3(p4-C)(pH)(CO)11] was reacted with alkynes and the coupling mechanism discussed.473 Reaction of [ O S ~ ( ~ - H ) ~ ( Cand O ) ~[Cp*W(0)2(o-C=C-CrCPh)] ~] afforded [O~~(CO),O(~-H)(~-~~-C(=CHP~)C=C)W(O)~C~*] 144 which is a mixture of at least threee different isomers: two were structurally ~ h a r a c t e r i s e d . ~ ~ ~ [Co2(CO),] adducts of several transition metal (W, Fe, Ru) acetylide containing complexes have been prepared and their structural characteristics elucidated spectroscopically and by X-ray crystallography, including 145 and

144

145

146

13: Hydrocarbon Transition Metal n-Complexes other than q-CjH5 and q-Arene Complexes 421

147

148

146?75478 The Ge- and Si- containing cycloalkynes 147 and 148 have been both shown to complex two [co(co)6] groups respectively.479A collection of oligomeric dehydroannulenes containing fused [CpCo(q4-butadiene)]or ferrocene units were described.480The Pauson-Khand reaction has been carried out on Cr and W tethered carbene-enyne complexes and the presence of the heterometal was found to stabilise Co intermediates?8' Compounds of type 149 have been prepared and replacement of one TMS group gave compounds of type 150. Significant electronic interaction between the metals was observed and density functional theory, ZINDO and ELF calculations were performed to aid in the understanding of the electronic interactions!82 Treatment of the tetrayne 151 with [co2(co)8] yielded a double addition (C=C 1 and 3) affording a C2 symmetric Arene capped clusters of type 152 have

151

152

been prepared and a statistically valid KekulC trigonal distortion observed in the solid state. The hindered rotation of the capping arene was investigated O~M~)~} using VT-NMR spectroscopy.484Treatment of [ C O ~ { ~ A - C ~ ( C (CO),] and other Co clusters with diphenyl-2-thienylphosphine has been described and a range of bi- and tri-cobalt systems isolated.485The BF30Et mediated addition of electron rich arenes to 1,3-dialkoxyhepta-2,S-diyne[co2(co)& has been described and shown to yield [7] metacyclophane-diyne~.~~~ [co2(co)6] complexation was only observed to occur to one alkyne in 153 and reduction of the uncomplexed alkyne with LiAlH4 was also reported.487 Nucleophilic attack by acetylides on substituted [(q6-fluorenyl)Cr(CO)3]complexes was described and [co2(co)6] adducts of the resultant alkynyl triple bonds made.488 The crystal structure of [{ RuCo2(CO),}2(p3-q2-p3-q2-

422

Organometallic Chemistry

154

153

HC-CCH20-C6H40CH2CrCH)] has been reported and two configurations of the metallic fragments observed.489A selection of diynes have been reacted with [co2(co)8] and the expected di-adducts formed and characterised; however, one unusal compound, 154, which formed by H migration and C-C coupling was also d e s ~ r i b e d . 4 ~Treatment ~ ~ ~ ~ ’ of a variety of di-propargylic systems and other diynes with [co2(co)8] led to the expected [co2(co)6]containing adducts which undergo exchange reactions with Na[CpMo(CO)2] to give mixed metal ~ l u s t e r s Reaction . ~ ~ ~ ~of~[ C ~ ~ N ~ C O ~ ( Cwith O ) ~COT ] gave [Co2Ni(C0)6(p3-q2:q3:q3-C8Hg)] in which the COT facially binds to a A Co2Ni face.497Compound 155 has been prepared and characteri~ed.4~~ selection of other dendritic alkynyl systems have been synthesised and the triple bonds coordinated to the [co2(co)6] group.501-502A collection of compounds of type 156 have been prepared.503Dendrimers capped with

Sol-Pd

Pd

Pd

Pd-Sd

P-M(C0)s 155

156

hemilabile o-diphenylphosphinylcarboxylic acids which were then Pd functionalised using [Pd(q3-C4H7)(q4-COD)].This system was found to be very effective in hydrovinylation r a c t i o n ~ Pd . ~ ~complexes containing bridging vinylcarbene ligands were found to be effective C-C bond forming reagents.505 Treatment of cis-[Pt(C6F5)2(C-CR)2I2- with a range of Rh and Ir diene containing complexes afforded compounds of type 157, 158 and 159.506 Reaction of tvans-[PtH(C-C-2-py)(PPh3)2] with c ~ ~ - [ P ~ ( C ~ F ~ ) ~ (afTHF)~] forded initially an acetylide bridged dimer, which eventually rearranged to triR

157

158

159

13: Hydrocarbon TransitionMetal .n-Complexesother than q-CsHJand q-Arene Complexes 423

and tetrametallic compounds.507The cluster [Pt2(C~4(C-cPh)8]2has been prepared and structurally characterised with dimerisation through weak Pt-Pt interactions noted in the solid state: these cleave on dissolution. The luminesent properties of this compound were also de~cribed.’~~ The trimeric form of this compound [ P ~ ~ ( C U ~ ( C = Chas P ~ )also ~ ] ~been described and shown to exist as at least three different polym~rphs.’~~ The crystal and molecular structure of [{Ag3(C=CBuf)2),]has been determined and the acetylide groups form both CJ and 7c-bonds to Ag?O The coordination polymer 160 has been

n

structurally characterised.” The acetylide dianion has been fully encapsulated in several different polyhedral silver cages and the compounds structurally ~haracterised.’~~ A large range of Ag sandwich complexes have been prepared in which there are q2-interactions to pericyclic ring systems. The presence of a [ClOJ was shown to give both one and three-dimensional stability to the structures.

’’

8.3 Ferrocenyl Containing Complexes. - Treatment of [(CP-TMS)~T~(-CZCFC)~](Fc = ferrocenyl) with [Pd(PPh&] led to to the isolation and characterisaction of the tweezer-complex [(Cp-TMS)2Ti(-C=CFc)2.Pd(PPh3)]. Cyclic voltammetry showed that q2-coordination of the two triple bonds to the Pd centre significantly modifies the electrochemical behaviour of the complex.5141,l -Ferrocenyldicarboxylic acid has been used to form trimetallic compounds derived from Cu containing tweezer complexes of [Cp2Ti(CrCR)2].515Reduction of [(r1’-C~H,,_.~Me,)TiC12](n = 0, 4, 5) in the presence of ethynyl ferrocene afforded compounds of type 161.’16 FTIR spectroscopy was used to study the rotational isomerisation of 162 in pentane and liquid xenon; this methodology also showed confirmational differences in 161517Reaction of [ R u ~ ( C O )with ~ ~ ] [CpFe(q5-CSH4-CrCCHO)]led to the

161

162

163

isolation of two new alkyne coordinated clusters which were fully characterised and their reactivity investigated.’18 The ferrocenylethynyl silanes 164 have been prepared and characterised. The triple bonds were shown to complex

424

Organometallic Chemistry

[CO~(CO)~] groups; however, for the tris- and tetra-alkynyl silanes only two [co2(co)6] moieties could be incorporated on steric Compound 165 has been prepared and characterised from iodoethynylferrocene.520 Ferrocene-containing pyrazole ligand sets have been shown to bridge Rh(1) metal centres in diene and carbonyl containing complexes. The bite angle is such that weak Rh-Rh interactions in the solid state were observed.521A collection of [Rh(q4-COD)] complexes containing sterogenic phosphines based on a ferrocene backbone have been prepared and their utility in asymmetric hydrogentaion investigated (ee 97%).522The phosphaferrocene-containingcomplex 166 has been prepared and fully ~ h a r a c t e r i s e d . Compound ~~~ 167 has been

166

167

prepared and characterised. Its ability to undergo oxidative addition has been studied and the process was shown to proceed by a non-disoociative pathway: the implications for the Heck reaction were discussed.524The solid-state structure of [Pd(q3-CI0Hl5)CpFe (C5H3-CH(Me)PR’2-2-PR2}]was reported and it was found that one ally1 terminus is in the P-Pd-P plane and the other 0.37A below. This distortion was said to have an electronic rather than steric origin.525 A collection of [Pd(q3-allyl)]-containing complexes with phosphinoferrocenyloxazoline ligand sets have been prepared and their use in allylation reactions investigated (ee 82-92%) .526 Insertion of PhC2Ph into chiral cyclopalladated ferocene has been described and crystal structures of the resulting products presented.527

References 1. 2.

3. 4. 5. 6.

K.R. Flower, Orgunometallic Chemistry, The Royal Society of Chemistry, Cambridge, 2000, Vol. 28. R.N. Grimes, J. Organomet. Chem., 1999,581, 1. C. Mealli, A. Tenco, A. Galindo, E.P. Carreno, Inorg. Chem., 1999,38,4620. G. Erker, Chem. Soc. Rev.,1999,28, 307. P. Choukroun, P. Cassoux, Acc. Chem. Rex, 1999,32,494. N.Wheatley, P. Kalck, Chem. Rev.,1999,99,3379.

13: Hydrocarbon Transition Metal n-Complexes other than q-CJHJand q-Arene Complexes 425

7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 37. 36. 38. 39. 40. 41. 42. 43.

44. 45. 46. 47.

E. Sappa, J. Organomet. Chem., 1999,573,139. W.J. Youngs, C.A. Tessier, J.D. Bradshaw, Chem. Rev., 1999,99,3154. H. Butenschon, Synlett, 1999,680. U.H.F. Bum, Y. Rubin, Y. Tobe, Chem. SOC.Rev., 1999,28,107. S.E. Gibson, M.A. Peplow, Adv. Organomet. Chem., 1999,44,275. C. Bruneau, P.H. Dixneuf, Acc. Chem. Res., 1999,32,311. A.C. Comely, S.E. Gibson, J. Chem. SOC.,Perkin Trans. 1, 1999,223. C-H. Jun, J-B. Hong, D-I. Lee, Synlett, 1999, 1. J.H. Rigby, Tetrahedron, 1999,554521. K.H. Dotz, P. Tomuschat, Chem. SOC.Rev.,1999,28, 187. K. Oshima, J. Organomet. Chem., 1999,575,l. H-J. Knolker, Chem. SOC.Rev., 1999,28, 151. K. Ruck-Braun, M. Mikulas, P. Amrhein, Synthesis, 1999,727. N. Iwasawa, Synlett, 1999, 13. B. Weyershausen, K.H. Dotz, Eur. J. Inorg. Chem., 1999,1057. E-i. Negishi, Chem. Eur. J., 1999,5,410. J. Organomet. Chem., 1999,576,l-317. Y. Yamamoto, U. Radhakrishnan, Chem. SOC.Rev., 1999,28,199. C.L. Sterzo, Synlett, 1999, 1705. B. Rybtchiniski, D. Milstein, Angew. Chem. int. Ed. Engl., 1999,38, 870. J.A. Daw, M. Poliakoff, Chem. Rev., 1999,9!9,495. G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. In$. Ed. Engl., 1999, 38,428. L-C. Song, Y.H. Zhu, Q-M. Hu, J. Chem. Res. ( S ) , 1999,56. M. T a m , F.E. Hahn, Inorg. Chim. Acta, 1999,288,47. M. Catellani, F. Baroni, G. Bocelli, S. Ghelli, J. Organomet. Chem., 1999, 583, 106. S-E. Eigemann, R. Schobert, J. Organomet. Chem., 1999,585,115. M. Torrent, M. Duran, M. Sola, J. Am. Chem. Soc., 1999,121, 1309. M.L. Walters, M.E. Bos, W.D. Wuff, J. Am. Chem. SOC.,1999,121,6403. P. Zanello, F. Laschi, M. Fontani, C. Mealli, A. Ienco, K. Tang, X.Jin, L. Li, J. Chem. Soc., Dalton Trans., 1999, %5. T.E. Bitterwolf, A.A. Saygh, J.T. Bays, C.A. Weiss, W.B. Scallorn, J.E. Shade, A.L. Rheingold, L. Liable-Sands, J. Organomet. Chem., 1999,583,152. M.E. Krafft, M.J. Procter, K.A. Abboud, Organometallics, 1999,18, 1122. M.J. Calhorda, I.S. Goncalves, E. Herdtweck, C.C. Romao, B. Royo, L.F. Veiros, Organometallics, 1999, 18, 3956. N.A. Vinson, C.S. Day, M.E. Welker, I. Guzei, A.L. Rheingold, Organometallics, 1999,18,1824. K-H. Yih, G-H. Lee, Y. Wang, J. Organomet. Chem., 1999,588,125. C.A. Gamelas, E. Herdtweck, J.P. Lopes, C.C. Romao, Organometallics, 1999, 18, 506. A. Kuhl, L.J. Farrugia, P.J. Kocienski, Acta Crystallogr., 1999, C55, 2041. A.J. Pearson, I.B. Neagu, J. Org. Chem., 1999,64,2890. C . Borgmann, C. Limberg, E. Kaifer, H. Pritzkow, L. Zsolnai, J. Organomet. Chem., 1999,580,214. J. Yin, L.S. Liebeskind, J. Am. Chem. SOC.,1999,121,5811. Q.D. Shelby, G.S. Girolami, Organometallics, 1999,18,2297. T. Szymanska-Buzar, K. Kern, A.J. Downs, T.M. Greene, L.J. Morris, S. Parsons, New J. Chem., 1999,23,407.

426 48. 49.

50.

51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73.

74. 75. 76. 77.

Organometallic Chemistry

T. Szymanska-Buzar,K. Kern, J. Organornet. Chem., 1999,592,212. F-W. Grevels, J. Jacke, W.E. Klotzbucher, F. Mark, V. Skibbe, K. Schaffner, K. Angermund, C. Kriiger, W. Lehmann, S. Ozkar, Organometallics, 1999, 18, 3278. J.D. Debad, P. Legzdins, S.A. Lumb, S.J. Rettig, R.J. Batchelor, F.W.B. Einstein, Organometallics, 1999,18, 3414. Y-R. Wu, G-H. Lin, R.J. Madhushaw, K-M. Horng, C-C. Hu, C-L. Li, F-L. Liao, S-L. Wang, R-S. Liu, Organometallics, 1999,18, 3566. R.J. Madhushaw, S.R. Cheruku, K. Narkunan, G-H. Lee, S-M. Peng, R-S. Liu, Organometallics, 1999,18, 748. L-H. Shiu, Y-L. Li, C-L. Li, C-Y. Lao, W-C. Chen, C-H. Yu, R-S. Liu, J. Org. Chem., 1999,64,7552. D. Ekeberg, E. Uggerud, H-Y. Lin, K. Sohlberg, H. Chen, D.P. Ridge, Organometallics, 1999,18,40. B.J. Drovin, S.G. Kukolich, J. Am. Chem. Soc., 1999,121,4023. L. Deng, P. Margl, T. Zeigler, J. Am. Chem. Soc., 1999,121,6479. E.A.H. Griffiths, G.J.P. Britovsek, V.C. Gibson, I.R. Gould, Chem. Commun., 1999,1333. L.D. Field, B.A. Messerle, R.J. Smernik, T.W. Hambley, P. Turner, J. Chem. Soc., Dalton Trans., 1999,2557. J.J. Schneider, N. Czap, D. Blaser, R. Boese, J. Am. Chem. Soc., 1999,121, 1409. C. Schulz, M. Tohier, S. Sinbandhit, V. Guerchais, Inorg. Chim. Acta, 1999,291, 449. K. Ruck-Braun, C. Moller, Chem. Eur. J., 1999,5, 1038. K. Ruck-Braun, T. Martin, M. Mikulas, Chem. Eur. J., 1999,5, 1028. S. Nakanishi, M. Yasui, N. Kihara, T. Takata, Chem. Lett., 1999,843. S.V. Ley, L.R. Cox, B. Middleton, J.M. Worrall, Tetrahedron, 1999,55 3515. R.W. Bates, E. Fernandez Megia, S.V. Ley, K. Ruck-Braun, D.M.G. Tilbrook, J. Chem. SOC.Perkin Trans. 1 , 1999, 1917. R. Schobert, H. Pfab, A. Mangold, F. Hampel, Inorg. Chim. Acta, 1999,291,91. R. Schobert, H. Pfab, J. Bohmer, F. Hampel, A. Werner, J. Chem. Res. ( S ) , 1999, 578. K. Umezawa-Vizzini, T.R. Lee, J. Organornet. Chem., 1999,579, 122. M.A. Bennett, G. Chung, D.C.R. Hockless, H. Neumann, A.C. Willis, J. Chem. SOC.,Dalton Trans., 1999, 3451. J.K. Paulasaari, N. Moiseeva, R. Bau, W.P. Weber, J. Organornet. Chem., 1999, 587,299. K. Hiraki, A. Nonaka, T. Matsunaga, H. Kawano, J. Organornet. Chem., 1999, 574, 121. I. del Rio, R.A. Gossage, M.S. Hannu, M. Lutz, A.L. Spek, G. van Koten, Organornetallics, 1999,18, 1097. T. Suzuki, M. Shiotsuki, K. Wada, T. Kondo, T-a. Mitsudo, Organometallics, 1999,18,3671. J.G Planas, M. Hirano, S. Komiya, Chem. Lett., 1999,953. C. Slugovc, K. Mereiter, R. Schmid, K. Kirchner, Organometallics, 1999, 18, 1011. K. Mauthner, K.M. Soldonzi, K. Mereiter, R. Schmid, K. Kirchner, Organometallics, 1999,18,4681. C. Slugovc, K. Mereiter, R. Schmid, K. Kirchner, Eur. J. Inorg. Chem., 1999, 1141.

13: Hydrocarbon Transition Metal .n-Complexesother than q-CjH5 and q-Arene Complexes 427 78. J.A. Gutierrez, M.E.N. Clemente, M.A. Paz Sandoval, A.M. Arif, R.D. Ernst, Organometallics, 1999,18, 1068. 79. C. Six, B. Gabor, H. Gorls, R. Mynott, P. Philipps, Organometallics, 1999, 18, 3316. 80. X. Dai, N. Kano, M. Kako, Y. Nakadaira, Chem. Lett., 1999,717. 81. C-W. Chang, Y-C. Liu, G-H.Lee, Y. Wang, J. Chem. SOC., Dalton Trans., 1999, 4223. 82. M.L. Spera, W.D. Harman, Organometallics, 1999,18, 1559. 83. M.L. Spera, W.D. Harman, Organometallics, 1999,18,2988. 84. H.D. Mui, J.L. Brumaghim, C.L. Gross, G.S. Girolami, Organometallics, 1999, 18,3264. 85. J.D. Jewson, L.M. Liable-Sands, G.P.A. Yap, A.L. Rheingold, K.H. Theopold, Organometallics, 1999,18,300. 86. J.J. Schneider, N. Czap, D. Blaser, R. Boese, J. Organomet. Chem., 1999, 584, 338. 87. G. Albertin, S. Antoniutti, E. Bordignon, M. Carlon, Organometallics, 1999, 18, 2052. 88. A. Sisak, J. Organomet. Chem., 1999,586,48. 89. E. Bleuel, M. Laubender, B. Weberndorfer, H. Werner, Angew. Chem. Int. Ed. Engl., 1999,38, 156. 90. J. Gil-Rubio, B. Weberndorfer, H. Werner, J. Chem. Soc., Dalton Trans., 1999, 1437. 91. H. Song, K. Lee, J.T. Park, I-H. Suh, J. Organomet. Chem., 1999,584,361. 92. K. Ohta, M. Hashimoto, Y. Takahashi, S.H. Kichi, M. Akita, Y. Moro-oka, Organometallics, 1999,18, 3235. 93. K. Osakada, H. Takimoto, T. Yamamoto, J. Chem. Soc., Dalton Trans., 1999, 853. 94. S.A. Westcott, A.K. Kakkar, N.J. Taylor, D.C. Roe, T.B. Marder, Can. J. Chem., 1999,17,205. 95. A. Vigalok, B. Rybtchinski, L.J.W. Shimon, Y. Ben-David, D. Milstein, Organometallics, 1999,18,895. 96. C.P. Lenges, P.S. White, M. Brookhart, J. Am. Chem. SOC.,1999,121,4385. 97. M. Murakami, K. Itami, Y. Ito, Organometallics, 1999,18, 1326. 98. M. Paneque, P.J. Perez, A. Pizzano, M.L. Poveda, S. Taboada, M. Trujillo, E. Carmona, Organometallics, 1999,18,4304. 99. R.P. Hughes, H.A. Trujillo, J.W. Egan, A.L. Rheingold, Organometallics, 1999, 18,2766. 100. S . Niu, M.B. Hall, J. Am. Chem. Soc., 1999,121,3992. 101. F. Torries, E. Sola, M. Martin, J.A. Lopez, F.J. Lahoz, L.A. Oro, J. Am. Chem. Sor., 1999,121, 10632. 102. E.Sola, J. Navarro, J.A. Lopez, F.J. Lahoz, A. Oro, H. Werner, Organometallics, 1999,18,3534. 103. C-S. Chin, W. Maeng, D. Chong, G. Won, B. Lee, Y.J. Park, J.M. Shin, Organometallics, 1999,18,22 10. 104. I. Dubuc, M-A. Dubois, F. Belanger-Garikpy, D. Zargarian, Organometallics, 1999,18,30. 105. A. Michalak, T. Zeigler, Organometallics, 1999, 18, 3998. 106. E.C. Bencze, I. Papai, J. Mink, P.L. Goggin, J. Organomet. Chem., 1999,584,118 107. H. Hagelin, M. Svensson, B. Akermark, P-0. Norrby, Organometallics, 1999,18, 4574.

428

Organometallic Chemistry

108. S. Porth, J.W. Bats, D. Trauner, G. Geister, J. Mulzer, Angew. Chem. Int. Ed. Engl., 1999,38,2015. 109. M.M. Olmstead, L. Hao, A.L. Balch, J. Organomet. Chem., 1999,578,85. 110. A.D. Burrows, N. Choi, M. McPartlin, D.M.P. Mingos, S.V. Tarlton, R. Vilar, J. Organomet. Chem., 1999,573,313. 111. K. Selvakumar, M. Valentini, M, Worle, P.S. Pregosin, A. Albinati, Organometallics, 1999,18, 1207. 112. M.L. Ferrara, F. Giordana, I. Orabona, A. Panunzi, F. Ruffo, Eur. J. Inorg. Chem., 1999,1939. 113. J. Vicente, M-T. Chicote, C. MacBeath, J-F. Baeza, N. Bautista, Organometallics, 1999,18,2677. 114. S.A.Suejda, L.K. Johnson, M. Brookhart, J. Am. Chem. SOC.,1999,121,10634. 115. B. Biswas, M. Sugimoto, S. Sakaki, Organometallics, 1999,18,4015. 116. V. Branchadell, M. Moreno-Manas, F. Pajuelo, R. Pleixats, Organometallics, 1999,18,4934. 117. T. Suzuki, H. FFjimoto, Inorg. Chem., 1999,38, 370. 118. H. Hagelin, B. Akermark, P-0. Norrby, Chem. Eur. J., 1999,5,902. 119. H. Hagelin, B. Akermark, P-0. Norrby, Organometallics, 1999,18,2884. 120. I. Macsari, K. J. Szabo, Organometallics, 1999,18,701. 121. 0. Kuhn, H. Mayr, Angew. Chem. Inr. Engl., 1999,38,343. 122. C. Amatore, A. Jutand, G. Meyer, L. Mottier, Chem. Eur. J., 1999,5,466. 123. 0. Hamed, P.M. Henry, C. Thompson, J. Org. Chem., 1999,64,7745. 124. Y. Uozumi, H. Danjo, T. Hayashi, J. Org. Chem., 1999,64,3384. 126. A. Riahi, J. Muzart, J. Organomet. Chem., 1999,585,256. 125. H. Nakamura, H. Iwama, M. Ito, Y. Yamamoto, J. Am. Chem. SOC.,1999, 121, 10850. 127. I. Macsari, E. Hupe, K.J. Szabo, J. Org. Chem., 1999,64,9547. 128. D.B. Leznoff, C. Rancurel, J-P. Sulter, S.J. Rettig, M. Pink, 0. Khan, Organometallics, 1999, 18, 5097. 129. J. Ruiz, J.M. Marti, F. Florenciano, G. Lopez, Polyhedron, 1999, 18, 2281. 130. J. Albert, J.M. Cadena, J. Granell, G. Muller, J.I. Ordinas, D. Panyella, C. Puerta, C. Sanuclo, P. Valerga, Organometallics, 1999,18, 3511. 131 M. Gomez, S. Jansat, G. Muller, D. Panyella, P.W.N.M. van Leeuwan, P.C. Kamer, K. Goubitz, J. Fraanje, Organometallics, 1999,18,4970. 132. A. Dervisi, P.G. Edwards, P.D. Newman, R.P. Tooze, S.J. Coles, M.B. Hursthouse, J. Chem.Soc., Dalton Trans., 1999, 1113. 133. P. Kocovsky, S. Vyskocil, 1. Cisarova, J. Sejbal, I. Tislerova, M. Smrcina, G.C. Lloyd-Jones, S.C. Stephen, C.P. Butts, M.Murray, V. Langer, J. Am. Chem. SOC., 1999,121,7714. 134. J.P. Cahill, D. Cunneen, P.J. Guiry, Tetrahedron Asymm., 1999,10,4157. 135. B. Crociani, S. Antonaroli, G . Bandoli, L. Canovese, F. Visentin, P. Uguagliati, Organometallics, 1999,18, 1137. 136. L. Canovese, F. Viseutin, G. Chessa, A. Niero, P. Uguagliati, Inorg. Chim. Acta., 1999,293,44. 137. A. Sakkoke, H. Koshino, T. Nakata, Organometallics, 1999,18, 5108. 138. A. Macchioni, G. Bellachioma, G. Cardaci, M. Travaglia, C. Zuccaccia, B. Milani, G. Corso, E. Zangrando, G. Mestroni, C. Cafragna, M. Formica, Organometallics, 1999, S8, 3061. 139. Y. Takao, T. Takeda, J-y. Watanabe, J-i. Setsune, Organometallics, 1999, 18, 2936.

13: Hydrocarbon Transition Metal z-Complexesother than q-CsHJand q-Arene Complexes 429

140. R. Fernandez-Galon, B.R. Manzano, A. Otero, J. Organomet. Chem., 1999,577, 271. 141. R. Fernandez-Galon, B.R. Manzano, A. Otero, N. Poujaud, M. Kubicki, J. Organomet. Chem., 1999,579,321. 142. H. Adams, J.C. Anderson, R. Cubbon, D.S. James, J.P. Mathias, J. Org. Chem., 1999,64,8256. 143. Y-L. Tung, W-C. Tseng, C-Y. Lee, P-F. Hu, Y. Chi, S-M. Peng, G-H. Lee, Organometallics, 1999,18,864. 144. K. Tsutsumi, T. Kawase, K. Kakiuchi, S. Ogoshi, Y. Okada, H. Kurosawa, Bull. Chem. SOC.Jpn., 1999,72,2687. 145. D.A. Singleton, B.E. Schulmeier, J. Am. Chem. Soc., 1999,121,9313. 146. J. Uddin, S. Dapprich, G. Frenking, Organometallics, 1999, 18,457. 147. S . Creve, H. Oevering, B.B. Coussens, Organometallics, 1999,18, 1967. 148. L.L. Wright, S.J. Moore, J.A. McIntyre, S.M. Dowling, J.D. Overcast, G.R. Grisel, K.K. Nelson, P.R. Rupert, W.T. Pennington, Organometallics, 18,4558. 149. D. Steinborn, V.V. Potechin, M. Gerisch, C. Bruhn, H. Schmidt, Transition Met. Chem., 1999,24,67. 150. M.E. Cucciolito, A. Panunzi, F. Ruffo, V.G. Albano, M. Nonari, Organometallics, 1999, 18, 3842. 151. V.G. Albano, M.L. Ferrara, M. Monari, A. Panunzi, F. Ruffo, Inorg. Chim. Acta, 1999,285,70. 152. M.R. Plutino, S. Otto, A. Roodt, L.I. Elding, Inorg. Chem., 1999,38, 1233. 153. C . Zuccaccia, A. Macchioni, I. Orabona, F. Ruffo, Organometallics, 1999, 18, 4367. 154. X. Zhang, E.J. Watson, C.A. Dullaghan, S.M. Gorun, D.A. Sweigart, Angew. Chem. Int. Ed. Engl., 1999,38,2206. 155. Y.A. Lee, Y.K. Chung, Y.S. Sohn, Inorg. Chem., 1999,38,531. 156. L. Maresca, G. Natile, Inorg. Chim. Acta, 1999,285, 301. 157. J.P. Graham, A. Wojcicki, B.E. Bursten, Organometallics, 1999,18, 837. 158. M.B. Abrams, J.C. Yoder, C. Loeber, M.W. Day, J.E. Bercaw, Organometallics, 1999,18,1389. 159. F.U. Axe, J.W. Andzelm, J. Am. Chem. Soc., 1999,121,5396. 160. R.D.J. Froese, D.G. Musaev, K. Morokuma, Organometallics, 1999,18, 373. 161. M. Horacek, V. Kupfer, U. Thewalt, P. Stepnicka, M. Polasek, K. Mach, Organometallics, 1999, 18, 3572. 162. V.V. Burlakov, A.V. Usatov, K.A. Lyssenko, M. Y. Antipin, Y.N. Novikov, V.B. Shur, Eur. J. Inorg. Chem., 1999, 1855. 163. H. Lee, J.B. Bonanno, T. Hascall, J. Cordaro, J.M. Hahn, G. Parkin, J. Chem. Soc., Dalton Trans., 1999, 1365. 164. M. Horacek, P. Stepnicka, R. Gyepes, I. Cisarova, K. Mach, P. Pellny, V.V. Burlakov, W. Baumann, A. Spannenberg, U. Rosenthal, J. Am. Chem. SOC., 1999,121,10638. 165. P.M. Pellny, F.G. Kirchbauer, V.V. Burlakov, W. Baumann, A. Spannenberg, U. Rosenthal, J. Am. Chem. SOC,.1999,121,8313. 166. J.C.W. Lohrenz, M. BUM, M. Weber, W. Thiel, J. Organomet. Chem., 1999,592, 11. 167. M.D. Fryzuk, P.B. Duval, S.S.S.H. Mao, S.J. Rettig, M.J. Zaworotko, L.R. MacGillivray, J. Am. Chem. SOC.,1999, 121, 1707. 168. A. Yamazaki, Y. Nishihara, K. Nakajima, R. Hara, T. Takahashi, Organometallics, 1999, 18, 3105.

430

Organometallic Chemistry

169. L.W.M. Lee, W.E. Piers, M. Parvez, S.J. Rettig, V.G. Young, Organometallics, 1999,18,3904. 170. J. Pflug, R. Frohlich, G. Erker, J. Chem. SOC.,Dalton Trans., 1999,2551. 171. M. Dahlmann, G. Erker, M. Nissinen, R. Frohlich, J. Am. Chem. SOC.,1999, 121,2820. 172. B. Castellano, E. Solari, C. Floriani, N. Re, A. Chiesi-Villa, C. Rizzoli, Chem. Eur. J., 1999,5, 722. 173. H.C. Strauch, B. Wibbeling, R. Frohlich, G. Erker, H. Jacobsen, H. Berke, Organometallics, 1999,18, 3802. 174. P.N. Riley, J.R. Parker, P.E. Fanwick, I.P. Rothwell, Organometallics, 1999, 18, 3579. 175. C. Mongin, Y. Ortin, N. Lugan, R. Mathieu, Eur. J. Inorg. Chem., 1999,739. 176. M.W. Bengough, D.M. Thompson, M.C. Baird, G.D. Enright, Organometallics, 1999,18,2950. 177. D. Lentz, S. Willemsen, Organometallics, 1999,18, 3962. 178. S.U. Son, S.J. Paik, I.S. Lee, Y-A. Lee, Y.K. Chung, W.K. Seok, H.N. Lee, Organometallics, 1999,18,4114. 179. L.E. Helberg, T.B. Gunnoe, B.C. Brooks, M. Sabat, W.D. Harman, Organometallics, 1999,18, 573. 180. T.B. Gunnoe, M. Sabat, W.D. Harman, J. Am. Chem. SOC., 1999,121,6499. 181. Y-X. He, D. Sutton, J. Organomet. Chem., 1999,572,213. 182. W.D. Jones, G.P. Rosini, Organometallics, 1999,18, 1754. 183. M. Rosi, A. Sgamellotti, F. Franceschi, C. Floriani, Inorg. Chem., 1999, 38, 1520. 184. S. Mori, E. Nakamura, Tetrahedron Lett., 1999,40, 5319. 185. R.R. Conry, W.S. Striejewske,A.A. Tipton, Inorg, Chem., 1999,38,2833. 186. B.F. Straub, F. Eisentrager, P. Hofmann, Chem. Commun., 1999,2507. 187. H. Celio, K.C. Smith, J.M. White, J. Am. Chem. SOC.,1999,121, 10422. 188. L.P. Wu, M. Munakata, T. Sowa, M. Maekawa, Y. Suenaga, Y. Kitamori, Inorg. Chim. Acta, 1999,290,251. 189. C. Kayran, F. Kozanoglu, S. Ozkar, S. Saldamli, A. Tekkaya, C.G. Kreiter, Inorg. Chim. Acta, 1999,284, 229. 190. A. Tekkaya, S. Ozkar, J. Organomet, Chem., 1999,590,208. 191. J.L. Davidson, H. Richzenhein, B.J.S. Thiebaut, K. Landskron, G.M. Rosair, J. Organomet. Chem., 1999,592,168. 192. T. Suzuki, M. Siotsuki, K. Wada, T. Kondo, T-a. Mitsuda, J. Chem. Soc., Dalton Trans., 1999,4231. 193. M. Biihl, W. Baumann, R. Kadyrov, A. Borner, Helv. Chim. Acta, 1999,82,811. 194. J.G. Donkervoort, M. Biihl, J.M. Ernsting, C.J. Elsevier, Eur. J. Inorg. Chem., 1999,27. 195. M.A. Alonso, J.M. Casares, P. Espinet, K. Soulantica, Angew. Chem. Int. Ed. Engl., 1999,38, 533. 196. M. Valentini, K. Selvakumar, M. Worle, P.S. Pregosin, J. Organomet. Chem., 1999,587,244. 197. J. Orsini, W.E. Geiger, Organornetallics, 1999,18, 1854. 198. B. de Bruin, J.A. Brands, J.J.J.M. Donners, M.D.J. Donners, R. de Gelder, J.M.M. Smits, A.W. Gal, A.L. Spek, Chem. Eur. J., 1999,5,2921. 199. S.A. Westcott, N.J. Taylor, T.B. Marder, Can. J. Chem., 1999,77, 199. 200. A. Ferrari, M. Merlin, S. Sostero, H. Ruegger, L.M. Venanzi, Helv. Chim. Acta, 1999,82,1454.

13: Hydrocarbon Transition Metal n-Complexesother than q-C5H5andq-Arene Complexes 43 1

201. C. Pettinari, M. Pellei, G. Cavicchio, M. Crucianelli, W. Panzeri, M. Colopietro, A. Cassetta, Organometallics, 1999,18,555. 202. Y. Kishimoto, P. Eckerle, T. Miyatake, M. Kainosho, A. Ono, T. Ikariya, R. Noyori, J. Am. Chem. SOC.,1999,121, 12035. 203. A.D. Burrows, M. Green, J.C. Jeffery, J.M. Lynam, M.F. Mahon, Angew. Chem. In?.Ed. Engl., 1999,38, 3043. 204. T.V. Rajanbabu, B. Radetich, T. You, T.A. Ayers, A.L. Casalnuovo, J.C. Calabrese, J. Org. Chem., 1999,64, 3429. 205. J. Holz, D. Heller, R. Stunner, A. Borner, Tetrahedron Lett., 1999,40, 7059. 206. L. Dahlenburg, V. Kurth, J. Organomet. Chem., 1999,585,315. 207. T. Miura, T. Imamoto, Tetrahedron Lett., 1999,40,4833. 208. M.T. Reek, A. Gosberg, Tetrahedron Asymm., 1999,10,2129. 209. N. Derrien, C.B. Dousson, S.M. Roberts, U. Berens, M.J. Burk, M. Ohff, Tetrahedron Assymm., 1999,10,3341. 210. 0. Pamies, G. Net, M. Widhalm, A. Ruiz, C. Claver, J. Organomet. Chem., 1999, 587, 136. 21 1. I.D. Kostas, C.G. Screttas, J. Organomet. Chem., 1999,585, 1. 212. R.M. Deshpande, A. Fukuoka, M. Ichikawa, Chem. Lett., 1999,13. 213. M. Dieguez, A. Ruiz, C. Claver, M.M. Pereira, M.T. Flor, J.C. Bayon, M.E.S. Serra, A.M. dA.R. Gonsalves, Inorg. Chim. Acta, 1999,295,64. 214. H. Doucet, E. Fernandez, T.P. Layzell, J.M. Brown, Chem. Eur. J., 1999,5, 1320. 215. C-C. Lin, C-W. Lin, A.S.C. Chan, Tetrahedron Asymm., 1999,10,1887. 216. C. Bianchini, D.G. Burnaby, J. Evans, P. Frediani, A. Meli, W. Oberhauser, R. Psaro, L. Sordelli, F. Vizza, J. Am. Chem. Soc., 1999,121,5961. 217. H. Yang, H. Gao, R.J. Angelici, Organometallics, 1999,18,2285. 218. A. Fuerte, M. Iglesias, F. Sanchez, J. Organomet. Chem., 1999,588, 186. 219. B. de Bruin, R.J.N.A.M. Kicken, F.N.A. Suos, M.P.J. Donners, C.J. den Reijer, A.J. Sandee, R. de Gelder, J.M.M. Smits, A.W. Gal, A.L. Spek, Eur. J. Inorg. Chem., 1999,1581. 220. 0.Pamies, M. Dieguez, G. Net, A. Ruiz, C. Claver, J. Chem. Soc., Dalton Trans., 1999,3439. 221. S . Sjovall, M. Johansson, C. Andersson, Organometallics, 1999,18,2199. 222. S. Sjovall, P.H. Svensson, C. Andersson, Organometallics, 1999,18, 5412. 223. Y. Kataoka, M. Imanishi, T. Yamagata, K. Tani, Organometallics, 1999, 18, 3563. 224. H-F. Klein, E. Auer, A. Dal. U. Lempke, M. Lempke, T. Jung, C. Rohr, U. Florke, H-J. Haupt, Inorg. Chim. Acta, 1999,287, 167. 225. M. Abla, T. Yamamoto, Bull. Chem. SOC. Jpn., 1999,72, 1255. 226. Y. Pan, G.B. Young, J. Organomet. Chem., 1999,577,257. 227. P.Burger, J.M. Baumeister, J. Organomet. Chem., 1999,575,214. 228. J. Visente, I. Saura-Llamas, J. Turpin, M.C. de Arellano, P.G. Jones, Organometallics, 1999,18,2683. 229. A. Fukuoka, A. Sato, K-y. Kodama, M. Hirano, S. Komiya, Inorg. Chim. Acta, 1999,294,266. 230. T.A.K. Al-Allaf, J. Organomet. Chem., 1999,590,25. 231. A. Klein, K-W. Klinkhammer, T. Scheiring, J. Organomet. Chem., 1999, 592, 128. 232. C.M. Haar, S.P. Nolan, W.J. Marshall, K.G. Moloy, A. Prock, W.P. Giering, Organometallics, 1999,18,474. 233. J.H. Rigbv. J.H. Mever. Svnlett. 1999. 860.

432

Organometallic Chemistry

234. J.H. Rigby, N.C. Warshakoon, A.J. Payen, J.Am. Chem. Soc., 1999,121,8237. 235. C.A. Merlic, J.C. Walsh, D.J. Tantillo, K.N. Houk, J. Am. Chem. SOC., 1999, 121,3596. 236. H. Schirmer, T. Labahn, B. Flynn, Y-T. Wu, A de Meijere, Synlett, 1999,2004. 237. 0 . Woisetschlager, K. Siinkel, W. Weigand, W. Beck, J. Organomet, Chem., 1999,584,122. 238. P. Uebelhart, A. Linden, H-J. Hansen, Y.A. Ustynyuk, O.A. Trifonova, N.G. Akhmedov, V.I. Mstislavsky, Helv. Chim. Acta, 1999,82, 1930. 239. H. Kunkely, A. Vogler, J. Organomet. Chem., 1999,572, 131. 240. G.M. Aston, S. Badriya, R.D. Farley, R.W. Grime, S.J. Ledger, F.E. Mabbs, E.J. Mclnnes, H.W. Morris, A. Ricalton, C.C. Rowlands, K. Wagner, M. Whitely, J. Chem. Soc., Dalton Trans., 1999,4379. 241. J. Cambridge, A. Choudhary, J. Friend, R. Garg, G. Hill, Z.J. Hussain, S.M. Lovett, M.W. Whiteley, J. Organomet. Chem., 1999,577,249. 242. E. Bjurling, M.H. Johansson, C-M. Anderson, Organometallics, 1999,18, 5606. 243. E. Bjurling, C-M. Andersson, Tetrahedron Lett., 1999,40, 1981. 244. Y-0. Yeung, A.C.H. Ng, D.K.P. Ng, Inorg. Chim. Acta, 1999,288,266. 245. J.R. Porter, M.L. Snapper, Synthesis, 1999, 1407. 246. E. Louattani, J. Suades, Inorg. Chim. Acta, 1999,291,207. 247. N.E. Carpenter, M.A. Khan, K.M. Nicholas, Organometallics, 1999,18, 1569. 248. H-J. Knolker, H. Goesmann, R. Klauss, Angew. Chem. Int. Ed. Engl., 1999, 38, 702. 249. H.-J. Knolker, E. Baun, H. Goesmann, R. Klaus, Angew. Chem. Int. Ed. Engl., 1999,38,2064. 250. H.J. Knolker, A. Braier, D.J. Brocher, P.G. Jones, H. Piotrowski, Tetrahedron Lett., 1999,40, 8075. 251. A.V. Malkov, A. Auffrant, C. Renard, E. Rose, F. R-Munch, D.A. Owen, E.J. Sandoe, G.R. Stephenson, Inorg. Chim. Acta, 1999,296, 139. 252. A.V. Malkov, L. Mojovic, G.R. Stephenson, A.T. Turner, C.S. Creaser, J. Organomet. Chem., 1999,589,103. 253. C. Guillou, F. Bintein, J-P. Biron, C. Thal, Tetrahedron Lett., 1999,40,4331. 254. A.S. Abd-El-Aziz, W. Boraie, N.T. Gavel, Organometallics, 1999,18, 1562. 255. V. Reboul, C. Guillou, C. Thal, Tetrahedron Lett., 1999,40, 8355. 256. H-J. Knolker, H. Hermann, D. Herzberg, Chem. Commun., 1999, 831. 257. H-J. Knolker, D. Herzberg, Tetrahedron Lett., 1999,40, 3547. 258. H-J. Knolker, E. Baum, T. Hopfmann, Tetrahedron, 1999,55,10391. 259. H-J. Knolker, W. Frohner, Tetrahedron Lett,, 1999,40,6915. 260. M-C. Yeh, L-W. Chuang, Y-S. Hsieh, M-S. Tsai, Chem. Commun., 1999,805. 261. 2.Goldschmidt, E. Genizi, H.E. Gottlieb, J. Orgunomet. Chem., 1999,587, 81. 262. H. Mayr, K.H. Miiller, A.R. Ofial, M. Biihl, J. Am. Chem. Soc., 1999, 121, 2418. 263. S. Yamazaki, Z. Taira, J. Organomet. Chem., 1999,578,61. 264. T-a. Mitsudo, T. Suzuki, S-W. Zhang, D. Imai, K-i. Fujita, T. Manate, M. Shiotsuki, Y. Watanabe, K. Wada, T. Kondo, J, Am. Chem. SOC.,1999, 121, 1839. 265. A. Birri, J.W. Steed, D.A. Tocher, J. Organomet. Chem., 1999,575,242. 266. T. Vallant, W. Simanko, H. Brunner, U. Mayer, H. Hoffmann, R. Schmid, K. Kirchner, R. Suagera, G. Schiigeral,M. Ebel, Organometallics, 1999,18,3744. 267. S. Feng, J. Klosin, W.J. Kruper, M.H. McAdon, D.R. Neithamer, P.N. Nickias, J.T. Patton, D.R. Wilson, K. Abboud, C.L. Stern, Organometallics, 18, 1159.

13: Hydrocarbon Transition Metal n-Complexes other than q-CjH5 and q-Arene Complexes 433

268. M. Horacek, V. Kupfer, U. Thewalt, M. Polasek, K. Mach, J. Organomet. Chem., 1999,579,126. 269. A. Georg, C.G. Kreiter, Eur. J. Inorg. Chem., 1999,651. 270. C.G. Kreiter, N.K. Wachter, G.J. ReiO, Eur. J. Inorg. Chem., 1999, 655. 271. E. Rose, C. Le Corre-Susanne, F. R-Munch, C. Renard, V. Gagliardini, F. Teldji, J. Vaissermann, Eur. J. Inorg. Chem., 1999,421. 272. A. Hosang, U. Englert, A. Lorenz, U. Ruppli, A. Salzer, J. Organomet. Chem., 1999,583,47. 273. G. Roidl, V. Enkelmann, U.H.F. Bunz, Organometallics, 1999,18,4. 274. G. Roidl, V. Enkelmann, R.D. Adams, U.H.F. Bunz, J. Organornet. Chem., 1999,578,144. 275. V. Wolfart, M. Ramming, R. Gleiter, B. Nuber, H. Pritzkow, F. Rominger, Eur. J. Inorg. Chem., 1999,499. 276. H. Wadepohl, F-J. Paffen, H. Pritzkow, J. Organornet. Chern., 1999,579,391. 277. F. Slowinski, C. Aubert, M. Malacria, Tetrahedron Lett., 1999,40,707. 278. F. Slowinski, C. Aubert, M. Malacria, Tetrahedron Lett., 1999,40, 5849. 279. T. Dzwiniel, N. Etkin, J.M. Sryker, J. Am. Chem. SOC.,1999,121,10640. 280. P-M. Pellny, V.V. Burlakov, N. Peulecke, W. Baumann, A. Spannenberg, R. Kempe, V. Francke, U. Rosenthal, J. Organomet. Chem., 1999,578,125. 281. P-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, W. Baumann, A. Spannenberg, U. Rosenthal, J. Am. Chem. SOC.,1999,121,8313. 282. A.J. Ashe, S. Al-Ahmed, J.W. Kampf, Organometallics, 1999,18,4234. 283. M. Dahlmann, G. Erker, R. Frolich, 0. Meyer, Organometallics, 1999, 18, 4459. 284. G.J. Pindado, M. Thornton-Pett, M.B. Hursthouse, S.J. Coles, M. Bochmann, J. Chem. Soc., Dalton Trans., 1999, 1663. 285. P.T. Witte, A. Meetsma, B. Hessen, Organometallics, 1999,18, 2944. 286. K. Mashima, Y. Matsuo, K. Tani, Organometallics, 1999,18, 1471. 287. H.C. Strauch, G. Erker, R. Frohlich, M. Nissinen, Eur. J. Inorg. Chem., 1999, 1453. 288. H.C. Strauch, K. Bergander, G. Kehr, R. Frohlich, G. Erker, Eur. J. Inorg. Chem., 1999,1461. 289. L. Stahl, T. Zhan, M.L. Ziegler, R.D. Ernst, Inorg. Chim. Acta, 1999,288, 154. 290. 0,Gonziilez-Blanco,V. Branchadell, R. Gree, Chem. Eur. J., 1999,5,1722. 291. A. Pfletschinger,H. Schmalz, W: Koch, Eur. J. Inorg. Chem., 1999, 1869. 292. W. Imhof, A. Gobel, D. Braga, P. De Leonardis, E. Tedesco, Organometallics, 1999,18,736. 293. T. N. Danks, M.E. Howells, M.J. Ackland, J. Organornet. Chem., 1999,579, 53. 294. S . Nakanishi, K. Kumeta, T. Takata, Inorg. Chim. Acta, 1999,291,231. 295. M. Franck-Neumann, P. Geoffroy, D. Hanss, Tetrahedron Lett., 1999,40, 8487. 296. Y. Takemoto, N. Yoshikawa, C. Iwata, T. Tanaka, T. Ibuka, H. Ohishi, J. Am. Chem. Soc., 1999,121,9143. 297. K. Tanake, T. Watanabe, K-y. Shimamoto, P. Sahakitpichan, K. Fuji, Tetrahedron Lett., 1999,40,6599. 298. A-A.S. El-Ahl, Y.K. Yun, W.A. Donaldson, Inorg. Chim. Acta, 1999,296,261. 299. D. Berger, M. Dubs, A. Gobel, W. Imhof, M. Kotteritzsch, M. Rost, B. Schonecker, Tetrahedron Assym., 1999,10,2983. 300. I. Ripoche, J-L. Canet, J. Gelas, Y. Troin, Eur. J. Org. Chem., 1999, 1517. 301. M. Franck-Neumann, L. Miesch-Gross, C. Gateau, Tetrahedron Lett., 1999,40, 2829.

434

Organometallic Chemistry

302. R. Widmair, J.J. Alexander, J.A.K. Baur, M. Srebnik, D. Desurmont, C.A. Homrighausen, Inorg. Chim. Acta, 1999,290, 159. 303. R. Boese, W.R. Roth, D. Blaser, R. Latz, A. Baumen, Acta Crystallogr., 1999, C55, (i). 304. S.L. Ingham, S.W. Magennis, J. Organomet. Chem., 1999,574,302. 305. O.V. Gusev, A.M. Kal'sin, L.M. Morozova, P.V. Petrovskii, K.A. Lussenko, O.L. Tok, A.F. Noels, S.R. O'Leary, P.M. Maitlis, Organometallics, 1999,18,5276. 306. C. Gemel, K. Kirchner, R. Schmid, K. Mereiter, Acta Crystallogr., 1999, C55, 2053. 307. V. Kulsomphob, K.A. Ernst, K.C. Lam, A.L. Rheingold, R.D. Ernst, Inorg. Chim. Acta, 1999,296, 170. 308. D.B. Grotjahn, G.A. Bikhanova, J.L. Hubbard, Organometallics, 1999,18, 5614. 309. M. Bosch, M. Laubender, B. Weberndorfer, H. Werner, Chem. Eur. J., 1999, 5, 2203. 310. S. Tobisch, R. Taube, Organometallics, 1999, 18, 5204. 311. S. Tobisch, R.Taube, Organometallics, 1999,18, 3045. 312. P-M. Pellny, F. Kirchbauer, V.V. Burlakov, A. Spannenberg, K. Mach, U. Rosenthal, Chem. Commun., 1999,2505. 313. P. Stepnicka, R. Gyepes, I. Cisarova, M. Horacek, J. Kubista, K. Mach, Organometallics, 1999,18,4869. 3 14. R. Choukroun, Y. Miquel, B. Donnadieu, A. Igau, C. Blandy, J. P. Majoral, Organometallics, 1999,18, 1795. 315. D. Rehder, C. Bottcher, C. Collazo, R. Hedelt, H. Schmidt, J. Organomet. Chem., 1999,585,294. 316. C. Garcia-Yebra, F. Carrero, C. Lopez-Mardomingo, M. Fajardo, A. Rodriguez, A. Antinolo, A. Otero, D. Lucas, Y. Mugnier, Organometallics, 1999,18, 1287. 317. M. Etienne, C. Carfagna, P. Lorente, R. Mathieu, D. de Montauzon, Organometalks, 1999,18, 3075. 318. I.M. Bartlett, N.G. Connelly, A.J. Martin, A.G. Orpen, T.J. Paget, A.L. Rieger, P.H. Rieger, J. Chem. SOC.,Dalton Trans., 1999,691. 319. T.S. Buzar, T. Glowiak, I. Czelusniak, J. Organomet. Chem., 1999,585,215. 320. N.M. Agh-Atabay, J.L. Davidson, U. Dullweber, G. Douglas, K.W. Muir, J. Chem. SOC.,Dalton Trans., 1999, 3883. 321. P.K. Baker, M.G.B. Drew, D.S. Evans, A.W. Johans, M.M. Meehan, J. Chem. Soc., Dalton Trans., 1999,2541. 322. P.K. Baker, M.G.B. Drew, M.M. Meehan, J. Chem. SOC.,Dalton Trans., 1999, 765. 323. N.G. Connelly, W.E. Geiger, S.R. Lorelace, B. Metz, T.J. Paget, P. Winter, Organometallics, 1999,18, 3201. 324. I.M. Bartlett, S. Carlton, N.G. Connelly, D.J. Harding, O.D. Hayward, A.G. Orpen, C.D. Ray, P.H. Rieger, Chem. Commun., 1999,2043. 325. T.W. Crane, P.S. White, J.L. Templeton, Organometallics, 1999,18, 1897. 326. A.J. Nielson, C.E.F. Ricard, J. Chem. Soc., Dalton Trans., 1999, 2021. 327. Y. Nakayamo, H. Saito, N. Veyama, A. Nakamura, Organometallics, 1999, 18, 3149. 328. A.C. Filippou, B. Lungwitz, G. K-Kohn, Eur. J. Inorg. Chem., 1999, 1905. 329. H. Chen, D.B. Jacobson, B.S. Freiser, Organometallics, 1999,18, 1774. 330. H. Chen, D.B. Jacobson, B.S. Freiser, Organometallics, 1999,18, 5460. 331. T. Mao, Z. Zhang, J. Washington, J. Takats, R.B. Jordan, Organometallics,1999, 18,2331.

13: Hydrocarbon Transition Metal n-Complexes other than q-CsH5 and q-Arene Complexes 435 332. K.B. Renkema, K.G. Caulton, New J. Chem., 1999,23, 1027. 333. J.H. Hardesty, J.B. Koerner, T.A. Albright, G-Y. Lee, J. Am. Chem. SOC.,1999, 121,6055. 334. E. Perez-Carreiio, P. Paoli, A. Lenco, C. Mealli, Eur. J. Inorg. Chem., 1999, 1315. 335. B. Windmiiller, 0. Nurnberg, J. Wolf, H. Werner, Eur. J. Inorg. Chem., 1999, 613. 336. G. Liu, M.Garland, Organometallics, 1999,18,3457. 337. L. Dahlenburg, K. Herbst, J. Chem. SOC.,Dalton Trans., 1999,3935. 338. J. Koch, I. Hyla-Kryspin, R. Gleiter, T. Klettke, D. Walther, Organometallics, 1999,18,4942. 339. B.L. Edelbach, R.J. Lachicotte, W.D. Jones, Organometallics, 1999,18,4660. 340. K. Siinkel, U. Birk, Polyhedron, 1999,18,3187. 341. M.A. Bennett, C.J. Cobley, D.C.R. Hockless, T. Klettke, Aust. J. Chem., 1999, 52, 51, 342. M. Horacek, V. Kupfer, U. Thewalt, P. Stepnicka, M. Polasek, K. Mach, J. Organomet. Chem., 1999,584,286. 343. R. Choukroun, C. Lorber, B. Donnadieu, B. Henner, R. Frantz, C. Guerin, Chem. Commun., 1999,1099. 344. C . Elschenbroich, 0. Schiemann, 0. Burghaus, K. Harms, J. Pebler, Organometallics, 1999,18,3273. 345. F.G.N. Cloke, J.C. Green, C.N. Jardine, M.C. Kuchta, Organometallics, 1999, 18, 1087. 346. J-F. Capon, P. Schollhammer, F.Y. Petillon, J. Talarmin, K.W. Muir, Organometallics, 1999,18,2055. 347. J.T. Barry, J.C. Bollinger, M.H. Chisholm, K.C. Glasgow, J. Huffman, E.A. Lucas, E.B. Lubkovsky, W.E. Strieb, Organometallics, 1999,18,2300. 348. R. Khayatpoor, J.R. Shapley, Organometallics, 1999,18, 1353. 349. S . Doherty, M. Waugh, T.H. Scanlan, M.R.J. Elsegood, W. Clegg, Organometallics, 1999,18,679. 350. S . Doherty, G. Hogarth, M. Waugh, T.H. Scanlan, W. Clegg, M.R.J. Elsegood, Organometallics, 1999,18,3178. 351. A.J. Carty, G. Hogarth, G.D. Enright, J.W. Steed, D. Georganpoulou, Chem. Cornmun., 1999,1499. 352. N. Choi, G. Conole, M. Kessler, J.D. King, M.J. Mays, M. McPartlin, G.E. Pateman, G.A. Solan, J. Chem. SOC.,Dalton Trans., 1999, 3941. 353. A. Zimniak, J. Zachara, M. Olejnik, J. Organomet. Chem., 1999,589,239. 354. B. Zhu, R. Wang, J. Sun, J. Chen, J. Chem. SOC.,Dalton Trans., 1999,4277. 355. S . Barlow, L.M. Henling, M.W. Day, S.R. Marder, Chem. Commun., 1999, 1567. 356. M.I. Bruce, B.W. Skelton, A.H. White, N.N. Zaitseva, Aust. J. Chem., 1999, 52, 413. 357. J. Heck, G. Lange, M. Malessa, R. Boesse, D. Blaser, Chem. Eur. J., 1999,5,659. 358. C.E. Anson, N. Sheppard, B.R. Bender, J.R. Norton, J. Am. Chem. SOC.,1999, 121, 529. 359. R.D. Adams, 0-S. Kwon, J.L. Perrin, J. Organomet. Chem., 1999,584,223. 360. R. Roers, F. Rominger, R. Gleiter, Tetrahedron Lett., 1999,40, 3141. 361. H. Schottenberger, K. Wurst, M.B. Buchmeiser, J. Organomet. Chern., 1999,584, 301. 362. J.A. Dunn, W.J. Hunks, R. Ruffolo, S.S. Rigby, M.A. Brook, M.J. McGlinchey, Organometallics, 1999,18, 3372.

436

Organometallic Chemistry

363. R.J. Baxter, G.R. Knox, P.L. Pauson, M.D. Spicer, Organometallics, 1999, 18, 197. 364. R.J. Baxter, G.R. Knox, J.H. Moir, P.L. Pauson, M.D. Spicer, Organometallics, 1999,18,206. 365. F-E. Hong, J-Y. Wu, Y-C. Huang, C-K. Hung, H-M. Gau, C-C. Lin, J. Organomet. Chem., 1999,580,98. 366. R.J. Baxter, G.R. Knox, P.L. Pauson, M.D. Spicer, Organometallics, 1999, 18, 215. 367. X. Verdaguer, A. Moyano, M.A. Pericas, A. Riera, A. Alvarez-Larena, J-F. Piniella, Organometalics, 1999,18,4275. 368. J. Castro, A. Moyano, M.A. Rericas, A. Riera, A, Alvarez-Larena, J.F. Piniella, J. Organomet. Chem., 1999,585, 53. 369. S.M. Draper, M. Delamesiere, E. Champeil, B. Twamley, J.J. Byrne, C. Long, J. Organomet. Chem., 1999,589,157. 370. C. Moreno, J.L. Gomez, R-M. Medina, M-J. Macazaga, A. Arnanz, A. Lough, D.H., Farrar, S. Delgado, J. Organomet. Chem., 1999,579,63. 371. N.E. Carpenter, K.M. Nicholas, Polyhedron, 18,2027. 372. G.G. Melikyan, A. Deravakian, S. Myer, S. Yadsgar, K.I. Hardcastle, J. Ciurash, P. Toure, J. Organomet. Chem., 1999,578,69. 373. D. Gree, V. Madiot, R. Gree, Tetrahedron Lett., 1999,40,6399. 374. Y. Fukase, K. Fukase, S. Kusumoto, Tetrahedron Lett., 1999,40, 1169. 375. M.A. Soler, V.S. Martin, Tetrahedron Lett., 1999,40, 281 5. 376. A.M. Montana, D. Fernandez, Tetrahedron Lett., 1999,40,6499. 377. S.M. Draper, C. Long, B.M. Myers, J. Organomet. Chem., 1999,588, 195. 378. P.M. Breczinski, A. Stumpf, H. Hope, M.E. Krafft, J.A. Casalnuovo, N.E. Schore, Tetrahedron, 1999,55,6797. 379. R.J. Baxter, G.R. Knox, P.L. Pauson, M.D. Spicer, J. Organomet. Chem., 1999, 579, 90. 380. R.J. Baxter, G.R. Knox, M. McLaughlin, P.L. Pauson, M.D. Spicer, J. Organomet. Chem., 1999,579, 83. 381. W. Kerr, M. Mclaughlin, P.L. Pauson, S.M. Robertson, Chem. Commun., 1999, 2171. 382. M. Isobe, S. Takai, J. Organomet. Chem., 1999,589, 122. 383. F-E. Hong, Y-C. Chang, R-E. Chang, C-C. Lin, S-L. Wang, F-L. Liao, J. Organomet. Chem., 1999,588,160. 384. T. Rajesh, M. Periasamy, Organometallics, 1999,18,5709. 385. E. Montenegro, A. Moyano, M.A. Pericas, A. Riera, A. Alvarez-Larena, J-F. Piniella, Tetrahedron Asymm., 1999,10,457. 386. V. Derdau, S. Laschat, I. Dix, P.G. Jones, Organometallics, 1999,18, 3859. 387. M. Ahmar, F. Antras, B. Cazes, Tetrahedron Lett., 1999,40, 5503. 388. Y. Gimbert, F. Robert, A. Durif, M-T. Averbuch, N. Kann, A.E. Greene, J. Org. Chem., 1999,64,3492. 389. T. Sugihara, Y. Okada, M. Yamaguchi, M. Nishinzawa, Synlett, 1999,771. 390. T. Sugihara, Y. Okada, M. Yamaguchi, M. Nishinzawa, Synlett, 1999, 768. 391. M. Isobe, R. Nishizawa, T. Nishikawa, K. Yoza, Tetrahedron Lett., 1999, 40, 6927. 392. R. Saeeng, M. Isobe, TetrahedronLett., 1999,40, 1911. 393. C. Mukai, J.S. Kim, H. Sonobe, M. Hanaoka, J. Org. Chem., 1999,64,6822. 394. M. Kitamura, K. Ohmori, K. Suzuki, Tetrahedron Lett., 1999,40,4563. 395. N. Iwasawa, H. Satoh, J. Am. Chem. SOC.,1999,121,7951.

13: Hydrocarbon Transition Metal .n-Complexesother than q-CjHS andq-Arene Complexes 437

396. 397. 398. 399. 400. 401. 402. 403. 404. 405. 406. 407. 408. 409. 410. 41 1. 412. 413. 414. 415. 416. 417. 418. 419. 420. 421. 422. 423. 424. 425. 426. 427. 428.

M.M. Patel, J.R. Green, Chem. Commun., 1999, 509. G. Szalontai, J. Sovago, F. Ungvary, J. Organomet. Chem., 1999,586, 54. A.C. Comely, S.E. Gibson, N.J. Hales, Chem. Commun., 1999,2075. C.J. Cardin, P.B. Hitchcock, M.F. Lappert, C. MacBeath, N.J.W. Warhurst, J. Organomet. Chem., 1999,584,366. F.A. Cotton, E.V. Dikarev, S-E. Stiriba, Organometallics, 1999,18,2724. M. Maekawa, K. Sugimoto, T. K-Sawa, Y. Suenaga, M. Munakata, J. Chem. SOC.,Dalton Trans., 1999,4357. M.P. Devery, R.S. Dickson, B.W. Skelton, A.H. White, Organometallics, 1999, 18, 5292. Y. Suzuki, R. Hirotani, H. Komatsu, H. Yamazaki, Chem. Lett., 1999, 1299. J.M. Hoerter, R.C. Schnabel, P.A. Goodson, D.M. Roddik, Organometallics, 1999,18,5’7€7. N. Kanematsu, M. Ebihara, T. Kawamura, Inorg. Chim. Acta, 1999,292,244. J.R. Torkelson, R. McDonald, M. Cowie, Organometallics, 1999,18,4134. J.J. Schneider, U. Denninger, R. Goddard, C. Kruger, C.W. Lehmann, J. Organomet. Chem., 1999,582,188. S . Pasykiewicz, A. Pietrzykowski, L. Bukowska, L. Jerzykiewicz, J. Organomet. Chem., 1999,585,308. T. Murahashi, H. Kurosawa, J. Organomet. Chem., 1999,574,142. T. Hosokawa, T. Tsuji, Y. Mizumoto, S-I. Murahashi, J. Organomet. Chem., 1999,574,99. A.C. Albeniz, P. Espinet, Y-S. Lin, B. Martin-Ruiz, Organometallics, 1999, 18, 3359. C.P. Butts, J. Crosby, G.C. Lloyd-Jones, S.C. Stephen, Chem. Commun., 1999, 1707. J. Stein, L.N. Lewis, Y. Gao, R.A. Scott, J. Am. Chem. SOC.,1999,121, 3693. P. Schulte, G. Groger, U. Behrens, J. Organomet. Chem., 1999,584, 1. A. Koracs, G. Frenking, Organometallics, 1999,18,887. E. Delgado, E. Hernandez, N. Mansilla, T. Moceno, M. Sabat, J. Chem. Soc., Dalton Trans., 1999, 533. H. Lang, K. Kohler, G. Rheinwald, L. Zsolnai, M. Biichner, A. Driess, G. Huttner, J. Strahle, Organometallics, 1999,18, 598. S . Back, R.A. Gossage, G. Rheinwald, I. del Rio, H. Lang, G. van Koten, J. Organomet. Chem., 1999,582, 126. H. Lang, S. Weinmann, I.Y. Wu, T. Stein, A. Jacobi, G. Huttner, J. Organomet. Chem., 1999,575,133. R. Fandos, C. Hernandez, A. Otero, A. Rodriguez, M.J. Ruiz, J.L.G. Fierro, P. Terreros, Organometallics, 1999,18,2718. M.L.H. Green, N.H. Popham, J. Chem. Soc., Dalton Trans., 1999, 1049. Y. Yamaguchi, N. Suzuki, T. Mise, Y. Wakatsuki, Organometallics, 1999, 18, 996. C. Amatore, A. Ceccon, S. Santi, J.N. Verpeaux, Chem. Eur. J., 1999,5,3357. P.K. Baker, D.E. Belcher, Polyhedron, 1999,18,729. J.D. King, M.J. Mays, C.E. Pateman, P.R. Raithby, M.A. Pennie, G.A. Solan, N. Choi, G. Conole, M. McPartlin, J. Chem. Soc., Dalton Trans., 1999,4447. J.E. Davies, M.J. Mays, P.R. Raithby, K. Saveswaran, G.P.Shields, J. Organomet. Chem., 1999,573,180. K. Beck, J.A. Bauer, J.J. Alexander, Acta Crystallogr., 1999, C55,2020. W.H. Leung, E.Y.Y. Chan, W-T. Wong, Inorg. Chem., 1999,38,136.

438

Organometallic Chemistry

429. I.T. Chizhevsky, I.A. Lobanova, P.V. Petrovskii, V.I. Bregadze, F.M. Dolgushin, A.I. Yanovsky, Y.T. Struchkov, A.L. Chistyakov, I.V. Stankevich, Organometallics, 1999, 18,726. 430. M.L. Buil, M.A. Esteruelas, J. Modrego, E. Onate, New J. Chem., 1999,23,403. 431. 0.Pamies, G. Net, A. Ruiz, C.Bo, J.M. Poblet, C. Claver, J. Organomet. Chem., 1999,586,125. 432. D.S.A. George, R.W. Hilts, R. McDonald, M. Cowie, Organometallics, 1999, 18, 5331. 433. L.R. Falvello, J. Fornies, A. Martin, J. Gomez, E. Lalinde, M. T. Moreno, J. Sacristan, Inorg. Chem., 1999,38, 31 16. 434. J.M. Casas, J. Fornies, F. Martinez, A.J. Rueda, M. Tomas, A.J. Welch, Inorg. Chem., 1999,38,1529. 435. J.P.H. Charmant, J. Fornies, J. Gomez, E. Lalinde, M.T. Moreno, A.G. Orpen, S. Solano, Angew. Chem. Int. Ed. Engl., 1999,38,3058. 436. H. Lang, A. del Villar, G. Rheinwald, J. Organomet. Chem., 1999,587,284. 437. C.J. Adams, P.R. Raithby, J. Organomet. Chem., 1999,578, 178. 438. M.A. Cusado, J.J. P-Torrente, A.M. Ciriano, A.J. Edwards, F.J. Lahoz, L.A. Oro, Organometallics, 1999,18, 5299. 439. P-M. Pellny, V.V. Burlakov, W. Baumann, A. Spannenberg, R. Kempe, U. Rosenthal, Organometallics, 1999,18,2906. 440. M.A.F. Hernandez-Gruel, J.J. Perez-Torrente, M.A. Ciriano, F.J. Lahoz, L.A. Oro, Angew. Chem. Int. Ed. Engl., 1999,38,2769. 441. M.A. Hsu, W-Y. Yeh, S-M. Peng, J. Organomet. Chem., 1999,18,32. 442. N-Y. Yeh, M.A. Hsu, S-M. Peng, G-H Lee, Inorg. Chim. Acta, 1999,294,232. 443. M.I. Bruce, J-F. Halet, S. Kahlal, P.J. Low, B.W. Skelton, A.H. White, J. Organomet. Chem., 1999,578,155. 444. P.K. Baker, M.M. Meehan, J. Organornet. Chem., 1999,582,259 445. A.B. Antenova, A.A. Johansson, N.A. Deykhina, D.A. Pogrebnyakov, N.I. Pavlenko, A.I. Rubaylo, F.M. Dolgushin, P.V. Petrovskii, A.G. Ginzburg, J. Organomet. Chem., 1999,577,238. 446. S . Mihan, K. Sunkel, W. Beck, Chem. Eur. J., 1999,5, 745. 447. V.W-W. Yam, S.H-F. Chong, K.M-C. Wong, K.K. Cheung, Chem. Commun., 1999,1013. 448. J. Zachara, A. Zimiak, Acta Crystallogr., 1999, C55,58. 449. R.W. Eveland, C.C. Raymond, D.F. Shriver, Organometallics, 1999,18,534. 450. Z-X. Wang, H. Zhao, Polyhedron, 1999,18, 1131. 451. S . Ali, A.J. Deeming, G. Hogarth, N.A. Mehta, J.W. Steed, Chem. Commun., 1999,2541. 452. M.I. Bruce, P.A. Humphrey, B.W. Skelton, A.H. White, K. Costuas, J.F. Halet, J. Chem. Soc., Dalton Trans., 1999,479. 453. P. Nombel, N. Lugan, B. Donnadieu, G. Lauigne, Organometallics, 1999,18,187. 454. R.D. Adams, U.H.F. Bunz, W. Fu, G. Roidl, J. Organomet. Chem., 1999, 578, 55. 455. C.S-W. Lau, W-T. Wong, J. Orgunomet. Chem., 1999,589, 198. 456. C.S-W. Lau, W.T. Wong, J. Chem. Soc., Dalton Trans., 1999,2511. 457. C.S-W. Lau, W-T. Wong, J. Chem. Soc., Dalton Trans., 1999,607. 458. M.I. Bruce, B.W. Skelton, A.H. White, N.N. Zaitseva, J. Chem. Soc., Dalton Trans., 1999, 1445. 459. M.I. Bruce, B.W. Skelton, A.H. White, N.N. Zatseva, Aust. J. Chem., 1999, 52, 681.

13: Hydrocarbon Transition Metal n-Complexesother than q-CJHSand q-Arene Complexes 439

460. H.G. Ang, S.G. Ang, S. Du, J. Chem. SOC.,Dalton Trans., 1999,2963. 461. C.J. Adams, M.I. Bruce, B.W. Skelton, A.H. White, Aust. J. Chem., 1999, 52, 409. 462. C.J. Adams, M.I. Bruce, B.W. Skelton, A.H. White, J. Chem. Soc., Dalton Trans., 1999,2451. 463. C.J. Adams, M.I. Bruce, B.W. Skelton, A.H. White, J. Organomet. Chem., 1999, 573, 134. 464. C.J. Adams, M.I. Bruce, B.W. Skelton, A.H. White, J. Organomet. Chem., 1999, 584,254. 465. C.J. Adams, M.I. Bruce, B.W. Skelton, A.H. White, J. Organomet. Chem., 1999, 589, 213. 466. L.T. Byrne, J.P. Hos, G.A. Koutsantonis, B.W. Skelton, A.H. White, J. Organomet. Chem., 1999,592,95. 467. M.I. Bruce, B.W. Skelton, A.H. White, N.N. Zaitseva, J. Chem. Soc., Dalton Trans., 1999, 13. 468. T. Kochi, Y. Nomura, Y. Ishii, Y. Mizabe, M. Hidai, J. Chern. SOC.,Dalton Trans., 1999,2575. 469. V. Ferrand, G. Suss-Fink, A. Neels, H. S-Evans, Eur. J. Inorg. Chem., 1999, 853. 470. A.J. Poe, C. Moreno, Organometallics, 1999,18, 5515. 471. W-Y. Yeh, M-A. Hsu, S-M. Peng, G-H. Lee, Organometallics, 1999,18,880. 472. P.J. Low, K.A. Udachin, G.D. Enright, A.J. Carty, J. Orgunomet. Chem., 1999, 578, 103. 473. Y. Chi, C. Chung, W-C. Tseng, Y-C. Chou, S-M. Peng, G-H. Lee, J. Organomet. Chem., 1999,574,294. 474. T.K. Huang, Y. Chi, S-M. Peng, G-H. Lee, Organometallics, 1999,18, 1675. 475. Y.T. Shiu, R.J. Madhushaw, W-T. Li, Y-C. Lin, G-H. Lee, S-M. Peng, F-L. Liao, S-L. Wang, R-S. Liu, J. Am. Chem. SOC.,1999,121,4066. 476. M-C. Chung, A. Sakurai, M. Akita, Y. Moro-oka, Organometallics, 1999, 18, 4684. 477. M.I. Bruce, B.C. Hall, P.J. Low, B.W. Skelton, A.H. White, J. Organomet. Chem., 1999,592,74. 478. M.I. Bruce, B.D. Kelly, B.W. Skelton, A.H. White, J. Chem. SOC.,Dalton Trans., 1999,847. 479. L. Guo, J.M. Hrabusa, M.D. Senskey, D.B. McConville, C.A. Tessier, W.J. Youngs, Organometallics, 1999, 18, 1767. 480. U.H.F. Bunz, G. Roidl, M. Aitman, V. Enkelmann, K.D. Shimizu, J. Am. Chem. SOC.,1999, 121, 10719. 481. J. Pares, J.M. Morento, S. Ricart, J. Barluenga, F.J. Fananas, J. Organomet. Chem., 1999,586,247. 482. P.J. Low, R. Rousseau, P. Lam, K.A. Uddachin, G.D. Enright, J.S. Tse, D.D.M. Wayner, A.J. Carty, Organometallics, 1999,18, 3885. 483. R.D. Adams, U.H.F. Bum, W. Fu, L. Nguyen, J. Organomet. Chem., 1999,578, 91. 484. H. Wadepohl, K. Buchner, M. Herrmann, H. Pritzkow, J. Organornet. Chem., 1999,573,22 485. J.D. King, M. Monari, E. Norlander, J. Organomet. Chem., 1999,573,272. 486. R. Guo, J.R. Green, Chem. Commun., 1999,2503. 487. B. Caro, M-C. Seneschal-Tocquer, F.R. LeGuen, P. Lepoul, J. Organomet. Chem., 1999,585,43.

440

Organometallic Chemistry

488. F.E. Hong, J.W. Liaw, B-J. Chien, Y.C. Chang, C-C. Lin, S-L. Wang, F-L. Liao, Polyhedron, 1999,18,2737. 489. X.N. Chen, J. Zhang, Y-Q. Yin, W-L. Wang, Chem. Lett., 1999,583. 490. X-N. Chen, J. Zhang, S-L. Wu, Y-Q. Yin, W-L. Wang, J. Sun, J. Chem. Soc., Dalton Trans., 1999, 1987. 491. X.N. Chen, J. Zhang, E-R. Ding, Y-Q. Yin, J. Sun, J. Chem. Rex ( S ) , 1999,218. 492. J. Zhang, X.N. Chen, Y-Q. Yin, X-Y. Huang, J. Organomet. Chem., 1999, 579, 304. 493. X.N. Chen, J. Zhang, Y-a. Yin, X-Y. Huang, J. Sun, J. Organomet. Chem., 1999, 579, 227. 494. X.N. Chen, J. Zhang, E-R. Ding, Y-Q. Yin, J. Sun, Polyhedron, 1999,18,1555. 495. X.N. Chen, J. Zhang, Y-Q. Yin, X-Y. Huang, Organometallics, 1999,18,3164. 496. J. Zhang, X.N. Chen, Y-Q. Yin, W-L. Wang, X-Y. Huang, J. Orgunomet. Chem., 1999,582,252. 497. H. Wadepohl, S. Gebert, R. Merkel, H. Pritzkow, Chem. Commun., 1999,389. 498. E.C. Constable, C.E. Housecroft, B. Krattinger, M. Neuburger, M. Zehnder, Organometallics, 1999,18, 2565. 499. E.C. Constable, 0. Eich, C.E. Housecroft, J. Chem. SOC.,Dalton Trans., 1999, 1363. 500. K. Briining, H. Lang, J. Organomet. Chem., 1999,592, 147. 501. C. Kim, I. Jung, J. Organomet. Chem., 1999,588,9. 502. P.I. Dosa, C. Erben, U.S. Iyer, K.P.C. Vollhardt, I.M. Wasser, J. Am. Chem. SOC.,1999, 121, 10430. 503. T. Murahashi, E. Mochizuki, Y. Kai, H. Kurosawa, J. Am. Chem. SOC.,1999, 121,10660. 504. N.J. Hovestad, E.B. Eggeling, H. Jorg, H. Johann, T.B.H. Jastrzebski, U. Kragl, W. K e h , D. Vogt, G. van Koten, Angew. Chem. Int. Ed. Engl., 1999, 38, 1655. 505. S. Ogoshi, K. Tsutsumi, T. Shinagawa, K. Kakiuchi, H. Kurosawa, Chem. Lett., 1999,123. 506. I. Ara, J.R. Berenguer, E. Eguizabal, J. Fornies, E. Lalinde, F. Martinez, Organometallics, 1999,18,4344. 507. J.R. Berenguer, E. Eguizabel, L.R. Favello, J. Fornies, E. Lalinde, A. Martin, Organometallics, 1999,18, 1653. 508. V.W-W. Yam, K-L. Yu, K-K. Cheung, J. Chem., SOC.Dalton Trans., 1999,2913. 509. J.P.H. Charmant, J. Fornies, J. Gomez, E. Lalinde, R.I. Merino, T.M. Morino, A.G. Orpen, Organometallics, 1999, 18, 3353. 510. K.A. Al-Farhan, M.H.J’far, O.M. Abu-Salah, J. Organornet. Chem., 1999, 579, 59. 51 1. P.D. Prince, P.J. Cragg, J.W. Steed, Chem. Commun., 1999, 1 179. 512. G-C. Guo, G-D. Zhou, T.C.W. Mak, J. Am. Chem. SOC.,1999.121,3136. 513. M. Munakata, L.P. Wu, G.L. Ning, T. K-Sowa, M. Maekawa, Y. Suenaga, N. Maeno, J. Am. Chem. Soc., 1999,121,4968. 514. S. Back, G. Rheinwald, H. Lang, Organometallics, 1999,18,4119. 515. W. Frosch, S. Back, H. Lang., Organometallics, 1999,18, 5725. 516. P. Stepnicka, R. Gyepes, I. Cisarova, V. Varga, M. Polasek, K. Mach, Organometallics, 1999,18,627. 5 17. B.V. Lokshin, M.G. Ezernitskaya, V.I. Zdanovich, A.A. Koridze, J. Organomet. Chem., 1999,580,36. 518. C.S-W. Lau, W-T. Wong, J. Organomet. Chem., 1999,588, 113.

13: Hydrocarbon Transition Metal n-Complexes other than q-CjHj andtpArene Complexes 441

519. N.W. Duffy, B:H. Robinson, J. Simpson, J. Organomet. Chem., 1999,573,36. 520. M.I. Bruce, B.K. Skelton, M.E. Smith, A.H. White, Aust. J. Chem., 1999, 52, 431. 521. J. A. Campo, M. Cecano, J.V. Heras, E. Pinilla, M. Ruiz-Bermejo, R. Torres, J. Organomet. Chem., 1999,582, 173. 522. F. Maienza, M. Worle, P. Steffanut, A. Mezzetti, F. Spindler, Organometallics, 1999,18,1041. 523. X. Sava, N. Mezailles, F. Mathey, P. Le Floch, Organometallics, 1999,18,807. 524. J. Jutland, K.K. Hii, M. Thornton-Pett, J.M. Brown, Organometallics, 1999, 18, 5367. 525. A. Albinati, P.S. Pregosin, Inorg. Chim. Acta, 1999,296,246. 526. J. Park, Z. Quan, S. Lee, K.H. Ahn, C-W. Cho, J. Organomet. Chem., 1999,584, 140. 527. G. Zhao, Q-G. Wang, T.C.W. Mak, J. Organomet. Chem., 1999,574,311.

14 Transition Metal Complexes of Cyclopentadienyl Ligands BY IAN R. BUTLER

1

General Introduction

There has been a small change in the presentation format from that of the previous year' in that the cyclopentadienyl ligand classification has been simplified: there are no distinctions between mono- and bis-cyclopentadienyl ligands, and thus the classifications are by periodic table grouping only. The general abbreviations fc, 1,l'-disubstituted ferrocene, Fc, monosubstituted ferrocene, Cp = q5-C5H5;Cp' = qS-C5H4Me, Cp* = q5-C5Me3, Cps = non-specific Cp, Fp = Fe(C0)2Cp, dppf = 1,l'-bisdiphenylphosphinoferrocene are applied throughout. A number of cyclopentadienyl complexes and their reaction chemistry have been reported in a metal-vinylidene review.2 The geometric and electronic structures of carbocene (C5R5)2C and silicocene (C5R5)2Si,R = H, Me, have been studied using density functional calculations. The results show that carbocene would behave entirely differently from silicocene with the former preferring a classical dicyclopentadienylcarbene structure and the latter preferring a distorted structure. Comparisons are made with the known decamethylsili~ocene.~ The reaction of [LiC5Me4R], LiCp' where R='Pr, n B ~ H , (2 equivs), with lead(I1) chloride results in the formation of Pb(CpS)2 species which are either oils (iPr, "Bu) or a crystalline solid (H). One solid product has been crystallographically characterised indicating a bent metallocene structure with ca. 140" ring-metal-ring angle. Typically the Pb-C bond lengths span a large range (2.66-2.88 in the crystalline product: Some multidecker sandwich anions of plumbocene have also been obtained: the chemistry involves the addition of cyclopentadienyl salts to Cp2Pb and Cp2Sn to give n-anions of general formula [Cp2x+lE,]-. In this manner the structures of the new complexes [Cp3Sn]- .[Li(12-~rown-4)~]+, [Cp2Pb(p-Cp)Na.( 15-crown-5)], [Cp5Pb2]-[K(2,2,2-crypt)]+.thf, [Cp2Ph(pCp)Pb(p-Cp)Cs.(18-crown-6)] and [Cp5Pb2]- .[Li(12-crown-4)2]+.2thfhave been r e p ~ r t e d . ~ The magnesiation of isocyclopentadiene and the subsequent formation of metallocene halides has been discussed. The structure of exo(isodicyc1opentadienyl)butyl/magnesium.TMEDA complexes have thus been elucidated.6The (ally1)zSi-bridged Cp2Na cation has been found to crystallise as a polymer chain in which the sodium cations bridge the [(allyl)2Si(C5H4)2]2-units.7 A portion of the structure is shown as 1.

A)

OrganometallicChemistry, Volume 29 0The Royal Society of Chemistry, 2001 442

14: Transition Metal Complexes of Cyclopentadienyl Ligands

443

1

The use of cyclopentadienyl complexes feature widely in a general review of optically active organometallic complexes in which the chiral centre is the metal.’ The electronic structures of electron-poor dinuclear organometallic compounds of general formula [(CpM)(CpM’)]p-COT, M, M’ = V, Cr, Fe, Co, have been described in a detailed theoretical study.’ Another interesting structure is reported in a paper which deals with the q6-coordination of arsenine to titanium, vanadium and chromium. Metal vapour synthesis was used in this study as the synthetic means. For example [(q6-C5H5As)2Ti] is the first example of an unsubstituted 15 heteroarene sandwich complex to be crystallographically characterised.lo 2

Main Group, Lanthanides and Actinides

The catalytic reduction of azides and hydrazines has been achieved using a reduced uranocene dichloride complex (Na/Hg/azobenzene).l 1 The synthesis and reactions of bispentamethylcyclopentadienyluranium(1V) thiolates has been achieved. These compounds are simply obtained by treatment of [u(Cp*)2(C1)2]with NaSR. The product thiolates undergo reactions with C02 and CS2 to afford the insertion products of general structure [u(Cp*)2(SR)(E2CSR)], E = 0, R = ‘Bu; E = S, R = Me, ‘Pr, ‘Bu, and [U(Cp*)2(E2CSR)2],E = 0, R = ‘Bu; E = S, R = Me, ‘Bu. Mixed insertion complexes may be obtained simply by consecutive reactions with CS2 then C02. The insertion reactions are reversible in that their thermolysis leads to expulsion of the C02 or CS2.l2 The metallation of 2,2-bis(1’-indene)propane has been used as a route toward the synthesis of [(inden~l)~Yb(DME)] complexes. The X-ray structures of the representative products have been determined.l 3 The metathesis reactions of the dilithium salts of 1,2-bis(indeny1)ethane with either YbC13 or LnC13in thf, followed by removal of the thf and replacement with Et20, yielded the [(ethylene bis(q5-indenyl)]Ln(III) chloride][LiCl(Et20)]salt. Interestingly the ratio of isomers present (rac or meso) is dependent on whether Lu(rac) or Yb(meso) is used. The reaction of the meso ytterbium complex with NaN(TMS)2 furnishes a product which has been crystallographically characterised and is shown to catalyse the cyclic hydroamination of primary amino olefins.l4 The first bis(2-dimethylaminoethylindeny1)lanthanide complexes, namely [(Me2N(CH2)2C9H6)2M], M = Sm, Yb, have been prepared by the reaction of [(Me2N(CH2)2C9H6)K] with SmI2 or YbI2.

444

Organometallic Chemistry

Both complexes have been structurally characterised. The variable temperature NMR spectra of a range of uranium dimers [Cp”2UX]2 and [Cps2UX]2, where Cp” = l,3-(Me3Si)2C5H3and Cps = 1,3-(Me3C)2C5H3,have been examined. It has been observed that at low temperature the complexes adopt their solid state conformational structures whereas above room temperature there is a rapid halide exchange process.16 Samarium triiodide reacts with [Me2Si(C5Me4K)ZI in thf to give [Me3Si(CSMe4)2SmI(thf)]in high yield, which on further reaction with the less bulky KC5MeS in toluene affords [Me2Si(C5Me4)2Sm(C5Me5)].These complexes do not polymerise ethylene (50 psi) in contrast with [Cp*,Sm] complexes: thus the bulky substituted cyclopentadienyl rings clearly block access to the metal centre.17 The same research group have also investigated the formation of solvated complexes of general formula [Cp*Ln]2(p-qs:qS:CsHs),where M = Yb, Eu. A thorough structural characterisation is included in this work.” Meanwhile the crystal structure of [Nb(=NAr)c~’~Cll; Cp’ = q5-C5H4SiMe3, Ar = C6H40Me-4 has been determined. l9 A convenient synthesis has been developed for half sandwich and hydrido complexes of yttrium. The method uses the reaction of v(CH2SiMe3)3(thf)2] with silyl-substituted cyclopentadienes followed by reaction with H2 (at 4 and bar).20 A neutron diffraction study on [Cp*Y(OC6H3‘Bu2)CH(SiMe3)2] [Cp*La(CH(SiMe3)}2]at low temperature has shown that C-H bonds are not lengthened by coordination to lanthanide metals.21 The crystal structure of [Na(1S-crown-6)][UCp*2(SBut)(S)],the first example where an f-block element contains a metal-sulfur bond, has been reported. This compound was obtained by treatment of the complex [C~*~U(S‘BU)~] with Na(Hg) in the presence of the crown ether.22 The crystal structure of the yttrium complex ~ ~ c - [ O ( C H ~ C H ~ C ~ H ~ ) ~ ] Y C H ~ SiMe3, where C9H6= a substituted indenyl, has also been obtained, in which the metal is held centrally by the unusual coordination mode of the ligand. 23 It is shown as 2. C6

c12

2

445

14: Transition Metal Complexes of Cyclopentadienyl Ligands

2

Titanium, Zirconium and Hafnium

A further range of complexes derived from Cp2Ti(SR)2 have been prepared. These are dimethylplatinum(I1) derivative^.^^ The first titanium and zirconium perfluorovinyl complexes have been prepared. These are complexes of the types [Cp2M(CF=CF2),]X2-, (M = Ti, Zr), two of which (X = F, C1) have been structurally characterised. The synthetic method follows that previously published by the same authors and involves a two step, one pot reaction of CF3CH2F with BuLi and Following on from work reported in previous issues in this series, a further 27 ansa bis(fluoreny1idene)zirconium dichloride complexes have been prepared. Characteristically included is the complex testing in ethylene p~lymerisation.~~ The cyclic voltammetry of a range of trimethylsilyl- and methyl-substituted zirconocene dichlorides have been studied. The results obtained have been interpreted in terms of the structural properties of the molecules.26 A series of titanocene acetylides (including ferrocene acetylides) have been used as 'building blocks' for heterobimetallic transition metal complexes. Included are chemical oxidations and complexation reactions.27A theoretical study (density functional theory) has been carried out on titanocene olefin metathesis2*The reactions of [Cp2Ti(q2Me3SiC2SiMe3)],which is used as a convenient source of titanocene, with 1,4substituted 1,3-butadiynes give rise to a range of titanacyclocumulenes of the generic structure [Cp2Ti{q4-(1-2-3-4)-RC4R>].In the case where R = Ph, the complex is found to be unstable in solution and it leads to dimeric products which are shown as 3 and 4.29The solid state NMR spectra of the complexes /

Ph

Ph

3

Ph

4

[Cp2M(q 1-C5H5)2] have been investigated, where M = Ti and Hf.An intramolecular sigmatropic shift occurs and it was possible to follow the rearrangement of the single bonded cyclopentadienyl ligands. This thus provides a valuable addition to the data which are used (solution NMR) in many undergraduate lectures as examples of fluxional inorganic molecules.30The crystal structures of [q5-(C,HMe4)2Ti(p-H)2Mg(thf)(p-Cl)]~ and [(q5-C5HMe4)2TiOCMe3]have been reported in a study into the head to tail dimerisation of tert-butylacetylene catalysed by the usual reduced titanocene dichloride mixture (CptTiC12/ Mg/thf).31 Bis(2-piperidinoindenyl)titanocene(III) complexes have been used to control the allyl ligand reactivity: 2,3-disubstituted titanocyclobutane complexes are formed by free radical alkylation at the allyl central carbon.32 The intermolecular hydroamination of alkynes catalysed by dimethyltitanocene has been reported. Essentially the reaction of diphenylacetylene with

446

Organometallic Chemistry

aniline catalysed by dimethyltitanocene at 80-90 "C leads to the formation of N-( 1,2-diphenyiethylidene)aniline, which may be reduced to give the secondary amine or treated with silica to give the usual ketone by imine h y d r ~ l y s i sThe .~~ formation of titanium-thiolate-aluminium-carbidecomplexes whch involves multiple C-H bond activation has been reported. The reaction chemistry A new generainvolves the interactions of [ C P ~ P ~ ~ P N ) T ~ (with S R )A1Me3.34 ~] tion of titanocene catalysts have been developed for the enantioselective epoxide ring opening reactions which is based on the rational design of the catalyst.35The titanocene-catalysed intramolecular ene reaction involving the cycloisomerisation of enzynes and dienynes has been investigated in which titanocene dicarbonyl is used as catalyst.36The absolute bond enthalpies have been determined for a series of titanocene, zirconocene and hafnocene halide complexes.37 The reactions of [(C9H7)ZrC13] with disodium salts of linked cyclopentadienyl ions give the dinuclear zirconocenes [(CH2)n(C5H4)2][CgH7)ZrC12]2 family of complexes. It is claimed that these dinuclear catalysts show increased activity in comparison with similar mononuclear catalysts in ethene polymeri~ation.~* Further ethene polymerisation catalysts of the type bis( 1-R'-2-R-3R'-trisubstituted)zirconium dichlorides, R, R = alkyl groups, have been developed.39 An interesting insertion of acetonitrile into the Zr-P bond of [CpS2ZrC1(PHCy)], Cpf = q5-C5EtMe4, has been observed. The product complex [Cpf2ZrC1(N=C(Me)(PHCy))]exists as a mixture of E and 2 isomers in the ratio 1:13. A slow room temperature decomposition of this compound results in the formation of [Cp2(Cl)Zr(p-N=CMe-CMe=N)Zr(Cl)Cpfzlwhere the alkylideneamido ligands dimeri~e.~' In a synthetic programme the reactions of the dilithium salt of (dimethylsilanediy1)cyclopentadiene with MCb, M = Zr, Hf, in toluene afford [M {(SiMe2)(Cp2)C12}],which in turn has been reacted with alkyl organolithium reagents or Grignard reagents to give the alkyl chloride metathesis products. In addition, two p-0x0 complexes [Zr{ (SiMe2)(q5-C5H&R}2(p-0)], R = CH3, Bz, which were obtained in the metathesis reactions with MeL or (Bz)2Mg(thf), where traces of water were present, have been structurally ~haracterised.~' In a similar vein the series of Si2Me4-bridged zirconocene dichlorides have been prepared and structurally characterised. The preparation uses conventional synthetic methods beginning with the metathesis reactions of C1SiMe2SiMe2C1 and indenyl lithium reagents followed by reaction with ZrC4.42The electronic structure and the geometry of bis(tetrahydridoborat0)bis(cyclopentadienyl)zirconium(IV) has been studied using UV spectroscopy, PES and X-ray d i f f r a ~ t i o nThe . ~ ~ oxidation of (91-alkenylzirconoceneswith VO(OiPr)2Cl at low temperature resulted in intramolecular coupling yielding (E,E)-dienes whereas (E-1- 1-alkenyl-1-alkynylzirconocenes yielded (0 enzymes. This is a particularly easy synthetic method of coupling.44A range of chiral silicon-bridged zirconocene dichlorides and yttrio- and lanthanidocene dichlorides have been prepared and fully characterised. These new complexes are formulated as [MeRSi(C5H4)(C5Me4)MX],,X = C12, M = Zr, n = 1, X = Cl, M = Y, La, n = 2. More surprisingly the zirconocenes are active in ethene

14: Transition Metal Complexes of Cyclopentadienyl Ligands

447

polymerisation in the presence of methylal~moxane.~~ In related work the reactions of the lithium salts of 1- and 2-(o-alken- 1-yl)indenes with zirconium tetrachloride has furnished the corresponding zirconocene dichloride~.~~ Again a range of unbridged mixed-ring zirconocenes have been developed in addition to a series of mixed ligand zirconocenes which contain the 2-arylindenyl and 1methyl-2-arylindenyl ligands. These complexes are also olefin polymerisation catalysts after methylaluminoxane activation. The study seeks to identify the specific effects of ligands on the rate of polymerisation establishing the relative contribution of each. The conclusion is that bis(2-arylindenyl) and the mixed (1-methyl-2-arylindeny1)(2-arylindenyl)zirconocenedichlorides have similar activity and both are superior to the activity of bis( 1-methyl-2-phenylindeny1)zirconocene dichlor ides.47 Further C2-symmetric species (Cp’h M C12, (Cp’ = C5H4C(Me)2CHMe2,M = Ti, Zr, Hf have been prepared as potential silane dehydropolymerisation catalysd8 Another zirconocene family active in the formation of isotactic polypropylene are the newly developed aminoboranediyl-bridged zirconocenes p&NB(q5-C5H4)2]ZrClz and [Pri2NB(q 1C9H&]ZrC12 c0mplexes,4~and the effects of the alkyl groups in zirconocene alkyls in the series of complexes [(1,2-Me2Cp)2ZrR]f[CH3P(C6F5)3] - with regard to olefin polymerisation have been quantified. 50 An interesting new strategy has been developed for zirconocene catalyst design whereby a donor is placed on one cyclopentadienyl ring and an acceptor on the other. The interaction between the substituents thus determines the relative angle between the two cyclopentadienyl rings. This could lead to switchable catalysts? The controlled synthesis of a range of mixed metal (Zr/Ir) complexes involves the reaction between [Cp’2Zr(SH)2], Cp’ = q5-1,3-di-t-butylcyclopentadienyl, and iridium halide salts. Five and six-membered carbocycles may be obtained from zirconacyclopentanes, which involves carbometallation with an alkyne/CuCl mixture.53 Fryzuk and co-workers have continued their investigations into the reactivity of zirconium alkylidenes in which an [q5C5H3- 1,3-(SiMe2CH2PPri2)2]is a key ligand.54The mechanisms of stereocontrol for doubly silylene-bridged C , and C1 symmetric zirconocene catalysts for propylene polymerisation have been studied and the synthesis of a range of the doubly silyl-bridged complexes has been described.55 The reactions of zirconacyclopentadienes with CO in the presence of Bu”Li have been investigated. A range of substituted cyclopentenones may be obtained in high yield using this synthetic meth~dology.’~ The structurally unusual complex [P{ Z ~ ( H ) C P ~ ) ~B>P]b+- has been prepared directly from [Cp2ZrHC1]in a one-step ~ynthesis.’~ The activation of [Cp’ZrMe2] with new perfluoroaryl diboranes has been investigated and the solution chemistry and ethylene polymerisation chemistry developed.58In two related papers which appear ‘back-to-back’ the synthesis of ansa-zirconocenes is reported by catalysed Mannich-type additions.59960 Alkyl zirconocene chloride has been used as an ‘unmasked’ acyl anion: the regioselective acylation of cyclohexanone with nonaoylzirconocene chloride in the presence of palladium catalysts results in either 1,2- or 1,4-acylation depending on the catalyst used.61 The carbon-carbon cleavage reactions and

’-

’’

448

Organometallic Chemistry

the selective transformations of five-membered zirconacycles have been studied in detail. Essentially the work has been developed to prepare a number of zirconacycles, which may then be de-complexed to yield, for example, tetrasubstituted butadienes.62A new synthetic route towards enantiopure biphenylbridged titanocenes and zirconocenes has been developed and the resultant complexes have been observed to be highly efficient catalysts for imine hydr~genation.~~ A range of heterobimetallic ansa-zirconocenes have been prepared in which rhodium is incorporated onto the bridge. The general structure of these complexes is [LRh(q2-CH2=CH)2Si(q5-C5H2-2,4-Me2)2ZrC12], where L = q5C9H7, Cp or Cp*. These complexes again are highly active after activation with methylaluminoxane in the polymerisation of a-olefins.64In the polymerisation of propenes with zirconocene catalysts labelling experiments have detected stereo-errors in the isolactic polymerisation which were due to Dtransfer from the polymer to a methyl group. In an effort to establish a mechanism for the reaction the cation [Cp2Zr(iso-butyl)]+has been used as a model system in a density functional study to establish the reason.65 The reactions of a-phosphinozirconaindene and cumulenes afford stable zwitterionic monomeric five-coordinate products in the formal [3+2] cycloadditions.66 Unbridged sterically crowded zirconocene dichlorides may be obtained in high yield in the reactions of dialkylzirconium dichlorides with two equivalents of an appropriate fulvene in hydrocarbon medium.67A broad range of zirconocene and hafnocene halides which contain metal complexes appended to the cyclopentadienyl rings have been obtained. The work utilised, for example, the complex [M {(q-C5H4)CMe2(q2-C9H6)(Cp)C1], M = Zr, Hf, which was reacted with [(Rh(C0)2C1)]2 to yield the Rh-indenyl complexes which were then yet further modified.68 'An unexpected alkyl-substituent exchange' has been observed during the formation of a bis(zirconocene) complex which contains a planar fourcoordinate carbon. The complex in question is [{ C ~ ~ Z r ) ~ ( p - p ~ : p ~ CH3CCCH3)( ~ - K ~ - C ~ C C H ~ S ~ ( C H ~ ) , )The I + BCH2Si(CH3)3 P~-. was originally attached to the zirconium centre.69 Zirconocene polyoxometalates have been studied in detail as a source of polyoxometalate for transfer rea~tion.~' In a paper targeted at models for intermediates in metallocene-catalysed alkene polymerisation zwitterionic d'-zirconium-alkyl alkenes have been observed.71 The hydrogen exchange between hydride and methyl ligands in [Cp*Os(dmpm)(CH3)H'], dmpm = (dimethylphosphino)methane,has been investigated using density functional theory calculation^.^^ The reactivities of permethylzirconocene and permethyltitanocene towards disubstituted 1,3butadiynes have been investigated. 73 A low temperature NMR investigation has shown that there is an interaction between the pendant phosphines and the zirconium centre and between an ortho-H in the complexes [Zr(q5CSH4CMe2PPh2)l2+ [MeB(C6F5)3]24- and [Zr(q-C5H4Me2Ph2I2'[MeB(C6F5)3]2- respectively. These complexes are obtained directly from the neutral species on treatment with two equivalents of B(C6F5)3.74The treatment of 1-zircona-4-phosphaindenewith PBr3 results in the formation of a 1-bromo-

14: Transition Metal Complexes of Cyclopentadienyl Ligands

449

1,44iphosphaindene which itself is a useful synthetic reagent.75 Further titanocene bis-alkynes have been prepared in which the cyclopentadienyl ring contains a phosphine, phosphine oxide or phosphine sulfide substituent, for example [(q5-C5&R)2Ti(C=C'Bu)2], R = PPh2, P(O)PPh2, P(S)PPh2. The phosphine may then be subsequently complexed (with Cu, Mo) to afford bimetallic or trimetallic species ( C U ) . ~A~ broad range of permethylated [Me%]-ansa-bridged titanocenes have also been prepared and characterised. The dialkyl complexes of the type we2Si(C5H4)]TiR2thermally eliminate alkanes to yield the fulvene complexes.77A novel zirconocene catalyst design strategy has been used in the synthesis of thermoplastic elastic polypropenes: essentially tailor-made indenyl and fluorenyl zirconium dichlorides have been prepared.78A mechanistic study on the formation of the zirconium alkylidene complex [(q5-CsH3-1,3-(SiMe2CH2PP*2))2Zr=CHR(C1)], R = %Me3, Ph, has been carried The first direct observation of the stereochemistry of the initial propene insertion step in a metallocene catalyst has been reported." The enantioselective addition of alcohols to ketones has been observed to be catalysed by planar chiral azaferrocenes.* Again the asymmetric hydrogenation of unfunctionalised tetrasubstituted olefins using a cation zirconocene catalysis has been reported.82 Further work has been carried out on the asymmetric formation of a-amino acid esters using chiral zirconocene comp~exes.'~ Finally the formation of silazirconacyclopentene has been observed in the reaction of zirconocene dichloride with Me2PhSiLi in the presence of a diary1 alkyne.85 4

Vanadium, Niobium and Tantalum

The acidolysis of [Cp'2TaH3], Cp' = q5-tB~C5&with tduoroacetic acid results in the formation of [Cp'2Ta(H)(OCOCF3)2],whereas H - loss on reaction with electrophiles (CPh3+or H+) gives the cation [CP'~T~(H)~]+. The latter cation may be trapped as a solvated adduct [ C P ' ~ T ~ ( H ~ ) ( S M ~ ~ or) ] B F ~ the corresponding PF6- salt (after reaction with FcH+PF6-). A number of ligands can then be added which result in the formation of [Cp'Ta(Hk(L)]+ salts.86The one electron oxidation of VCp2 using [FcCp2]+in toluene results in the formation of the 14-electron FCp2]' cation, which for the first time has been isolated in an unsolvated form. V(CO)6 reacts with vanadocene to give [Cp2V(p-OC)V(CO)5]as a short-lived species which has been characterised in solution by infrared spectroscopy. An elegant labelling experiment in which V(13CO)6was used followed by the addition of l2C0 resulted in the formation of the [vCp2('2CO)2]~( 13co)6] product thus demonstrating that no ligand distribution occurs. Vanadocene also reacts with [co2(co)8] to give [C~~VCO(CO)~] which decomposes to [vCp2(CO)2][Co(CO)4]at room temp e r a t ~ r eThe . ~ ~reaction of VCp2 with A r P ( c ~ c P h ) Ar ~ , = 2,4,6-t-BuC6H2), yields the vanacyclopropene phosphane [Cp2V(q2-PhC=C)P(C=CPh)Ar].This complex may be further reacted with HC1 to revert either to the starting ligand

450

Organometallic Chemistry

or to an alkenyl alkynyl phosphane.88 Attempts to obtain (CP$)~Vwhere Cps = C5(iPr),HS--nfrom the reaction of reduced (Zn)VC13 and K[Cp$] in thf at room temperature simply resulted in the formation of the zincocenes (Cp$);?Znwhereas in refluxing thf the vanadocenes were indeed formed. The use of aluminium as a reducing reagent allows a room temperature synthesis.89 A detailed NMR relaxation study has been carried out on [Cp'2TaH3MPPh3][PF6].90 An unprecedented sulfur transfer has been observed in the reaction of complexes [ C P * ~ T ~ HCp* ~ ] ,= q5-C5H4+Bu or q5-C5H2-1,2-Me2-4-'BuCpwith propylene sulfide. One such product of the reaction is [CpS2Ta(=S)(S-'Pr)],on which a crystallographic structure determination has been carried out. Subsequently the reactivity of the products towards a range of electrophiles has been studied." The ansa-bridge in a tantalocene has been shown to promote olefin insertion and reductive elimination reactions. The complexes used in the investigations were [{ Me2Si(C5Me4)} 2Ta(q2-C2H4)H] and [ { Me2Si(C5Me4))2TaH3.92The reaction chemistry of a series of [Cp$TaLn] compounds, Cps = (q5-C5H4PPh2),has been explored including the formation of bimetallic complexes in its reaction with metal ~ a r b o n y l s . ~ ~

5

Chromium, Molybdenum and Tungsten

The triazidogermyl complexes ~ ~ ~ ~ S - [ ( ~ ~ - C ~ R ~ ) W ( C O ) ~ has (PM~~)~ been prepared in the direct reaction of the analogous GeC13 complex with sodium a ~ i d eThe . ~ ~tungsten hydride [Cp(C0)3WH] reacts with the carbene complexes [(CO)5W=C(H)C6H4R-p]whereby the carbene inserts into the W-H bond to give the benzyl complexes [Cp(C0)3WCH2C6H4-R-p].Similar reactions occur with manganese and chromium carbene complexes. The thermodynamics of the reaction are also discussed in this paper. 95 The synthesis and structure of the dark green decaphenyltungstenoceniumtri-iodide has been reported. This compound was obtained by iodine oxidation of the corresponding metallocene. The metallocene was prepared as previously reported from [(C2Ph2)W(qgCgPhs)] by thermolysis. The structure of this compound is shown as 5.96 The reaction of [(CpCr(CO)2}2(p,q2-P2)]with LiBEt3H at low temperature affords three new phosphanido complexes namely [ { c ~ C r ( C 0 )2(~p-PH2)( ) pH)], [ {CpCr(CO)2}2(p-PH),{(CpCr)2(p,q1:q ':q5:q5-P5)}], all of which have been characterised by single crystal X-ray diffraction. One of these is a tripledecker sandwich complex which contains a cyclic P5 unit as its middle layer.97 A theoretical investigation (density functional calculations) has been carried out to examine the thermal stability of Group 6 bis(cyclopentadieny1)- and ethylene-bridged bis(cyclopentadieny1)monocarbonyl complexes. The dissociation energies calculated for [Cp2M(CO)] are 99 (for Cr), 186 (for Mo) and 194 (for W) kJ mol-' which are consistent with the experimentally observed data where the Cr-compound is the least stable. In the case of the ansa-bridged compound of chromium the calculated energy is higher (1 12 kJ mol-') which again concurs with the relative enhanced stability observed.98The reaction of

14: Transition Metal Complexes of Cyclopentadienyl Ligands

45 1

5

CpMoC12 with the mixed phosphine thioether ligands Ph2PCH2CH2SR (R=H, CH3) yields the simple addition product which proved difficult to isolate in the case where R = H (R = CH3 may be isolated as a crystalline solid). The former compound disproportionates rapidly to give a mixture of [CpMo(SCH2CH2PPh2)2]+Cl- and [CpMoC1(SCH2CH2PPh2)]2.” The molecular structures of the family of complexes of generic formulae [(W(Co)Cp)2(CL-C8[Co(CL-dppm),(C0)6 - 2m]n], m = 0, 1, = 1 2, have been reported in an investigation into the reactivity of [(w(co)3cp)(~-c8)] with 100 [Co(C1-dppm)m(C0)8-%I* A dual, experimental (stopped-flow) and theoretical (density functional theory) investigation into the phosphine exchange in 15-electron [CpCrC12(PR3)] complexes has been carried out. lo’ The periodic trends in the metal-metal bonding in cubane cluster complexes [Cp4Me4E4], M = Cr, Mo, E = 0, S, have been examined in a theoretical investigation and the calculated trends in structure and bonding have been established.lo2 Meanwhile the synthesis of the cluster [Mo(Cp)018]- has been re-investigated.lo3 A range of complexes of the type [Cp*M(C0)3(BH2PMe3)]has been prepared by the photolysis of [Cp*M(C0)3Me], M = Mo, W in the presence of BH3.PMe3.lW The facile metal promoted oxidation of q4-1,3-diphosphacyclobutadieneby water or methanol has been observed in the synthesis of [CpSMoC1(CO)(q41,3-P2C2Buf2)],Cps = Cp, Cp* and related complexes.lo’ The mixed sandwich compound [CpMo(q6-C6Ph6)]was obtained unexpectedly during the thermolysis of [CpMo(Bn)(q2-PhC2Ph){ P(OMe)3}]. It undergoes reversible one electron oxidation and reduction. An adduct which was formulated as [CpMo(r16-C6Ph6)][FPFs]was obtained which may be oxidised cleanly but the [PF6]- anion is released upon attempted reduction. lo6 The reaction of [Cp2MH2], M = M o , W, with AgPF6 in a molar ratio of 2:l in acetone at low temperatures yields the complexes [( C P ~ M ( C L ~ - H ) ~ ] ~ A ~ ) P F ~ while the reaction with equimolar quantities of the two metal hydrides and the

452

Organometallic Chemistry

silver salt furnishes the mixed-metal complex [Cp2Mo(p2-H)2Ag(pH)2WCp2]PF6.lo7 The reaction of SiN'BuCHCHNtBu abbreviated as SiL with molybdenocene or tungstenocene dihydrides results in the insertion of the silanediyl group to yield [Cp2M(H)(SiLLH)]. In addition the reaction of [Cp2Mo(PEt3)]with the same ligand upon irradiation gives [Cp2Mo(SiLL)].lo* The reaction of MoC15 with [Me2Si(C5Me&]Li affords the complex [Me2Si(C5Me4)2]M~C12 in the presence of NaBH4 and CHC13. A comparison of this complex with the similar non-ansa bridged complex indicates that the presence of the bridge is responsible for C-H and C-C activation reaction^.'^' The selective oxidation of [Cp2MoS2] and [Cp2MoS4] to give [ C ~ ~ M O S and ~O] [Cp2MoS40]respectively has been achieved using m-chloroperbenzoic acid. In the latter complex the oxygen atom is attached to the 2-sulfur atom in the ring; however, the addition of oxygen has been shown to occur at the 1-S atom initially before it migrates. lo Water soluble molybdenocene complexes result in the H/D exchange on the a-carbon atom in addition to its incorporation into the Cp rings. This study in addition to its general interest in the preparation of labelled alcohols will be useful as a teaching model."' The use of fluorinated alkoxy ligands of the type [OCH(CF&]- has been reported as the key to the successful preparation of [CpzMo(OR)2]complexes.' l 2 [Cp2MoC12] has been used in the aqueous phosphoester bond cleavage in dimethyl phosphate. This is claimed to be the first reported case of an organometallic complex which hydrolyses an unactivated phosphate diester in water.' l 3 A highly reactive 33-electron cluster of general formula [Cp2M02(pPPh2)(CO),] has been reported.' l4 A short method of synthesis of [Cp2WX2] from [CpW(q3-CsH5)(CO)2]has been described which is complemented by the synthesis of a range of mixed ring indenyl analogues of tungstenocene [(ind)CpW12].Furthermore a stepwise route to bis-indenyl tungsten derivatives is reported. The key to the synthesis is the transformation reactions of cationic cyclopentadienyl complexes [CpW(q4C5H6)(CO)2]' and their indenyl analogues using photolysis as a method of decarbonylation. The iodide is introduced from its tetrabutylammonium salt. l 5 The preparation of [W2(p-COH)Cp2(pL-PPh2)2][BF4] has been reported: it is formed by protonation of the corresponding p-CO complex and it reacts with oxygen to form the hydroxocarbonyl species [W2Cp2(OH)(pPPh2)2(CO)][BF4].1'6

6

Manganese and Rhenium

The intriguing complex [Cp5CpMn(C0)3]has been structurally characterised and it has been shown to undergo dissociative coalescence to fullerene c60 and related carbon clusters induced by laser desorptiodionisation. l 7 The synthesis and characterisation of a 'novel inorganic benzene' complex has been reported [(Cp*Re)2(p-q6:q6-B4H4C02(CO)s]]. l8 Meanwhile the 'ultrafast ring closure energetics and dynamics' of cyclopentadienyl tricarbonyl manganese complexes has been examined. l 9

'

'

14: Transition Metal Complexes of Cyclopentadienyl Ligands

453

Cyclopentadienylrhenium tricarbonyl has been used as a catalyst in the regiospecific end-functionalisation of alkenes: the method employs Re-catalysed borylation under photochemical conditions. 120 A polymer-supported phosphazine has been used as a stable reagent in a three-component synthesis of substituted cyclopentadienyltricarbonylrhenium complexes: essentially the method uses a triphenylphosphine supported polymer to which is attached a diazocyclopentadiene. T h s is then reacted with a labile rhenium carbonyl derivative in the presence of a nucleophile which yields the nucleophilesubstituted cyclopentadienyl rhenium tricarbonyl product. 120a

7

Iron, Ruthenium and Osmium

The reaction rates for the alkylations of [CpFe(dppe)CNl, [CpRu(dppe)CN] and [CpRu(CO)(PPh3)CN] have been determined and it is observed that the reactions are first order in both the complex and alkylating agent.12' The coupling of a metallocenyl group to a non-cyclic ortho-phenylenediamine precursor followed by ring closure and oxidation has been used as a synthetic route towards ferrocene-containing benzimidazolium salts. From these precursor salts a number of carbenes have been prepared which include thiourea, azine and W(O), Hg(I1) and Pd(I1) complexes.'22 In another paper from the same research group a range of mono- and 1,l'-di- and pentamethylferrocenes have been oxidised to their corresponding cations at 25°C by hydrogen peroxide in the presence of horseradish peroxidase. The kinetics of the oxidation process have been fully investigated and the results have been compared with those in an earlier study (J. Biol. Inorg. Chem., 1997, 2, 182).123 Organometallic labels have been attached to the C-terminus of amino acids and peptides. Ferrocene (as the ethylamine) has been attached in this manner and its conformational interchange in solution has been studied by NMR.'24 N-Ferrocenyl-a-amino acids have been used as precursors towards 2-ferrocenyl-4R-5(4H)-oxazolones. A range of metal complexes were subsequently prepared from the oxazolones (Pd(II), Pt(II), Ir(1)). In the case of Ir (as Cp*IrC12) trimetallic and pentametallic complexes were obtained.12* The condensation of carotenoid polyene dialdehydes, 1,l'-ferrocene dialdehydes and 9-ferrocenyf-2,7-dimethylnonatetraenalwith the Fischer carbene complexes [(OC)5W=C(NMe2)CH2SiMe3]or [(OC)5M=C(Me)(OMe)],M = Cr, W, in the presence of Bu"Li or SiMe3Cl/NEt2furnishes a range of bis-carbenes of which the ferrocene complex is pre-eminent, shown as 6. More interesting, however, is the preparation of the complex 7, which uses similar chemistry beginning with the monosubstituted ferrocene. This re-awakens the general interest in the molecular wire area, which was initially pioneered by Lehn, which has yet to be fully exploited.'26 An interesting paper describes the synthesis of peralkylated cyclopentadienyl complexes. The method builds on the synthesis of pentamethylcyclopentadiene developed by Jutzi. The method begins with pentanone3- which is condensed

Organometallic Chemistry

454

(OC),W&

7

wit . is0butyr aldehyde to form trans-4,6-dimetllylhept -5 -en-3-one and subsequently 3,5-diisopropyl-2,6-dimet h yl-2,3,5,6-tetrahydro-y-pyrone. Dehydration gives 2,5-dimethyl-3,4-diisopropylcyclopent-2-en1-one. Finally the reaction of either methylmagnesium bromide or isopropylmagnesium chloride is used to prepare the pentasubstituted cyclopentadienyl precursors. A range of novel metallocenes were prepared which include octaisopropylferrocene (amended procedure) which was structurally characterised. 27 Some very interesting structural chemistry is reported in a paper documenting the reaction chemistry of [Cp*Rh(CO)] with the triphosphaferrocene [CpFc(q5-P3Cp’2B~2)]. 12* A number of ferrocenyl ketones have been prepared which include an azido function in the ortho-position of the aryl ring in the substituent ketones. The compounds are essentially prepared by Friedel-Crafts

14: Transition Metal Complexes of Cyciopentadienyl Ligands

455

acylation methodology. The chemistry of the azido functionality is fully explored in a 12 page paper.12’ A ferrocenoyl functionalised thiourea ligand has been used in the photochemical generation of an iron complex.130 An extremely useful synthesis of Nsubstituted 2-aza-[3]-ferrocenophane series has been reported. The method uses 1,l’-ferrocenedimethanol as a precursor which in the presence of a primary amine and RuC12(PPh& forms the appropriate ferrocenophane. 31 Arylferrocenylethynes react with mercuric acetate in acetic acid to yield the appropriate addition compounds. This synthesis may have broader implications in the synthesis of materials for non-linear optical applications in future synthetic programmes.132 A range of dialkylaminomethylferrocenes of the type FcCH2NRR’ have been prepared. The synthesis is essentially the classic method adopted in the synthesis of FcCH2NMe2. In this case the R groups are Et2, (CH2CH=CH2)2, [(CH2CH&0], and [(Me)(CH2Ph)].133 In a related paper the synthesis and electrochemistry of ferrocenemethylamine and its conjugated acid together with the crystal structure of ferrocenemethylammonium chloride are detailed. The reported synthesis is based on the reductive amination of ferrocene carboxaldehyde.134 The reaction of (FcN)Li, FcN = dimethylaminomethylferrocenyl,with silicon tetrachloride has been reinvestigated and the (FcN)SiC12product has been crystallographically characterised. The silane was subsequently methylated by treatment with methylmagnesium chloride. The redox processes of these dinuclear compounds have been investigated and structure-reactivity conclusions have been drawn. 35 The templated (Ni) reaction of 3-ferrocenyl-3-chloropropenolwith 1,2diaminobenzene gives a stable nickel chelate of a doubly ferrocene-substituted chelate complex of tetrama[ 14lannulene. This is an interesting reaction which should be exploited in future ferrocene-based sensor work given the ease of preparation of the ferrocene starting materials and the ease of product formation.13‘ The synthesis of 1,1-bis(1”,2”,3”,4“,5”-pentamethylferrocen-1’y1)ethene has been documented as a prototype of two metallocenes bridged by an sp2-vinylidene carbon centre. The synthesis began with 6-N,N-dimethylamino-6-methylfulvene which was developed to a pentamethylferrocene-substituted fulvene and a Cp-geminally substituted ethene.137 Again the synthesis and reactive stability of ferrocenyl(2,4,6-trimethoxyphenyl)carbenium salts have been examined. A number of ferrocenyl methanols were prepared from the carboxaldehyde which were treated with perchloric acid or tetrafluoroboric acid to give carbenium salts. 138 A number of palladium(I1) and Pt(I1) compounds which contain bi- and terdentate ferrocenyl ligands obtained from Schiff base chemistry have been obtained. The ligands used are generalised as [CpFc(q5-CSH4)CH=NR]; R = (CH2)2N(CH3)2; (CH&SCH2CH3; and

’

CH(COOCH3)(CH2)2SCH3.13’ The acylation of ferrocene using arylene bis acid chlorides has been reinvestigated and it has been observed that it is possible to isolate the intermediates which are partially reacted, i. e. the monosubstituted acid chlorides. An X-ray structure of one of these is highlighted in the paper, which comprises four independent molecules in which the substituent is remarkably

456

Organometallic Chemistry

well ordered. This work will clearly lead to new methodology for non-linear applications when chiral unsymmetrically substituted products are developed.140 Further work has been carried out on samarium iodide coupling reactions of acylferrocenes or ferrocenyl alkyl alcohols. Acyl ferrocenes can be reduced to the alcohols at low temperature or fully reduced to the alkyl compounds at higher temperature. A short investigation of the now well-used SmI2-coupling of ferrocene carboxaldehyde to the vinyl or pinacolic products is also included in this work.'41 The solid state reactions of anhydrous iron(I1) chloride and sodium, potassium and thallium cyclopentadienides have been studied using ball mill r e a ~ t 0 r s . l ~ ~ In the continuing work of ferrocene-based donor-acceptor complexes the novel n-donor-n-acceptor complex 1-(4,5-dimethyl-1,3-ditbiol-2-ylidene-l, 1ferrocenyl-3,3-dicyanopropenehas been prepared and characterised as a black crystalline solid. A detailed description of the crystal structure is given in which the variation in bond lengths and torsional geometry is used to provide information on the degree of intramolecular electron transfer.143The synthesis and crystal structures of two isomeric ferrocenylsilatranes have been reported in a short paper dealing essentially with catalytic coupling (e.g. Heck) reactions. 144 The reaction of 1,1'-diacetylferrocenewith excess piperidine and a stoichiometric quantity of TiC14 gives a product in which the two functional groups are coupled into a ferrocene 'framework'. The initial success led to the Tick-mediated condensations in the presence of morpholine, pyrrolidine or methylisopropylamine. 45 A novel trinuclear n-butyltin cluster which incorporates three ferrocene carboxylate units has been prepared. This compound [(Bu"SnCl(FcC02),>(O)(OH)] was simply obtained in the reaction of ferrocene carboxylic acid and Bu"S~(OH)~CI in 1:1 stoichiometry.146 The interesting reaction of [Cp*2Ru2C4] with excess norbornadiene in ethanol has yielded the ruthenocene complex [Cp*Ru(qS-CSH&H1 I)] where the substituent is tricyclo[4.2.1.02ys]non-7-en-3yl.Essentially the two norbornadiene fragments couple to

14: Transition Metal Complexes of Cyclopentadienyl Ligands

457

form the substituent cyclopentadienyl ring. The structure of this molecule is shown as 8.147 A range of cycloalkylated ferrocenes which have been identified as potential liquid-burning modifiers for composite rocket fuels have been prepared in the Friedel-Crafts alkylation of ferrocene with cyclohexene or 2-cyclooctene.14' Non-enzymic kinetic resolution of propargyl alcohols has been carried out using a planar chiral DMAP derivative @MAP fused to ferrocene).'49 Further work on anion sensing and recognition has been carried out using a range of ferrocene-appended macrocycles. Pendant phosphines were attached to the ferrocenyl rings which were subsequently reacted with metal carbonyls or metal bipyridines to afford bimetallic or trimetallic species.150 7.1 Ferrocenylphosphine Ligand Chemistry. - A range of ruthenium bimetallic complexes of bisdiphenylphosphinoruthenocene have been reported. 51 The neutral complexes [(PFc2Ph)AuR], R = C1, C6Fs, and the cationic complexes [Au(PFc2Ph)(PPh3)]C104,PR3= PFc2Ph, PPh3, have been prepared. 152 Furthermore a range of [(Cp*Rh(M))]complexes which contain 1,l'bis(diphenylphosphinomethy1)ferrocene (dppm) or dppf have been prepared in the direct reactions of [Cp*RhCl2I2with the ligands. In the presence of NaPF6 new cationic complexes of the type [CpRhCl(dppf-P,P)](PF6)are obtained. 53 The half modified dppf [Fc(q5-C5Me4P(S)Ph2)Fc(C5Me$Ph2)(L) has been prepared and reacted with [RhCl(C0)2] to give a [4]-ferrocenophane complex [(L)Rh(CO)Cl] together with the more unusual [(L)Rh(CO)(pCl)(CO)(Rh(L)]+. 54 The factors which affect the oxidative addition to the [(dppf)PdCl2]complex have been further investigated: in this work the synthesis of [(dppf)Pd(q2methylacrylate)] and its oxidative additions of arylelectrophiles have been studied. A thorough investigation shows that the oxidative addition process is non-di~sociative.'~~ A C2-symmetric analogue of dppf has been prepared. It is complexed as [M(C0)4(1-PPhz-q5-cgH6)2Fe].This work documents the preparation and characterisation of 1,3-bis(diphenylphosphino)indene from indene and chlorodiphenylphosphne. Deprotonation of this compound and reaction with FeC12 yields the unstable complex bis( 1,3-bis(diphenylphosphino)indenyliron(II) which decomposes to bis(1-diphenylphosphinoindenyl)ir~n(II).'~~ The same research group report the synthesis and electrochemistry of the ligand pPh(CH2CH2-q5-C5H&Fe]. Subsequently a range of complexes (Mo, Pd, Pt) were prepared and fully characterised. lS7 Diferrocenylphenylphosphine (PF2Ph) forms a neutral gold(1) complex [AuR(PFc2Ph)]or the cationic complex [Au(PFc2Ph)(PR3)]C104dependent on the reaction conditions, whereas the reaction with [Au(c6F5)2cl] and [Au(CGF5)3(OEt2)] give the yellow air-stable species [Au(C6F&Cl(PFc2Ph)] or [Au(C~F&(PFC~P~)] respectively. 58 The rhodium and iridium coordination chemistry of 3,4-dimethylphosphanefmocene, L, has been explored. Of most interest is the iridium complex pr(L)3(COD))[BF4], which under hydrogen pressure yields the cationic species

'

'

Organometallic Chemistry

458

[Ir(L)4H2]+.This continues the now longstanding interest of the Mathey group in this area.'59 7.2 Ferrocenophanes. - Following the success of a range of ferrocenophanes and their ring opening polymerisations further phosphaferrocenophanes have been prepared. These are obtained in the reaction of 1,l'-dilithioferrocene with diisopropylaminodichlorophosphine.The X-ray structure of one of these new molecules is reported. The crucial C-P-C angle is 88.8" and the ring tilt angle is 27.8", which is slightly larger than in the related ferrocenophanes with chloride, alkyl or phenyl substituents.160 A [4]-ferrocenophane, namely [1,2B2(NMe2)2{1,1'-(SC5&)2Fc}], which contains a B-B bond on the bridge, has been described. Essentially the paper is an extension of the work on [B2(NMe2)4]which has been previously reacted with 1,2-diolsand thiols. Two further papers from the Manners research group on ferrocenophanes are as follows: the first describes the synthesis of phosphonium-bridged[11ferrocenophanes'62 followed by a study in their ring opening and the second describes the synthesis and characterisation of hexaferrocenylcyclotrisiloxane and tetraferrocenyldisiloxanediol.63 Manners has also reported the selective synthesis of 1-stanna-2-boraferrocenes via an unexpected rearrangement reaction. Bis- 1,1'-trimethylstannylferrocene reacts with RBC12 at low temperature to afford the ortho-borato complex in which one stannyl moiety is cleaved from the unsubstituted ring. With two equivalents of RBCl2 a chloride transfer to the tin occurs with formal elimination of a methyl group. Another feature article on polyferrocenylsilanes has been presented by Manners on the ring opening of ferrocenop h a n e ~ . In '~~ a general study on the reactions of organocopper complexes the reaction of l,l'-[F~(BBrMes)~] has been studied with two equivalents of [CU(M~S)~. toluene]. The product is the related l,l'-[F~(BBrMes)~] which is obtained as a red oil in 97% yield? A mixed ring ferrocenophane, namely [Fe(q 5-C9Me6)(q5-C5H4SiMe2)], has been prepared. The synthesis involves the preparation of a mixed indenylcyclopentadienyldimethylsilaneligand from which the ferrocenophane then derives. Although the synthesis is conventional, the work seeks to derive some important structural data of these ring strained materials. 167 The reaction of 1,1'-ferrocenylenedithiol in pyridine at 20 "C gave, in the presence of thionyl chloride, the 1,1'-( 1,2,3-trithia[3]ferrocenophane-2-0xidewhich may be easily reduced to the well known trisulfane. Although the methodology is very simple, clearly there is scope for the synthesis of a range of ferrocenophanes of this type containing a variety of inorganic and organic spacers between two cyclopentadienyl-sulfur substituents.

'

'@

'

7.3 Materials. - A number of new 'push pull' ferrocene complexes which contain heteroaromatic rings (furan and thiophene derivatives) have been prepared in the general reactions of ferrocene carboxaldehyde with Wittig reagents. A typical compound prepared is shown in 9. The paper contains four X-ray structural determinations of the product molecules and electrochemical

14: Transition Metal Complexes of Cyclopentadienyl Ligands

459

and UV/vis data. 16’ The preparation of and crystallographic determination of [C702FcH] has been carried out. The molecular packing diagram is compared with that of the related Cm ferrocene compound reported earlier.l7O The crystal structures of eight key synthetic intermediates in ferrocene and fluorene chemistry have been reported in one paper. The ferrocenes are trimethylsilylethynylferrocene, 1-iodoethynylferrocene, l,l’-bis-(2-hydroxy-2-methylbut-3yn-4yl)ferrocene, 5-(hydroxy-5-methylhexa-1,3-diyn-1-yl)ferrocene-o- 3-3hydroxy-3-methyliodobut-1-yne, endo- 1-hydroxy-1-ethynylferroceno[2.3.a]indene, (z)-[2-(4-nitrophenyl)-1-chloroethenylferrocene] and (Z)-[2-(4-acetylpheny1)- 1-chloroethenylferrocene]. This paper presents a useful comparison given to broad range of structural data in~1uded.l~~ The first air stable primary phosphine namely ferrocenylmethylphosphine has been prepared by the removal of ‘formaldehyde’ from ferrocenylmethylbis(hydroxymethy1)phosphine using Na2S205. The first complexes of this useful ligand have thus been reported.172 The asymmetric induction in the synthesis of ferrocene-substituted bicyclic pyrazolines has been studied and a reasonably high diastereomeric selectivity has been 0 b ~ e r v e d . lYet ~ ~ more chemistry has appeared on ferrocenyloxazolines. The 1-0xazolinyl-1’-diphenylphosphinoferrocenepreparation is reported together with that of 1-oxazolinyl-1’-phenylthioferrocene. The synthetic methodology makes use of the monolithiation of dibromoferrocene. The reactions of the product complexes with alkylpalladium dimers are also re~0rted.l~~ The enantioselective addition of alcohols to ketones has been observed to be catalysed by planar chiral azaferrocenes.175 The asymmetric transfer hydrogenation of ketones has been achieved using chiral oxazolinylferrocenylphosphines as ligands to Ru(I1). This is the latest in a series of transfer hydrogenation studies using ferrocene-based ligands which began 15 years The asymmetric synthesis of [3](1,l’-) and [3]( 1,1’)(3)(3,3‘)]-ferrocenophanes has been achieved in a synthetic scheme which involves the reaction of (R)-a-ferrocenylalcohols with acetic acidlmethanol to afford the ethyl 3ferrocenjlpropanoates (after BF3.0Et2]. Subsequent Friedel-Crafts cyclisation of the hydrolysed esters yielded chiral ferro~enophanes.’~~ A new range of chiral PPFA based ruthenium complexes have been prepared - a detailed coordination study has been carried out to evaluate the potential of these compounds as catalyst^.'^^ Following on the recent work of the Brunner group, a range of ferrocenyldiphosphines which contain stereogenic phosphorus esters have been prepared. The method of synthesis adopted is the use of chiral borane precursors in the reaction with ferrocenyllithium. The new complexes have been tested in asymmetric hydrogenation reactions. The enantiomeric excesses compare favourably with other chiral ferrocenes

460

Organometallic Chemistry

(96%+).'79 The synthesis of the first of a family of chiral monophosphine ligands bearing an aryl substituent in the 2-position has been reported. This is a natural extension to the work of Kajn reported in earlier years.'80 A number of ferrocenylethynylsilanes together with their complexes derived from cobalt or carbonyl have been described. The compounds are obtained in the reaction of the lithium salt of ethynylferrocene with aryl and alkyl chlorosilanes. Thereafter the two series of ethynylsilanesprepared were directly reacted with dicobalt octacarbonyl The structure of one of the products has been determined."' The reaction of diphenylacetylene with a number of planar chiral halogeno-bridged cyclopalladated ferrocene compounds has been carried out. Essentially the acetylene inserts either once (1: 1 stoichiometry) or twice (excess alkyne) into the metal-C bond. The crystallographic structures of several product complexes are reported.182 The achiral ferrocene diol 1,l'bis(diphenylhydroxymethy1)ferrocene has been obtained in the direct lithiation reaction of ferrocene with n-butyllithium in the presence of benzophenone. While the former reaction is not new a similar reaction on chiral bisoxazolinyl ferrocenes gives a number of new chiral products.'83 The N,N-bis(ferroceny1methy1idene)-P-phenylenediamine and N[(ferrocenylmethylidene)aniline have been prepared by Schiff base condensation reactions. These compound were subsequently used to prepare charge transfer complexes (e.g. with TCNQ, TCNE, DDQ etc.). Mossbauer spectroscopy was subsequently used to examine the Fe(II)/Fe(III) ratio in the products. 184 The synthesis, structure and redox behaviour of gold and silver complexes of 3-ferrocenylpyridinehave been examined. A number of neutral, e.g. [AuCl(Fcpyr)], or cationic, e.g. [Au(Fcpyr)(PPh,)]OTf, complexes have been obtained. Overall six new complexes have been obtained in this study.18' A tetramethylgermylbiscyclopentadienyl ligand has been reacted with [Fe(CO)5] to give a range of bimetallic complexes which exhibit interesting metal-ligand interactions and rearrangements.' 86 The vanadium(II1) and titanium(1V) complexes of N,N-dimethylaminomethylferrocene have been further investigated. The following products have been prepared: [Cp2Ti(L)C1],[CpTi(L),Cl3_,], x = 1, 2, 3 and [v(L)2Cl], L = diprot onated (2-ferrocenyl)-N,N-dimethylaminomethylferrocene. 87 A range of ferrocenylethynylnaphthalenesand acenaphylenes have been prepared by palladium catalysed coupling of appropriately substituted iodo aryls with ferrocenyl acetylenes. The product complexes were subsequently reacted with cobalt carbonyl to afford a range of interesting ferrocene-substituted polyarenes.188The effect of protonation on the NMR spectra of a range of pyridine substituted acylferrocenes has been explored.189 The end functionalisation of a number of these polymers has been achieved using the terminal ferrocenyl lithium to ring-open ethylene sulfide to create a terminal thiol group thus enabling attachment to gold surfaces.190 1,l'Ferrocenylbiscarboxaldehyde has been reacted with a polychloroarylmethylphosphonium salt to yield the diarylvinyl derivative. This carefully chosen side group was then subjected to treatment with Bu"4NOH and p-chloranil to form the diradical complex in which it has been shown that the ferrocene skeleton acts as a ferromagnetic complex."' Ferrocenecarboxaldehyde condenses with

'

14: Transition Metal Complexes of Cyclopentadienyl Ligands

46 1

dipyrromethane to yield a single atropisomer of a,a-5,1Sbis(ferroceny1)2,8,12,1 8-tetrabuty1-3,7,13,17-tetramethylporphyrin 10 in which electrochemical measurements show that the ferrocene units couple (shown by two independent oxidations).192 A 1,4,8,11-tetrakis(4-ferrocenyl-3-azabutyl)-1,4,8,11-tetrazacyclotetradecane has been prepared as a polyammonium receptor, 11, for electrochemical anion sensing.193

C

W

b 10

11

A range of ferrocene substituted nucleobases have also been reported, e.g. ferrocenyl derivatives of cytosine, thymine and uracil.194 Again, further ferrocene-substituted prophyrins in which a vinyl group acts as a spacer between the ferrocene and the porphyrin have been prepared.195A ferrocenelinked biscyclam has been prepared as an unusual trimetallic complex.196 A further example of self-assembled ferrocenes on gold surfaces has appeared: a ferrocenealkyl thiol has been self-assembled with an alkylcarboxylic acid. The monolayers on gold were subjected to a detailed electrochemical study. 197 An extremely rapid oxygen transfer reaction has been observed from a sulfoxide to a carbonyl ligand in the early-late bimetallic complex which contains a Ru-Zr bond. On addition of a sulfoxide the oxygen is transferred to a rutheniumcarbonyl ligand which then inserts into the Ru-Zr bond as a metal carboxalato ligand and the sulfoxide is transformed to a coordinated s ~ 1 f i d e . lThe ~~ reactions of [CpRu(L)(L’)(CrCPh)], L = PPh3, L’ = P(OMe3)and related complexes with H(Ph)C=C(CN)2result in the formation of cyclobutenyl complexes of the type [CpRu(L)(L’){C=C(Ph)CH(Ph)C(CN)2)]which then transform into butadienyl complexes.199 A range of q5-pyrdzolato ruthenium complexes have been prepared in a

462

Organometallic Chemistry

synthesis which involves the reaction of [Cp*RuC1]4 with four equivalents of the appropriate pyrazole salt.200The reaction of 1,1'-dilithioferrocene with 1,2dichlorotetramethylsilylgermane results in the formation of a [1,1'-tetramethylsilylgermyl]ferroceneophane, which on subsequent reaction with methyllithium and triphenylgermyl chloride results in ring opening to [(qS-CSH4SiMe3)Fc(qsCSH4Ge(Me)2Ge(Ph)3].Although attempts have been made to obtain the polymers (in similarity with other ferroceneophanes) little polymeric material has yet to be isolated. Nevertheless this is an interesting development. In the same work the reactions of (Fp)-SiMe2GeMe~(Fp)with LDA have been inyestigated and it has been shown that the bridging silyl and germyl groups migrate in turn (Si first) to the cyclopentadienyl rings.201 Tetrameric complexes [C~FC(CO)(~-CN)~CU(PCY~)-~]~, x = 1, 2, have been obtained in the reactions between [K][CpFc(CO)(CN)2] with [ C U ( C H ~ C N ) ~ ] [ B FFollowing ~ ] . ~ ~ ~ the usual reduction of [Cpf2TiC12], Cp* = Cp, Cp* and tetramethylcyclopentadiene, by magnesium metal in thf the reaction of (trimethylsi1yl)ethynylferroceneor phenylethynylferrocene yielded the corresponding q2-acetylene complexes [Cpf2Ti(q2-FcC=CR)]. The catalytic head to tail dimerisation reactions of HCrCSiMe3 showed that the phenylethynyl titanium complex is an excellent catalyst at 60 "C although the turnover numbers are less than half those of the corresponding [Cp*2Ti(q2Me3SiC=CSiMe3)] complex.203Beginning with (Pauson-Khand reaction generated) 2-ferrocenyl-3-methylcyclopentenoneand 2-ferrocenylcyclopentenone a range of substituted ferrocene complexes were prepared in which ferrocenylcyclopentadienes were key intermediates. The molecular structures of four complexes are included in the paper. A number of unsymmetrically substituted biferrocenes were also prepared which is a testament to the versatility of the reported reaction procedures.204 The Diels-Alder reactions of 3-ferrocenyl2,4,5-triphenylcyclopentadienonehave also been investigated. In particular the reaction with diphenylacetylene yields C6PhsFc whereas the reaction of 2,4,5triphenylcyclopentadienonegives C7Ph6FcH which on subsequent treatment with [Et30][sbCl6] yields the ferricinium complex [C7Ph6FcH]+[SbC16]which has been characterised by X-ray crystallography.20s A number of osmametalloceophanes with different ring sizes have been obtained in the cyclisation reactions of [Fc or RU(~-CSH~CH~(CH),CH20Tf)2] with Na2[Os(CO),]. The ferrocene complexes obtained in general are electrochemically characterised as showing one-electron reversible oxidation whereas the corresponding ruthenocene complexes show two-electron irreversible behaviour accompanied by their chemical reactions.206 with ferThe reaction of 1,8-dich1oro-9,10-dihydro-9,10-ethanoanthracene rocene under normal reducing Friedel-Crafts conditions (Al/A1Cl3) affords only one isolabie iron-containing product which was identified as [endo-(q6( 1,8-dichloro-9,lO-dihydro-9,lO-ethanoanthracene)-FcCp] (PF6).207The reaction of biruthenocene with excess para-benzoquinone and BF3.Et20 gave the (BF4)2 in which the CloHs unit is a complex [CpRu(p2-q6:q6-CI~H8)RuCp] fulvalene unit with an unusual coordination mode. The reaction of this and the reaction complex with Br2 yielded [B~C~RU(IV)[FV]RU(IV)C~B]~+

'

14: Transition Metal Complexes of Cyclopentadienyl Ligands

463

with triphenylphosphine resulted in addition to one cyclopentadienyl ring to P +further P ~ ~ )metal ] . ~cyclophane ~~ work ferrogive [ C ~ R ~ " F V R U * * ( C ~ H ~ In cene has been reacted with [3n]cyclophane under reducing Friedel-Crafts conditions to yield four [3n] cyclophane complexes. The NMR spectra of the products is the main feature of this work with a detailed analysis given.209 The Mossbauer spectroscopic parameters of three dibromoborylferrocenes and those of a related dichloroboryl ferrocene have been reported and the results thus obtained have been discussed in terms of the known crystal structures of these complexes.2l o Again, further Mossbauer results have been reported for the half-open 1,l'-biferrocene complex.2* In a general synthetic paper on the incorporation of vinyl thiophenes into organometallics (Mn(q5thienyls) etc., a range of coupled ferrocenes have been prepared by Wittig coupling reactions.212In a paper intriguingly entitled 'Tuning the link of doubly silyl-bridged ferrocenes', a range of new disila-indacene ligands have been reported. The salts of the ligands were duly converted into their respective metallocenes on reaction with FeC12 to give R2Si-bridged dinuclear ferrocenes. The electrochemistry of the new metallocenes was established and disc~ssed.~' Further work has been carried out on the modified Suzuki coupling reaction of iodoferrocene to give a wide variety of acyl-substituted f e r r ~ c e n e s . ~ ~ ~ The reaction of one equivalent of BuLi with 2-cyclopentadienyl-2-fluorenylpropane gives the lithium salt which is a precursor to metallocenes and metallocene dichlorides; l,l'-bis[2-(2-fluorenyl)propyl]ferrocene and the titanocene, zirconocene and hafnocene dichlorides were thus prepared.215A range of biologically active ferrocenylalkylpolyfluorobenzimidazoles, obtained in the reaction of a-hydroxylalkylferrocenes with polyfluoroalkylbenzimidazoles in the presence of HBF4, have been produced. Following separation and resolution using chiral HPLC the products were obtained. The structure obtained indicated the presence of hydrogen bonding as a normal feature of these molecules. It will be of interest to observe how the biological testing proceeds in the light of the success of other ferrocene-based pharmaceuticals.216The regiospecific hydrosilation of the star-[C6(CH2CH2CHCH2)6] with [FcSiMe2H] catalysed by Karstedt catalyst results in the formation of the hexaferrocene complex [C6{(CH&SiMe2Fc}61. This is a useful method for appending ferrocenes to d e n d r i r n e r ~Continuing .~~~ their elegant work on stannyl substituted ferrocenes Herberhold and Wrackmeyer have published the synthesis of 1,4distanna-[4]-ferrocenophane by Pt(0) catalysed alkyne distannation. Essentially 1,1,2,2-tetramethyl-1,2-distanna-[2]-ferrocenophane reacts with monosubstituted alkynes in the presence of a catalytic quantity of [(PPh3)2Pt(CH2=CH2)]to yield the product ferrocenophanes by stannation of the C r C bond.218A series of end-capped ferrocene containing heterobimetallic compounds have been prepared and the crystal structure of one representative complex, [CpFe(q 5-C5H4CH=CH-th-Pt(PPh&)(Br)], th = 2,Sdisubstituted thiophene, has been reported. The synthesis uses traditional Wittig methods using ether ferrocene carboxaldehyde in its reactions with thiophene derived Wittig reagents and the converse, i.e. the reactions of thienylaldehydeswith the well known bromide salt of triphenylphosphonium ethyl ferrocene. The most

464

Organometallic Chemistry

interesting aspect of the work is the ‘stoppering’ of the complex using the oxidative addition reaction of aryl halides with Pd(PPh& which puts to good use the earlier work associated with the isolation of such adducts by Brown and co-workers over the past 10 years or In a paper describing synthetic methodology towards homopropargyl alcohols from aldehydes it has been shown that the reaction of 1,l’-ferrocenebiscarboxaldehyde with 2-methylpropynyl bromides give a C-0-C-bridged ferrocenophane bearing alkynyl groups which may be further functionalised. Although at first sight this may appear to be a curiosity it is apparent that such materials are ideal for incorporation into sensors given the relative stereochemistry and ease of synthesis.220The reaction of dilithioferrocene, TMEDA and ClSiMe2(CH=CH2)gives the expected metathesis product at low temperature. This compound is then a useful reagent for the preparation of a broad range of ferrocene-containing products. In this work the vinyl silane is hydrosilylated with C12MeSiH and Ph2MeSiH to provide yet more precursor compounds. For example the product of the hydrosilylation with C12MeSiH gives [CpFe(q5CSH&iMe2(CH2)2SiMeC12)]2 which was further reacted with lithioferrocene to give the pentametallic metathesis product. Again, it is easy to see how such an approach will be incorporated into the existing methods of ferrocene-dendrimer preparations.221The ruthenium oxazinylferrocenylphosphinecomplex [RuC1~(PPh~)(oxazolinyl-ferrocenylphosphane)]has been observed to be a useful complex for asymmetric hydrogen transfer reactions of a variety of substrates.222 The reaction of 2-bromobenzoylferrocene with the CoreyBakstri-Shibata catalyst followed by the reaction with BH3.Me2S, Ac20/ pyridine and dialkylamine has been used as a method of producing a new range of chiral ferrocenes. These may be ortho-lithiated and the bromide on the initial benzoyl group is further transformed into a diphenyl moiety. Testing of the new ligands as rhodium complexes give excellent chiral inductions (e.e.s >90%).223The same research group have also shown that ferrocenylamines are excellent catalysts for the enantioselective substitution of unsymmetrical ally1 chlorides with dialkyl zincs in the presence of The rapid asymmetric synthesis of a range of planar chiral ferrocenes which bear a stereogenic centre in the P-position of the side chain has been developed. The starting compounds again are acylferrocenes from which chiral imines are obtained in five simple steps.225 The reductive lithiation of a range of ferrocenyl carbinols has led to the synthesis of a broad range of a-carbon substituted ferrocenyldiphosphine ligands.226In a paper on self assembly of quinodimethanes a ferrocene-substituted macrostructure has been formed from the molecule 12 using SnC12 as a dehydrating reagent.227A polycationic ferrocenyldendric compound which contains 24 ferrocenyl units has been prepared. The ferrocene is attached as ferrocenecarbonyl chloride to a suitably prefunctionalised dendritic material with pendant alkylamine groups. Arene cyclopentadienyl iron cations have similarly been attached.228 The synthesis of chiral C2-symmetric bisferrocenyldiamines has been reported. They are obtained from the R-(FA) by reaction with methyl iodide and subsequent treatment with a bi~methylamine.~~~ In a superb paper on the use

14: Transition Metal Complexes of Cyclopentadienyl Ligands

k

I, II

465

fe

of fluorescence in the high-throughput screening of Heck coupling reactions ferrocenylphosphines have been used as crucial complexes for screening purposes.230The reactions of formylcynichrodene and ferrocene carboxaldehyde have been shown to yield 1,2-bis[(q5-cyclopentadienyl)dicarbonylnitrosylchromium)]ethene and 1,2-diferrocenylethenerespectively. The structure of has been the chromium complex (I924 { (CO)2(NO)Cr(q5-C5H4)2}(CH2=CH2)] reported. Although the McMurray coupling of such systems is well established there no doubt will be many more examples to come in this area of A range of polymerisable terthienyl Ru(11) complexes have been prepared in a study on terthienyl-based redox-switchable hemilabile l i g a n d ~ A . ~stable ~~ and recoverable chiral Lewis acid catalyst has been developed. It is prepared in the one-pot synthesis in which a chiral bisphosphine, cyclopentadiene and [ R u ~ ( C O ) ~are ~ ] refluxed together followed by treatment with Me1 in acetone.233A useful synthesis of biruthenocene has been reported. The method involves the oxidation of ruthenocene with an excess of p-benzoquinone and BF3. This yields biruthenocenium (BF4)2 which can be reduced to biruthenocene with TiC13.234The chemistry of dimetalloboranes has been developed beginning with [Cp*RuClz]2 in its reaction with Li(BH4) to give nidu-1,2(CPR”’2(P-H)(B4H9)1.235 A facile synthesis of 1,2-dibromoferrocenehas been reported236and this has been followed by work on the ortho-lithiation of l,l’-dibr~moferrocene.~~~ The same research group have also published the formation of precursors to poly 1,1’-ferrocenylacetylene derivative^.^^' Subsequently the dilithiation of dibromoferrocene was also reported.239

8

Cobalt, Rhodium and Iridium

A new coordination mode of aldehydes is observed in the complex [Cp*Co{ (C(0)H)2C,H4>].240The isomerisation of aldehydes using cyclopentadienylrhodium(dialky1)carbonyl complexes, which are generated in situ from [Cp*Rh(C2H3Me)*], has been investigated and the mechanism has been

466

Organometallic Chemistry

elucidated using labelling experiment^.'^' The reaction of [CpCo(S2C6H4)] with [M0(C0)3(py)~] and BF3 affords the trinuclear cluster complex [(C~CO(S~C~H~)}~MO(CO)~].~~~ In a feature account the chemistry of Co, Rh cyclopentadienyldithiolene complexes is fully described. This article contains a wealth of information running to 114 references.243A delocalised analogue of the bicobaltocene cation which is derived from the reduction of a d6/d6 (fulvalendiyl)bis(cobaltacarborane) has been described in the continuing work of the Grimes group in carborane chemistry.2q4An unusual Me-0 bond cleavage reaction has been observed in an iridium metallated crown ether complex [Cp*Ir(q6-C18Hz806)][BF4].245 Following on from earlier work on the synthesis of cationic fulvene Rh complexes from [Rh2(p-C1)(COD),] with t B ~ C 2 HGreen , and co-workers have reported the mechanism of formation of a cyclopentene-substituted cyclopentadienyl-Rh(C0D) complex. In this work the mechanism of dimerisation, trimerisation and cyclisation of alkynes has been studied in A key intermediate in the formation of the double-bookshelf cluster [(cp*Rh)2M0602o(OMe)~]~-,namely [Cp*RhMo308(0Me),]-, has been observed by electrospray ionisation mass spectrometry.247The chemically triggered macroassembly of metallomacrocycles has been reported. Essentially the work involves the self-assembly of half-sandwich complexes which is acid ~ a t a l y s e d . ~ ~The ' half-sandwich bimetallic complexes [M ( ~ ~ - ( c p ) C o [P(=O)(OCH~)~]~}(K~-NO~)(L)], M = Ni, Co has been achieved from the reaction of CoC12 with mononuclear adducts containing 'Klani's' tripodal l i g a ~ ~ The d . ~proton ~ ~ transfer reaction by means of hydrogen bonding in protonated [(T~~-C~H~CH(CH)~~NM~)I~(PP~~)H~] has been the subject of an NMR investigation. Essentially the 4-N-methylpiperidylcyclopentadienyl complex is protonated at the piperidyl nitrogen with one equivalent of HBF4 and the second equivalent then protonates at the metal centre?' The photoinduced reaction of [Cp*Rh(C0)2] with alkanes in liquid Xe or Kr has been investigated by time-resolved IR. The reaction rates for the conversion to the final oxidation addition product species [Cp*Rh(CO)(R)(H)] have thus been ~btained.'~' An interesting theoretical investigation into the acetylene trimerisation using 'CpCo' has been carried The black crystalline complex [(q5-1,2,4-tri-tert-butylCp)2Co]has been obtained by reduction of the corresponding chloro-dimer. The electrochemistry of this compound (as cation) has been investigated and one reversible one electron reduction observed.253The reaction of [ ( C S R ~ ) C O ( C ~ H with ~ ) ~a] range of pentafulvenes gives the complexes of general structure [("RS)CO(C~H~R'R")],R, R' = H, Me, Ph etc. The molecular structure of one of the cobaltocenes produced, R = Me, R', R" = Ph, is shown as 13.254The catalytic hydrogenation of the C=C bond in the side chain of facial alkylenylbenzene ligands in the cobalt clusters [{ CpCo}3(p3-C6H5(CR')(CHR2))]results in the formation of [ (CpCo)3(~3-C6H5(CHR')(CH2R2))]at 20 "C and one atmosphere. The structure of one of the hydrogenated products, R' =Ph, R2= H, has been discussed.255

14: Transition Metal Complexes of Cyclopentadienyl Ligands

467

13

Beginning with carbomethoxycyclopentadienide, diphenylacetylene and chlorotris(triphenylphosphine)cobalt(I) the compound [q5-(s)-2-(4-methylethy1)oxazolinyl-cyclopentadieny I)-(q 4- tetraphenylcyclobutadiene)cobalt has been obtained. Overall this is a five step synthesis with all steps having a 70% or greater yield. The palladium complex of the oxazoline was then prepared which continues the work of this group following on from the earlier ferrocenyl oxazoline The direct reaction of phosphoric acid with [Cp2Co][OH] which was obtained in situ by water oxidation of cobaltocene yielded the salt [ C ~ ~ C O ] [ H ~ P O ~ ] The . ~ H ~work O . compares the role of C-H- .-0and C-H-.-Cl hydrogen bonds in the solid state.257Hydrogendeuterium exchange and transfer reactions catalysed by [Cp*Rh(olefin)2] complexes have been investigated: a range of complexes of the type shown in which the olefin contains bulky silyl substituents have been prepared and when these materials are reacted with deuterated solvents D is incorporated into the olefinic sites.258 The fascinating ‘box’ complexes [NE~~]~([M(C~*R~)(CN)~]~[MO(CO)~]~), M = K, Cs, are obtained in the reaction of [Cp*Rh(CNh]- with [(“rl-C6H3Me3)Mo(CO)31in the presence of K+ or C S + . ~ ~ ~ 9

Nickel, Palladium and Platinum

The reaction between nickelocene and ‘BuLi has been investigated and it is observed that the unstable complex [CpNi‘Bu] which is initially formed decomposes by either P-H elimination or Ni-C bond cleavage, the former affording [(NiCp)3CCH(CH&] while the latter decomposition mode gives a range of products which include [{ Ni(C5HiBu))2/C5H;Bu]. The latter product has been structurally characterised.2mThey have also reported the reaction of nickelocene and sodium in the presence of terminal alkenes in clusters and (p3-alky1idyne)triwhich [(~~3-hydrido)-(p3-alkylidyne)-trinickel] nickel clusters are formed.261

468

Organometallic Chemistry

References 1.

2. 3. 4.

I.R. Butler, in Organometallic Chemistry, Vol. 28, ed. M. Green, Royal Society of Chemistry, Cambridge, 1999. C. Bruneau and P.H. Dixneuf, Ace. Chem. Res., 1999,32,846. W. W. Schoeller, 0. Friedrich, A. Sundermann and A. Rozhenko, Organometallics, 1999, 18, 2099. W.J. Evans, R.D. Clark, K.J. Forrestal and J.W. Ziller, Organometallics, 1999, 18,2401.

5. \

M.A. Beswick, H. Gornitzka, J. Karcher, M.E.G. Mosquera, J.S. Palmer, P.R. Raithby, C.A. Russell, D. Stdke, A. Steiner and D.S. Wright, Organometallics, 1999,18,1148

6.

7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

0. Gobley, S. Gentil, J.D. Schoss, R.D. Rogers, J.C. Gallucci, P. Meunier, B. Gautheron and L.A. Paquette, Organometallics, 1999, 18,2531 S. Harder, M. Lutz and S.J. Obert, Organometallics, 1999, 18, 1808. H. Brunner, Angew. Chem. Int. Ed. Engl., 1999,38, 1195. U. Richter, J. Heck and J. Reinhold, Znorg. Chem., 1999,38,77. C. Elschenbroich, J. Kroker, M. Nowotny, A. Behrendt, B. Metz and K. Harms, Organometallics, 1999, 18, 1495. R.G. Peters, B.P. Warner and C.J. Burns, J. Am. Chem. Soe., 1999, 121, 5585. C. Lescop, T. Arliguie, M. Lance, M. Nierlich and M. Ephritkhine, J. Organomet. Chem., 1999,380, 137. A.V. Khrostov, B.M. Bulychev, V.K. Belsky and A.I. Sizov, J. Organomet. Chem., 1999,584, 164. A.T. Gilbert, B.L. Davis, T.J. Enge and R.D. Broene, Organometallics, 1999, 18,

2125. C. Qian, H. Li, J. Sun and W. Nie, J. Organomet. Chem., 1999,585, 59. W.W. Lukens, Jr., S.M. Beshouri, A.L. Stuart and R.A. Andersen, Organometallies, 1999, 18, 1247. W.J. Evans, D.A. Cario, M.A. Greci and J.W. Ziller, Organometallics, 1999, 18, 1381.

18. 19.

20. 21. 22. 23. 24. 25. 26.

27. 28.

W.J. Evans, M.A. Johnston, M.A. Greci and J.W. Ziller, Organometallics, 1999, 18, 1460. A. Antiiiolo, M. Fajardo, C. Huertas, A. Otero, S. Proshar and A.M. Rodriguez, J. Organomet. Chem., 1999,585, 154. K.C. Hultzch, T.P. Spaniol and J. Okuda, Angew. Chem. Znt. Ed. Engl., 1999, 38, 227. W.T. Klooster, L. Brdmmer, C.J. Schaverien and P.H.M. Budzelaar, J. Am. Chem. Soc., 1999,121, 1381. L. Ventelon, C. Lescop, T. Arliguie, P.C. Leverd, M. Lance, M. Nierlich and M. Ephritikhine, Chern. Commun., 1999,659. C. Qian, G. Zou and J. Sun, J. Chem. Soc., Dalton Trans., 1999, 519. N. Nakahara, M. Hirano, A. Fukuoko and S. Komiya, J. Organomet. Chem., 1999,572, 8 1. K.K. Banger and A.K. Brisdon, J. Organornet. Chem., 1999,582, 301. P. Schertl and H.G. Alt, J. Organomet. Chem., 1999,582, 328. S. Back, R.A. Gossage, G. Rheinwald, I. del Rio, H. Lang and G . van Koten, J. Organornet. Chem., 1999,582, 126. F.U. Axe and J.W. Andzelm, J. Am. Chem. Soc., 1999,121,5396.

14: Transition Metal Complexes of Cyclopentadienyl Ligands 29. 30. 31.

32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45.

46. 47. 48. 49. 50. 51. 52.

53. 54. 55.

56.

469

P.-M. Pellny, V.V. Burlakov, N. Peulecke, W. Baumann, A. Spannenberg, R. Kempe, V. Francke and U. Rosenthal, J. Organomet. Chem., 1999,578,125. E.J. Munson, M.C. Donokey, S.M. DePaul, M. Ziegeweid, L. Phillips, F. Separovic, M.S. Davies and M.J. Aroney, J. Organomet. Chem., 1999, 577, 19. M. HoraEek, I. Cisafova, J. cejka, J. Karban, L. Petrusova and K. Mach, J. Organomet. Chem., 1999,577, 103. C.A.G. Carter, R. McDonald and J. Stryker, Organometallics, 1999, 18,820. E. Haak, I. Bytschkov and S. Doye, Angew. Chem. Int. Ed. Engl., 1999, 28, 3389. F. Guerin and D.W. Stephan, Angew. Chem. Int. Ed. Engl., 1999,38,3698. A. Gansauer, T. Lauterbach, H. Bluhm and M. Noltemeyer, Angew. Chem. Int. Ed. Engl., 1999,38,2909. S.J. Sturla, N.M. Kablaoui and S.L. Buchwald, J. Am. Chem. Soc., 1999, 121, 1976. W.A. King, S. Di Bella, A. Gulino, G. Lanza, I.L. Fragala, C.L. Stern and T.J. Marks, J. Am. Chem. Soc., 1999,121,355, S.K. Noh, J. Kim, J. Jung, C.S. Ra, D.-0. Lee, H.-B. Lee, S.W. Lee and W.S. Huh, J. Organomet. Chem., 1999,580,90. B.Y. Lee,J.W. Han, Y.K. Chung and S.W. Lee, J. Organomet. Chem., 1999,587, 181. U. Segerer, S. Blaurock, J. Sieler and E. Hey-Hawkins, Organometallics, 1999, 18,2838 T. Cuenca, P. Gomez-Sal, C. Martin, B. Roy0 and R. Royo, J. Organornet. Chem., 1999,588, 134. 0.Perez-Camacho, S. Yaknjazhanski, G . Cadenas, M.J. Rosalez-Hoz and M.A. Leyva, J. Organomet. Chem., 1999,585, 18. B. Sztaray, E. Rosta, 2. Bocskey and L. Szepes, J. Organomet. Chem., 1999, 582, 267. T. fshikawa, A. Ogawa, T. Hirao, J. Organomet. Chem., 1999,575,76. H. Schumann, K. Zietzke, R. Weimann, J. Demtschuk, W. Kaminsky, A.-M. Schauwienold, J. Organomet. Chem., 1999,574,228. H. Schumann, D.F. Karasiak, S.H. Miihle, R.L. Halteman, W. Kaminsky, U. Weingarten, J. Organomet. Chem., 1999,579,356. C.D. Tagge, R.L. Kravchenko, T.K. La1 and R.M. Waymouth, Organometallics, 1999, 18, 380. B.J. Grimmond, J.Y. Corey and N.P. Ruth, Organometallics, 1999,18,404. A.J. Ashe 111, X.Fang and J.W. Kampf, Organometallics, 1999, 18,2288. C.L. Beswick and T.J. Marks, Organometallics, 1999,18,2410. K.A.O. Starzewski, W.M. Kelly, A. Stumpf and D. Freitay, Angew. Chem. Int. Ed. Engl., 1999, 38,2439. M.A.F. Hernandez-Gruel, J.J. Perez-Torrente, M.A. Ciriano, F.J. Lahoz and L.A. Oro, Angew. Chem. Int. Ed Engl., 1999,38,2769. Y. Liu, B. Shen, M. Kotora and T. Takahashi, Angew. Chem. Int. Ed Engl., 1999,38, 856. M.D. Fryzuk, P.B. Duval, S.S.S.H. Mao, S.J. Pettig, M.J. Zaworotko and L.R. MacGillivray, J. Am. Chem. Soc., 1999, 121, 1707. D. Veghini, L.M. Henling, T.J. Burkhardt and J.E. Bercaw, J. Am. Chem. Soc., 1999,121,564. T. Takahashi, S. Huo, R. Hara, Y. Noguchi, K. Nakajima and W.-H. Sun, J. Am. Chem. SOC., 1999,121, 1094.

470

Organometallic Chemistry

M. Driess, J. Aust, K. Merz and C. von Wullen, Angew. Chem. Znt. Ed. Engl., 1999,38,3677. 58. V.C. Williams, C. Dai, Z. Li, S. Collins, W.E. Piers, W. Clegg, M.R.J. Elsegood and T.B. Marder, Angew. Chem. Int. Ed. Engl., 1999,38,3695. 59. S . Kniippel, G. Erker and R. Frohlich, Angew. Chem. Znt. Ed. Engl., 1999, 38, 1923. 60. S.-0. Bai, X.-H. Wei, J.-P. Guo, D.-S. Liu and Z.-Y. Zhou, Angew. Chem. Znt. Ed. Engl., 1999,38, 1927. 61. Y. Hanzawa, N. Tabuchi, K. Saito, S. Noguchi and T. Taguchi, Angew. Chem. Int. Ed. Engl., 1999,38,2395. 62. T. Takahashi, M. Kotord, R. Hard and Z . Xi, Bull. Chem. SOC.Jpn., 1999, 72, 259 1 . 63. M. Ringwald, R. Stiirmer and H.H. Brintzinger, J. Am. Chem. SOC.,1999, 121, 1524. 64. Y. Yamaguchi, N. Suzuki, T. Mise and Y. Wakatsuki, Organometallics, 1999, 18, 996. 65. J.C.W. Lohrenz, M. Buhl, M. Weber and W. Thiel, J. Organomet. Chem., 1999, 592, 1 1 . 66. V. Cadierno, M. Zablocka, B. Donnadieu, A. Igau and J.-P. Majordl, Organometallics, 1999, 18, 1882. 67. J.J. Eisch, F.A. Owuor and X. Shi, Organometallics, 1999, 18, 1583. 68. M.L.H. Green and N.H. Popham, J. Chem. Soc., Dalton Trans., 1999,1049. 69. J. H u g , R. Frohlich and G. Erker, J. Chem. SOC.,Dalton Trans., 1999,2551. 70. E.V. Radkov, V.G.Young Jr. and R.H. Beer, J. Am. Chum. SOC.,1999,121,8953. 71. C.P. Casey, D.W. Carpenetti 11 and H. Sakurai, J. Am. Chem. Sac., 1999, 121, 9483. 72. R.L. Martin, J. Am. Chem. SOC.,1999, 121,9459. 73. P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, W. Baumann, A. Spannenberg and U. Rosenthal, J. Am. Chem. Soc., 1999, 121,8313. 74. M.L.H. Green and J. SaBmannshausen, Chem. Commun., 1999, 115. 75. P. Rosa, L. Ricard, F. Mathey and P. Le Floch, Chem. Commun., 1999,537. 76. E. Delgado, E. Hernandez, N. Mansilla, M. Moreno and M. Sabat, J. Chem. SOC.,Dalton Trans., 1999, 533. 77. H. Lee, J.B. Bonanno, T. Hascall, J. Cordaro, J.M. Hahn and G. Parkin, J. Chem. Soc., Dalton Trans., 1999, 1365. 78. U. Dietrich, M. Hackman, B. Rieger, M. Klinga and M. Leskela, J. Am. Chem. SOC.,1999, 121,4348. 79. M.D. Fryzuk, P.B. Duval, S.S.S.H. Mao, M.J. Zawarotko and L.R. MacGilh a y , J. Am. Chem. SOC.,1999, 121, 2478. 80. M. Dahlmann, G . Erker, M. Nissinen and R. Frohlich, .I. Am. Chem. SOC.,1999, 121,2820. 81. B.L. Hodons, J. C. Ruble and G.C. Fu, J. Am. Chem. SOC.,1999,121,2637. 82. M.V. Troutman, D.H. Appella and S.L. Buchwald, J. Am. Chem. Soc., 1999, 121, 49 17. 83. J.A. Tunge, D.A. Gately and J.R. Norton, J. Am. Chem. Soc., 1999,121,4520. 84. M.V. Troutman, D.H. Appella and S.L. Buchwald, J. Am. Chem. Sac., 1999,121, 4917. 85. M. Mori, S. Kuroda and F. Dekura, J. Am. Chem. SOC.,1999,121,5591. 86. P. Sauvageot, A Sadorge, B. Nuber, M.M. Kubicki, J.-C. Leblanc and C. Moise, Organometallics, 1999, 18, 2 1 33. 57.

14: Transition Metal Complexes of Cyclopentadienyl Ligands

47 1

87. F. Calderazzo, I. Ferri, G. Pampaloni and U. Englert, Organometallics, 1999, 18, 2452. 88. R. Choukroun, Y.Miguel, B. Donnadieu, A. Igau, C. Blandy and J.P. Majoral, Organometallics, 1999, 18, 1795. 89. J.S. Overby, K.C. Jayaratne, N.J. Schoell and T.P. Hanusa, Organometallics, 1999,18, 1663. 90. V.I. Bakhmultov, E.V. Vorontsov, E.V. Bakhamutova, G. Bovii and C. Moise, Znorg. Chem., 1999,38, 121. 91. A. Sadorge, P. Sauvageot, 0. Blacque, M.M. Kubcki, C. Moise and J.-C. Leblanc, J. Organornet. Chern., 1999,575,278. 92. J.H. Shin and G. Parkin, Chem. Commun., 1999,885. Dalton Trans., 93. C. Poulard, S. Boni, P. Richard and C. Moise, J. Chem. SOC., 1999,2725. 94. A.C. Filippou, R. Steck and G. Kociok-Kohn, J. Chem. SOC.,Dalton Trans., 1999,2267. 95. H. Fischer and H. Junglaus, J. Organomet. Chem., 1999,572, 105. 96. W.-Y. Yeh, S.-M. Peng and G.-H. Lee, J. Organomet. Chem., 1999,572, 125. 97. P. Sekar, M. Scheer, A. Voigt and R. Kirmse, Orgunometallics, 1999,18,2833. 98. J.C. Green and C.N.Jenkins, J. Chem. SOC.,Dalton Trans., 1999,3767 99. D. Mordles, P. Poli, P. Richard, J. Andrien and E. Collange, J. Chem. Soc.. Dalton Trans., 1999,867. 100. M.I. Bruce, B.D. Kelly, B.W. Skelton and A.H. White, J. Chem. SOC., Dalton Trans., 1999,847. 101. E. Collange, D. Duret and R. Poli, J. Chem. SOC.,Dalton Trans., 1999, 875. 102. J.E. McGrady, J. Chem. Soc., Dalton Trans., 1999, 1393. 103. A. Proust, R. Thouvenot and P. Herson, J. Chem. SOC., Dalton Trans., 1999, 51. 104. Y . Kawano, T. Yasue and M . Shimoi, J. Am. Chem. SOC., 1999,121,11744. 105. A.S. Weltar, C.D. Andrews, A.D. Burrows, M. Green, J.M. Lynam, M.F. Mahon and C. Jones, Chern. Comrnun., 1999,2147. 106. I.C. Quarmby, R.C. Hemod, F.J. Feher, M. Green and W.E. Geiger, J. Organomet. Chem., 1999,577, 189. 107. H. Brunner, D. Mijolovic, B. Wrackmeyer and B. Nuber, J. Organomet. Chern., 1999,579,298. 108. S.H.A. Petri, D. Eikenberg, B. Neumann, H.-G. Stammler and P. Jutzi, Organometallics, 1999,18,2615. 109. D. Churchill, J.H. Shin, T. Hascall, J.M. Hatin, B.M. Bridgewater and G. Parkin, Organometallics, 1999,18,2403. 110. A.Z. Rys, A.-M. Lebuis, A. Shaver and D.N. Harpp, Organometallics, 1999, 18, 1113. 111. C. Balrarek and D.R. Tyler, Angew. Chem. Int. Ed. Engl., 1999,38, 2406-2408. 112. M. Hunger, C. Limberg and P. Kircher, Angew. Chem. Int. Ed. Engl., 1999, 38, 1012. 113. L.Y.Kuo and L.A. Barnes, Inorg. Chem., 1999,38,8 14. 114. M.E. Garcia, V. Riera, M.T. Rueda and M.A. Ruiz, J. Am. Chem. SOC.,1999, 121,4060. 115. I.S. Goncalves, E. Herdtweck, C.C. Romao and B. Royo, J. Organomet. Chem., 1999,580, 169. 116. M.E. Garcia, V. Riera, M.T. Rueda and M.A. Ruiz, J. Am. Chern. SOC.,1999, 121, 1960.

472

Organometaiiic Chemistry

117. M.P. Barrow, J.K. Cammack, M, Goebel, I.M. Wasser, K.P.C. Vollhardt and T. Drewello, J. Organomet. Chem., 1999,572, 135. 118. S. Ghosh, M. Stang and T.P. Fehlner, J. Am. Chem. SOC.,1999,121,745. 119. T. Jiao, Z. Pary, T.J. Burkey, R.F. Johnston, T.A. Hemer, V.D. Kleiman and E.J. Heilweil, J. Am. Chem. SOC.,1999, 121,4618. 120. H. Chen and J.F. Hartwig, Angew. Chem. In?. Ed. Engl., 1999,38,3391. 120a. F. Minutolo and J.A. Katzenellenbogen, Angew. Chem. Int. Ed. Engf., 1999, 38, 1617. 121. L.A. Cardoza and R.J. Angelici, Inorg. Chem., 1999,38, 1708. 122. B. Bildstein, M. Malaun, H. Kopacka, K.-H. Ongania and K. Wurst, J. Organomet. Chem., 1999,572, 177. 123. A.D. Ryabov, V.N. Gordl, E.V. ivanova, M.D. Reshetova, A. Hradsky and B. Bildstein, J. Organomet. Chem., 1999,589, 85. 124. A. Hess, 0. Brosch, T. Weyhermiiller and N. Metzler-Notte, J. Organomet. Chem., 1999,589,75. 125. W. Bauer, K. Polborn and W. Beck, J. Organomet. Chem., 1999,579,269. 126. 0 . Briel, A. Fehn and W. Beck, J. Organomet. Chem., 1999,578,247. 127. V. Quindt, D. Saurenz, 0. Schmitt, M. Schar, T. Dezember, G. Wolmershauser and H. Sitzmann, J. Organomet. Chem., 1999,579, 376. 128. C.S.J. Callaghan, P.B. Hitchcock and J.F. Nixon, J. Organomet. Chem., 1999, 584, 87. 129. P. Molina, A. TGrraga, J.L. Lopez and J.C. Martinez, J. Organomet. Chem., 1999,584,147. 130. D.-J. Che, G. Li, X.-L. Yao, Q.-J. Wu, W.-L. Wang and Y . Zhu, J. Organomet. Chem., 1999,584, 190. 131. I . Yamaguchi, T. Sakano, H. Ishii, K. Osakada and T. Yamamoto, J. Organomet. Chem., 1999,584,213. 132. L. Carollo, B. Floris, J. Organomet. Chem., 1999,583,80. 133. N.D. Reddy, A.J. Elias and A. Vij, J. Organomet. Chem., 1999,580,41. 134. H.B. Kraatz, J. Organomet. Chem., 1999,579,222. 135. W. Politzsch, C. Pietzsch, M. Puttnat, K. Jacob, K. Merzweiler, P. Zanello, A. Cinquantini, M. Fontani and G. Roeves, J. Organomet. Chem., 1999,587,9. 136. 0. Seidelmann, L. Beyer and R. Richter, J. Organomet. Chem., 1999,572,73. 137. O.M. Heigl, M.A. Herker, W. Hiller, F.H. Kohler, A. Schell, J. Organomet. Chem., 1999,574,94. 138. S. Natsume, H. Kuribard, T. Yamaguchi, T. Erdbi and M. Wada, J. Organomet. Chem., 1999,57486. 139. A. Caubet, C. Lopez, R. Bosque, X. Solans and M. Font-Bardia, J. Organomet. Chem., 1999,577,292. 140. S. Z. Ahmed, G. Ferguson, C. Glidewell, J. Organomet. Chem., 1999,585,33 1. 141. S.-J. Jong, J.-M. Fang and C-H Lin, J. Organomet. Chem., 1999,590,42. 142. V.P. Makhaev, A.P. Borisov and L.A. Petrova, J. Organomet. Chem., 1999, 590, 222. 143. A. Green, M.R. Bryce, A.S. Batsanov and J.A.K. Howard, J. Organornet. Chem., 1999,590, 180. 144. B. Pedersen, G. Wagner, R. Herrmann, W. Scherer, K. Meerholz, E. Schmiilzlin and C. Brluchle, J. Organomet. Chern., 1999,590, 129. 145. S. Kniippel, R. Frohlich and G. Erker, J. Organornet. Chem., 1999,586,218. 146. K.C. Swamy, S. Nagabrahmanandachari and K. Raghuraman, J. Organomet. Chem., 1999,587, 132. b

14: Transition Metal Complexes of Cyclopentadienyl Ligands

473

147. J.L. Brumaghim and G.S. Girolami, J. Orgunomet. Chem., 1999,586,258. 148. F.-W. Grevels, A. Kuran, S. Ozkar and M Zora, J. Organomet. Chem., 1999,587, 122. 1999,121, 5091. 149. B. Taa, J. Ruble, D.A. Hoic and G.C. Fu, J. Am. Chem. SOC., 150. J.E. Kingston, L. Ashford, P.D. Beer and M.G.B. Drew, J. Chem. Suc., Dalton Trans., 1999,251. 151. S.P. Yeo, W. Henderson, T.C.W. Mak and T.S.A. Hor, J. Organomet. Chem., 1999,575,171. 152. M.C. Gimeno, P.G. Jones, A. Laguna and C. Sarroca, J. Orgunomet. Chem., 1999,579,206. 153. J.-F. Ma and Y. Yamamoto, J. Organomet. Chem., 1999,574, 148. 154. R. Broussier, M. Laly, P. Perron, B. Gautheron, I.E. Nifantlev, J.A.K. Howard, L.G. Kuz’mina and P. Kalck, J. Orgunomet. Chem., 1999,587, 104. 155. A. Jutland, K.K. Hii, M. Thornton-Pett and J.M. Brown, Orgunometallics, 1999, 18, 5367. 156. J.J. Adams, D.E. Berry, J. Browning, D. Burth and O.J. Curnow, J. Organomet. Chem., 1999,580,245. 157. J.J. Adams, O.J. Curnow, G. Huttner, S.J. Smail and M.M. Turnbull, J. Orgunomet. Chem., 1999,577,44. 158. M.C. Gimeno, P.G. Jones, A. Laguna and C. Sarroca, J. Organomet. Chem., 1999,579,206. 159. X. Sava, N. Mezailles, L. Ricard, F. Mathey and P. Le Floch, Organometullics, 1999, 18,807. 160. M. Herberhold, F. Hertel, W. Milius and B. Wrackmeyer, J. Orgunornet. Chem., 1999,582,352. 161. M.J.G. Lesley, U. Mock, N.C. Norman, A.G. Orpen, C.R. Rice and J. Starbuck, J. Orgunomet. Chem., 1999,582,116. 162. T.J. Peckham, A.J. Lough and I. Manners, Orgunometullics, 1999,18, 1030. 163. M.J. MacLachlan, J. Zheng, A.J. Lough, I. Manners, C. Mordas, R. LeSuer, W.E. Geiger, L.M. Liable-Sands and A.L. Rheingold, Orgunometullics, 1999, 18, 1337. 164. F. Jakle, A.J. Lough and I. Manners, Chem. Commun., 1999,453. 165. I. Manners, Chem. Commun., 1999,857. 166. F. Jakle and I. Manners, Organometallics, 1999,18,2628. 167. J. Tudor, S. Barlow, B.R. Payne, D. O’Hare, P. Nguyen, C.E.B. Evans and I. Manners, Orgunometallics, 1999, 18, 2281. 168. R. Steudel, K. Hassenberg and J. Pickardt, Orgunometullics, 1999,18, 2910. 169. K.R.J. Thomas, J.T. Lin and Y.S.Wen, J. Organomet. Chem., 1999,575, 301. 170. M.M. Olmstead, L. Hao and A.L. Balch, J. Orgunomet. Chem., 1999,578,85. 171. H. Schottenberger, K. Wurst and M.R. Buchmeiser, J. Organomet. Chem., 1999, 584,301. 172. N.J. Goodwin, W. Henderson, B.K. Nicholson, J. Fawcett and D.R. Russell, J. Chem. SOC.,Dalton Trans., 1999, 1785. 173. E.I. Klimova, M.M. Garcia, T.K. Berestneva, C.A. Toledano, R.A. Toskano and L.R. Ramirez, J. Orgunornet. Chem., 1999,585, 106. 174. J. Park, 2. Quan, S. Lee, K.H. Ahn and C.-W. Cho, J. Orgunomet. Chem., 1999, 584, 140. 175. B.L. Hodons, J. C. Ruble and G.C. Fu, J. Am. Chem. SOC.,1999,121,2637. 176. Y. Arikawa, M. Ueoka, K. Matoba, Y. Nishibayashi, M. Hidai and S. Uemura, J. Organomet. Chem., 1999,572, 163.

474

Organometallic Chemistry

177. A.J. Locke and C.J. Richards, Organometallics, 1999, 18, 3750. 178. F.A. Jalon, A. Lopez-Agenjo, B.R. Manzano, M. Moreno-hara, A. Rodriguez, T. Sturm and W. Weissensteiner, J. Chem. Soc., Dalton Trans., 1999,4031. 179. F. Maienza, M. Worle, P. Steffanut, A. Mezzetti and F. Spindler, Organometallies, 1999, 18, 1041. 180. H.L. Pederson and M. Johannsen, Chem. Commun., 1999,2517. 181. N.W. Duffy, B.H. Robinson and J. Simpson, J. Organomet. Chem., 1999, 573, 36. 182. G. Zhao, Q.-G. Wang and T.C.W. Mak, J. Organomet. Chem., 1999,574,311. 183. W. Zhang, Y . 4 . Yoneda, T. Kida, Y. Nakatsuji and I. Ikeda, J. Organomet. Chem., 1999,574, 19. 184. S.K. Pal, K. Alagesan, A.G. Samuelson and J. Pebler, J. Organomet. Chem., 1999,575,108. 185. E.M. Barranco, 0. Crespo, M. Gimeno, P.G. Jones, A. Laguna and M.D. Villacampa, J. Organornet. Chem., 1999,592,258. 186. W. Zie, B. Wang, X. Dai, S. Xu and X. Zhou, J. Chem. SOC.,Dalton Trans., 1999, 1143. 187. P.B. Hitchcock, D.L. Hughes, G.J. Leigh, J.R. Sanders and J.S. de Souza, J. Chem. Soc., Dalton Trans., 1999, 1161. 188. C.J. McAdam, J.J. Brunton, B.H. Robinson and J. Simpson, J. Chem. Soc., Dalton Trans., 1999,2487. 189. J.D. Carr, S.J. Coles, W.W. Hassan, M.B. Hursthouse, K.M .A. Malik and J .H.R. Tucker, J. Chem. Soc., Dalton Trans., 1999, 57. 190. M. Peter, R.G.H. Lammertink, M.A. Hempenius, M. van Os, M.W.J. Beulen, D.N. Reinhoudt, W. Knoll and G.J. Vancso, Chem. Commun., 1999, 359. 191. 0 . Elmer, D. Ruiz-Molina, J. Vidal-Gancedo, C. Rovida and J. Veciana, Chem. Commun., 1999,579. 192. P.D.W. Boyd, A.K. Burrell, W.M. Campbell, P.A. Cocks, K.C. Gordon, G.B. Jameson, D.L. Officer and Z. Zhao, Chem. Commun., 1999,637. 193. J.M. Lloris, R. Martinez-Manez, M.E. Padilla-Tosta, T. Pardo, J. Soto, E. Garcia-Espaiia, J.A. Ramirez, M.I. Burguete, S.V. Luis and E. Sinn, J. Chem. Soc., Dalton Trans., 1999, 1779. 194. A. Houlton, C.J. Isaac, A.E. Gibson, B.R. Horrocks, W. Clegg and M.R.J. Elsegood, J. Chem. Soc., Dalton Trans., 1999, 3229. 195. A.K. Burrell, W.M. Campbell, D.L. Officer, S.M. Scott, K.C. Gordon and M. R. McDonald, J. Chem. SOC.,Dalton Trans., 1999, 3349. 196. F. Bellonard, F. Chuboro, J.J. Yaouanc, H. Handel and Y.L. Mest, New J. Chem., 1999, 1133. 197. M.W.J. Beulen, F.C.J.M. van Veggel and D.N. Reinhoudt, Chem. Commun., 1999,503. 198. S. Fabre, B. Findeis, D.J.M. Trosch, L.-H. Gade, I.J. Scowen and M. McPartlin, Chem. Commun., 1999,577. 199. C.-W. Chang, Y.-C. Lin, G.-H. Lee and Y. Wang, J. Chem. SOC.,Dalton Trans., 1999,4223. 200. J.R. Perera, M.J. Heig, H.B. Schlegl and C.H. Winter, J. Am. Chem. Soc., 1999, 121,4538. 201. S. Sharma, N. Caballero, H. Li and K.H. Pannell, Organometallics, 1999, 18, 2855. 202. D.J. Darensbourg, W.-Z. Lee, M.J. Adams, D.L. Larkins and J.H. Reibenspies, Inorg. Chem., 1999,38, 1378. b

14: Transition Metal Complexes of Cyclopentadienyl Ligands

475

203. P. Stepnicka, R. Gyepes, I. Cisafova, V. Varga, M. PolBSek, M. HoraEek and K. Mach, Organometallics, 1999, 18,627. 204. Y.K. Kang, K.S. Shin, S.-G. Lee, I.S. Lee and Y.K. Chung, Organometallics, 1999, 18, 180. 205. H.K. Gupta, S. Brydges and M.J. McGlinchey, Organometallics, 1999, 18, 115. 206. E. Lindner, I. Krebs, R. Fawzi, M. Steimann and B. Speiser, Organometallics, 1999, 18,480. 207. M. del R. Benites, F.R. Fronczek and A.W. Maverick, J. Organomet. Chem., 1999,577,24. 208. M. Watanabe, M. Sat0 and T. Takayama, Organometallics, 1999, 18, 5201. 209. T. Satou, K. Takehara, M. Hirakida, Y. Sakamoto, H. Takemura, H. Miura, M. Tomonou and T. Shinyozu, J. Organomet. Chem., 1999,577,58. 210. J. Silver, D.A. Davies, R.M.G. Roberts, M. Herberhold, U. Dorfler and B. Wrackmeyer, J. Organomet. Chem., 1999,590,71. 21 1. T.-Y. Dong, C.-K. Chang and C.-H. Cheng, J. Organomet. Chem., 1999, 587, 46. 212. I.S. Lee, H. Seo and Y .K. Chung, Organometallics, 1999, 18, 109 1 . 21 3. F.H. Kohler, A. Schell and B. Weber, J. Organomet. Chem, 1999,575,33. 214. C. Imri, C. Laibser, P. Engelbrecht and C.W. McCleland, J. Chem. Soc., Perkin Trans., 1999,2513. 21 5. R. Broussier, M. Laly, P. Perron, B. Gautheron, S. McKoyan, P. Kalck and N. Wheatley, J. Organomet. Chem., 1999,574,267. 216. L.V. Snegur, V.I. Boev, Y.S. Nekrasov, M.M. Ilyin, V.A. Davankov, Z.A. Starikova, A.I. Yanovsky, A.F. Kolomiets and V.N. Babin, J. Organomet. Chem., 1999,580,26. 217. J. Ruiz, E. Alonso, J.-C. Blais and D. Astruc, J. Organomet. Chem., 1999, 582, 139. 218. M. Herberhold, U. Staffl and B. Wrackmeyer, J. Organomet. Chem., 1999, 572, 76. 219. K.R.J. Thomas, J.T. Lin and K.-J. Lin, Organometallics, 1999,18, 5285. 220. H. Kundu, S. Prabhakar, M. Vairamani and S. Roy, Organometallics, 1999, 18, 2782. 221. B. Garcia, C.M. Casado, I. Cuadrado, B. Alonso, M. Morhn and J. Losada, Organometallics, 1999, 18,2349. 222. Y. Nishibayashi, I. Takei, S. Uemura and M. Hidai, Organometallics, 1999, 18, 2291. 223. T. Ireland, G. Grossheimann, C. Wieser-Jeunesse and P. Knochel, Angew. Chem. Int. Ed. Engl., 1999,38, 3213. 224. F. Dubner and P. Knochel, Angew. Chem. Int. Ed. Engl., 1999,38,379. 225. D. Enders, R. Peters, R. Lochtman and G. Raabe, Angew. Chem. Int. Ed. Engl., 1999,38,2421, 226. T. Ireland, J.J. Almena Perce and P. Knochel, Angew. Chem. Znt. Ed Engl., 1999, 38, 1457. 227. J. Ipaktschi, R. Hosseinzadeh and P. Schalf, Angew. Chem. Int. Ed Engl., 1999, 38, 1658. 228. C. Valerio, E. Alonso, J. Ruiz, J.-C. Blais and D. Astruc, Angew. Chem. Znr. Ed. Engl., 1999,38, 1747. 229. J.-H. Song, D.-J. Cho, S.-J. Jeon, Y.-H. Kim, T.-J. Kim and J.H. Jeong, Inorg. Chem., 1999,38,892. 230. K.H. Shaughnessy, P. Kim and J.F. Hartwig, J. Am. Chem. Soc., 1999,121,2123.

476

Organometullic Chemistry

231. Y.-P. Wang, X.-H. Lui, B.-S. Lui, W.-D. Tang, T.-S. Lin, J.-H. Liaw, Y. Wang and Y.H. Lui, J. Orgunomet. Chem., 1999,575,310. 232. D.A. Weinberger, T.B. Higgins, C.A. Mirkin, L.M. Liable-Sands and A.L. Rheingold, Angew. Chem. Znt. Ed. Engl., 1999,38,2565. 233. A.P. Kundig, C.M. Saudan and G. Bernardinelli, Angew. Chem. Znt. Ed. Engl., 1999,38, 1220. 234. M. Watanabe, M. Sato, A. Nagasawa, M. Kai, I. Motoyama and T. Takayama, Bull. Chem. Sac. Jpn., 1999,72,715. 235. X. Lei, M. Shang and T.P. Fehlner, J. Am. Chem. Soc., 1999,121, 1275. 236. 1.R.Butler and M.G.B. Drew, Inorg. Chem. Comm. 1999,2,234. 237. I.R. Butler, S. Mussig and M. Plath, Inorg. Chem. Comm. 1999,2,424. 238. I.R. Butler, A.L. Boyes, G. Kelly, S.C. Qualye, T. Herzig and J. Szewczyk, Inorg. Chem. Commun., 1999,2,403. 239. I. R. Butler, M.G.B. Drew, C.H. Greenwell, E. Lewis, M. Plath, S. Mussig and J. Szewczyk, Inorg. Chem. Commun., 1999,2, 576. 240. C.P. Lenges, M. Brookhart and P.S. White, Angew. Chem. Znt. Ed. Engl., 1999, 38, 552. 241. C.P. Lenges and M. Brookhart, Angew. Chem. Znt. Ed. Engl., 1999,38,3533. 242. M. Nihei, T. Nankawa, M. Kurihara and H. Nishihara, Angew. Chem. Znt. Ed. Engl., 1999,38, 101 1 . 243. A. Sugimeri, T. Akiyama, M. Kajitani and T. Sugiyama, Bull. Chem. Soc. Jpn., 1999, 72, 879. 244. T.T. Chin, R.N. Grimes and W.E. Geiger, Inorg. Chem., 1999,38,93. 245. H. Amouri, J. Vaissermann, M.N. Rager and Y. Besace, Inorg. Chem., 1999, 38, 1211. 246. A.D. Burrows, M. Green, J.C. Jeffery, J.M. Lynam and M.F. Mahon, Angew. Chem. Znt. Ed. Engl., 1999,38, 3043. 247. S . Takara, S. Ogo, Y. Watanabe, N. Nishikawa, I. Kinoshita and K. Isobe, Angew. Chem. Znt. Ed. Engl., 1999,38,3051. 248. T. Habereder, M. Warchhold, H. Noth and K. Severin, Angew. Chem. In?. Ed. Engl., 1999,38, 3225. 249. M. Akita, D. Ma, S. Hikachi and Y. Mom-oka, J. Chem. Soc., Dalton Trans., 1999,987. 250. M.M. Abad, I. Atheaux, A. Maisonnat and B. Chaudret, Chem. Commun., 1999, 381. 251. B.K. McNamara, J.S. Yeston, R.G. Bergman and C. Moore, J. Am. Chem. Soc., 1999,121,6437. 252. J.H. Hardesty, J.B. Koerner, T.A. Albright and G.-Y. Lee, J. Am. Chem. SOC., 1999,121,6055. 253. J.J. Schneider, N. Czap, D. Spickermann, C.W. Lehmann, M. Fontani, F. Laschi and P. Zanello, J. Organornet. Chem., 1999,590,7. 254. H. Wadepohl, F.-J. Paffen and H. Pritzow, J. Organornet. Chem., 1999,579, 391. 255. H. Wadepohl, K. Buchner, M. Herrmann and H. Pritzkow, J. Organomet. Chem., 1999,573,22. 256. A.M. Stevens and C.J. Richards, Orgunometallics, 1999,18, 1346. 257. D. Braga, S.M. Draper, E. Chanpeil and F. Grepioni, J. Organomet. Chem., 1999,573, 73. 258. C.P. Lenges, P.S. White and M. Brookhart, J. Am. Chem. Soc., 1999, 121,4383. 259. K.K. Klausmeyer, S.R. Wilson and T.B. Rauchfuss, J. Am. Chem. Soc., 1999, 121,2705.

14: Transition Metal Complexes of Cyclopentadienyl Ligands

477

260. S. Pasynkiewicz, A. Pietrzykowski, L. Bukowska and L. Jerzykiewicz, J. Organomet. Chem., 1999,585,308. 261. A. Pietrzykowski, P. Buchalski and L.B. Jerykiewicz, J. Organomet. Chem., 2000, 597, 133.

Author Index

In this index the number in parenthesis is the Chapter number of the citarion and this is followed by the reference number or numbers of the relevant citations within that Chapter

Aarset, K.(1) 8 1 Abad, J.-A. (12) 184 Abad, M.M.(14) 250 Abbas, S. (8) 16 Abbenhuis, H.C.L.(10.1) 79 Abboud, K.A. (13) 36,267 Abd-El-Aziq AS. (2) 90; (13) 254

Abd-Elzaher, M.M. (10.3) 53 Abe, H.(2) 195 Abe, M. (1 1) 268 Abedin, M.J. (1 1) 153 Abernethy, C.D.(10.3) 45; (1 1) 54

Abla, M.(13) 225 Abney, K.D.(5) 43 Abrams, M.B.(4) 60; (13) 158 Abu-Salah, O.M.(2) 204; (11) 234; (13) 510

Acebron, S.(10.3) 25 Achatz, U. (1) 335 Ackermann, L. (8) 40,43 Ackermann, M.N.(12) 190 Ackland, M.J.(13) 293 Adams, C.J. (2) 187; (9) 112; (1 1) 115-120; (13) 437,461-465

Adam, H. (12) 227; (13) 142 A h , J.J. (14) 156, 157 Adams, K.V.(11) 56 Adam, M.J. (14) 202 Adams, R.D.(9) 39-43; (1 1) 92, 172-174; (13) 274,359,454, 483 Adolfson, H. (8) 90 Agami, C.(2) 5 Aga~wal,S.(4) 115, 120,129 Agh-Atabay, N.M.(13) 320 Agren, H. (1) 3 14 Aguirre, A. (2) 190 Ahlberg, P.(1) 150; (2) 57,58 Ahlbracht, H.(I) 27 Ahlers, W.(10.1) 44 Ahlgrh, M. (1) 409; (9) 146; (1 I)

30 1 Ahmar, M.(13) 387 Ahmed, A. (2) 14,110 Ahmed, M.(8) 46; (1 1) 257 Ahmed, S.Z.(14) 140 Ahn, K.H.(13) 526; (14) 174 Aiken, J.D., III (11) 4 Aime, S.(11) 159 Ainscough, E.W.(1 1) 169 Aitman, M.(13) 480 Ajmem, RK.(12) 190 Akasaka, T. (1) 124 Akazome, M. (2) 167 hermark, B. (1) 381-383; (12) 163; (13) 107,118, 119 Akhmedov, N.G.(1) 175; (13) 23 8 Akin, A. (2) 61 Akita, M. (11) 72,292; (12) 21, 44,SO; (13) 92,476; (14) 249 Akiyama, T. (14) 243 M e r m a n , O.S. (2) 113 Akther, J. (1 1) 165 Alagesan, K.(14) 184 Al-Ahmad, S.(13) 282 Alaimo, P.J. (12) 1 11 Al-Allaf, T.A.K. (13) 230 Alam, S.(11) 153 Alayrac, C.(2) 28 Albanese, D.(2) 117 Albano, V.G.(9) 155; (1 1) 3 12, 313; (12) 233; (13) 150, 151 Albeniz, A.C. (12) 140; (13) 41 1 Albert, J. (13) 130 Albert, K.(1) 259; (1 1) 16 Albertin, G. (13) 87 Albinati, A. (13) 111,525 Albrecht-Schmitt, T.E.(9) 98; (11) 80 Albright, T.A. (1) 377; (10.4) 32; (13) 333; (14) 252 Alcalde, M.I.(10.2) 22 Alder, RW.(1) 4

479

Alemany, L.B. (6) 62 Alcmany, P. (1) 94 Alexander, J.J. (1) 224; (9) 72; (13) 302,427

Al-Farhan, K.A. (2) 204; (1 1) 234; (13) 5 10 Ali, A. (1 1) 97; (13) 45 1 Ali, M. (10.3) 42 Ali, T. (8) 100 Alih, F.M.(12) 153 Alikhani, M.E.(1) 15,200,337 Al-Juaid, S.S.(2) 42, 50; (3) 36; (4) 17

Allen, A., Jr. (12) 189 Allen, J.G.(8) 94 Allendoerfer, RD. (6) 74 Almena Perce, J.J. (14) 226 Alonso, B.(14) 22 1 Alonso, D.A. (1) 373 Alonso, E. (1) 263; (2) 77; (14) 217,228

Alonso, M.A. (13) 195 Alt, H.G.(14) 26 Althaus, H. (7) 70,87,88,90 Aludin, M.-S. (4) 124 Alvarez, M.A. (10.3) 58 Alvarez, S. (1) 26 1 Alvarez-Larena, A. (9) 130; (13) 367,368,385

Alvarez-Toledano, C.(1 1) 79 Alves, O.L.(1 1) 149 Amatore, C.(13) 122,423 Amberger, H.-D. (4) 149 Amburose, C.V.(7) 96 Amelunxen, K.(6) 75 Amcmiya, T. (1 1) 25 1 Amor, F.(4) 101 Amoroso, A.J. (9) 158; (1 1) 46 Amouri, H.(14) 245 Amrhein, P. (13) 19

h i , H. (2) 164 Anada, M. (8) 64 Anccl, J.-E. (2) 69

480 Andersen, R.A. (14) 16 Anderson, C.-M. (13)242,243 Anderson, D.R. (2)55 Anderson, J.C. (13) 142 Anderson, O.P.(2) 181;(5) 14, 20,21;(9) 141, 142 Andersson, C. (12)102, 103;(13) 221,222 Andersson, P.G. (1) 373,411;(3) 61 Andrews, C.D. (7)29;(14) 105 Andrews, L. (1) 5 1, 190-197,203, 321,322;(4)156;(6)73;(9) 12,20 Andrews, P.C. (5)3;(7)75 Andrien, J. (1 4) 99 Andzelm, J.W. (1) 361;(13) 159; (14)28 Anfang, s.(4) 11 Ang, H.G.(7)79;(9) 11 1, 113, 156;(1 1) 105,106,114,283; (13) 460 Ang,, S.G. (7)79;(9)1 1 1, 113, 156;(1 1) 105, 106, 114;(13) 460 Angelici, R.J. (7)10;(9)36,52, 132;(10.4)5; (11) 195;(13) 217;(14)121 Angermund, K.(13)49 Angles, P.(5) 42 Anson, C.E.(10.1)26;(13)358 Anthony, J.C. (1) 232 Antiiiolo, A. (10.2)1, 11, 12,27; (13) 316;(14)19 Antipin, M.Y.(4)54;(10.1)54; (13) 162 Antonaroli, S.(13) 135 Antonczak, S.(1) 145 Antonidti, P.(1) 34,80;(2)63 Antoniutti, S.(1 3) 87 Antonova, A.B. (1 1) 307;(13) 445 Antoulinakis, E.G.(8)62 Antras, F.(13) 387 Anulewicz-Ostrowska, R.(6)67 h i , M.(1) 380 Aoki, K.(1 1) 112 Aoyama, T.(2)34 Aparana, K.(6)52 Apeloig, Y.(3)31 Appella, D.H.(8)97,98;(14)82, 84 Am, I. (12) 194;(13)506 A r a b , I. (13) 112 h i , T.(2) 167 Araki, K.(2) 199 Amnyos, A. (8)9 Arbez-Gindre, C. (2) 114

Organometallic Chemistry Arbuznikov, A.V. (1) 122 Avarvari, N. (7)50,55,56 (13)388 Arce, A.J. (10.4)33;(1 1) 25, 164, Averbuch, M.-T. Aviyente, V. (2)61 170, 171 Axe, F.U.(1) 361;(13) 159;(14) Arduengo, A.J., I11 (2) 144;(7) 28 118 Axten, J.M. (8)60 Ardura, D.(1 1) 3 14 Arends, I.W.C.E. (10.4)9 Ayers, T.A. (13)204 Ayllon, J.A. (1) 267 Argo, A.M. (1 1) 208 Arguello, J.E.(2)41 h m , K.A. (1 1) 153, 165 Puzena, U.(2)4 Arif, A.M. (12)198;(13) 78 Arikawa, Y.(1 1) 277;(14) 176 Arita,T. (11) 13 Arliguie, T.(14) 12,22 Baar, C.R. (12) 157 Armentrout, P.B.(4) 157 Babb, R. (1) 287 Babin, V.N. (14)216 Armstrong, D.R (1) 25;(2)30, Babu, R.P.K.(2) 44 128;(3) 4 Babushkin, D.E.(1) 103 Arnanz, A. (10.3)35; (13) 370 Arndtsen, B.A. (12)160 Baceiredo, A. (7)24,25,28;(9) 33 Arnold, F.P.,Jr. (1) 302 Bach, 1. (12)146 Arnold, J. (6)43.80; (10.1)9; Bachert, I. (9) 144;(1 I) 275,276, (10.2)10 3 19 Arnold, P.L. (1 2) 204 Arnold, U.(1) 305 Bachmann, R.E.(3) 42;(6)35 Aroney, M.J. (14)30 Back, S.(10.1)58;(13) 418,514, Arredondo, V.M. (4)132-134 515;(14)27 Artus, G. (1) 142,238 Backvali, I.-E. (8)82 hlmozhiraja, S.(1) 52 Bacskay, G.B. (1) 392 Arvidsson, P.I. (2)56-58;(3) 60 Badriya, S.(10.3)33; (13) 240 Bz, B.-J. (6)40,79 Asakura, K. (1 1) 326 Asano, Y . (2)6 Bz, J.-Y. (5)71 Asanuma, T.(4) 117 Bxk, C.-K. (5) 73 Asaumi, T.(8)33;(1 1) 139 Baerends, E.J.(1) 204,205,213, Aschi, M. (1) 336 289;(1 1) 15 Ashby, M.T.(1) 171 Baeza, J.-F. (13) 113 Ashe, A.J., I11 (6)21;(7)80;(13) Bagatur'yants, A.A. (1 1)29 282;(14)49 Bai, S.-0. (2)139;(14)60 Ashford, L.(14)150 Baik, M.-H. (1) 250;(1 1) 76 Asintatham, V.S.(1) 171 Bailey, A.J. (9)49 Aspley, C.J. (9)27 Baird, M.C.(10.1)25;(13)176 Asplund, M.C.(9)3; (12) 14 Baker, P.K.(9)66;(1 1) 82;(1 3) Assclbcrghs, 1. (12)68 321,322,424,444 Aston, G.M.(10.3)33;(13)240 Bakhmutov, V.1.(1) 293;(3) 39; (14)90 Astruc, D.(14)217,228 Atheaux, I. (14)250 Bakhmutova, E.V.(1) 293;(3) 39; Atwi-Nsiah, F.H.(12)126 (1 1) 29;(14)90 Atwood, D.A. (6)41.95 Bakkcr, M.J. (1 1) 161 Balaich, G.J.(5) 43 Atwood, J.D. (9) 136 Auban-Senzier, P.(1 1) 206 Balasubramanian, K.(1)159 Aubart, MA. (10.2)25 Balazs, G. (2)132 Aubert, C.(13)277,278 Balch, A.L. (1) 3 18;(2)222;(I 1) Aubke, F. (1) 222;(9)91 238;(13) 109;(14)170 Auer, E. (13) 224 Ball, G.E. (9)32;(1 1) 273 Auffrant, A. (13) 25 1 Balzarek, C.(14)11 1 Aullbn, G.(1)261 Bandini, M. (2)163 Bandoli, G.(12)100;(13) 135 Ault, B.S.(1) 53;(5) 22;(6)56 Bandt, P. (3) 61 Aumann, R.(10.3)50 Aurell, M.J. (1) 37 Banger, K.K. (1) 296;(2)68;(14) Aust, J. (14)57 25

48 1

Author Index Banham, R.B. (2) 68 Bansal, RK. (7) 46 Bansho, K.(9) 46 Baratta, W. (12) 226 Barberio, G. ( 12) 168 Barbier, D.B. (7) 39 Barbieri, R (1) 92 Barbosa, F.(1) 7 Barbour, L.J. (2) 131, 148 . Barckholtz, T.A. (1) 288 Barclay, J.E. (1 1) 82 Barday, E.(6) 28 Barfield, M. (5) 11 Barkley, J.V. (9) 29; (1 1) 35 Barlmeyer, M. (9) 138 Barlow, S.(13) 355; (14) 167 Barluenga, J. (1) 236; (13) 48 1 Barnes, H.E.(12) 190 Barnes, L.A. (14) 113 Barney, A.A. (6) 13 Barone, G. (1) 92 Baroni, F.(13) 31 Barrado, G. (6) 8 Barranw, E.M. (2) 219; (1 1) 241; (14) 185 Bamtt, A.G.M. (8) 46,47 Barron, A.R (6) 61,62,91 Barrow,M.P.(14) 117 Barry, J.T. (13) 347 Bartels, B. (8) 21 Barth, D.(7) 94 Barthelat, J.C. (1) 273 Bartholomew, G.P.(I) 29 1 Bartik, T. (10.4) 40 Bartlett, I.M. (1) 170; (10.3) 36; (13) 318,324 Barton, L. ( 5 ) 35 Bartusseck, I. (9) 144; (1 1) 275, 276 Barybin, M.V.(10.2) 3 1 Basch, H.(1) 394 Bas% S. (9) 49 Bassindale, M.J.(8) 54 Basu, K.C. (2) 5 1 Batchelor, RJ. (10.3) 15; (13) 50 Bates, R.W. (13) 65 Batra, R (1) 6; (2) 62 Bats, J.W. (1) 165; (13) 108 Batsanov, A.S. (1) 167; (5) 57; (14) 143 Battle, S.L.(3) 14; (7) 122 Bau, R. (13) 70 Baudry-Barbier, D. (4) 4 1,46,7 1, 104, 108 Bauer, A. (1) 143; (9) 53 Bauer, J.A.K. (1) 224; (13) 302, 427 Bauer. W. (14) 125 I

.

I

Baum, E. (7) 104; (13) 249,258 h u m , G. (1) 246 Ba~mann,R (10.1) 12-15 Baumann, W. (1) 309; (10.1) 47, 48,5032; (13) 164, 165, 193, 280,28 1,439; (14) 29,73 Baumeister, J.M. (13) 227 Baumen, A. (13) 303 Baumgartner, T.(2) 98; (7) 23 Bauschlicher, C.W. (1) 54 Bautista, N. (13) 113 Baxter, R.J. (12) 117; (13)363, 364,366,379,380 Baydn, J.C. (1) 369; (13) 213 Bays, J.T. (13) 37 Bazan, G.C. (10.1) 29,80 Beachley, O.T., Jr. (6) 74,78, 95 Bcak, P.(2) 17,51,55,78 Beck, B.C.(6) 76,77 Beck, K. (1) 224; (1 1) 260; (13) 427; (14) 126 Beck, W. (2) 185; (10.4) 30; (13) 237,446; (14) 125 Becker, G. (7) 84 Becker, T.M.(9) 72; (10.4) 25 Beckerle, K.(4) 47 . Beckett, M.A. (6) 16 Beckhaus, R (1) 278 Bedlingfield, K.M. (8) 94 Beer, P.D.(14) 150 Beer, RH.(14) 70 Begtmp, M.(2) 26; (3) 12 Behrendt, A. (7) 83; (14) 10 Behrens, K.(1) 35; (2) 60 Behrens, U. (2) 147, 149; (13) 414 BClanger-Garidpy, F.( 12) 193; (13) 104 Belcher, D.E. (13) 424 Belderrain, T.R(12) 153 Bellachioma, G. (12) 187; (13) 138

Bellamy, D. (6) 26; (9) 81; (10.4) 3,4 Bellandi, F. (1 1) 146, 147 Bellemin-Laponnaz, S.(10.4) 16 Beller, M. (8) 29,8 1 Bellonard, F. (14) 196 Belsky, V.K.(4) 22,53; (14) 13 Beltrami, R.(1 1) 137 Bclyakov, S.(1) 88 Benakki, R. (5) 59 Bhard, M. (1) 121 Bence, E.C. (13) 106 Bencze, E.(1) 3 13 Ben-David, Y.( 12) 27,96; (13) 95 Bender, B.R (13) 358 Bender, J.E. N (1) 101

Bender, R. (1 1) 334 Bendikov, M. (3) 31 Bendix, M.(1) 236 Bengough, M.W.(13) 176 Benites, M.dcl R.(14) 207 Benito,M.(11)315,316 Bennett, B.L. (12) 159 Bennett, M.A. (13) 69,341 (9) 45 Benson, J.W. Benter, M. (1) 69; (6) 83,92 Benyei, A.C. (9) 125,127 Benzi, P.(1) 80 Bera, J.K. (1 1) 227,228 Bercaw, J.E. (4) 60; (10.1) 62; (13) 158; (14) 55 Bcrclaz, T. (7) 56 Berends, T. (7) 98 Bcrcngucr, J.R (1 1) 219; (12) 194, 196; (13) 506,507 Berens, U.(13) 209 Berestneva, T.K. (14) 173 Bergamini, P.(12) 154 Bergamo, M. (1 1) 65 Bergander, K. (10.1)41;(13)288 Berger, D. (8) 31; (1 1) 134; (13) 299 Berger, S.(3) 46 Bergerat, P.(1) 141 Bergman, B. (1 1) 153 Bergman, R.G.(2) 37; (9) 48; (10.1) 71; (10.2) 10,25; (12) 91, 111,112;(14)251 Bergstad, K.(8) 82 Berhamo, M. (1 1) 64 Bcringhelli, T. (1 1) 64,65 Berke, H.(1) 132, 134, 142,226, 238; (6) 7;(10.2) 19; (10.4) 36,37; (13) 173 B e d , D.J. (12) 74 Bemardi, P. (2) 168 Bernardinelli, G. (8) 101; (14) 233 Bemasconi, C.F. (10.3) 42,43 Bemdt, A. (1) 23; (2) 46 Bemhardt, E.(1) 222; (9) 91 Bemo, P. (10.1) 6 Berrien, J.-F. (2) 157, 158 Berry, A. (7) 92 Bcrry, D.E.(14) 156 Bcrtrh, J. (1) 265; ( 5 ) 37 Bertrand, G. (2) 180; (3) 26; (7) 1, 24,25,27,28; (9) 33 Bertuleit, A. (10.1) 35 Bertz, S.H.(2) 161 Besace, Y.(14) 245 Beshouri, S.M.(14) 16 Beste, A. (1) 72 Beswick, C.L. (6) 9; (10.1) 63; (14) 50

482 Bochkarev, M.N. (4)10,36,45, Beswick, M.A. (2)152;(7) 120; 6 1-63,66,92,93 (9) 158;(1 1) 46;(14)5 Bettenhausen, M. (1 1) 39 Bochmann, M. (10.1)11,26,46, Betzer, J.-F. (2) 175 60,61;(13)284 Beulen, M.W.J. (2) 141;(14)190, Bock, H.(1) 44;(2) 126 197 B h k e i , Z.(1) 130;(2)1 16;(14) Beverwijk, V. (7)15;(12)181 43 Beyer, L.(14) 136 Bode, B.M. (1) 364 Beyer, M. (1) 335 Bodenbinder, M. (1) 222;(9)91 Bian, W.S.(1) 45 Mhm, V.P.W. (12)6,176,208 Bianchi, M.(1 1) 142 Boehme, C.(1) 68,70;(9)6, 128 Bianchini, C.(10.4)39;(12)76, B h e , U.(1) 278 229;(13)216 Bohmer, J. (13) 67 Bickelhaupt, F.(1) 237;(2)121; Boerakker, M.J. (12) 120 (7) 11, 15;(12)181 Bijmer, A. (1) 309,310;(13) 193, Bickelhaupt, F.M.(1) 144,237; 205 (2) 113;(7)1 1 Boersma, J, (1) 29;(2) 127;(10.3) Biesemans, M. (1) 91,93 18-20,46 Bikhanova, G.A. (13)308 Boese, R. (5) 27;(7) 14, 105; Bildstein, B. (2)35;(14) 122, 123 (10.3)60;(13)59,86,303, Bilgin, B. (12) 186 357 Bill, E.(1) 222;(9)91 Boesveld, W.M. (2)95 Billups, W.E.(10.4)42 Boettcher, C. (13) 315 Binger, P.(7)59,60 Boev, V.I.(14)216 Bintein, F.(13)253 Boganov, S.E.(1) 98 Birg, C.(3)3 Bohanna, C.(12)70 Birge, R.R. (2) 183 Bohling, J.C. (12)198 Birk, U.(12) 192;(13)340 Bohme, A. (8) 27 Biron, J.-P. (13)253 Bohres, E. (7)52;(1 1) 215 Birri, A. (13) 265 Boldyrev, A.I. (1) 47-50 Biswas, B. (1) 108;(12) 137;(13) Bollinger, J.C. (13)347 115 Mmont, C. (2)80 Bitterwolf, T.E.(13) 37 Bonaga, L.V.R. (8) 34 Bjerregaard, T.(3) 12 Bonanno, J.B. (10.1)65;(13) 163; Bjurling, E. (1 3) 242,243 (14)77 Blacker, A.J. (8) 20 Bond, A.M. (9) 67,69 Blackwell, H.E. (8)56 Bondybey, V.E.(1) 335 Blacque, 0.(14)91 Boni, S.(14)93 Blber, D.(7) 14;(10.3)60;(13) Bonitatebus, P.J., Jr. (8) 39,50; 59,86,303,357 (12)219 Blais, J.X. (14)217,228 Bonomo, L.(2)146;(3) 19;(10.1) Blake, A.J. (2)200 24 Blake, M.E. (1) 4 Bor, G.(1 1) 184 Blandy, C.(13)314;(14)88 Boraie, W. (2)90;(13)254 Blanford, C.F.(1 1) 325 Bordignon, E.(1 3) 87 Blank, T.(6)94 Bordonaba, M.(1 1) 199 Blaschke, U.(10.1)42,43 Bordoni, S.(12)234 Blaser, U.(7)105 Borge, J. (12)68 Blaurock, S,(14)40 Borgmann, C.(13) 44 Blceke, J.R (12)116 Borisov, A.P. (14)142 Bleuel, E.(13) 89 Borner, A. (8)95 Bley, B.(1) 222;(9)91 Borosky, G.L.(1) 114 Blomberg, M.R.A.(1) 334,395 Borovik, A.S. (6)91 Blower, P.3. (1) 406 Borowski, M.(1 2) 186 Bluhm, H.(14)35 Bos, M.E. (10.3)4 1; (13) 34 Bo, C.(1) 121,256;(13)431 Bosch, M.(13) 309 Boccaleri, E. (1 1) 5 Bosque, R. (1) 398;(12)33;(14) Bocelli, G.(13) 3 1 139

Organometallic Chemistry Bott, S.G. (6)62,91 Bottomley, F. (1 1) 54 Bouaoud, S.-E. (1 1) 334 Bouhdid, A. (1)93 Bouherour, S.(1 1) 296 Bourassa, J. (1 1) 225 Bourguignon, J. (2)26 Bourissou, D. (7) 1,28;(9)33 Bourret, E.D. (6)80 Bovii, G.(14)90 Bowcrs, M.T.(1) 328 Bowmaker, G.A. (1 1) 230 Boyd, E.P. (1 1) 22 Boyd, P.D.W.(1) 162;(14)192 Boyd, R.J. (1) 79 Boyd, S.L.(1) 79 Boyes, A.L. (14)238 Boymond, L. (3) 11 Bozhenko, K.V.(1) 43 Bradd, K.J. (12)95 Braddock, D.C.(8) 46 Bradley, A. (8) 79 Bradley, D.C. (6)39 Bradshaw, J.D. (2)83;(13)8 Braeuchle, C.(14) 144 Braga, A.L.(2)74 Braga, D.(1) 181;(9)133;(11) 27,66;(13) 292;(14)257 Braier, A. (13) 250 Brain, P.T. (1) 296 Bramrner, L. (14)21 Branaleon, L.(6) 15 Branchadell, V. (1) 179,218,389; (13) 116,290 Brand, U.(9) 15 1; (11) 288 Brands, J.A. (12)123;(13)198 Brandt, D.E.(9)45 Brandt, P. (1) 373,411 Brandts, J.A.M. (1)29;(2) 127; (10.3)18-20,46 Brandukova-Szmikowski, N.E. (4) 120, 129 Brase, S.(8) 19 Brassington, D.S. (6)16 Braun, L.(6) 10 Braun, T.(12)145 Braunschweig, H.(2) 143;(1 1) 73 Braunstein, P. (9)144;(1 1) 1, 275,276,291,296,319,334 Bravo, R.(1)1 Bravo-Zhivotovskii, D. (3)3 1 Breczinski, P.M. (13) 378 B r b , J.L. (1) 28 Breeze, S.R (6) 12 Bregadze, V.l.(5) 54;(13) 429 BrQault, J.-M. (10.4)19 Breit, B. (8) 28 Bremand, N. (2)22

483

Author Index Bremberg, U. (1) 386,387 B r e w J. (4) 97 Breternitz, H.-J (2) 165 Breunig, H.J. (7) 70,85,87,88,

Brlining, K. (13) 500 Bmhn, C. (11) 221; (13) 149 Bnunaghim, J.L. (12) 25,221;

90,95,101,116 Brice, M.D. (6) 46

Bruneau, C. (10.3) 2; (12) 53; (13)

Bridgewater, B.M.(10.3) 21; (14)

Brunner, H. (9) 129; (1 1) 282;

109

Briel, 0. (14) 126 Bringmann, G. (1) 155 Brinkman, P.H.P. (12) 143 Brintzinger, H.-H. (1) 131; (14) 63

Brisdon, A.K. (1) 296; (2) 68; (14) 25

Britovsek, G.J.P. (1) 347; (10.3) 1; (12) 15; (13) 28,57

Brittingham, K.A. (10.4) 13 Bnmn, D. (2) 182 B d , J. (1) 166 Bmhler, R (9) 91 Brock, J.R (10.3) 30 Brodie, A.M. (1 1) 169 Broecher, D.J. (13) 250 Broechler, R. (1) 222 Broene, R.D. (4) 50; (14) 14 Broenstrup, M. (1) 336 Bromley, S. (1 1) 45 Broo, A. (1) 150 Brook, M.A. (13) 362 Brookhart, M. (12) 139; (13) 96, 114; (14) 240,241,258

Brooks, B.C. (13) 179 Brooks, K.A. (2) 47; (5) 45 Brooksby, P.A. (1 1) 6 Brorson, M. (1 1) 57 Brosch, 0. (14) 124 Brossier, P. (9) 37 Broughton, S.G. (12) 227 Broussier, R. (14) 154,215 Brown, D.A. (10.4) 25 Brown, J.M. (12) 162; (13) 214, 524; (14) 155

Brown, L.O.(11) 44 Brown, M.A. (1) 55; (6) 93 Brown, N.C.(9) 81; (10.4) 4 Brown, S.J. (10.1) 2 Browning, J. (14) 156 Bruce, A.E. (1 1) 244 Bruce, M.I. (1) 252,255; (9) 108, 112, 154;(10.3)31; (11)23, 90,91,113,115-121,128, 264; (12) 59,60,72,82; (13) 356,443,452,458,459,461465,467,477,478,520; (14) 100 Bruce, M.R.M. (1 1) 244

Bruckmann, J. (7) 59

(13) 84; (14) 147 12; (14) 2 (13) 266; (14) 8, 107

Brunton, J.J. (14) 188 Bryan, J.C. (1) 26 Bryce, M.R.(14) 143 Brydges, S. (14) 205 Bu, H.-B. (3) 13 Bubnov, Y.N. (1) 115 Buchalski, P. (14) 261 Buchmeiser, M.B. (13) 36 1; (14) 171

Buchowicz, W. (12) 209 Buchwald, S.L.(8) 5,9,35,36, 97,98; (14) 36,82,84

Buckmelter, A.J. (2) 107 Budzelaar, P.H.M. (14) 21 Biichner, H. (14) 255 Biichner, K. (1 I) 190; (13) 484 Biichner, M. (13) 417 Biihl, M.(1) 180,2 12,2 15,296, 308,309,344,362; (10.2) 24; (13) 166,193,194,262; (14) 65 Buil, M.L. (1) 258,306; (12) 40, 70,235; (13) 430 Bukowska, L. (11) 213; (13) 408; (14) 260 Bulgakov, R.G. (4) 150 Bulychev, B.M. (4) 22,53,54; (14) 13 Bundens, J.W. (1) 8; (6) 37 Bunz, U.H.F. (1 1) 92; (13) 10, 273,274,454,480,483 Burckhardt, U. (10.2) 30 Burger, P. (13) 227 Burgey, C.S. (8) 110 Burghaus, 0. (13) 344 Burguete, M.I. (14) 193 Buriez, B. (12) 75 Burk, M.J. (8) 94; (13) 209 Burkey, T.J. (14) 119 Burkhardt, T.J. (14) 55 Burlakov, V.V. (10.1) 47-52,54, 55; (13) 162,164,165,280, 281,312,439; (14) 29,73 Burnaby, D.G. (13) 216 Burns, C.J. (14) 11 Burns, C.T. (6) 68 Burns, I.D.(12) 75 Burrell, A.K. (14) 192, 195 Burrows, A.D. (7) 29; (13) 110, 203; (14) 105,246

Burstcn, B.E. (1) 183, 186, 203, 288; (9) 11-13; (13) 157

Burth, D. (14) 156 Burzlaff, N. (10.4) 31 Bu~~hmann, H.-J. (1) 11 Buschmann, R. (2) 149 Busetto, L.(12) 234 Bushnell, J.E. (1) 328 Bustello, E. (12) 57,58 Busujima, T. (8) 112 Butcher, R.J. (4) 40 Butenschiin, H. (13) 9 Butler, 1.R (14) 1,236-239 Butts, C.P. (13) 133,412 B w , T . - S . (13) 319 Buzard, D.J. (8) 12 Buzzard, D.J. (2) 196 Byrne, J.J. (1 1) 194; (13) 369 Byrne, L.T.(1 1) 122; (13) 466 Bytheway, I. (1) 268 Bytschkov, 1. (14) 33 Caballcro, N. (2) 142; (14) 201 Cabeza, J.A. (1 1) 3 14 Cabral, J. (2) 100 Cabrera, A. (7) 96 Cacchi, S. (8) 128 Cadena, J.M. (13) 130 Cadcnas, G. (14) 42 Cadierno, V. (1) 378; (10.1) 7476; (12) 11,68,81,86; (14) 66 . Cahiez, G. (3) 11 Cahill, J.P. (13) 134 Cai, R.-F.(4) 2,5,7,49,51 Cai, Y. (4) 13,55 Cai, Z.S. (1) 3 I Calabrese, J.C. (2) 144; (13) 204 Calderazzo, F. (14) 87 Calderoni, F. (9) 140; (1 1) 36 Calhorda, M.J. (1) 173,174,219, 253,305; (9) 4, 121; (1 1) 17, 160; (13) 38 Callaghan, C.S.J. (7) 35; (14) 128 Calligaris. M. (1) 285 Calvo-Perez, V. (I 1) 186 Camanyes, S. (1) 265 Cambridge, J. (13) 24 1 Cameron, P.A. (6) 46 Caminade, A.M. (7) 71; (10.1) 76 Cammack, J.K. (1) 143; (14) 117 Campagna, S. (2) 84 Campana, C.F. (9) 157; (11) 51, 206 Campazzi, E. (2) 129; (4) 75,76 Campbell, W.M. (14) 192, 195 Camp, J.A. (13) 521

484

Cimpora, J. (12) 12,174, 180 C a m p , K.R (8) 110 Camus, E. (4) 104 Canac, Y.(7) 28; (9) 33 Canadell, E. (1 1) 206 Canales, F. (1 1) 240 Canales, S. (1 1) 242 Cancilla, M. (1) 318 Canet, J.-L. (13) 300 Cano,D.A. (4) 34 Canovese, L. (13) 135,136 Cantrell, G.K. (10.3) 48 Cao, R. (11) 30 Capon, J.-F. (10.3) 32; (13) 346 Capparelli, M.V.(1 1) 171 Capps, K.B.(1) 143; (9) 53 C h i , G. (12) 187; (13) 138 CBrdenas, D.J. (2) 176; (3) 62; (12) 179 Cardin, C.J. (13) 399 Cardoza, L.A. (10.4) 5; (14) 121 CarfBgna,C. (10.2) 13; (12) 187; (13) 138,317 Cariati, E. (1 1) 85,225 Cario, D.A. (14) 17 Carlon, M. (13) 87 Carlton, S. (13) 324 Carmichael, A.J. (8) 136 Carmichael, D.(1) 62; (6) 90; (7) 34-36 Carmona, E. (1) 283; (12) 12,97, 98, 153, 174, 180,228; (13) 98 Caro, €3. (13) 487 Caro, C.F. (3) 1 Carollo, L. (3) 64; (14) 132 Caron, B.(3) 15 Carpenetti, D.W., I1 (14) 71 Carpenter, G.B.(1 1) 28; (12) 166 Carpenter, J.D. (5) 22 Carpenter, N.E. (13) 247,371 Can; A.G. (10.1) 60 Can;J.D. (14) 189 Carmiio, E.P. (1) 260; (13) 3 Carrillo-Hemosilla, F. (10.2) 1, 11, 12;(13)316 Carter, C.A.G. (10.1) 67; (14) 32 Carty, A.J. (1) 254,286; (11) 71, 111,262; (12) 38,39,65, 158; (13) 351,472,482 Carvalho, N.N. (10.4) 6 Casado, A.L. (12) 140 Casado, C.M. (14) 221 Casado, h3.A. (1 1) 252,253 Casalnuovo, A.L. (13) 204 Casalnuovo, J.A. (13) 378 Casares, J.M. (13) 195 Casas, J.E. (1 1) 245

Casas, J.M. (1) 263; (2) 220; (13) 434

Caselli, A. (10.2) 7 b e y , C.P. (14) 71 Cassani, M.C. (2) 130; (4) 16; (12) 234 Cassetta, A. (13) 201

Cassoux, P. (13) 5 Castarlenas, R (1) 269 Castellano, B. (10.2) 6; (13) 172 Castellari, C. (9) 155; (1 I) 3 12, 3 13

Castiglioni, M. (1) 80 Castillo, S.(1) 338 Castro, A. (10.2) 26 Castro, J. (13) 368 Catalano, V.J. (1 1) 235 Cataldo, L. (7) 56 Catellani, M. (13) 3 1 Catt, J.D.(2) 115 Caubet, A. (14) 139 Caulton, K.G.(1) 239,299,398; (12) 33,43,54,223,224; (13) 332 Cauzi, D.(9) 104; (1 1) 109 Cavaglioni, A. (1) 292; (7) 1 12; (12) 94 Cavalheiro, C.C.S. (10.3) 61 Cavallo, L. (1) 346,375; (12) 135 Cavazza, C. (12) 34 Cavell, K.J.(12) 206 Cavell, RG. (2) 44; (3) 25; (6) 52; (7) 4749 Cavicchio, G. (13) 201 Cazes, €3. (13) 387 Cecano, M. (13) 52 1 Ceccon, A. (13) 423 Cecconi, F. (3) 34 Cefalo, D.R. (8) 49 cejka, J. (14) 31 Celio, H. (13) 187 Cenini, S, (9) 103; (1 1) 136, 137 Ceriotti, A. (9) 145; (1 1) 37,47 Cesaro, S.N. (1) 202 Chakraborty, D. (6) 54 Challenger, S. (8) 96 Chamberlin, R.M. (1) 176; (10.2) 29 Champeil, E. (1 1) 194; (13) 369; (14) 251 Chan, A.S. (4) 42; (8) 70; (13) 215 Chan, E.Y.Y.(13) 428 Chan. K.S. (12) 92 Chan, K.W.K. (1) 396 Chan, M.C.-W. (12) 64 Chan, M.S.W. (1) 340 Chan, W.-H. (1 1) 23 1

Organomefallic Chemistry Chandler, B.D.(1 1) 325 Chang, C.C. (9) 84; (10.4) 1 Chang, C.-W. (12) 55,67; (13) 81; (14) 199,211 Chang, M.C. (1) 343 Chmg, R.-E. (11) 193; (13) 383 Chang, S.C.(10.4) 42 C h g , Y.-C. ( I 1) 193; (13) 383, 488

Chang, Y.K. (4) 105 Chaniotakis, N.A. (1) 93 Chanon, M. (1) 39, 40 chao, C.S. (7) 97 Chao, H.-Y. (1 1) 231 Chapouland, V.G. (2) 135 Charmant, J.P.H. (2) 188; (3) 40; (1 1) 50,328; (13) 435,509

Chassaing, C. (2) 13 Chatani, N. (8) 30,33,72-74; (9) 105-107; (1 1) 130,135,139 Chattejee, A. (1) 10 Chattcjee, S. (9) 143; (1 1) 256 Chatterton, C. (8) 137 Chaudrct, B. ( I ) 267,273; (12) 2; (14) 250

Chauhan, K.K. (8) 100 Che, C.-M. (11) 231; (12) 64 Che, D.-I. (14) 130 Chen, C.-L. (12) 161 Chen, C.-y. (3) 56 Chcn, C.Y.L. (2) 214 Chen, G. (1 1) 157 Chen, H. (1) 333,405; (3) 57; (8) 71,75; (12) 17; (13) 54,329, 330; (14) 120 Chen, H.-C. (9) 84; (10.4) 1 Chen, H.-S. (1 1) 60 Chen, J. (1) 60,61; (9) 52,60,70, 75, 132;(10.4)46,47;(11) 195,244; (13) 354 Chen, J.-T. (12) 161 Chen, W. (1) 48; (8) 137; (1 1) 55 Chen, W.-C. (13) 53 Chen, X.-N.(1 1) 187, 192,265, 295,329; (13) 489-496 Chen, Y .-C. (2) 177; (10.3) 5 1 Chen, Z.-N. (1 1) 196 Cheng, C.-H. (14) 211 Cheng, D.(1) 38; (2) 76 Cheng, E.C.-C. (1 1) 4 1 Cheng, Y.-X. (4) 24,25 Chent, W. (5) 36 Cheruku, S.R.(10.3) 26; (13) 52 Chesnut, D.J.(2) 183 Chesnut, R W . (10.1) 7 Chcssa, G. (13) 136 Cheung, K.K. (10.4) 2,38; (1 1) 41,49,229; (12) 64; (13) 447,

Author Index 508

Chi, K.-M. (9) 84; (10.4) 1 Chi, Y.(11) 155; (13) 143,473, 474

Chiang, C.-C. (9) 84; (10.4) 1 Chiang, M.Y. (1 1) 75 Chicote, M.-T. (2) 211,213; (12) 182; (13) 113

Chien, B.-J. (13) 488 Chiesi-Villa, A. (1) 304; (10.1) 23; (10.2) 6; (10.3) 23,28,55; (13) 172 Chihara,T. (11) 123,124 Chin, C.S. (12) 124, 191; (13) 103 Chin, T.T. (5) 46; (14) 244 Chio~,L.-W. (9) 99; (1 1) 81 Chirik, P.J. (10.1) 62 Chisholm, M.H. (13) 347 Chistyakov, A.L. (1) 90, 146,293; (3) 39; (5) 54; (13) 429 chitsaz, s. (7) 100 Chitti, A. (9) 103 Chizhevsky, I.T.(5) 54; (13) 429 Cho, C.-W. (13) 526; (14) 174 Cho, D.-J. (14) 229 Cho, H.(12) 124, 191 Cho, J.-Y. (2) 177; (10.2) 17; (10.3) 51 Cho, S.-L. (5) 67,71,73 Choi, M.-Y. (12) 64 Choi, N. (1 1) 56,77,2 16; (13) 110,352,425 Choi, S.-H. (1) 295,303; (10.3) 11; (12) 201 Choi, Y.-Y. (9) 26; (1 1) 176, 177 Chong, D. (13) 103 Chong, S.H.F. (10.4) 38; (13) 447 Chong, 2.(5) 44 Chopra, A. (2) 161 Chou, S.-Y. (1 1) 287 Chou, Y.-C. (13) 473 Choudhary, A. (13) 24 1 Choukroun, R.(10.2) 14; (13) 5, 314,343; (14) 88 Chow, A. (1) 36 Chu, S.-Y. (1) 109-113,399-401; (12) 87,88 Chuang, J.X.(10.3) 51 Chuang, L.-W.(13) 260 Chuboro, F.(14) 196 Chui, K.(4) 3 1,84; (5) 65 Chung, C. (13) 473 Chung, G. (13) 69 Chung, M.C. (1 1) 292; (13) 476 Chung, T.C. (6) 2 Chung, Y.K. (13) 155, 178; (14) 39,204,2 12 Churakov, A.V. (5) 57

485

Churchill, D.G. (6) 78; (10.3) 21; (14) 109

Churchill, M.W. (6) 78 Cinellu, M.A. (2) 210; (12) 93 Cini, R. (1) 292; (7) 112; (12) 94 Cinquantini, A. (14) 135 Ciriano, M.A. (1 1) 198, 199,252, 253; (13) 438,440; (14) 52

Cisafova, I. (5) 48; (10.1) 47.56, 57; (13) 133,164,313,516; (14) 31,203 Cittadini, V. (1) 262 Ciurash, J. (11) 153; (13) 372 Clark, A.I. (9) 66; (1 1) 82 Clark, D.L. (4) 39,40 Clark, H.C.S.(10.1) 10 Clark, J.R (10.2) 15, 18 Clark, R.D. (4) 33; (14) 4 Clarke, M.L. (8) 20 Claver, C. (1) 256; ( I 1) 253; (13) 210,213,220,431 Clayden, J. (2) 14, 15,23,24, 110 Clays, K. (12) 68 C l e m W.(1) 105; (2) 30,49,50, 53,97; (6) 23,66; (12) 37,85; (13) 349,350; (14)58, 194 Clemente, M.E.N. (13) 78 Clendenning, S.B.(7) 61,62 Clcntsmith, G.K.B.(7) 35,43 CIBrac, R.(1 1) 206 Click, D.R. (4) 89 Clifford, A.A. (8) 127 Cloke, F.G.N. (1) 188; (2) 153; (7) 7,8,35,39; (10.1) 10,72; (12) 204; (13) 345 Cloninger, M.J. (2) 162 Closc, M.R. (9) 57 Clot, E. (1) 267,270,299,300; (12) 200,223 Clybume, J.A.C. (10.3) 45 Coat, F.(12) 71 Cobley, C.J. (13) 341 Cocks, P.A. (14) 192 Cogan, D.A.(2) 29 Cohen, T.(1) 38; (2) 76 Colacot, T.J. (2) 47; (5) 45 Colbert, M.C.B.(12) 62 Cole, J.M.(10.3) 17 Colebrook, S.A. (1) 403 Cole-Hamilton, D.J.(3) 63; (7) 72; (9) 125-127 Coleman, D.M. (4) 4 Coles,M.P.(10.2) 23 Coles, S.J. (2) 153; (10.1) 46; (12) 162; (13) 132,284; (14) 189 Coll, R.K. (1 1) 169 Collange, E.(1) 137, 139; (14) 99, 101

Collazo, C. (13) 3 15 Collier, W. (1) 100 Collin, J. (4) 43 Collins, S. (6) 23; (14) 58 Colombet, L. (7) 5 1 Colopietro, M.( I 3) 20 1 Colton, R. (9) 69 Comba, P.(1) 148 Comely, A.C. (13) 13,398 Comesse, S. (2) 5 Conan, F. (10.2) 4 Concolino, T.E.(4) 94; (6) 68; (12) 169

Conejero, S. (12) 68 Connell, B.T. (8) 110 Connelly, N.G. (1) 170; (6) 26; (9) 81; (10.3) 36; (10.4) 3,4; (13) 3 18,323,324 Connolly, 1. (9) 80 Conochi, S. (4) 74 Conole, G. (7) 121; (1 1) 56,77, 191; (13) 352,425 Conry, R R . (2) 178; (13) 185 Constable, E.C. (1 1) 167; (13) 498,499 Contreras, L.(1) 283

Converso, A. (8) 90 Cook, K.S. (10.2) 9 Cooke, P.A. (2) 200 Corbin, F. (2) 28 Cordaro, J. (10.1) 65; (13) 163; (14) 77

C o y , J.Y. (14) 48 Corlay, H.(8) 37 C o d i n i , P. (1) 346 Corrette, C.P.(4) 135 Corso, G. (12) 187; (13) 138 CortQ-Cofi&, E.(1 1) 79 Cosledan, F. (6) 45 Costa, E.(12) 154 Costuas, K.(1) 248,252; (13) 452 Costunas, K.(1) 152; (1 1) 19 Cotton, F.A. ( I ) 263; (1 1) 53; (13) 400

Couchman, S.M. (5) 56 Coucouvanis, D.(1 1) 260 Coumbarides, G.(6) 39 Cousins, R.P.C. (2) 9 Coussens, B.B.(1) 372,385; (13) 147

Coutrot, P. (2) 80 Cowie, J. (5) 49 Cowie, M.(12) 42.46, 105, 126, 129, 130; (13) 406,432

Cowley, A.H. (1) 66; (3) 14; (7) 122; (10.3) 45

Cox, L.R. f 13) 64 Cozzi, P.G. (2) 163

Organometallic Chemislry

486

Crabtree, R.H. (1) 270; (8) 125 Cracium, L. (5) 34 Cragg, P.J. (13)511 Cramp, S.M. (8) 46,47 Crane, T.W.(10.3) 38; (13) 325 Creaser, C.S. (13) 252 Creci, M.A. (14) 17 Cremer, U.(10.1) 79 Crescenzi, R (10.1) 23 Crespo, M. (12) 185 Crespo, 0. (2) 219; ( 5 ) 40,41; (1 1) 240,242; (14) 185 Creve, S.(1) 182,231,372; (7) 66; (13) 147 Crispin, X. (1) 28 Crispini, A. (12) 168 Cntchley, G. (9) 14; (11) 86 Crittendon, R.C. (6) 76 Crociani, B. (13) 135 Croft, M. (4) 97 Cronje, S.(10.3) 52 Crosby, J. (13) 412 Cross, RJ. (1 1) 220 Cross, W.I. (2) 68 Croucher, P.D. (6) 87 Crucianelli, M.(13) 201 Csiiregh, I. (1) 386,387 Cuadrado, I. (14) 221 Cubbon, R. (13) 142 Cubero, E. (1) 19 Cucciolito, M.E. (12) 233; (13) 150 Cueckel, C. (3) 17

Cuenca,T.(10.1)64;(14)41 Cui, C. (6) 5 1,65 Cui, D. (8) 69 Cui, M. (1) 128 Cui, X.L. (3) 38 Cuiarro, A. (3) 44 Cummins, C.C. (10.3) 30 Cunneen, D. (13) 134 Cunningham, D. (1 1) 293 Curnow, O.J. (14) 156, 157 C u m , D.P. (8) 132 Curtis, M.D. (2) 78 Cusado, M.A. (13) 438 Custelcean, R. ( 5 ) 34 Cutler, A.R. (10.4) 29 Czap, N.(13) 59,86; (14) 253 Czelusniak, I. (9) 58; (13) 3 19 Dabdoub, M.J. (2) 74 da Costa, M.H.R. (10.2) 23 Dagorne, S.(6) 82 Dahanukar, V.H.(2) 107 Dahl, L.F.(9) 157; (1 1) 51 Dahlenburg, L. (13) 206,337

Dahlmann, M. (10.1) 69,70; (13) 171,283; (14) 80 Dai, C. (6) 23; (14) 58 Dai, X. (13) 80; (14) 186 Dakapan, T.(3) 5 1 Dal, A. (1 I) 214; (13) 224 Dalby, C.I.(10.2) 23 DAlfonso, G.(9) 88; (1 1) 64,65 Dalko, P.I. (2) 12 Damant, G. (2) 68 Dambrin, V. (2) 164 Damoun, S.(1) 93 Dandin, 0. (3) 19 Daniel, C. (1) 206-209; (9) 23,68 Danjo, H.(13) 124 Danks, T.N.(13) 293 Danopoulos, A.A. (12) 203 Dapprich, S.(1) 3 12; (13) 146 Daran, J.C. (1) 273 Darensbourg, D.J. (1) 229; (9) 61; (14) 202 Dargel, T.K. (1) 161, 165 Das, A.R. (1 1) 165 Dash, A.K. (1 1) 33,257 Daub, I. (2) 3 1 Davankov, V.A. (14) 216 Davidson, F. (2) 144 Davidson, J.L. (13) 191,320 Davidson, M.G. (5) 30 Davidsson, c). (2) 56; (3) 60 Davies, D.A. (14) 210 Davies, H.M.L. (8) 57,61,62 Davies, J.E. (7) 13,121; (11) 56, 191; (13) 426 Davies, M.K. (9) 25 Davies, M.S.(14) 30 Davies, R.P. (2) 30.97 Davis, B.L.(4) 50; (14) 14 Davis, D.S. (8) 38 Davis, H.F. (4) 155 Davis, J.R (1) 287 Davis, W.M. (8) 49; (10.1) 12-18 Daw, J.A. (13) 27 Dawson, D.M. (10.1) 60 Day, C.S. (13) 39 Day, M.W. (4) 60; (10.1) 62; (13) 158,355 Day, RW. (1 1) 54 Deacon, G.B.(4) 9,W Dcbad, J.D.(10.3) 15; (13) 50 Debenham, J.S. (1) 410 De Blasio, N.(9) 126 de Bruin, B. (12) 120, 123; (13) 198,219 de Carvaho, A.B. (1) 55; (6) 93 Decken, A. (3) 14; (1 1) 54 Decker, C. (1 1) 11 Decker, J.M. (10.2) 2 1

Decker, S.A. (1) 223 Declcrq, J.P. (7) 18, 19 Decleva, P. (1) 30 Dedieu, A. (1) 286; (10.4) 16 Dcemie, R.W. (3) 65 Deeming, A.J. (10.4) 33; (1 1) 97, 164, 170, 171; (13) 451 Deetlefs, M. (10.3) 52 de Gelder, R (12) 120, 123; (13) 198,219 de Guigne, C. (2) 69 Dehnen, S.(1) 189; (4) 68 Dehnickc, K. (4) 11,78, 1 15; (7) 100; (11) 83 de Kanter, F.J.J. (1) 240 DeKock, R.L. (1) 279; (12) 126 Dekura, F. (14) 85 Deiamesiere, M. (1 1) 194; (13) 369 De Leonardis, P. (1) 181; (13) 292 Delgado, E.(13)416; (14) 76 Delgado, S.(10.3) 35; (13) 370 Della Pergola, R. (1 1) 34 Delmau, L.H.(1) 26 Dcloffre, A. (10.4) 19 de 10s Rios, I. (12) 76 Delpech, F. (1) 273 Delplancke, J.L. (3) 45 del Real, P.A. (10.1) 34 delRio,I.(12)77;(14)27 del Villar, A. (2) 186 Del Zotto, A. (12) 226 Demartin, F. (9). 140; (1 1) 36,48 de Maurera, M.A.M.A. (1) 55; (6) 93 Dembech, P. (2) 168 Dcmbeck, G. (10.3) 60 Dembinski, R. (10.4) 40,4 1 de Meijere, A. (13) 236 de Montauzon, D. (10.2) 13; (13) 3 17 Demsar, A. (3) 21 Demtschuk, J. (3) 18; (4) 32,48, 58,59, 100; (14) 45 Demuth, W.(2) 92 Deng, C.H. (1) 45 Deng, L. (1) 341,348,349,360; (12) 16; (13) 56 Deng, X.(4) 118, 122, 125 Den& Y.-H. (1 1) 3 1 Denise, B.(10.4) 19 Denk, M.K. (7) 64 Denker, M. (7) 101 Denninger, U. (13) 407 den Reijcr, C.J. (13) 219 DePaul, S.M. (14) 30 Dcravakian, A. (13) 372 Derdau, V.(13) 386

Author Index Derecskei-Kovacs, A. (1) 229;(9) 61 de Rege, F.M.(5) 43 de Rio, I. (13) 72,418 Demck, A. (8) 96 Derrien, N. (13) 209 Dervisi, A. (13) 132 Derwing, c. (2)59 de Saint Lamer, J.Y. (3) 30 De Sanctis, Y.(10.4)33;(1 1) 164, 170,171 Descharnps, B. (7)40 Deshpande, R.M. (13) 212 De Silva, D.S. (10.3)17 de Silva, E.N. (1 1) 230 Desmurs, P. (4)41, 108;(7)39 de Souza, J.S. (14)187 Desurmont, D. (13) 302 Deubel, D.V. (1) 357 Devery, M.P. (13) 402 de Villar, A. (13) 436 De Wall, S.L. (2)131,148 Deykhina, N.A. (1 1) 307;(13) 445 Dezember, T. (14)127 Dghaym, R.D. (12)160 Diana, E.( I 1) 5 Diaz, J.C. (11) 146 Di Bella, S.(1) 129;(14)37 Dickson, R.S.(7)9;(13) 402 Diefenbach, M. (1) 77,144,330, 336 Dieguez, M. (13) 213,220 Dieter, RK. (2)2, 170 Dietrich, H.-J. (8)63 Dietrich, U.(14)78 Dietzel, P. (2) 134 Dbz, J. (2) 190;(12)1 1 Diez-Barra, E. (10.2)12 Digeser, M.H. (3) 16, 17;(7)33, 81 Dijkstra, T.W. (10.1)6 Dikarev, E.V. (13) 400 Dilshad, R (11) 101 Dilworth, J.R. (10.3)16 Ding, E.-R (1 1) 329,330;(13) 491,494 Ding, K.(3)55;(8) 126 Ding, S.(8)42 Dinger, M.B. (2)217 Dinnebier, RE. (2)147 Di Trapi, A. (1 1) 170 Ditzel, E.J. (9)125 Di Valentin, C.(1) 358,359 Dix, I. (13) 386 Dixneuf, P.H.(10.3)2;(12)53; (13) 12;(14)2 Dixon, D.A. (1) 18;(2)137;(5)

487 Draper, S.M.(1 1) 194;(13) 369, 377;(14)257 Dress, K.R.(8)85 Drew, M.G.B. (9)66;(13) 32 1, 322;(14)150,236,239 Drewello, T. (14) 1 17 Driess, A. (13) 417 Driess, M. (14)57 Drljaca, A. (6)87 Drouin, B.J. (1) 227;(13) 55 Drouin, M.(1) 264;(2)201;(1 1) 218,324 Drury, W.J., 111 (8)116 Du, B.-H. (4)14;(6)24 Du, C.X.(3) 38; (1 1) 283 Du, S.(7)79;(9) 11 1, 113, 156; (11) 105, 106,114;(13)460 hian, D.-H. (2) 172 Duarte, M.T.(10.4)6 DuM, T. (2)125;(4)74,77 Dubner, F. (14)224 Dubois, M.-A. (13) 104 Dubourg, A. (7)18, 19 Dubs, M. (13) 299 Dubuc, 1. (13) 104 Duchateau, R.(10.1)79 Duckett, S.B.(1) 403;(9)30;(1 1) 9 Duda, L. (10.1)40 Dudding, T. (8)116 D u e ,N.W. (11) 6;(13) 519;(14) 181 Duflos, J. (2)26 Duharnel, L. (2) 69,70 Dullaghan, C.A. (12)165;(13) 154 Dullweber, U.(13) 320 DuMez, D.D. (10.4)26 Dumitrescu, I.S.(7) 117 Dumitrescu, L.S.(7)117 Dumkina, E.V. (4)93 Dumond, Y.(2)89 Dunbar, K.R. (1 1) 206 Dunbar, L.(2)97 Dunbar, RC. (1) 22, 160 Duncan, J.H.(2)99,101 Dunn, J.A. (13) 362 Dunn, S.(5) 52 Dunn, V. (3)32 Dupas, G.(2)26 Dupont, J. (12)101 55 Duran, M.(1) 360,376;(13) 33 Dowdy, E.D. (4)131 Durant, A. (3)45 Dowling, C.M. (6)3 1 Duret, D. (1) 137;(14)101 Dowling, S.M.(13) 148 Downs,A.J. (1) 5 1,65;(6)73;(9) Durif, A. (13) 388 Durkin, J.J. (7)82 62;(13) 47 Dunant, M.C. (9)25.66 Doye, S. (14)33 Duval, P.B.(10.1)38.39; (13) Drake, J.E. (2)132

12 Djukic, J.-P. (2)109 Do, Y.(4)112; (5) 74 Dobler, C.(8)81 Dobos, S. (1) 202 Doedens, R.J. (4)33 Darfler, U.(14)210 Diiring, M. (2) 88 Mring, S.(1) 132;(6)7 Doerrer, L.H. (6)8,25;(10.1)27 DMz, K.-H. (2)109;(10.3)3,4; (12)9;(13) 16,21 Dogra, K.(8)23 Doherty, S.(12)37,39,85;(13) 349,350 Dolg, M.(1) 33,45,185; (4) 144 Dotgushin, F.M.(5) 54;(9)150; (1 1) 307,320;(13) 429,445 Domingo, L.R. (1) 37 Dorningos, A. (4)73 Donaldson, S.M.(8)55 Doddson, W.A. (13)298 Donchev, A. (1) 67;(6)72 Dong, T.-Y. (14)21 1 Dong, Y.-B. (1 1) 259 Donkervoort, J.G. (1) 308;(13) 194 Donnadieu, B. (1) 267;(10.1)7476;(10.2)14;(1 1) 96;(12) 22;(13) 314,343,453;(14) 66,88 Donners, J.J.J.M. (12)123;(13) 198 Donners, M.P.J. (12) 123;(13) 198,219 Donohoe, D.J. (5) 49 Donohoe, T.J. (2) 9;(8) 83 Donokey, M.C. (14)30 Donovan-Merkert, B.T. (1 2) 1 18 Dorizon, P. (1) 384 Dormond, A. (4)46,71,104,108 Dosa, P.I.(13)502 dos Santos, D.A. (1) 28 Dossetter, A.G. (8)102 Doucet, H.(13) 214 Douglas, A.G. (5) 7 Douglas, G. (13)320 Dousson, C.B.(13) 209 Douthwaite, RE. (12)203 Dovesi, S.(1) 304;(10.3)23.39,

Orgartometallic Chemistry

488

167; (14) 54,79 Dye, J.L. (2) 91 Dyson, P.J. (9) 14,49; (1 1) 86, 144, 148 Dzierba, C.D. (8) 115 Dzwiniel, T. (13) 279 Eaborn, C. (2) 42,50; (3) 36; (4) 96 Eager, M.D. (10.4) 12 Earl, W.L. (11) 210 Earle, M.J. (8) 135, 136 Ebel, M. (13) 266 Eberle, T. (4) 101; (10.1) 36 Ebihara, M.(13) 405 Echavarren, A.M. (2) 176; (12) 179 Ecker, A. (7) 104 Eckerle, P. (13) 202 Eckert, J. (9) 78 Eckert,M.(ll) 131 Edelbach, B.L.(13) 339 Edelmann, F.T. (4) 45,62,69 Edwards, A.J. (11) 252; (13) 438 Edwards, G.L. (2) 67 Edwards, P.G. (13) 132 Egan, J.W., Jr. (12) 122; (13) 99 Eggeling, E.B. (9) 34; (13) 504 Egold, H. (9) 89 Eguchi, T. (9) 28,29; (1 1) 7,35 Eguidbal, E. (11) 219; (12) 194, 196; (13) 506,507 Ehara, M.(1) 199 Ehlers, A. (1) 2 13 Ehlers, A.W. (1) 240 Eich, 0. (13) 499 Eichhiifer, A. (1 1) 39 Eigemann, S.-E. (10.4) 45; (13) 32 Eikenberg, D. (14) 108 Einstein, F.W.B. (10.3) 15; (13) 50

Eisch, J.J. (14) 67 Eisenberg, R. (1) 403 Eisenstein, 0. (1) 239,270,299, 300,306,398; (9) 101; (12) 33,200,223,235 Eisentriiger, F. (2) 191; (8) 44; (12) 211; (13) 186 Eke, U.B.(2) 36 Ekeberg, D. (1) 405; (13) 54 Eklund, J.C. (9) 67,69 El-Ahl, A.-A.S. (13) 298 Elass,A. (1) 166 Elding, L.I.(13) 152 El-Hamruni, S.M.(2) 42,50; (3) 36

El-Hiti, G.A. (2) 11, 11 1, 124 Elias, A.J. (14) 133 El-Khateeb, M.(1 1) 108 Ellis, D.D. ( 5 ) 53,55,56,60; (9) 85; (10.4) 43; (11) 98 Ellis, D.J. (1 1) 144, 148 Ellis, J.E. (10.2) 31 Ellman, J.A. (2) 29 Elschenbroich, C. (7) 83; (13) 344; (14) 10 Elsegood, M.R.J. (6) 23; (1 1) 63; (12) 37,85; (13) 349,350; (14) 58, 194 Elsevier, C.J. (1) 308; (12) 13; (13) 194 Elsner, 0. (14) 191 Elvers, A. (7) 37 Emge, T. (4) 97 Emge, T.J. (4) 50 Enderle, B. (11) 210 Enders, D. (14) 225 Endo, M.(8) 84 Enge, T.J. (14) 14 Engel, V. (1) 206 Engelbrecht, P.(14) 214 Englert, U.( 5 ) 75; (6) 18,20; (10.4)22;(11)73,291; (13) 272; (14) 87 Englich, U. (3) 2 Enkelmann, V.(13) 273,274,480 Enright, G.D. (1) 254; (6) 12; (9) 76; (1 1) 71, 111,262; (12) 38, 39,65; (13) 176,35 1,472, 482 Enriquez,J.(11)79 Ephritikhine, M. (14) 12,22 Epstein, L.M. (1) 293; (3) 39 Erabi, T. (14) 138 Erben, C.(13) 502 Erbstein, F. (4) 58,59 Erdem, S.S.(2) 61 Erdik, E. (3) 5 1 Eremenko, I.L.(4) 36,62 Eriksen, B.L.(2) 26 Eriksson, J. (3) 60 Eriksson, M.(2) 161 Erker, G.(1) 132, 134; (6) 4,7; (10.1) 35,40-45,69,70; (10.2) 19; (13) 4, 170, 171, 173,283,287,288; (14) 59, 69,80,145 Ermilov, A.Y. (4) 148 Emst, K.A. (13) 307 Emst, R.D. (13) 78,289,307 Emsting, J.M.(1) 308; (13) 194 Escudie, J. (1) 97; (7) 18, 19 Esfarjani, K.(1) 32 Espenson, J.H. (8) 89; (10.4) 8,

10-15, 17.20 Espinet, P.(12) 140; (13) 195, 41 1 Esteghamatian, M. (6) 12 Esteruelas, M.A. (1) 258,306; (12) 40,70,73,74, 125,235, 236; (13) 430 Esteruelas, R (1) 269 Ethcridge, Z.C. (10.1) 3 Ethridge, R. (1) 100 Etienne, M. (10.2) 13; (13)317 Etkin, N. (13) 279 Evans, C.E.B. (14) 167 E v a , D.A. (8) 107-111 Evans, D.J.(1 1) 82 Evans, D.R (1) 162; ( 5 ) 17 Evans, D.S.(13) 32 1 Evans, J. (13) 216 Evans, P.A. (8) 22,51 Evans, W.J. (4) 23,33, 34,38,61, 67.91; (14)4, 17, 18 Eveland, R.W. (9) 98; (1 1) 74,80; (12)48;(13)449 Ewart, S.W. (10.1) 25 Eyman, D.P. (6) 57 Eymery, F. (2) 1 Ezernitskaya, M.G.(13) 517 Erne, A. (3) 50 Fabbri, G. (2) 168 Fabre, S. (14) 198 Fabrizi, G. (8) 128 Fabrizi de Biani, F. (9) 140, 145; (1 1) 36,47,3 19 Fachinetti, G. (12) 34 F d e r , N.L.R (1) 162; ( 5 ) 17 Fksler, T.F. (1) 406 Fagin, A.A. (4) 36,61 Faibish, N.C. (2) 55 Faigl, F. (2) 116 Fajardo, M.(10.2) 1, 11,27; (13) 316; (14) 19 Falvello, L.R. (2) 190; (3) 33,40; (11) 219,327,328; (12) 172, 195-197; (13) 433,507 Fan, G.(6) 89 Fan, H.-J. (1) 324 Fan, J.-S. (9) 84; (10.4) 1 Fan, M.-F. (1) 274,275 Fan, Y.(1 1) 283 Faiianas, F.J. (1) 236; (13) 48 1 Fandos, R (1 1) 254; (13) 420 Fang, J.-M. (14) 141 Fang, X.(6) 21; (7) 80; (14) 49 Fanizzi, F.P. (12) 171 Fanwick, P.E.(10.1) 3,4,7; (10.2) 15, 18,32; (13) 174

489

Author Index Famjian, A.A. (1) 32 Farbre, B. (6)18 Farley, R.D. (10.3)33;(13) 240 Farook, A. (2)50 Farrar, D.H.(9) 124;(10.3)35; (11) 180;(13) 370 Farrel, I.R. (9)22 Farmgia, L.J.(9)133;(1 I) 27,66; (13)42 Fau, S.(4)78 Faure, M.(11) 107;(12)22 Fausbnann, P.(9) 129 Faille, S.J.(3)41;(1 1) 248 Fawcett, J. (7)111;(11) 104;(14) 172 Fawzi, R.(12)31; (14)206 Fedorova, E.E.(4)63 Fedushkin, I.L.(4)36,58,61,66 Feeder, N.(2)97 Feher, F.J. (14)106 Fehlner, T.P.(1) 247;(6)27;(1 1) 58,99, 183, 186,211,286; (14)118,235 Fehn, A. (14)126 Feistel, G.R.(4)65 Fekl, U. (12)138 Feldgus, S.(1) 374 Felding, J. (3) 12 Femoni, C. (9)140,145;(1 1) 36, 47,48,313 Feng, J. (1) 128;(1 1) 202,203 Feng, J.K. (1) 31,120 Feng, S.(13) 267 Feng, X.(1) 263;(4)5 1 Fenske, D. (1 1) 39,40,197 Ferencic, M.(1) 153 Ferguson, G. (12)230;(14)140 Ferguson, M.(6)52 F e r n , J. (1) 89 Fernanda, M. (10.4)6 Fernandeq D.(13) 376 FemBndez, E.J.(2)221;(13) 214 Femandeq M.(8)121 Fedndez, S. (3) 33;(1 1) 327; (12)36, 172 Fedndez-Baeza, J. (10.2)1, 12 Fedndez-Galon, R.(13) 140, 141 Fedndez-Lopez, M.(10.2)12 Fedndez-Megia, E.(13) 65 Ferrand, V. (1) 25 1; (9)1 15; (1 1) 102,302,303,305;(13) 469 Ferrara, M.L. (13)112,15 1 Ferrari, A.(13)200 Ferraris, D.(8) 116 Ferraudi, G.(9)71 Ferreira, E.M. (8)98 Ferrence, G.M.(4)72

Ferrer, M. (1 1) 3 1 1 Ferri, F. (4)43 Ferri, I. (14)87 F6niz, M.(1 1) 159 Fettinger, J.C. (1) 139;(10.1)8 Fickert, C.(1) 284 Field, L.D.(7)110; (12) 84;(13)

Ford,P.C. (9)21;(1 1) 225;(12)

19 Forissier, K. (7)36 Formica, M.(12)187;(13) 138 Fornib, 1.(1) 263;(2)188;(3) 40;(1 1) 50,219,328;(12) 194-197;(13) 433435,506, 507,509 58 Fomstal, K.J. (4)38; (14)4 Fields, S.C. (6)14 Forster, B.(5) 37 Fiem, J.L.G.(13) 420 Forsyth, C.M.(4)90 Filippou, A.C.(13)328;(14)94 Fortin, D. (2)201 Findeis, B.(14)198 Fortunak, J.M.(2)84 Finke, R.G.(1 1) 4 Fortunelti, A.(1) 262 Finniss, G.M.(1 1) 206 Forhrsio, C.(1) 263 Finocchiaro, S.(1 1) 141 Fossheim, R. (1) 102 Fiorini, C. (2) 114 Foster, D.F. (3) 63 Firth, A.V.(10.1)33 Foth,M.(12)202 Fischbeck, U. (7) 8 Foubelo, F. (2)7,70 Fischer, A. (1) 163;(4)45 Foucat, S.(1) 84.86 Fischer, C.(4)79 Fischer, H.(10.3)47,49,53;(12) Fouque, E.(8)37 Fox, B.S.(1) 335 49;(14)95 Fox, M.A. (5) 30 Fischer, I. (12)101 Fraanje, J. (9) 119;(1 1) 162;(13) Fischer, RA.(1) 64,70; (9)128 131 Fischer, R.D.(2)184;(4)12 Fraenkel, G.(1) 36;(2)99-101 Fischer, R.W. (10.4)18,21 F~agall,I.L. (1) 129;(14)37 Fish, R.H.(8)130 Frampton, C.S. (2)15 Fisher, T.(8) 134 Franceschi, F. (1) 3 16;(13) 183 Fletcher, D.A.(5) 2 Francis, M.D.(1) 233;(7)9,44, FBirke, U. (9)89;(1 1) 32,214, 45,82 290;(13) 224 Francke, V. (10.1)50;(13) 280; Flor, M.T.(13)213 (14)29 Florenciano, F. (13)129 Franck-Neumann, M.(13) 295, Flores, F.X. (10.3)43 301 Flores, H.(1) 24 Francl, M.M.(1) 8;(6)37 Flores, M.A.(5) 31; (10.1)15 Frange, B.(6)28 Floriani, C. (1) 280,281,301, Frank, H.(2)59 304,311,316;(2) 129, 146; Franken, A. (5) 60;(1 1) 98 (3) 19,30;(4)75.76;(10.1) Frankland, A.D.(1 2) I84 23,24;(10.2)6.7;(10.3) 7, Frank, R (10.2)14;(13) 343 23,28,39,55;(12)7;(13) Franz, A.K.(2)155 172, 183 Fraser-Reid, B.(1) 410 Florio, S.(2) 17 Frediani, P.(1 1) 141, 142;(13) Floris, B. (3) 64;(14) 132 216 Flower, K.R (13) 1 Freedman, D.(4)97 Fluck, E.(7)57,58 Frei, H.(9)24 Flynn, B.(13)236 Freiser, B.S. (1) 333;(12)17;(13) Fogarasi, G.(1) 225 329,330 Fogassy, K. (2) 116 Freitay, D.(14)5 1 Folting, K.(12)43 Freixa, 2.(1) 369 Fonikwar, W.(3) 16 Frenking, G.(1) 68-70,72,184, Fontal, B. (1 1) 146,147 201,241,312,357,408;(2) Fontani, M.(1 1) 334;(13) 35; 198;(4)78;(9)2,6-8,128, (14)135,253 139;(12)164;(13) 146,415 Fontani, R (1) 3 17;(9)54 Frenzel, U. (12)218 Font-Bdh, M.(14)139 Fressignb, C.(1) 2 Foos, E.E.(6)85;(7) 123 Friedrich, 0.(14)3 Ford, J.G.(8)50

490 Friedrich, S. (1 1) 249 Friend, J. (13)241 Fries, G. (7)94 Frigyes, D.(1) 225 Frison, G. (7)50 Fr6hlich, R (1) 132, 134;(2)8; (6)4,7;(10.1)35,40-45,69, 70;(10.2) 19;(10.3)50;(13) 170, 171, 173,283,287,288; (14)59,69,80,145 Froehner, W. (13)259 Froese, R.D.J. (1) 342;(13) 161 Frohlich, N.(9)2 Fronczek, F.R (14)207 Fronzoni, G. (1) 30 Frosch, W.(10.1)58;(13)515 Frost, B.J. (1) 229;(9)61 Frost, C.G. (8) 100 Fly&, M.D. (10.1)37-39;(10.2) 8;(10.3)14;(13) 167;(14) 54,79 Fu, G.C. (8)2,3;(14)81, 149, 175 Fu, P.-F. (4) 98 Fu, W. (9)41;(11) 92;(13) 454, 483 Fu, Z.(8) 13 Fuchs, A. (7)31,32 Fiustner, A. (8)40,43,45;(12) 79 Fuerte, A. (13)218 Fuess, H.(10.4)6 Fuji, K.(3)54;(13) 297 Fujii, A. (4)126 Fujii, N.(2) 169 Fujii, T.(1) 52 Fujikawa, T.(12)35 Fujimatsu, H.(3) 50 Fujimoto, H.(1) 388,391;(13) 117 Fujimoto, M.(12)199 Fujita, E.(6)6 Fujita, K.(8) 14;(13)264 Fujita, M. (2)32 Fujiwam H.(2)32 Fujiwara, Y.(4) 141, 142 Fukase, K.(13)374 Fukase, Y.(13) 374 Fukuda, T.(2) 112 Fukuhara, H.(8)68 Fukumoto, H.(4) 1 16 Fukumoto, Y.(8)33;(9) 107;(1 1) 135, 139 Fukuoka, A. (1 1) 222;(1 3) 212, 229; (14)24 Fukushima, Y.(1 1) 222 Fukuta, Y.(1 1) 204 Fukuzawa, S.4. (4)35

F u ~H.-K. , (1 1) 30,284 Funaioli, T. (12)34 Fun& W.K-M. (1 1) 229 Furin, G.G. (1) 293;(3)39;(10.1) 55

Furuta, H.(2) 199 Fusek, J. (5)48 Gabaitsekgosi, R.(2)33 Gabbd, F.P. (3)35,42;(6)35 Gabor, B.(7)60;(1 3) 79 Gade, L.H.(1 1) 249;(14) 198 Gagliardini, V.(1 3) 271 Gais, H.(8)27 Gal, A.W. (12)120,123;(13) 198,219 Gatakhov, M.V. (10.2)26;(10.3) 25 Gaian, F. (1) 323 Galindo, A. (1) 260;(13) 3 Gallucci, J.C.(12)190; (14)6 Galvk, A.M. (10.4)6 Gamasa, M.P. (1) 378;(2) 190; (12) 11,68,81,86 Gambarotb, S.(2)125;(4)74, 77;(10.2)4 Gambaryan, N.P.(1) 293;(3) 39 Gamblin, S.D.(1) 16 Gamelas, C.A. (13)41 Ganicz, T.(4)96 Gansauer, A. (14)35 Ganter, B.(6) I8 Ganter, C.(12)154 Gao, H.(13) 217 G~o,J.-X.( I 1) 143 Gao, Q.(2) 115 G ~ oW.-Q. , (1 1) 259 Gao, X.L. (10.1)2 Gao, Y. (13) 413 Garcia, A.M. (1 1) 25 Garcia, B.(14)221 Garcia, M.E. (10.3)57,58;(14) 114,116 Garcia, M.M.(14) 173 Garcia-Ekpafia, E.(14)193 Garcia Fiem, J.L. (1 1) 254 Garcia-Granda, S.(1) 378;(2) 190;(1 1) 314;(12)68 Garcia-Mellado, 0.(1 1) 79 G ~ i a - Y e b - C.(1) 306;(10.2) 11; (12)235;(13)316 Gardiner, M.G.(12)205,207 Gar& R.(13) 241 Gariepy, F.-B. (13) 104 Garland,M.T. (1) 248,251; (9) 115, 134;(1 1) 19,25, 102, 200-203;(13) 336

Orgariometallic Chemistry Garlaschelli, L. (1 1) 20,34 Gamas, J. (1 1) 235 Garnovskii, A.D. (9)1 Ganioch, R.M.(5) 5 1,52 Gaschler, W.(1) 154 Gaspa~~ini, F. (8) 128 Gateau, C. (13) 301 Gately, D.A. (14)83 Gates, B.C. (1 1) 207-210,321 Gattinger, I. (1) 140 Gau, H.-M. (13)365 Gaudinski, C.M. (2) 181;(9) 141 Gaumont, A.C. (12) 162 Gautheron, B. (14)6, 154,215 Gautier, R.(7) 102;(1 1) 15, 18 Gavel, N.T.(2)90;(13) 254 Gbureck, A. (1) 284 Ge, M.F. (1) 120, 128 Gebcrt, S.(1 1) 318;(13)497 Geerlins, P.(1) 93 Geftakis, S.(9)32 Gchrhus, B. (2)40;(7)62 Geib, S.J. (10.2)21;(10.3)48 Geiger, W.E.(5) 46;(1 1) 189; (12)118;(13) 197,323;(14) 106, 163,244 Geiseler, G. (1) 23;(2)46 Geistcr, G. (13) 108 Gelabert, R.(1) 27 1 Gelas, J. (13) 300 Geldbach, T.(12)204 Gemel, C.(1) 153; (12)225;(13) 306 Genge, A.R.J. (7) 114;(9)80 Genizi, E.(13)26 1 Gentil, S.(14)6 Geoffroy, M.(7)56 Geoffroy, P.(13)295 Georg, A. (1 3) 269 Gcorganopoulou, D.(1 1) 71; (1 2) 38;(13)351 George, D.S.A. (12) 129;(13)432 GCrard, H.(1) 239,299,300;(9) 101;(12)200,223 Geremina, S.(1) 285,301 Gcrhard, A. (1) 72 Gcrisch, M.(1 1) 221;(13)149 Gerlach, C.P.(6)43;(10.1)9 Gervasio, G.(1 1) 145 Gharagozloo-Hubmann, K.(1) 44; (2)126 Ghcdini, M.(12) 168 Ghelli, S. (13) 31 Ghilardi, C.A. (3) 34 Ghitti, A. (1 1) 136 Ghiviriga, I. (10.3)56 Ghose, S.(9) 143;(1 1) 256 Ghosez, L.(8) 106

Author Index Ghosh, S. (6) 27; (1 1) 286; (14) 118

Giannini, L. (1) 304; (3) 30; (10.3) 23,28,55 Gibson, A.E. (14) 194 Gibson, D.H. (10.4) 24 Gibson, S.E. (13) 11, 13,398 Gibson, V.C. (1) 347; (6) 46,47; (10.2) 23; (10.3) 1, 16, 17; (12) 15; (13) 28,57 Gielen, M.(1) 91,93 Gielens, E. (10.1) 6 Giering, W.P. (12) 144, (13) 232 Giesbrecht, G.R (6) 43; (10.1) 9 Giesemann, J. (4) 107, 109 Giessner-Prettre, C. (1) 2 Gilbert, A.T. (4) 50; (14) 14 Gilbertson, R.D.(12) 115 Gilbertson, S.R(8) 13 Gill, K. (2) 13 Gillemot, G. (10.3) 28 Gillon, A.L. (1 1) 66 Gil-Rubio, J. (12) 13 1; (13) 90 Gimbert, Y. (13) 388 Gimeno, J. (1) 378; (2) 190; (12) 11,68,81,86; (14) 185 Gimeno, M.C.(2) 218-220; (5) 40.4 1; (1 1) 240-242,245; (14) 152, 158 Gingerich, K.A. (1) 118 Ginzburg, A.G. (11) 307; (13) 445 Giordana, F. (13) 112 Giordano, R. (1 1) 145 Girgsdies, F. (4) 58,63,66; (6) 10 Girolami, G.S. (2) 38; (12) 25,45, 221; (13) 46,84; (14) 147 Gisdakis, P. (1) 145, 358, 359 Gladysz, J.A. (10.4) 40,41; (12) 198 Glaesemann, K.R (1) 198 Glanz, M. (4) 8 Glasgow, K.C. (13) 347 Glassey, W.V. (1) 176; (10.2) 29 Gleason, J.D. (8) 115 Gleason, J.L. (8) 103 Gleich, D. (1) 297,368; (12) 2 17 Gleiter, R (I) 319; (13) 275,338, 360 Glidewell, C. (14) 140 Glorius, F. (8) 24 Glowiak, T. (9) 58; (13) 319 Glueck, D.S. (12) 169 Gobetto, R. (1 1) 159 Gobley, 0. (14) 6 Godbout, N. (1) 243 Goddard, R (7) 52; (9) 137; (11) 215; (12) 146; (13)407 Godefioy, I. (1) 251; (9) 115; (11)

102

Godfrey, RD. (5) 32 Godfrey, S.M.(7) 106 Godoy, F. (9) 47; (10.4) 28,34 Gijbel, A. (1) 181; (13) 292,299

Goebel, L. (1) 155 Goebel, M.(14) 117 Goerls, H. (10.1) 5; (13) 79 Goesmann, H. (13) 248,249 Goggin, P.L. (1) 313; (13) 106 Gogoll, A. (3) 32 Goh, L.Y. (1 1) 55 Gokel, G.W. (2) 131, 148 Goldberg, K.I. (12) 141 Golden, J.T. (2) 37; (12) 1 12 Goldfuss, B. (3) 29 Goldschmidt, 2.(13) 26 1 Golla, W. (7) 84 Gomes, P.T.(12) 203 Mrnez, A.V. (12) 73 Mmez, C. (2) 104,106 Gbmez, J. (2) 188; (1 1) 50,328; (12) 195,197; (13) 433,435, 509 Wmez, J.L.(10.3) 35; (13) 370 Gomez, M.(10.2) 26; (13) 131 Gomez, R. (10.1) 34 Gomez-Elipe, P. (2) 140; (12) 4 Gomez-Gallego, N. (10.3) 40 Gomez-Garcia, R. (10.1) 30 Gtjmez-Sal, P. (10.1) 34,64; (10.2) 22; (10.3) 25; (14) 41 Go@ves, I.S. (1) 173; (13) 38; (14) 115 Gonsalves, A.M.d'A.R (13) 2 13 Gontcharov, A.V. (8) 86 Godlez-Blanco, 0. (1) 179,218; (13) 290 Goodman, J.T. (10.1) 14 Goodson, P.A. (12) 106; (13) 404 Goodwin, N.J. (1 1) 104; (14) 172 Goossen, L.J. (8) 85 Goral, V.N. (14) 123 Gordon, J.C. (4) 39,40 Gordon, K.C. (14) 192,195 Gordon, M.S.(1) 198,364; (10.4) 11 Gorel'skii, S.I. (1) 211 Gormri-Magnet, S. (7) 24,25 G o r n i e H. (2) 152, 180; (3) 26; (7) 24,25,28; (9) 33; (14) 5 G o m , S.M.(12) 165; (13) 154 Gosberg, A. (13) 208 Gosage, RA. (2) 127; (10.3) 19, 20; (12) 77; (13) 72,418; (14) 27 Gdo, K. (6) 34 Gottfriedsen, J. (3) 18

49 1 Gottlich, R. (8) 91 Gottlieb, H.E.(13) 261 Gottschalk-Gaudig, T. (1) 239 Goubitz, K. (13) 131 Gould, 1.R (1) 347; (12) 15; (13) 57

Gountchev, T.I. (4) 80,8 1 Goursot, A. (1) 39,40 Grabowski, E.J.J. (3) 56 Grachova, E.V. (9) 150; (1 1) 320 Gmia-Yuste, S. (10.2) 1 GraE, D.D. (10.1) 18 Graf, V.W. (2) 150 Graham, J.P. (I) 183; (13) 157 Graham, T.W.(12) 42 Gmiff, C. (9) 104; (1 1) 109; (12' 153

Grandberg, K.1. (1 1) 29 Grande, C. (12) 185 Granell, J. (13) 130 GIXB, G. (8) 7 Grassian, V.H. (1) 14 Greatrex, R (5) 28 Greci, M.A. (4) 34,61,67,91; (14) 18

Gree, D. (13) 373

Gr&, R.(1) 179; (13) 290,373 Green, A. (14) 143 Grecn, D.C. (3) 2 Green, J.C. (1) 135, .' 88,266; (10.1) 10; (13) 34.'; (14) 98

Green, J.R (13) 396,4:6 Green, M. (7) 29; (13) 203; (14) 105,106,246

Green, M.L.H.(6) 8,25; (10.1) 27,28,61; (12) 203; (13) 421; (14) 68,74 Green, T.M. (13) 47 Greene, A.E. (13) 388 Greene, T.M.(1) 5 1; (6) 73; (9) 62 Greenwell, C.H. (14) 239 Gregiorio, J.R (10.4) 19 Greiner, A. (4) 11, 115, 120, 129 Grellicr, M. (12) 101 Grcpioni, F. (9) 97, 133; (1 1) 27, 66; (14) 257 Grevels, F.-W. (13) 49; (14) 148 Gridnev, I.D. (1) 1 15 Griffiths, E.A.H. (1) 347; (12) 15; (13) 57 Grime, R.W. (10.3) 33; (13) 240 Grimes, R.N. (5) 46; (13) 2; (14) 244 Gnmmond, B.J. (14) 48 Grisel, G.R (13) 148 Grison, C. (2) 80 Grob,T. (4) 11

492

Grobe, J. (7) 84 Grobelny, Z. (2) 92 Grber, G. (13) 4 14 Groeneveld, J.A. (1) 204,205 Gropen, 0. (1) 407 Grosche, M.(6) 29 Gross, C.L.(12) 25; (13) 84 Grossheimann, G.(14) 223 Grotjahn, D.B.(13) 308 Grubbs, R.H. (8) 41,42,48,56 Griin, K.(7)65 Griiner, B.( 5 ) 28,47 Grii-her, H.(7)21 Gnmer, B. ( 5 ) 19,48 Guan, J. (4) 12 Guari, Y.(12) 2 Gubin, S.P.(1) 211 Gudat, D.(1) 5; (2) 98; (7)17, 23 Guckel, C.(7) 81 Giinther, K.(7)59 Guerchais, V. (12) 23 1; (13) 60 Guerin, C.(10.2) 14; (13) 343 Guerin, F. (6) 71; (7) 22; (10.1) 2, 3 1,32; (14) 34 Guerra, G. (1) 346 Guijmo, D. (2) 77 Guillaumont, D. (1) 208,209; (9) 68 Guillemin, J.C. (7) 91 Guillemot, M.(12) 71 Guillon, E.(9) 144; (1 1) 275,276 Guillou, C. (13) 253,255 Guiry, P.J. (8) 17; (13) 134 Gulino, A. (I) 129; (14) 37 Gun'ko, Y.K.(2) 130; (4) 16, 17 GUMW,T.B. (13) 179,180 GUO,D.-S. (1 1) 259 Guo, G.4. (2) 202; (1 1) 233; (13) 5 12 GUO,J.-P. (2) 139; (12) 175; (14) 60 Guo, L.(13) 479 Guo, R (13) 486 Gupta, H.K. (14) 205 Gupta, N. (7) 46 Gupta, S.(7) 64 Gusev, O.V. (13) 305 Gutikrrez, A. (2) 7,70 GutiBrrez, J.A. (13) 78 GutiBrrez-Perez, R (1 1) 79 Gutierrez-Puebla, E. (1) 269,306; (12) 98,228,235 Guzei, LA. (4) 3; (9) 36; (13) 39 Guyr, 0.1.(10.2) 5 Gyepes, R. (10.1) 47,56,57; (13) 164,313,516; (14) 203 Gyr, T.(1) 148

Organometallic Chemistry Haak, E.(14) 33 Haak, S.(1 1) 303-306 Haaland, A. (1) 84 Haar, C.M.(12) 144; (13) 232 Habereder, T. (14) 248 Habermann,A.-I(. (2) 3 1 Hachey, M.R (1) 206 Hachiya, T. (9) 102; (1 1) 84 Hackman, M.(14) 78 Hagadorn, J.R. (6) 43; (10.1) 9 Hagelin, H.(1) 381-383; (13) 107, 118, 119 Hahn, c. (12) 109 Hahn, F.E. (12) 202; (13) 30 Hahn, J.M. (10.1) 65; (10.3) 21; (13) 163; (14) 77 Haider, J.J. (10.4) 21 Haiduc, I. (2) 132; (7) 117 Halamek, E. (5) 5 1 Hales, N.J.(13) 398 Halet, J.-F. (1) 252,255; (7) 102; (11) 15, 18,264; (13) 443, 452 Haley, M.M.(12) 115 Hall, B.C. (12) 59,60; (13) 477 Hall, M.B.(1) 123,294,404; (9) 135; (12) 89; (13) 100 Hall, R.J. (1) 117 Hallberg, A. (1) 387; (8) 132 Haller, J. (1) 355 Hallman, K. (1) 386,387 Halteman, R.L.(14) 46 Halut, S.(10.3) 57; (10.4) 19 Hambley, T.W.(12) 84; (13) 58 Hamed, 0. (13) 123 Hamilton, A. (2) 111 Hamley, P. (8) 54 Hampel, F. (13) 66,67 Han, J.W. (11) 260; (14) 39 Han,Y.(4) 112 Hanaola, M.(13) 393 Handel, H. (14) 196 Hanif, K.M.(1 1) 100,101 Hanks, J.R (7) 39 Hanna, J.V. (2) 193 Hannemann, F. (6) 32 Hannu, M.S.(12) 77; (13) 72 Hanquet, B. (6) 28 Hansen, H.-J. (13) 238 Hansen, K.B. (8) 120 Hansen,S.M.(1) 298; (8) 44;(12) 210,211 Hansen, T. (8) 61,62 Hanson, P.R(8) 52,53,59 Hanss, D.(13) 295 Hanusa, T.P. (3) 20; (14) 89 Hanzawa,Y.(14)61 Hao, H. (6) 51

Hao, L.(10.1) 59; (13) 109; (14) 170 Haquette, P.(10.4) 4 1 Ham, K.(3) 52 Ham, R (2) 72; (10.1) 73; (13) 168; (14) 56,62 Harakas,G.N. ( 5 ) 39 Hardcastle, K.I. (I 1) 153, 166; (13) 372 Harder, S.(14) 7 Hardesty, J.H. (1) 377; (13) 333; (14) 252 Hardie, M.J. ( 5 ) 3.33 Hardie, R.J. ( 5 ) 32 Harding, D.J.(13) 324 Harding, I.S. (6) 39 Harding, R.A. (9) 29; (1 1) 35 Haqi, RR (2) 9 Hiirkhen, A.U. (4) 8; (9) 146; ( I 1) 301 Harlan, C.J.(6) 6 . Harlow, K.J. (12) 52,80 H a m , W.D. (13) 82,83,179, 180 Harmat, V. (2) 116 Harmesen, R.J. (10.1) 79 Harms, K.(1) 23; (2) 46.66; (4) 11,78, 115; (7) 83, 102; (1 1) 83; (13) 344; (14) 10 Harpp, D.N. (14) 110 Harris,C.B.(1) 210; (9) 3,24; (12) 14 Hamson, D.G. (7) 22; (10.1) 2,3 1 Harrity, J.P.A. (8) 39, 54; (12) 2 19 Mod,J.F. (10.1) 59 Hartbaum, C.(10.3) 47 Had, F. (1) 253; (9) 121; (11) 160-163 Hartmann, S.(1 1) 214 Hartwig, J.F. (8) 4, 10,75; (14) 120,230 Harvey,J.N.(1) 330 Harvey, M.J. (3) 20 Harvey, P.D.(1) 264; (2) 201; (1 I) 218,324 Hanvell, D.E.(3) 28; ( 5 ) 36 Hascall, T. (6) 6, 11; (10.1) 65, 66; (10.3) 21; (13) 163; (14) 77, 109 Hashimoto, M.(4) 70; (13) 92 Hashimoto, S.(1) 20; (8) 64 Hashimoto, Y.(10.4) 7 Haskel, A. (12) 149 Hassan, W.W. (14) 189 Hassenberg, K.(14) 168 Hassner, L. (12) 27 Hatanaka, Y.(1 1) 129

Author Index Hatin, J.M. (14) 109 Hatop, H. (6) 63 Hattersley, A.D. (11) 333 Hauber, S.-0. (4) 21 Hauge, R.H. (10.4) 42 Haukka, M. (1) 409 Haupt, H.-J. (1 1) 32,214,290; (13) 224

Haupt, M. (1 1) 220 Haussinger, D. (10.1) 27; (12) 203 Havighurst, M.D. (5) 20 Havlas, Z. (1) 44; (2) 126 Hawes, A.C. (2) 11 Hawkes, G.E.(6) 39 Hawthorne, M.F. (3) 5,28; (5) 15, 36,39,54

493 172

Hendrickx, M.(1) 119,122 Henling, L.M. (13) 355; (14) 55 Henner, B. (10.2) 14; (13) 343 Hennessy, A.J. (8) 17 Henry, P.M. (13) 123 Hem, J.V.(13) 521 Herber, U. (12) 127 Herberhold, M. (5) 68-70; (14) 160,210,218

Herberich, G.E.(6) 28; (1 1) 29 I Herberich, J. (6) 18,20 Herbst, K. (13) 337 Herdtweck, E. (1) 70, 173,359; (6) 29; (9)128; (12) 109; (13) 38,41; (14) 115

Hay, B.P. (1) 18,21,26; (2) 137 Hayakawa, F. (4) 15 1 Hayakawa, H. (2) 119 Hayashi, A. (1) 3 18 Hayashi, R. (6) 14 Hayashi, R.K.(9) 157; (1 1) 5 1 Hayashi, T. (8) 65-67; (13) 124 Hayes, C.J. (2) 33; (8) 16 Hayward, O.D. (13) 324 Hazell, R.G. (8) 105 He, L. (9) 60 He, Y.-X. (13) 181 Healy, P.C. (1 1) 230 Heaton, B.T. (9) 28,29,31, 150;

Herker, M.A. (1) 140; (14) 137 Hermanek, S. (5) 9 Hermann, H. (13) 256 Hermann, J. (1) 11 Hermans, S. (1 1) 45 Hermansson, K. (5) 10 Hernandes, M.Z.(1) 55; (6) 93 Hernandez, C.(1 I ) 254; (13) 420 Hernandez, E. (13) 4 16; (14) 76 Hernandez-Gruel, M.A.F. (13)

(1 1) 7,8,35,320; (12) 95 Heck, J. (1) 133; (13) 357; (14) 9 Heckmann, G. (7) 57.58 Hedberg, C. (1) 41 1; (3) 61 Hedelt, R. (13) 315 Heeg, M.J. (1) 147; (4) 3,4 Heiberg, H. (1) 407 Heig, M.J. (14) 200 Heigl, O.M. (14) 137 Heilweil, E.J. (14) 119 Heinemann, F.W.(7) 30,37 Heinicke, J. (7) 46 Heinl, T.(1) 36 Heinze, K. (1) 142,238; (10.4) 36,37 Heitz, W. (4) 115 Helberg, L.E. (13) 179 Heller, D. (8) 95; (13) 205 Helmchen, G. (8) 21 Hemer, T.A. (14) 119 Hemod, RC. (14) 106 Hempenius, M.A. (2) 141; (14) 190 Henderson, K.W.(1) 25,105 Henderson, R A . (10.4) 6; (12) 142 Henderson, W. (2) 217; (3) 41; (1 1) 11, 104,248; (14) 151,

Herring, F.G.(2) 201 Herrmann, K.(4) 48 Herrmann, M. (1 1) 190; (13) 484;

440; (14) 52

Hernandez-Molina, R (1 1) 255 Heropoulos, G.A. (2) 122, 123, 136

(14) 255

Herrmann, R.(14) 144 Herrmann, W.A. (1) 297,368; (8) 40; (10.4) 18,21; (12) 6, 176, 205,207,208,217,218

Herson, P. (14) 103 Hertel, F. (14) 160 Hertwig, R.H.(1) 161; (4) 147 Herwig, J. (8) 29 Herzberg, D. (13) 256,257 Herzig, T. (14) 238 Herzog, A. (5) 15.39 Hess, A. (10.3) 12; (14) 124 Hcsschcnbrouck, J. ( I ) 301 Hessen, B. (4) 103; (10.1) 6; (13) 285

Heyduck, A.F. (6) 13 Hey-Hawkins, E. (14) 40 Hibbert, T.G.(5) 30 Hibbs, D.E. (1) 233; (7) 9, 16,45, 113; (9) 50

Hiberty, P.C. (7) 5 1 Hicks, F.A. (8) 36 Hicks, O.M. (6) 26; (10.4) 3 Hidai, M. (1) 257; (8) 99; (1 1)

250,251,269,300; (13) 468; (14) 176,222 Hieringer, W. (1) 297; (12) 217 Higgins, T.B. (14) 232 Higgitt, C.L. (9) 47; (10.4) 34; (12) 108 Hii, K.K.(13) 524; (14) 155 Hikichi, S. (12) 21; (14) 249 Hildbrand, S. (8) 23 Hilfenhaus, P. (1) 374 Hill, A.F. (7) 3; (12) 52, 75,79, 80 Hill, G.S.(12) 151; (13) 241 Hill, M.S. (4) 96 Hill, R.O. (1) 363 Hiller, W. (1) 140; (14) 137 Hillicr, A.C. (1 1) 63 Hillier, I.H. (1) 117 Hilmcrsson, G.(2) 56-58 Hilts, R.W. (12) 129; (13) 432 Himmel, H.-J. (1) 51; (6) 73 Hinkle, P.V.(12) 116 Hinrichs, R.Z.(4) 155 Hiraki, H. (1 2) 35 Hiraki, K. (13) 71 Hirakida, M. (14) 209 Hirano, M. (1 1) 13; (12) 28,29; (13) 74,229; (14) 24 Hirao, T. (14) 44 Hirosawa, C. (8) 34 Hirotani, R.(1 3) 403 Hirscb, C. (7) 89,98, 99 Hirth, U.A. (7) 65 Hirva, P. (1) 409 Hitchcock, P.B.(1) 233; (2) 40, 42,50,81,82,93-95, 130, 215; (3) 1,36; (4) 16, 17,96; (6) 45; (7) 7,8,35,39,43,45, 61,62,82; (10.1) 10,72; (12) 204; (13) 399; (14) 128,187 Hitchcock, S.R.(6) 14 Hnyk, D. (5) 24 Ho, D.M. (10.4) 25 Hoare, J.L. (12) 158 Hobert, A. (2) 3 1 Hoch, J. (13) 338 Hocklcss, D.C.R. (9) 149; (1 1) 272-274; (13) 69,341 Hodge, A.J. (12) 62 Hodgson, D.M.(2) 16 Hodgson, K.O.(4) 152 Hodons, B.L. (14) 81, 175 Hoerter, J.M. (12) 106; (13) 404 Horz, M.R. (10.3) 12 Hoff, C.D.(1) 143; (9) 53 Hoffman, D.M.(10.4) 32 Hofiann, H. (1) 70; (9) 128; (13) 266

494

Hoffmann, M. (5) 24 Hoffmann, R.W.(2) 66,96 Hofmann, M.(1) 23; (2) 46; (5) 27

Hofmann, P. (1) 298; (2) 191; (8) 44; (12) 210,211; (13) 186 Hogarth, G. (1) 249; (9) 65; (1 1) 71,97; (12) 38,39, 85; (13) 350,35 1,45 1 Hoic, D.A. (14) 149 Holbrey, J.D. (8) 136 Holl, M.M.B. (1) 101 Holladay, J.E.(2) 102 Hdand, A.W. (12) 141 Hollatz, C.(1 1) 237 Holmes, N.J. (7) 114, 115 Holmquist, R. (1 1) 153 Holthausen, M.C.(7) 52; (1 1) 2 15 Holub, J. (5) 48 Holubec, A.A. (8) 63 Holubova, J. (2) 190 Holz, J. (8) 95; (13) 205 Homrighausen, C.(1 1) 244; (13) 302 Hong, F.-E. (1 1) 193; (13) 365, 383,488 Hong, G.(1) 185; (4) 144 Hong, J.-B. (13) 14 Hong, M. (1 1) 30 Hope, H. (13) 378 Hopfmann, T. (13) 258 Hopkins, M.D.(10.3) 37 Hopman, M. (2) 50 Hoppe, D.(I) 35,36; (2) 8,59,60 Hopper, D.W.(8) 61 Hor, T.S.A. (14) 15 1 Horitek, M. (10.1) 47,53,56,57; (13) 161, 164,268,313,342; (14) 3 1,203 Homg, K.-M. (10.3) 34; (13) 51 Homung, F.M. (12) 83 Honocks, B.R (14) 194 Horswell, S.L. (1 1) 38 Hos, J.P. (11) 122; (13) 466 H a g , A. (10.4) 22; (13) 272 Hoskin, A.J. (10.1) 33 Hosmane, N.S.(2) 47; (4) 88; (5) 44,45 Hosmane, S.N. (2) 47; (5) 45 Hosokawa, T. (13) 410 Hosomi, A. (2) 209 Hcwseinzadeh, R. (14) 227 Hou, H. ( I 1) 283 Hou, Z. (4) 35, 105, 106, 121 Houbrechts, S. (12) 68 Houk, K.N. (1) 164,355,356; (3) 29; (13) 235 Houlton, A. (14) 194

Housecroft, C.E. (5) 4; (1 1) 167, 332,333; (13) 498,499

Hovestad, N.J. (13) 504 Hoveyda, A.H. (8) 39,49,50, 115;(12)219

Howard, J.A.K. (1) 272; (5) 30, 57; (10.3) 17;(11)29;(14) 143, 154 Howe, P.R.(1) 403 Howells, M.E. (13) 293 Howland, K. (1) 406 Hoy, V.J.(10.3) 17 Hoyau, S. (1) 9 Hoye, T.R. (8) 55 Hrabusa, J.M. (13) 479 Hradsky, A. (14) 123 Hmciar, P. (1) 169 Hsich, C.-H, (1) 230; (9) 74 Hsieh, Y.-S.(13) 260 HSU,M.-A. (1 1) 68.70; (13) 441, 442,471 Hu, C.-C.(10.3) 34; (13) 5 I Hu, C.-H.(1) 230; (9) 74 Hu, N.-X.(6) 12 Hu, P.-F. (13) 143 Hu, Q.-M. (9) 94; (1 1) 259; (13) 29 Hu, Q.4. (3) 59 Hu, X.(3) 57; (8) 7 1 Huang, D.(1) 299; (12) 43,223 Huang, H. (2) 54 Huang, J. (4) 42; (8) 6-8; (12) 2 14-2 16 Huang, J.4. (2) 177 Huang, L. (11) 212 Huang, R. (10.4) 14 Huang, R.H. (2) 91 Huang, S. (2) 115 T.-K. (1 1) 155; (1 3) 474 W. (9) 39; (1 1) 173 w.4. (3) 59 X.-Y. (4) 2,5, 15,49; (1 1) 187,259,265; (13) 492,493, 495,496 Hum& Y.-C. (13) 365 Huang, 2.(4) 26.51 Z.-E. (4) 2,5,7,49 Huangh, X. (2) 172 Hubbard, J.L. (13) 308 Hubbard, R.L.(3) 15 Huch, V. (2) 15 1 Hudeczek, P. (1) 141 Hudson, A. (2) 27 Hudson, S.A. (12) 174 Hiibler, K. (7) 2 Hue- F.F. (2) 104 Huertas, C. (10.2) 27; (14) 19 Hucrtas, S. (2) 213

Orgattometallic Chemistry Huffman, J.C. (1) 239; (13) 347 Hughes, A.K. (5) 57 Hughes, D.L.(14) 187 Hughes, R.P. (12) 110, 122; (13) 99

Hughes, S.J.(1) 167, 168 Huh, W.S. (14) 38 Huhmann-Vincent, J. (9) 83 Hui, J.W.-S. (1 1) 3 10 Hultzsch, K.C. (4) 47, 101, 110; (14) 20

Humphrey, D.G. (1) 249; (9) 65, 69

Humphrey, M.G.(9) 149, 152; (1 1) 270-274; (12) 66

Humphrey, P.A. (1) 252; (13) 452 Hung, C.-K. (13) 365 Hung, S.Y.-W. ( I I ) 298 Hunger, M. (14) 112 Hunks, W.J.(1 1) 243; (13) 362 Hunstock, E. ( I ) 219; (9) 4; (11) 17

Huo, S. (2) 72; (14) 56 Hupe, E. (13) 127 Hursthouse, M.B.(1) 233; (2) 153,221; (6) 16; (7) 9,45, 113;(9)50;(10.1)46;(11) 100, 101, 165; (12) 162; (13) 132,284; (14) 189 Hush, N.S.(1) 392 Hussain, Z.J. (13) 24 1 Hussein, K. (1) 273 Hutchinson, J.E. (1 1) 44 Huttner, G. (2) 208; (1 3) 4 17, 419; (14) 157 Huy, N.H.T. (7) 68 H w & C.-S.(2) 192 H w g , J.-W. (4) 112; (5) 74 H w g , W.-S. (1 1) 75 HWU,C.4.(10.4) 27 Hyla-Krispin, 1. (1) 3 19; (13) 338 Hyldtoft, L. (3) 53

Iapalucci, M.C. (9) 140, 145, 155; (11) 36,47,48,312,

313

Ibers, J.A. (4) 1 Ibrahim, A.M.A. (2) 184 Ibuka, T. (2) 169; (13) 296 Ichikawa, H. (2) 85,86 Ichikawa, M. (1) 234; (9) 5 1; (1 1) 222; (13) 212

Ichimura, AS. (2) 91 Ie, Y.(8)-74; (9) 106; (11) 130 Ienco, A. (1) 260,3 17,379; (3) 34; (9) 54; (12) 90; (13) 3,35

Igarashi, T.(2) 19 i g a ~ A. , (10.1) 74-76; (13) 3 14;

Aulhor Index (14)66,88 Iggo,J.A. (9)31, 150;(1 1) 8,320 Iglesias,M.(13)218

495

203;(1 4)246 Jehle, H. (1) 284 Jclinek, T.(5)28 Jellis, P.A. (5) 53,55;(9)85; Ignatovich, L.(1) 88 (10.4)43;(1 1)297 Ihara, E.(4)44,95,117 Jcnkins, C.N.(14) 98 Iida, T.(8)91 Jenkins, H.A. (1 1) 322;(12)148, Ikada, T. (1 1) 269 170 Ikariya, T. (9) 102;(1 1) 84;(13) Jennings, M.C.(2)223;(1 1) 243, 202 308,309;(12)157 Ikeda, I. (14) 183 Jcnsen, K.B. (8) 105 Ikeda, S.(8) 69 Jaballas, J. (5) 1 1,29 Jeon, H.-J. (1 1) 78 Ikuta, s.(1) 20 Jeon, S.-J. (14)229 Jacke, J. (13)49 Ilg, K.(12) 133 Jeong, J.H. (14)229 Jackson, J.E. (2)91 Ilyin, M.M.(14)216 JCrome, D. (1 1) 206 Jackson, P.(1) 77 Imai, D.(13)264 Jerzykiewicz, L.(1 1) 213; (1 3) Jacob, C.(3) 24;(12)95 Imamoto, T.(4) 121;(13)207 408;(14)260,261 Jacob, J. (10.4)10 Imanishi, M. (12)104; (13) 223 Jcwson, J.D. (13) 85 Imhof, W. (1) 181;(8) 31; (9)95; Jacob, K.(14) 135 J'far, M.H.(13)510 Jacob, R.G.(2)74 (1 1) 134;(13)292,299 Jha, N.K.(7)96 Jacobi, A. (2)208;(13) 419 h i , C.(14)214 . Jacobsen, E.N.(8) 102, 113, 118- Ji, W.(1 1) 280,283 Inagak~,A, (11) 88;(12)238 Jia, C.-S. (9)96 122 Inagaki,S.(1 1) 222 Jia, G. (1) 268 Jacobsen, H.(1) 132, 134,226, Inakuma, M.(1) 125 238;(6) 7;(10.2)19;(13)173 Jia, L.(2)47;(5) 45 Inanaga, J. (2)154 Jia, 2.(9)45 Jacobson, D.B.(1) 333; (12) 17; Incamito, C.D. (2) 133; (8) 10; Jiang, H. (8)129 (13)329,330 (12) 169 Jiang, T.(1 1) 244 Jacobson, R.A.(9)36 Ingham, S.L.(13)304 Jiikle, F. (2) 156;(6) 22;(14) 164, Jiao, T.(14) 119 Ino, I. (2)207 Jimcnez, I.G. (7) 102 166 Inomata, S.(9) 153;(1 1) 182,263 JimQez, M.V.(12)128 Ja'far, M.H. (2)204;(1 1) 234 Inoue, Y.(8) 68 Jafarpour, L.(10.1)37;(12)78, Jimhez-Tenorio, M.(12)57,58 Iorga, B.(2) 1 Jin, C.-X. (4)24,25;(5) 68-70 Ipaktschi, J. (14)227 220 Jin, H.(1) 286 Ireland, T. (2) 108;(14)223,226 Jahncke, M.(1 1) 107 Jain, C.B.(7)46 Jin, Q.-H. (1 1) 31 Irwin,M.J. (2)223 Jin, W . 4 . (4) 142 lainter, P.(10.3)54 Isaac, C.J. (14) 194 Jalkanen, K.J. (12)126 Jin, X.(1) 317;(9)54;(13) 35 Isaia, F. (2)200 Jalon, F.A. (14)178 Jnoff, E. (8)106 Ishida, Y.(2) 119 Jockisch, A. (1) 87 Ishifime, M.(3) 13 Jamcs, A.J. (1 1) 239 Johann, H. (13) 504 Ishii, A. (3)55; (8) 104, 126 James, D.S.(13) 142 Johannsen, B. (9)82 James, S.C.(7) 119 Ishii, H.(14) 13 1 Johannsen, M.(14)180 Ishii, T. (1 2) 5 1 Jameson, G.B. (14)192 Johans, A.W. (13)321 ishii, Y.(4)126-128,130;(8)93; Jamieson, J.Y. (8)49 Johansson, A.A. (1 1) 307;(13) (11) 300;(13) 468 Jamison, T.F.(8) 102 445 ishikawa, T.(14)44 Jandciu, E.W.(10.3) 13 Johansson, L. (12)155 Ishitani, H.(8) 117 Janiak, C.(6)10 Johansson, M.( 12) 102;(1 3)221, Jankowska, R (2) 103 Isobe, K. (1 1) 12,268;(14)247 242 Isobe, M.(13)382,391,392 Janousek, 2.(5) 25 Johansson, N. (1) 28 Itami, K. (8) 32;(13)97 Jansat, S.(13) 131 John, K.D. (10.3)37 Ito, H.(2)209 J a n , M.C. (12) 170 Johnson, A.L. (5) 57 Ito, M.(13) 125 Jaouen, G. (9)37 Johnson, B.F.G.(9) 14, 109, 110; Ito, Y.(8)25,32;(13)97 Jardine, C.N.(1) 135, 188;(13) (1 1) 3,45,86,125, 126 345 Itoh, K. (2)79;(8)78;(1 1) 112, Johnson, D.S.(8)109 Jastrzebski, J.T.B.H. (3)58;(13) 204 Johnson, L.K.(12) 139;(13) 114 504 Ivanov, S.V. (5) 14,21;(9) 142 Johnson, S.A. (10.2)8 Jaworska, M.(1) 177,307 Ivanova, E.V.(14) 123 Johnston, J.N.(8)108 Ivanova, S.M.(2) 181; (5) 14;(9) Jayaratne, K.C.(14)89 Johnston, M.A.(4) 67,91;(14) 18 Jean, Y.(1) 269 141,142 Jeffery, J.C. (5) 56;(1 1) 297;(1 3) Johnston, R.F.(14) 119 Iverson, C.N.(6)3

Ivy, R.(8)60 Iwama, H.(13)125 Iwao, M.(2)112 Iwasaki, T. (1) 10 Iwasawa, N.(9)63;(1 3) 20,395 Iwasawa, Y.(1 1) 326 Iwata, C. (13)296 Iyer, U.S.(13) 502 I d , K. (2)53

496

Jonas, V. (1) 76,201,221,226; (2)224;(3) 43;(9)8, 10 Jones, C.(1) 233;(7)3,9,16,29, 44,45,74,82,113;(9)50; (14) 105 Jones, P.G. (2)218-220;(7)20; (1 1) 240-242,245;(12) 182; (13) 228,250,386;(14) 152, 158, 185 Jones, R.A. (3) 14;(7) 122;(10.3) 45 Jones, W.D. (7)94;(12) 113, 114, 121, 152;(13) 182,339 Jong, S.-J. (14)141 Jonsson, M.(7) 1 16 Jonsson, S.Y.(8)82 Joorst, G.(12)20 Joos, S. (1) 335 Jordan, R.B. (9)116, 117;(12)41; (13) 33 1 Jordan, R.F.(6)59,82 Jorg, H. (13) 504 Jorgensen, K.A. (8)105 Josef, M. (5) 16 Jouany, C.(1) 99 Jouet, R.J. (6)85;(7) 123 Ju, T.D.(9)53 Judai, K.(1 1) 13 Julia, M.(2)3 1 Jun, C.-H. (8)76;(13) 14 Jung, I. (13) 501 Jung, J.H. (10.4)32;(14)38 Jung, S. (12)237 Jung, S.-J. (1 1) 287 Jung, T.(13) 224 Jungklaus, H.(10.3)49;(14)95 Junk, P.C.(4)90; (7)9 Jurkschat, K. (1) 93 Just, 0.(6)84 Justyniak, I. (6)60 Jutland, A. (13) 122;(14) 155 Jutland, J. (13) 524 Jutzi, P. (6)81,96;(14)108 Kabashima, S.(1) 257;( i 1) 250 Kabir, S.E.(11) 100, 101, 153, 165 Kablaoui, N.M. (14)36 Kadouri-Puchot, C. (2)5 Kadyrov, R.(1) 309,310;(13) 193 Karcher, J. (2) 152;(14)5 Kagoshima, N. (2)85 Kahlal, S.(1) 248,251,255;(9) 115;(1 1) 19, 102,264;(13) 443 Kahn, 0.(1) 141

Kai, M.(14)234 Kai, S.(1) 107 Kai,Y. (4)44,95;(11)217;(13) 503 Kaifer, E. (1 3) 44 Kaihara, M.(9)102;(1 I) 84 Kainosho, M.(13)202 Kaita, S. (4)106 Kajitani, M. (14)243 Kakareka, J.P.(1)89 W i n o , R. (12)183 Kakiuchi, F.(8)72-74;(9)106; (11) 130 Kakkar, A.K. (1 3) 94 Kako, M.(13)80 Kakuchi, K. (13) 144,505 Kalck, P. (10.3)6;(12)3; (13) 6; (14) 154,215 Kallinen, M.(1) 409 Kal'sin, A.M. (13) 305 Kaltsoyannis, N.(1) 249;(9) 65 Kalyanasundari, B. (3) 37 Kalyuzhnaya, E.S.(1 I) 15 1 Kamata, T.(4)136 Kamaura, M. (2)154 Kamer, P.C.J. (1)385;(13) 131 Kaminsky, W. (4)100;(14)45, 46 Kamitani, A. (9)107;(11) 135 Kampf, J.W. (I) 101; (6)21;(13) 282;(14)49 Kanai, M.(8)91 h e , K.M. (3) 15 Kanehisa, N. (4)44,95 Kaneko, T.(1 1) 205 Kanellakopulos, B.(4)149 Kanemasa, S. (8)114 Kanematsu, N.(13)405 Kang, B . 4 . (1 1) 196 Kang, H. (13)417 Kang, S.O. (5) 67,71-73 Kang, Y.(5) 72 Kang, Y.H. (2)105 Kang, Y.K. (14)204 Kann, N.(13) 388 Kannabe, T.(6)17 Kano, N.(13)80 Kar, H.M. (1 1) 235 Karakynakos, E.(1) 287 Kamm, A. (11) 171 Karasiak, D.F. (4)58;(14)46 Karban, J. (14)31 Karchava, A.V. (I 1) 29 Karl, M.(4)78, 115 Karlie, P. (12)20 Karlsson, A. (1) 150 Karsch, H.H.(2)48, 150;(12) 156, 167

Orgutiometallic Chemistry Kasani, A. (2)44;(3) 25 Kasatkin, A.N. (10.1)77 Kashimura, S.(3)13 Kashiwabara, K. (1 1) 277 Kashiwagi, K.(4)113 Kassebaum, J.D. (5)43 Kaszynski, P.(5) 6,7,25 Kataoka, 0.(8)64 Kataoka, Y.(3) 13; (12)104;(13) 223 Katayama, H. (12)188 Katayama, T.(9)35; (I 2)69 Kato, K. (2) 1 19 Katoh, K. (1)234;(9)5 1 Katritzky, A.R.(2) 13 Katsukawa, Y. (1 1) 289 Katzenellenbogen, J.A. (14)120a Kaufmann, D.E. (8) 18 Kaupp, M.(1)11,215,246,277, 282 Kawaguchi, H. (1 1) 277,285 Kawamura, K.(12)30 Kawamurq T.(1 3) 405 Kawanishi, T.(8)68 Kawano, H.(12)35;(13)71 Kawano, M.(9) 157;(1 1) 5 1 Kawano, Y.(1)234;(9)5 1;(14) I04 Kawasaki, S.4. (3)13 Kawasaki, Y. (4) 126 Kawase, T.(13)144 Kawashima, T.(6) 17 Kawatsura, M.(8)4 Kawazoe, Y. (1) 32 Kaxiras, E.(1) 127 Kaya, C.(9)17, 18 Kaya, K. (4)70, 151;(11) 13 Kayaki, Y. (12)183 Kayran, C.(13) 189 Kazmaier, U.(9)56 Ke, M.(12)82 Keenan, F.E.(1) 105 Kehr, G. (1) 132;(6)7,68;(10.1) 35; (13) 288 Keirn, W. (8)133;(13) 504 Keinan, E. (1 2) 149 Keiter, E.A. (9)45 Keiter, RL.(9)45 Keith, J. (2) 196 Keitsch, M.R (4)32 Kelly, B.D.(9)154;(10.3)31; (12)60,82;(13)478;(14) 100 Kelly, G. (14)238 Kelly, J.F. (1) 167 Kelly, W.M. (14)5 1 Kemmitt, R.D.W. (7)1 1 1 Kempe, R. (4)79;(10.1)50,5 1;

Author Index (13) 280,439;(14)29 Kemper, P.R(1) 328 Keng, T.-C. (1 1) 236 Kennedy, A.R. (1) 25, 105;(2)40, 128;(3) 4 Kennedy, J.D. (5) 25,28 Kern, K.(9)62;(13)47,48 Kerr, J.L. (9)38;(1 1) 185 Kerr, W.J. (1) 25;(13)381 Kervinen, T.(4)8 Keserii, G.M.(2) 116 Kessler, M.(1 1) 77;(13) 352 Kettle, S.F.A. (1 1) 5 Khabashesku, V.N. (1) 98 Khan, M.A. (1) 171;(13)247 Khan, M.S. (12)62 Khan, 0.(13) 128 Khan, S.I.(3) 29 Khansawai, P.(2)21 Khayatpoor, R.(13)348 Kheradmandan, S.(10.4)36 Khvostov, A.V. (4)22,53,54; (14) 13 Kimg, F.-M. (2) 177;(10.3)5 1 Kibino, N. (4)99 Kichi, S.H. (13) 92 Kickelbick, G.(9) 144;(1 1) 275, 276,319 Kicken, R.J.N.A.M. (13)219 Kida, T. (14)183 Kiefer, W.(1) 284 Kiely, C.J.(1 1) 38 Kiesman, W.F. (8) 94 Kihara, N.(13)63 Kim, C.(13)501 Kim, D.-H. (5) 67 Kim, J. (2)91;(14)38 Kim, J.H. (5) 74 Kim,J.S.(13)393 Kim, K.(2) 105 Kim, K.-C. (5) 17 Kim, K.S. (1) 59 Kim, L.(8) 60 Kim, P. (14)230 Kim, S.(8) 132 Kim,T.-J. (14)229 Kim, W. (9)65 Kim, W . 4 . (1) 249 Kim, Y.(4) 112;(6)40,79 Kim, Y.-H. (14)229 Kimblin, C.(6) 1 1 Kimura, M. (3)49,50 Kimura, S.(2) 119 Kincaid, K.(6)43;(10.1)9 King, B.T. (5) 16, 19 King, J.D.(11) 56,77, 188, 191; (13) 352,425,485 King, R.B. (5) 13

King, W.A. (1) 129;(9)78;(14) 37 Kingsbury, J.S.(8) 39;(12)219 Kingsley, A.J. (5) 57 Kingston, J.E. (14)150 Kink, J.D. (7)121 Kinoshita, I. (1 1) 12,268;(14) 247 Kinoshita, N. (3)54 Kinoshita, S.(2)65 Kinsley, S.A. (4)153, I54 Kira,M.(I) 116 Kirchbauer, F.G. (10.1)48,49; (13) 165,281,312;(14)73 Kircher, P.(14)1 12 Kirchner, K.(1) 153;(12)212, 225;(13)75,76,266,306 Kirij, N.V. (7) 103 Kirillov, E.N. (4) 10,36,45,62 Kirk, A.D. (9)64 Kirmse, R.(14)97 Kishi, N. (2) 19 Kishimoto, N.(1) 12 ’ Kishimoto, Y. (2)79;(13) 202 Kisko, J.L. (6) 1 1 Kitagawa, 0.(2)32 Kitagawa, S. (12)51 Kitajirna, S.(3) 13 Kitamori, Y.(13) 188 Kitamura, M.(13) 394 Kitamura, N.(4)124 fitamura, T. (4)141, 142 Kitgaki, S.(8) 64 Kittrcdge, K.W. (10.3)43 Kivekas, R.(5) 47.58.59 Kiyomori, A. (8) 9 Klahn, A.H. (9)47;(10.4)28,34 Klapctke, T.M. (1) 95 Klass, K. (10.1)40 Klausmeyer, K.K. (14)259 Klauss, R.(13) 248,249 Kleckley, T.S.(1) 176;(10.2)29 Klci, S.R.(10.3)30 Kleiber, P.D. (1) 60,61 Kleigrewe, N.(10.1)40 Kleijn, H.(3)58 Kleiman, V.D. (14) 119 Klein, A. (2)215;(12)150,185; (13)231 Klein, H.-F. (1 I) 214;(13) 224 Kleinhenz, S.(1) 276;(1 1) 52 Klemp, A. (6)63 Klett, J. (1 1) 226 Klettke, T.(1)319;(13) 338,341 Klimenko, N.M.(1) 43 Klimova, E.I. (14)173 Klinga, M.(14)78 Klinkhammer, K.W.(3) 3 1; (7)

497 84;(11)226; (12)150;(13) 23 1 Klippenstein, S.J. (1) 158, 160 Klobukowski, M.(1) 223 Kloo, L.(1) 163 Klooster, W.T.(1) 89;(14)21 Klose, A. (1) 301 Klosin, J. (13)267 Klotzbuchcr, W.E. (13) 49 Klyagina, A.P. (1)2 1 1 Knight, D.A. (3) 65 Knight, L.B.(1) 287 Knizek, J. (1) 95;(3)3, 17;(7)81 Knobler, C.B.(3)28;(5) 15,36, 39,54 Knoechel, P. (2) 108;(3) 11; (13) 250;(14)223,224,226 Knolker, H.-J. (13) 18,248,249, 256-259 Knocpfler-Muhlecker, A. (1 1) 247 Knoll, W.(2) 141;(14) 190 Knox, G.R.(12)117;(13) 363, 364,366,379,380 Knueppel, S.(14)59, 145 Knuppertz, J. (10.4)22 KO, B.-T.(6)64 KO, J. (5) 67,71-73 KO,S.(4) 123 Kobayashi, J. (6)34 Kobayashi, K. (1)124,126 Kobayashi, S.(8) 84, 112, 117 Kobayashi, T. (1 1) 138 Koberstein, R. (2)66,96 Kobliha, 2.(5) 5 1 Koch, 1. (1) 319; (12)26 Koch, L.(10.1)2 Koch, R. (1) 56,71;(6)33, 86 Koch, W.(1) 161, 165, 178;(4) 147 Kochi, J.K. (2)212;(6)1 Kochi, T. (1 I) 300;(13)468 Kocicnski, P.J.(I 3) 42 Kociok-Ktihn, G. (13) 328;(14) 94 Kockelmann, W. (1 1) 232 Kocovsky, P.(3)32;(13) 133 Kodama, K.-y. (13) 229 Kijhler, F.H. (1) 140, 141;(14) 213 Kiihler, K. ( 13)417 Koerner, J.B. (1) 377;(13) 333; (14)252 Koetteritzsch, M. (13) 299 Koga, K. (2)6 Koga, N.(1) 367;(4)145,146 Kohl, F.J. (1) 297;(8) 40;(12) 217,218 Kohn, R.D.(4)66

498 Koie, Y. (8) 1 1 Koizumi, T.a. (4)35, 121 Kojima, J. (8) 104 Kolczewski, S.(2)8 Kolehmainen, E.(1) 169 Kollann, C.(1 1) 73 Kolomeitsev, A.A. (7) 103 Kolomiets, A.F. (14)216 Komatsu, H.(13)403 Komiya, S. (12)28,29;(13) 74, 229;(14)24 Komiyama, S.(8) 117 Kondo, H.(1 1) 112 Kondo, M. (12)5 1 Kondo, T.(8) 14;(1 1) 138, 140; (13) 73, 192,264 Kondo, Y. (3)48 Kong, F.-S. (9)148;(1 1) 154, 158,317 Konze, W.V.(7)10;(12) 147 Koo, K. (4)98 Kooijman, H.(7) 15; (12)181 Kopacka, H.(2)35; (1 1) 247;(14) 122 Kopiske, C. (12)146 Koridze, A.A. (13) 517 Koschmieder, S.U.(3) 14;(7)122 Koshevoy, 1.0. (9)150;(1 1) 320 Koshino, H.(13)137 Kostas, I.D. (2) 113, 122, 123; (13) 21 1 Koster, M. (1 1) 73 Koterwas, L.A. (10.1)8 Kotora, M.(14)53,62 Kotov, V.Y. (1) 21 1 Kotz, K.T. (1) 210;(9) 3,24;(12) 14 Kourkine, I.V.(12)169 Koutsantonis, G.A. (1 1) 122;(13) 466 Kouvetakis, J. (1) 84 Kovacik, I. (12)169 Kovacs, A. (1) 184;(2) 198;(13) 415 Kovacs, K. (2)116 Kovba, V.M. (4)148 Kowalski, A S . (1) 171 Koyama, K.(4)95 Kozanoglu, F.(1 3) 189 Kozlowski, M.C. (8)107, 110 Kozlowski, P.M. (1) 242 I(raatz, H.-B. (12)27;(14) 134 Kriimer, 0. (I) 72 Krafczyk, R.(7) 118 Krafft, M.E. (8)34;(13)36,378 Kragl, U.(13)504 Kragten, D.D. (1) 370,371 Krajkowski, L.M.(6)78

Organometallic Chemistry Kramkowski, P. (1)246;(7)6; (11) 59 Kranenburg, M. (10.1)79 Krannich, L.K. (6)42 Krattinger, B.(13) 498 Krause, N.(2)159, 160, 171 Krause Bauer, J.A. (9)72;(1 1) 244 Krav-Ami, S. (9)15;(10.3)8 Kravchenko, R.L.(14)47 Krebs, I. (12)31; (14)206 KreiR1, F.R. (10.3)54 Kreiter, C.G.(13) 189,269,270 Kretschmer, W.P. (4)79 Kristensen, J. (3) 12 Krivykh, V.V.(1) 142;(10.4)37 Kroeker, S.(2) 193, 194 Krokcr, J. (7)83;(14) 10 Krska, S.W.(10.1)71 Kriiger, C.(7)59;(8) 115;(13) 49,407 Kruger, G.J. (10.3)52 Kruiswijk, E.(10.3)46 Krumm, B.(1) 95 Kruper, W.J. (13) 267 Ku, R . 4 . (2)177;(10.3)5 1 hang, S.-M. (1 1) 323 Kuballa, P. (5) 5 1 Kubas, G.J. (9)78,83;(12) 147 Kubicki, M.M. (13)141;(14)86, 91 Kubista, J. (10.1)56;(13)313 Kubo, K. (9)46 Kuchta, M.C.(13) 345 Kudin, K.N. (I) 98 Kuech, T.F. (4)4 Kiihl, 0.(1 1) 23 Kiihn, F.E. (1) 359 Kuendig, A.P. (14)233 Kuge, K. (1 1) 182 Kugler, E.L.(9)57 Kuhl, A. (13) 42 Kuhn, 0.(13) 121 Kuhn, P.(1) 222;(9)91 Kukolich, S.G.(1) 227;(13) 55 Kuleshov, S.P.(4)150 Kulkami, S.A. (1) 367;(4)146 Kulsomphob, V. (13) 307 Kumamoto, H. (2)1 19 Kumeta, K. (1 3) 294 Kummer, S.(7)30 Kundig, E.P. (8) 101; (9)55 Kundu, H.(14)220 Kunkely, H.(13)239 Kuntz, K.W. (8) 115 Kunz, K. (6)68 KUO,C.-Y. (6)64 Kuo, L.Y. (14)113

Kupfer, V. (10.1)53; (13) 161, 268,342 Kuran, A. (14)148 Kuribara, H.(14)138 Kurihara, M. (1 1) 267;(14)242 Kurikawa, T.(4)70, 15 1; (1 1) 13 Kuroda, S. (14)85 Kuroda-Sowa, T.(2)203,205207;(13) 401,513 Kurosawa, H. (1 1) 217;(13) 144, 409,503,505 Kurth, V. (13) 206 Kurushima, H.(8)66,67 Kusakabe, K. (8) 117 Kusnetzow, A. (2) 183 Kusumoto, S.(13) 374 Kuwano, R.(8) 25 Kuwata, S.(1) 257;( I I) 250,25I , 269 Kuzelka, J. (10.3)13 Kuz'mina, L.G. (1) 272;(10.3)17; (1 1) 29;(14)154 Kwon, 0.4.(1 1) 172;(13)359 La, D.S. (8) 49,50 Labahn, T. (4)37;(13) 236 Labinger, J.A. (10.1)62 Labouriau, A. (1 1) 210 Laboy, J.L. (1) 53 Lachiotte, R.J. (10.1)29, 80; (12) 152;(13) 339 Lagum A. (2)218-220;(5) 40, 41;(1 I) 240-242,245;(14) 152, 158,185 Laguna, M. (2)220,221;(1 1) 245 L a g ~ n aM.-C. ~, (2)21 1 Lahoz,F.J. (1 1) 199,252;(12)99, 125, 128;(13) 101, 102,438, 440;(14)52 Laibser, C.(14)214 Laikov, D.N.(1) 175,397 Lake, C.H. (6)42 Lal, T.K.(14)47 Lalinde, E.(2)188;(3)40;(1 1) 50,219,328;(12)194-197; (13)433,435,506,507,509 Laly, M. (14)154,215 Lrun, K.-C. (2)133;(13) 307 Lam, P.(1) 254;(12)65;(13) 482 La Manna,G.(1) 92 Lamb, E. (2)49;(6)66 Lambeit, C.(1) 154 Lameyer, L.(4)69 Lammertink, RG.H. (2) 141;(14) 190 Lammertsma,K. (1) 240;(7)67 Lance, M.(14)12,22

499

Author Index Landis, C.R. (1) 374 Landskron, K. (13) 191 Lanfranchi, M. (9) 59; (10.2) 12; (12) 171

Lang, H. (2) 186,208; (10.1) 58; (13) 419,436,500,514,515; (14) 27 h g , J.-P. (11) 278,279,285 Langdon, A.G. (2) 216 Lange, G. (13) 357 Langer, P. (2) 88 Langer, V. (3) 32; (13) 133 Langford, C.H. (9) 64 Langridge-Smith, P.R (9) 14; (11) 86 Lanter, C. (2) 100 Lantero, D.R (10.2) 17 Lanza, G.(1) 129; (14) 37 Lao,C.-Y. (13) 53 Lapinte, C. (12) 61,71 Lappert, M.F. (2) 40,81,82,9395, 130,215; (3) 1; (4) 16, 17; (6) 45,51; (13) 399 Lam-Shchez, A. (10.2) 12 Lathed, M. (1) 387; (8) 132 Larkins, D.L. (14) 202 h e n , S.C. (1) 14 Laschat,S. (13) 386 Laschi, F. (1) 317; (2) 130; (4) 16; (9) 54; (1 1) 3 19; (13) 35; (14) 25 3 Lastra, E. (12) 11,81 Latajka, Z. (1) 73 Latronico, M. (2) 146 La@ R (13) 303 Lau, C.P. (1) 275 Lau,C.S.-W. (11) 89,93-95; (13) 45547,518 Laubender, M.(13) 89,309 Lauigne, G. (13) 453 Lauterbach, T. (14) 35 Lavastre, 0. (8) 124 Lavayssihre, H. (1) 84,86 Lavigne, G. (11) 96, 110; (12) 8, 22 Lawonn, K. (1) 41 1; (3) 61 Lawrenq E.T. (7) 110 Lawson, D.B. (1) 279 Lawson, G.T.(3) 24 Lawson, Y.G. (7) 120 Layh, M.(2) 81,82,215 hyzell, T.P.(13) 214 Leadbeater, N.E. (9) 114; (1 1) 87 Leaveson, W. (9) 25.73 Lebel, H. (8) 119 Leblanc, J . 4 . (14) 86,91 Lebreton, J. (2) 164 Lebrilla, C.B. (1) 3 18

Lebuis, A.-M. (11) 108; (14) 110 Le Corre-Susanne, C. (13) 271 Lectka, T. (8) 111, 116 Ledger, S.J. (10.3) 33; (13) 240 Lee, B.Y. (13) 103; (14) 39 he,C.E. (1) 176; (10.2) 29 Lee, C.-F. (2) 166 Lee, C.H. (6) 49 Lee, C.-M. (1) 230; (9) 74 Lee, C.W. (8) 42 Lee, C.-Y. (13) 143 Lee, D.-H. (1) 270 h, D.4. (13) 14 Lee, D.-0. (14) 38 Lee, D.W. (9) 100; (12) 23 Lee, E.P.F. (1) 16 Lee, F.-Y. (9) 84; (10.4) 1

Lehmann, W. (13) 49 Lehotkay, T. (10.3) 54 Lei, X.(1 1) 99, 183,211; (14)

LCC,G.-H. (1) 230; (2) 177; (9)

Lcong, W.K. (7) 107; (1 1) 24,26, 157, 175 Leoni, P. (1) 262 Lepoul, P. (13) 487 Lerner, H.-W. (6) 75 Lerou, J.J. (1) 370,37 1 Lcscop, C.(14) 12.22 Lcskcla, M. (14) 78 Lesley, M.J.G. (14) 161 Le Stang, S. (12) 6 1 LeSuer, R (14) 163 Letov, A.V. (10.1) 55 Leung, K.S.-Y. (9) 122, 123; (1 1) 178, 179,181 Leung, W.H. (13) 428 Leung, W.-P. (2) 93,94; (4) 18 Levacher, V. (2) 26 LeVan, D. (7) 84 Levason, W. (7) 114, 115; (9) 80 Lcverd, P.C. (14) 22 Lewinski, J. (6) 60 Lewis, E. (14) 239 Lewis, J. (9) 158; (1 1) 46; (12) 62 Lewis, L.N. (13) 413 Ley, S.V. (13) 64,65 Leyva, M.A. (14) 42 Leznoff, D.B. (10.3) 14; (13) 128 Li, C.-J. (3) 10 Li, C.-K. (9) 158; (1 1) 46 Li, C.-L. (10.3) 34; (13) 51,53 Li, G.(14) 130 Li,H.(2) 142; (4) 52; (14) 15, 20 1 Li, J. (1) 186,203; (8) 129; (9) 12, 13 Li, J.J. (2) 51 Li, L. (1) 3 17; (9) 54; (13) 35 Li, L.-M. (1) 187; (4) 143 Li, P. (1) 14; (2) 20 Li, Q.4. (1 1) 330 Li, S. (9) 135

74, 131;(10.3)26,51;(11) 68,70, 155,266,287; (12) 47, 55,67; (13) 40,52,8 1, 143, 442,471,473-475; (14) 96, 199 LCC,G.-Y. (1) 377; (13) 333; (14) 252 Lee, H. (8) 76; (10.1) 65; (13) 163; (14) 77 Lee, H.-B. (14) 38 Lee,H.N. (13) 178 Lee, I.S.(13) 178; (14) 204,212 Lee,J. (11) 271,273 Lee, J.-D. (5) 73 Lee, J.-H. (2) 177; (10.3) 51 Lee, K. (13) 91 Lee, K.-J. (2) 177; (10.3) 5 1 Lee, K.K.-H. (1 1) 103,261 Lee, L.(1 1) 75 Lee, L.W.M. (6) 5; (10.1) 68; (13) 169 Lee, M. (9) 65 Lee,M.H. (4) 112 Lee, M.Y. (1) 249 Lee, S. (13) 526; (14) 174 Lee, S.-G. (14) 204 Lee, S.W. (14) 38,39 Lee, T.R (10.4) 32; (12) 24; (13) 68 Loe,W.-Z. (14) 202 Lee, Y.A.(13) 155, 178 Leech, M.A. (6) 8 Leeson, M.A. (7) 108; (10.4) 23 LeFlWh, P. (7) 41,50,53-56; (13) 523; (14) 75,159 LeGuen, F.R (13) 487 Legzdins, P. (1) 138; (10.3) 10, 13, 15,29; (13) 50 Lehmann, C.W. (8) 45; (10.2) 5; (13) 407; (14) 253

235

Lei, 2.(8) 121 Leigh, G.J.(14) 187 Leiner, A. (8) 54 Leithe, A.W. (12) 167 Leiva, C. (10.4) 28 Lemenovskii, D.A. (1) 272 Lempke, M.(13) 224 Lempke, U. (13) 224 Lenco, A. (13) 334 Lenges, C.P. (13) 96; (14) 240, 241,258

Lentz, D.(13) 177 Le Ny, J.P. (10.4) 16

5 00 Li, S.-Y. (9) 84; (10.4) 1 Li, T. (1) 244 Li, W . 4 . (2) 200 Li, W.-T. (9) 131; (11) 266; (13) 475

Li, X. (1) 47-50; (4) 118, 122, 125; (6) 84

Li, X.-W. (6) 76,77 Li, X.-Y. (12) 56 Li, Y. (12) 230 Li, Y.-L. (13) 53 Li, Z. (6) 23; (14) 58 Li, Z.R.(1) 120 Lia,, G. (12) 56 Liable-Sands, L.M. (2) 133; (4) 3, 4,94; (6) 85; (7) 123; (10.3) 12; (13) 37,85; (14) 163,232 Liang, B.Y. (1) 322 Liang, L.C. (10.1) 12, 13,16 Liao, F.-L. (9) 13 1; (10.3) 34; (1 1) 193,266; (13) 51,383,475, 488 Liao, Y.-H. (2) 36 Liaw, J.-H. (14) 23 1 Liaw, J.W. (13) 488 Liaw, W.-F. (1) 230; (9) 74; (1 1) 287 Libert, V. (3) 45 Liddle, S.T. (1) 105; (2) 30,49, 97; (6) 66 Liebeskind, L.S. (13) 45 Liebl, M. (12) 79 Liebman, J.F. (7) 26 Light, M.E. (6) 16 Lightfoot, P. (9) 125 Likholobov, V.A. (11) 15 1 Lim, N.K. (12) 160 Limberg, C. (1) 325; (13) 44; (14) 112 Lin, C . C . (6) 58,64; (1 1) 193; (13) 215,365,383,488 Lin, C.-H. (6) 58,64; (14) 141 Lin, C.-W. (13) 215 Lin, G.-H. (10.3) 34; (13) 51 Lin, G.-Y. (1) 230; (4) 73; (9) 74 Lin, H.-Y. (1) 405; (13) 54 Lin, I.J.B.(2) 214 Lin, J. (4) 27-30 Lin, J.T. (12) 173; (14) 169,219 Lin, K.-J. (12) 173; (14) 219 Lin, T.-S. (14) 23 1 Lin, W. (9) 45; (12) 45, 189 Lin, Y.-C.(9) 131; (1 1) 266; (12) 47,55,67; (13) 475; (14) 199 Lin, Y.H. (4) 24,25 Lin,Y.-S. (13)411 Lin, Z. (1) 268,274,275,295, 303; (10.3) 11; (12) 56,201

Lin, 2.-M. (3) 59 Lindeman, S.V.(2) 2 12 Linden, A. (13) 238 Lindner, D.C. (10.3) 12 Lindner, E. (12) 31; (14) 206 Lindsay, E.M.(9) 64 Lindsay Smith, J.R. (9) 27 Link, H. (1 1) 197 Linton, D.J. (2) 30 Lippard, S.J. (10.1) 19-22 Lippolis, V. (2) 200 Lipshutz, B.H.(2) 196 Lipshutz, B.L. (8) 12 Lis, T. (10.4) 40,41 Littke, A.F. (8) 2,3 Little, I.R. (10.2) 23 Liu, C.-W. (1) 324; (1 1) 236 Liu, 0.4. (2) 93,94, 139; (14) 60 Liu, F.€. (6) 24 Liu, G. (9) 134; (1 1) 200,201; (13) 336

Liu, H. (8) 85,86 Liu, H.-J. (2) 103 Liu, H.-Q. (1 1) 196 Liu, J. (6) 24; (1 1) 22 Liu, L.-K. (2) 36 Liu, P.€. (1 1) 259 Liu, Q . (4) 42 Liu, R . 4 . (9) 131; (10.3) 26,34; (11)266; (13)51-53,475

Liu, S.-H. (9) 84; (10.4) 1 Liu, S.-T. (2) 177; (10.3) 5,51; (12) 161

Liu, X. (1) 38,396; (2) 76 Liu, Y. (7) 107; (9) 120; (1 1) 24, 175,281; (14) 53

Liu, Y.-C. (13) 81 Liu, Y.-H. (12) 161 Liu, Z. (4) 3 1, 82; (5) 64 Llamazares, A. (1) 238 Lledos, A. (I) 26 1,265,269,27 1, 283,354

Lloris, J.M. (14) 193 Lloyd-Jones, G.C. (1 3) 133,4 12 Lluch, J.M. (1) 265,271 LO,K.K.-W. (2) 189; (10.4) 35; (1 1) 223,224; (12) 5

Lo, K.M.4. (12) 5 Lo, Y.-H. (12) 47 Lobanova, LA. (5) 54; (13) 429 Lobbia, G.G. (6) 30 Lobkovsky, E.B. (1) 176; (10.2) 29

Lochtman, R. (14) 225 Locke, A.J. (14) 177 Lockhart, C.C. (2) 115 Lodowski, P. (I) 307 Loeber, C. (4) 60; (13) 158

Orgartomelallic Chemislry Loft, M.S. (8) 20 Logsdon, B.C. (9) 36 Lohman, J.A.B. (1) 403 Lohrenz, J.C.W. (1) 344; (13) 166; (14) 65

Lokshin, B.V. (13) 517 Lomnicki, S. (1 1) 152 Long, C. (1 1) 194; (13) 369,377 Long, D. (1 1) 280 Lang, N.J. (1) 151; (12) 62 Longato, B. (12) 100 Longo, E. (1) 55; (6) 93 Longo. P. (1) 346 Longoni, G. (9) 29, 140,145, 155; (1 1) 35-37,47,48,3 12, 3 13

Loos, D. (1) 169 Lopes, I. (4) 73 Lopes, J.P. (13) 4 1 Ldpez, A.M. (12) 73,74 Lopez, C. (12) 76; (14) 139 Lbpez, J.A. (12) 99, 180; (13) 101,102

Lopez, J.L. (14) 129 Lopez-Agcnjo, A. (14) 178 L6pez-Mardomingo, C. (10.2) 11; (13) 316

Ldpez-Ortiz, F. (1) 236 Lorbcr, C. (10.2) 14; (13) 343 Lorciace, S.R. (13) 323 Lorente, P. (10.2) 13; (13) 317 Lorenz, A. (13) 272 Lork, E.(7) 85,87,88,90, 95, 101, 116

Losada, J. (14) 22 1 Losehand, U. (1) 82, 83

Loss, s. (7) 21 Louattani, E. (13) 246 Lough, A.J. (6) 22; (7) 64;(10.3) 35; (13) 370; (14) 162-164 Love, J.B. (10.1) 10 Lovel, S . (10.4) 26 Lovett, S.M. (13) 241 Low,K.S. (5) 51 Low, M.K.L. (1 1) 280,283 Low, P.J. (1) 254,255; (1 1) 111, 264; (12) 59,60,65,72,82; (13) 443,472,477,482 Lowe, J.P. (9) 30; ( I 1) 9 Lozano, M.I. (2) 213 Lu, G.-L. (9) 94 Lu, H . 4 . (1) 187; (4) 143 Lu, J. (9) 60 Lu, K.-L. (9) 84; (10.4) 1; (1 1) 62 Lu, T.-H. (1 I ) 33 Lu, X. (1) 199 Lubkovsky, E.B. (13) 347 Lucas, D. (10.2) 1I; (13) 316 Lucas, E.A. (1 3) 347

Author Index Lucenti, E. (1 1) 85 Ludvig, G.(1) 384 Ludwig, M. (12) 163 Lugan, N.(10.4) 44; (1 1) 96; (13) 175,453

Luh, T.-Y. (2) 166 Lui, B.-S. (14) 23 1 Lui, X.-H. (14) 231 Lui, Y.H. (14) 23 1 Luinstra, G.A. (12) 143 Luis, S.V.(14) 193 Lukens, W.W., Jr. (14) 16 Lukevics, E. (1) 88 Lulinski, S.(3) 23; (6) 67; (1 1) 246

Lum, M.W. (1 1) 26 Lumb, S.A. (10.3) 15,29; (13) 50 Luna-Garcia, H. (1) 338 Luneau, D. (10.4) 7 Lungwitz, B. (13) 328 Lunin, V.V. (1) 397 Lupinetti, A.J. (1) 201; (5) 20; (9) 8

Luque, F.J. (1) 19 Lushchi, M. (2) 5 Lussenko, K.A. (13) 305 Luther-Davies, B. (12) 66 Lutz, M. (1) 240; (12) 77,209; (13) 72; (14) 7

Luukkanen, S. (1) 409 Lynam, J.M. (7) 29; (13) 203; (14) 105,246

Lyssenko, K.A. (10.1) 54; (13) 162

Ma, D. (14) 249 Ma, H. (4) 6,55 Ma,H.-Z. (4) 13 Ma, J.-F. (4) 119; (10.3) 22; (14) 153

Ma, Y. (1 1) 231 Mabbs, F.E. (10.3) 33; (13) 240 McAdam, C.J. (14) 188 McAdon, M.H. (13) 267 McAlees, A.J. (12) 230 McArdle, C.P. (2) 223 McArdle, P.A. (1 1) 293 Macazaga, M.-J. (10.3) 35; (13) 370

MacBeath, C. (13) 113,399 McCammon, C. (5) 23 McCart, M.K. (1 1) 319 McCarthy, C. (2) 15 -hi, P.(1 1) 20,37,48 Macchioni, A. (12) 187; (13) 138, 153

McCleland, C.W. (14) 214

50 1

McConville, D.B.(10.1) 16; (13) 479

McCormac, P.B. (8) 135, 136 McCrindle, R.(12) 230 McDonagh, A.M. (1 2) 66 Macdonald, C.L.B. (1) 66 McDonald, F.E. (4) 132, 133 McDonald, M.R (14) 195 McDonald, R. (2) 44; (3) 25; (4) 72, 73; (6) 52; (7) 47-49; (10.1) 67; (12)42,46, 105, 126, 129, 130; (13) 406,432; (14) 32 MacDougall, J.M. (2) 64 McElwee-White, L. (10.3) 56,61 McFarlane, W. (2) 53 MacGillivray, L.R. (10.1) 38,39; (13) 167; (14) 54,79 McGlinchey, M.J. (13) 362; (14) 205 McGrady, J.E. (1) 104,245,403; (6) 38; (1 1) 14; (14) 102 Macgregor, S.A. (1) 228; (9) 9; (10.3) 9 McGuinks, D.S.(12) 206 Mach, K. (10.1) 47,49,53,56, 57; (13) 161, 164,268,312, 313,342,516; (14) 31,203 Machado, F.B.C.( I ) 1 Macias, R (5) 35 Mclndoe, J.S. (9) 14; (1 1) 10,86 McInnes, E.J.L. (10.3) 33; (13) 240 Mclntyre, J.A. (13) 148 McKarns, P. (6) 53 McKeown, A.E. (1) 105 Mackewitz, T. (1) 233 Mackie, S.C. (1) 149 McKinley, A.J. (1) 287 Mackinnon, A. (5) 30 McKoyan, S.(14) 215 MacLachlan, M.J. (14) 163 MacLaren, D.C. (1) 149 McLaughlin, M. (13) 380,381 McLemore, D.K. (5) 12 McMahon, C.N. (6) 62 McMahon, M.T. (1) 243 McMahon, T.B.(1) 9 McMeeking, R.F. (5) 2 McMurran, J. (1) 84 McNamara, B.K. (9) 48; (12) 91; (14) 25 1 McNeil, W.S. (10.4) 26 McPartlin, M. (7) 121; (1 1) 56, 77, 191,216,249; (13) 110, 352,425; (14) 198 MacQueen, D. (1) 228; (9) 9; (10.3) 9

McQuillan, A.J. (1 1) 6 Macsari, 1. (1) 390; (13) 120, 127 Maddaluno, J. (1) 2 Madcma, A. (5) 39 Madhushaw, R.J. (9) 131; (10.3) 26,34; (1 1) 266; (13) 5 1,52, 475 Madiot, V. (13) 373 Madsen, R. (3) 53 Madura, I. (3) 23; (1 1) 246 Maeda, R. (2) 112 Mackawa, M. (2) 203,205-207; (13) 188,401,513 Maeng, W. (13) 103 Maeno, N. (13) 513 Maercker, A. (2) 92 Maeyama, K.(9) 63 Magennis, S.W. (13) 304 Magnier, E. (8) 37 Maguire, J.A. (2) 47; (4) 88; (5) 44,45 Magull, I. (4) 37 Mahapatra, H. (11) 151 Mahicu, J. ( I ) 166 Mahler, W. (7)118 Mahon, M.F. (7) 29; (9) 143; (1 1) 256; (13) 203; (14) 105,246 Mahon, P.J. (9) 69 Maia, I.A. (6) 39 Maienza, F. (13) 522; (14) 179 Maigrot, N. (7) 54-56 Mair, F.S. (1) 25 Maisonnat, A. (14) 250 Maisse, A. (2) 109 Maitlis, P.M. (1 3) 305 Maitre, P. (7) 5 1 Maiwald, S.(4) 109, 149 Majoral, J.P. (7) 71; (10.1) 74-76; (13) 314; (14) 66,88 Majumdara, D. (1) 159 Mak, K.W. (12) 92 Mak, T.C.W. (2) 93,94,202; (4) 18, 31,82-87; (5) 18,6166; (10.3) 22; (1 1) 233, 323; (12) 92; (13)512,527;(14) 151, 182 Makarov, V.M. (4) 93 Makhaev, V.P. (14) 142 Makioka, Y. (4) 141,142 Malacria, M. (13) 277,278 Malagu, K. (7) 91 Malaun, M. (2) 35; (14) 122 Maleika, R (4) 115 Malessa, M. (13) 357 Malget, J.M. (5) 56 Malik, K.M.A. (6) 16; (1 1) 100, 101, 165; (14) 189 Malisch, W.(1) 284; (7) 65

502 MaUcin, V.G. (1) 215 Malkina, O.L.(1) 215 Malkov, A.V. (13) 25 1,252 Malone, Y .M. (8) 17 Maluso, T. (2) 145 Malyugina, S.G. (1) 175 Manassero, M. (2) 210; (1 1) 34; (12) 93 Manate, T. (13) 264 Manceron, L. (1) 200 Mancheiio, M.J. (10.3) 40 Mandal, S.K. (10.4) 25 Mandel, A. (4) 37 Manger, M. (7) 94 Mangold, A. (13) 66 Mann,G. (8) 10 Manners, I. (2) 140, 156; (6) 22; (12) 4; (14) 162-167 Manning, A.R. (1 1) 293 Manriquez, V. (10.4) 28 Mansilla, N. (13) 416; (14) 76 Mantovani, N. (10.4) 39 Manzano, B.R(13) 140,141; (14) 178 Manzel, M. (1) 23 Manzi, L. (9) 29; (1 1) 35 Manzoni, M.R. (10.1) 15 Manzur, I. (1 1) 25 Mao, L. (4) 119 Mao, S.(10.1) 38,39 Mao, S.S.S.H.(13) 167; (14) 54, 79 Mao, T. (12) 41; (13) 331 Mao, T.-F. (9) 116, 117 Mapolie, S.(12) 20 Marabello, D. (1 1) 145 Marais, C.F. (1) 363 Marais, E.K. (10.3) 52 Marchetti, F. (12) 34 Marchi, A. (10.4) 39 Marder, S.R.(13) 355 Marder, T.B. (6) 23; (13) 94, 199; (14) 58 Marek, H. (3) 47 Marek, I. (2) 22 Mares, F. (4) 152 Maraca, L. (12) 171; (13) 156 Margl, P. (1) 341,348,349; (12) 16; (13) 56 Margrave, J.L. (1) 98; (10.4) 42 Mark, F. (13) 49 Marks, T.J. (1) 129; (4) 98, 132134; (6) 9; (10.1) 63; (14) 37, 50

Marler, B. (1 1) 42 Marques, N. (4) 73 Marr, C.(9) 125 Marsden, C.J. (1) 273; (7) 25,27,

Organometallic Chemistry 28 Marsden, C.P. (8) 58 Marshall, W.J. (2) 144; (7) 118; (12) 144; (13) 232 Marti, J.M. (13) 129 Martin, A.J. (1) 151, 170; (10.3) 25,36; (1 1) 219; (12) 195197; (13) 318,433,507 Martin, C.(10.1)64;(14)41 Martin, K. (2) 101 Martin, M. (1) 269; (12) 125; (13) 101 Martin, R.L. (12) 18; (14) 72 Martin, T.P. (4) 65; (13) 62 Martin, V.S.(13) 375 Martinengo, S.(1 1) 20 Martinez, A.P. (12) 125, 128 Martinez, F. (12) 194; (13) 434, 506 Martinez, J.C.(14) 129 Martinez, P. (2) 77 Martinez-Cmz, L.A. (12) 174 Marthez-Garcia, M.A. (1 1) 79, 3 14 Martinez-Manez, R. (14) 193 Martin-Matute, B. (2) 176 Martin-Ruiz, B. (13) 411 Martins, A.H. (12) 203 Martins, E.O.(8) 103 Martins, J.C. (1) 91,93 Maruo, T. (4) 44 Maruoka, K. (2) 10,85,86 Maruyama, Y. (1) 32 Marvelli, L. (10.4) 39 M a , T. ( 5 ) 75 Mascetti, J. (1) 323 Maschmeyer, T. (1 1) 45 Masciocchi, N. (1 1) 37 Maseras, F. (1) 265,283,354, 398; (12) 33 Mashima, K.(4) 116; (10.2) 20; (13) 286 Masi, D. (10.4) 39; (12) 229 Mason, C.P. (8) 96 Massa, W. (1) 23; (2) 46; (4) 11, 78,115 Masse, C.E. (8) 88 Massick, S.M. (9) 21; (12) 19 Massiot, P.(12) 174 Mast, K.(7) 86 Mastroianni, S.(10.2) 23 Masuda, Y.(8) 15 Mata, J.A. (1) 235; (9) 16 Matano, Y.(7) 78; (10.4) 26 Matarc, G.J. (3) 15 Mateo, C. (2) 176 Mathes,C.(8) 45 Mathey, F. (1) 62; (6) 90; (7) 34,

36,40,41,50,53-56, 68; (13) 523; (14) 75,159 Mathias, J.P. (13) 142 Mathieson, T.J. (2) 216; (3) 41; ( I 1) 248 Mathieu, R. (10.2) 13; (10.4) 44; (13) 175,317 Mathur, C.(2) 151 Mathur, P. (9) 143; (1 1) 33,256, 257 Mathur, S.(2) 151 Matoba, K.(7) 97; (14) 176 Matousek, P. (9) 22 Matschiner, R (1) 154 Matseev, A. (1) 220 Matsubara, K. (1 1) 88; (12) 238 Matsuda, I. (1 1) 204 Matsumoto. N. (10.4) 7 Matsumoto, S. (3) 50 Matsunaga, T. (1 3) 7 1 Matsuno, K.(8) 64 Matsuo, S. (3) 49 Matsuo, Y. (10.2) 20; (13) 286 Matsuzaka, H.(12) 5 1 Mattson, R.J. (2) 115 Matzger, A.J. (1) 143 Maulitz, A.H. (7) 84 Maung, N. (3) 63; (6) 89 Maurette, L. (12) 22 Mauthner, K.(12) 212; (13) 76 Mauz, E. (1 0.3) 47 Maverick, A.W. (14) 207 Mawby, R.J. (9) 30; (1 1) 9 Maya, C.M. (12) 174 Mayer, J.M. (10.4) 26 Mayer, M. (1) 220 Mayer, U. (13) 266 Maynard, H.D.(8) 48 Mayne, C.L. (10.4) 40 Mayr, A. (10.3) 59; (10.4) 2; (12) 175 Mayr, H.(1) 180; (13) 121,262 Mayrarguc, J. (2) 157, 158 Mays, M.J. (7) 13, 121; (1 1) 56, 77, 191; (13) 352,425,426 Mazikres, S.(1) 84,86 Meadows, E.S.(2) 148 Mealli, C. (1) 219,260,317, 379; (9) 4,54; (11) 17; (12)90; (13) 3,35,334 Mecoui, T. (2) 87 Medina, R.-M. (10.3) 35; (13) 370 Mechan, M.M. (13) 32 1,322,444 Meerholz, K. (14) 144 Meetsma, A. (4) 103; (10.1) 6,79; (13) 285 Mehltretter, G. (8) 8 1 Mehta, N.A.(1 1) 97; (13) 45 1

Author Index Mei, Y.-H. (1 1) 28 1 Meidine, M.F. (7)5 Meier, RJ.(1) 104;(6)38 Mele, F. (1) 75 Meli, A. (13)216 Melikyan, G.G. (13) 372 Melle, S.(1) 69;(6)92 Mendizabal, F.(1) 315 Meneghetti, M.R. (12) 101 Menges, F. (10.1)42 Mentesa, A. (7) 11 1 Menzel, M. (2)46 Menzer, S.(7)67 Merabet, M. (1 1) 334 Mercandelli, P.(9)90;(1 1) 64,65 Mercier, F.A.G.(1) 91 Mereiter, K.(1) 153;(12)212, 225;(13)75-77,306 Merino, R.I. (2) 188;(1 1) 50; (13) 509 Merkel, R. (11) 318;(13) 497 Merlic, C.A. (1) 164; (13) 235 Merlin, M.(13)200 Merz, K. (14)57 Merzweiler, K.(14) 135 Messerle, B.A. (12)84;(13) 58 Messmer, A.(1) 226 Mest, Y.L.(14) 196 Mestres, R. (1) 37 Mestroni, G. (12) 187;(13) 138 Metz, B. (7)83;(13) 323;(14)10 Metz, H.(12)210 Metz, M. (1) 298 Metzler-Notte, N. (14) 124 Metmer, P.(2)28 Meunier-Prest, R (1) 139 Meunir, P.(14)6 Meyer, G.(4)9;(13) 122 Meyer, J.H.(13)233 Meyer, 0.(1) 132;(6)7;(10.1) 43,69;(10.3)50; (13) 283 Meyer, T.Y. (10.2)21;(10.3)48 Meyers, E.A. (6) 24 Meyer-Zaika, W. (1 1) 43 Mezailles, N. (7)41,54,56;(13) 523;(14)159 Mezzetti, A. (13)522;(14) 179 Mhche, G.L.(2)103 Miao, B.(2) 25 Michalak, A. (1) 351;(12) 134; (13) 105 Micha-Screttas, M. (2) 122, 123, 136 Michl, J. (1) 98;(5) 19 Middleton, B.(13)64 Midollini, S.(3)34 Miehr, A. (1) 70;(9) 128 Miesch-Gross, L.(13)301

503 Miguel, Y. (1 4) 88 Mihan, S.(2)185;(13)446 Mijolovic, D.(1 1) 282;(14)107 Mikami, K.(3) 55; (8) 104, 126 Mikoluk, M.D. (7)47-49 Mikulas, M. (13)19,62 Milani, B.(12)187;(13) 138 Milestone, N.B.(2)216 Milet, A. (1) 286 Milius, W.(5) 23,68-70;(14)160 Millar, S.J.(8)1 1 1 Miller, S.L.(10.2)17 Miller, S.M. (2) 181;(5) 14,20, 21;(9)141,142 Miller, T.A. (1) 288 Miller, T.F., 111 (1) 123 Millet, D.B.(12)63 Milstcin, D. (12) 1,27,96,107, 108, 177, 178;(13) 26,95 Mimoun, H.(3) 30 Min, S.-K. (5)73 Minaev, B. (1) 208,314 Minghetti, G.(2)210; (12)93 Mingos, D.M.P. (1 1) 216;(13) 110 Mink, J. (1) 313 Minkwitz, R. (7)89,98,99 Minutolo, F.(14)120a Minyaev, R.M. (1) 74 Miquel, Y.(13) 314 Mirkin, C.A. (14)232 Mise, T.(13)422;(14)64 Mitchell, K.(1 1) 82 Mitsudo, T. (8) 14;(1 1) 138, 140; (13)73,192,264 Mitsui, T.(1 1) 182 Mittcrbiick, M. (2)35 Mitzel, N.W.(1) 82,83 Miura, H. (14)209 Miura, K.(8)56 Miura, T.(13)207 Miuri Y.(4) 136 Miwa, Y.(2) 169 Miyagi, K. (9)29;(11) 35 Miyajima, K.(4)70, 151 Miyasaka, H.(10.4)7 Miyasaka, T.(23 1 19 Miyatakc, T. (1 3) 202 Miyoshi, K.(9)46;(12)30 Mizobe, Y.(1 1) 269,300;(13) 468 Mizoe, N. (1) 365,366,380;(12) 136 Mizuguchi, M. (9) 102;(1 1) 84 Mizumoto, Y.(13) 410 Mobcrg, C.(1) 386,387 Mobley, T.A. (3)46 Moceno, T.(13) 416

Mochizuki, E. (1 1) 217;(13) 503 Mock, U. (14)161 Modrego, J. (I) 258;(12)74;(13) 430 Miiller, C.(13) 61 Moellcr, S. (1) 284 Mogi, K.(1) 394 Mohamed, A.A. (1 1) 244 Mohamud, S.I.(10.1)79 Moinea, J. (8) 131 Moir, J.H. (1) 25;(13) 364 Moise, C. (14)86,90,91,93 Moiseeva, N.(13) 70 Mojovic, L.(13) 252 Mol, J.C. (12)209 Molander, G.A. (4)32, 13 1, 135 Molina, P.(14)129 Molincr, V. (1) 235;(9)16 Moloy, K.G. (12)144;(13)232 Monari, M. (9)155;(1 1) 188, 312,313;(12)233;(13) 151, 485 Monge, A. (1) 283;(12)98,228 Mongin, C.(10.4)44;(13) 175 Moniz, G.A. (8)63 Montalvo, V.G.(7) 117 Montana, A.M. (13) 376 Montenegro, E.(1 3) 385 Moore, C.B.(9)48;(12)91;(14) 25 1 Moore, H.W. (2)64 Moore, S.J. (13)148 Morales, D.(1) 139;(14)99 Morh, M. (14)221 M o m , P.H. (1) 25 Mordas, C.(14) 163 Moreno, C.(9) 118;(10.3)35; (11) 168;(13)370,470 Moreno, M.T. (1) 271;(2) 188; (3) 40;(1 1) 50,328;(12) 195, 197;(13) 433,435;(14)76 Moreno, N. (1)265 Moreno-Hara, M. (14) 178 Moreno-Manas, M. (1) 389;(13) 116 Morento, J.M. (13) 481 Moret, M.(9)90;(1 1) 64,65 Morgan, A.J. (8)88 Morgan, J.P. (8)41 Mori, M. (14)85 Mori, S.(1) 41,320;(2)197;(13) 184 Morikawa, J. (2)86 Morikita, T.(1 2) 29 Morimoto, T.(8) 30;(9)105, 107; (11) 135 Morimoto, Y. (9)35; (12)69 Morino, T.M. (13) 509

5 04 Moritani, Y.(8) 98 Morken, J.P. (8) 123, 124 Morley, C.P.(7) 44 Moro, M. (8) 68 Morokuma, K. (1) 342,394; (13) 161

Moro-oka, Y. (11) 72,292; (12) 21,44,50; (13) 92,476; (14) 249 Morozova, L.M. (13) 305 Morran, P.D.(1) 403 Moms, H.W. (10.3) 33; (13) 240 Moms, L.J. (9) 62; (13) 47 Morton, M.S. (12) 119, 152 Moscardi, G. (1) 345 Moskowitz, H. (2) 157, 158 Mosquera, M.E.G. (2) 152; (14) 5 Moss, J.R. (1) 167, 168,363; (10.3) 27 Motevalli, M. (6) 39 Motherwell, W.B. (8) 37,79 Motohsa, S.(7) 97 Motoori, F. (12) 232 Motoyama, I. (14) 234 Mottier, L. (13) 122 Mountford, P. (7) 7; (10.1) 72 Moyano, A. (9) 130; (13) 367, 368,385 Moyer, B.A. (1) 26 Mstislavsky, V.I. (1) 175; (13) 238 Miihle, S.H. (4) 10,48; (7) 93; (14) 46 Miiller, J.F.K. (1) 6,7; (2) 43,45, 62 Muller, K.H. (1) 180; (13) 262 Muller, M. (1 1) 73 Miiller, P.(3) 21; (6) 48,61 Miiller, T.E. (11) 133 Mugnier, Y. (10.2) 11; (13) 316 Mui, H.D. (12) 25; (13) 84 Muir, K.W.(10.3) 32; (12) 157; (13) 320,346 Mukai, C. (13) 393 Mulford, D.R (10.2) 15 Mullen, G.E.D. (1) 406 Muller, G.(13) 130, 131 Mullin, J.L. (1) 89 Mullins, S.M.(10.2) 10 Mulvey, R.E. (1) 105; (2) 40,97, 128; (3) 4 Mulzer, J. (13) 108 Munakata, M.(2) 203,205-207; (13) 188,401,513 Mundt, 0. (7) 84 Murioz, E. (1) 37 Mufioz, J. (1) 121,318 Muiioz-Hernandez, M.-A. (6) 4 1

Organametallic Chemistry Munson, E.J. (14) 30 Murahashi, S.4. (13) 410 Murahashi, T. (1 1) 217; (13) 409, 503

Murai, S.(8) 30, 33,72-74; (9) 105-107; (11) 130, 135, 139

Murakami, F.(7) 12 Murakami, M. (8) 32; (13) 97 Murase, H. (3) 13 Mumta, M. (8) I5 Murillo, C.A. (1 1) 53 Murray, M. (13) 133 Muny, J.A. (8) 110 Mumgavel, R.(6) 54; (10.2) 5 Musaev, D.G.(1) 342,394; (1 3) 161

Musashi, H. (12) 44 Musashi, Y. (1) 365,366; (12) 136

Mushtaq, I. (7) 106 Mussig, S.(14) 237,239 Mustah, B.A. (4) 150 Muzart, J. (13) 126 Myer, S.(13) 372 Mycrs, B.M. (13) 377 Myers, J.K. (8) 113 Mylvaganam, K. (1) 392 Mynott, R. (7) 59,60; (13) 79 Mysov, E.I. (10.1) 55 Nagabrahmanandachari, S.(14) 146

Nagai, S. (1) 234; (9) 5 1 Nagao, S.(4) 151; (1 1) 13 Nagasawa, A. (14) 234 Nagase, S.(1) 124, 126 Nagashima, H. (11) 1 12 Nagata, A. (8) 78 Nagayama, K.(12) 183 Nagayama, S. (8) 84, 112 Nagel, V. (1) 284 Naidoo, K.J. (1) 167, 168,363 Naito, S.(1 1) 150 Nakadaira, Y. (13) 80 Nakahara, N. (14) 24 Nakai,T. (2) 18, 19 Nakajima, A. (4) 70, 151; (1 1) 13 Nakajima, K. (2) 72, 174; (10.1) 73; (13) 168; (14) 56

Nakajima, T. (1) 106 Nakamura, A. (2) 119; (4) 116; (10.3) 24; (13) 327

Nakamura, E. (1) 41,320; (2) 197; (3) 52; (13) 184

Nakamura, H. (13) 125 Nakamura, K.(1) 326 Nakamura, M. (3) 52

Nakaniura, T. (4) 141; (9) 102; (1 1) 84

Nakanishi, S. (12) 44; (13) 63, 294

Nakano, H. (1) 198 Nakano, T. (4) 127, 128 Nakano, Y.(4) 126 Nakata, T. (13) 137 Nakatsuji, H. (1) 199 Nakatsuji, Y. (14) 183 Nakayama, H. (9) 29; (1 1) 35 Nakayama, Y.(4) 116; (10.3) 24 Nakayamo, Y.(13) 327 Nakazawa, H. (9) 46; (12) 30 Namyslo, J.C. (8) 18 Nankawa, T. (1 1) 267; (14) 242 Narkunan, K.(10.3) 26; (13) 52 Narshall, E.L. (10.2) 23 Natile, G. (12) 171; (13) 156 Natsume, S.(14) 138 Naumann, D.(7) 103 Nauss, J.L.(1) 224; (9) 72 Navarra, R. (1 2) 172 Navarro, J. (12) 99; (13) 102 Navarro, R. (3) 33; (1 1) 327 Navratil, 0. (5) 5 1 Neagu, I.B. (13) 43 Neander, S. (2) 147, 149 Neels, A. (1) 25 1; (9) 115; (I I) 102, 107, 302, 304-306; (13) 469 Nefedov, O.M. (1) 98 Nefedov, S.E. (4) 36,62 Negishi, E.4. (2) 89; ) 13) 22 Negishi, Y.(4) 15 1 Nkgrel, J.-C. (1) 39,40 Neithamer, D.R. (1) 176; (10.2) 29; (13) 267 Nekrasov, Y.S.(14) 216 Nelson, J.D. (8) 22 Nelson, K.K. (13) 148 Nemukhin, A.V. (1) 17; (4) 148 Neretin, I.S.(5) 30, 57 Nesterov, V.V. (4) 54 Net, G. (1) 256; (13) 210,220, 43 1 Nethaji, M. (1 1) 227, 228 Ncuburgcr, M. (2) 43,45; (13) 498 Neumann, B. (6) 8 1,96; (7) 14, 76; (9) 138; (14) 108 Neumann, H.(13) 69 Neumuller, B. (4) 115; (7) 57, 100 Neurock,’M. (1) 37 1 Ncuschiitz, M. (1 1) 291 Newcombe, N.J. (8) 83 Newman, P.D. (13) 132 Ng, A.C.H. (13) 244

Author Index Ng, D.K.P. (10.3)22;(13)244 Ng, S.M. (1) 275 Ng, T.-L. (6)89 Ng, W.S. (12)56 Nguyen, K.A. (7)67 Nguyen, L. (13) 483 Nguyen, M.T. (1) 182,231; (7)66 Nguyen, P. (2) 140;(12)4;(14) 167 Ni, J. (2)20 Nice, L.E.(2) 170 Nicholas, J.B. (1) 18,21,26;(2) 137 Nicholas, K.M. (9)92;(13)247, 371 Nichols, P.J. (7)75 Nicholson, B.K.(2)216;(3) 41; (7) 108;(10.4)23;(11) 10, 11, 104,248;(14)172 Nickias, P.N. (13) 267 Nicolas, M.(6) 18 Nie, W.(4)52,56;(14) 15 Niecke, E.(1) 5; (2)98;(7) 17, 23,31,32 Niedner-Schatteburg, G. (1) 335 Nief, F. (4)41;(7)38,54 Nieger, M.(1) 5,284; (2)98, 109; (6)55,69;(7) 17,23,31,32, 109 Nielson, A.J. (13)326 Niemeyer, M. (4)21; (1 1) 226 Nierlich, M. (14) 12,22 Niero, A. (13) 136 Nifantev, I.E. (14) 154 Nihei, M.(1 1) 267;(14)242 Nijhoff, J. (1) 253;(9) 121;(11) 160-163 Nikitina, L. (1) 384 Nikonov, G.I.(1) 272 Ning, G.L. (2)203,205,206;(13) 5 13 Nishibayashi, Y. (8) 99;(14)176, 222 Nishida, R.(3) 13 Nishihara, H.(1 1) 267;(14)242 Nishihara,Y. (10.1)73;(13) 168 Nishikawa, K. (1 1) 12 Nishikawa, N. (14)247 Nishimura, Y. (8)92 Nishinzawa, M.(13)389,390 Nishitani, T.(4) 130 Nishiura, M.(4) 121, 123 Nishiyama, M. (8) 1 1 Nishiyama, Y.(2)79 Nishizawa, R.(13)391 Nishizawa, T. (13)391 Nissinen, M.(10.1)70;(13) 171, 287; (14)80

505

Oakes, S. (8) 127 Oanunzi, A. (12)233 100 Oberhammer, H.(7)84 Nixon, D.M.(1 1) 332 Nixon, J.F.(1) 233;(7)5,7,8,35, Oberhauser, W. (1 3) 216 Oberhoff, M.(10.1)41 39,42,43,61,62,82;(10.1) Obcrt, S.J. (14)7 72;(14)128 Oberthur, M. (4)79 Nobata,M. (11) I12 Ochal, 2.(6)60 Noble, M.J.(6)74 Ockwig, N. (1 1) 260 Nobrega, J.A. (1)55; (6)93 Oderaotoshi, Y.(8) 114 Nocera, D.G. (6)13 Odom, A.L. (10.3)30 Nodono, M. (4) 1 1 1 O'Dowd, H.(2) 120 Noels, A.F. (13) 305 Noth, H. (1) 95;(3) 3, 16, 17;(6) ODwyer, L. (1 1) 293 Oelckers, B. (9)47;(10.4)34 75,94;(7)33,81;(14)248 Oevering, H.(1) 372,385;(13) Noguchi, S.(14)61 147 Noguchi, Y. (2)72;(14)56 Officer, D.L. (14)192, 195 Noh, S.K. (14)38 Nolan, S.P.(8)6-8;(12)78, 144, Ofial, A.R.(1) 180;(13)262 Ogasawara, M.(8)65-67 214-216,220;(1 3) 232 Ogawa, A. (14)44 Noll, B.C.(5) 16 Ogawa, H.(1 1) 124 Noll, R.J. (1)334 Noltemeyer, M.(3)21.22;(6)5 1, Ogawa, T. (2) 199 Ogino, H.(1) 234;(9)51, 153; 54,61,63,65;(10.2)5; (14) (11) 182,263,331 35 Nombel, P. (1 1) 96,129;(13)453 Ogle, C.A. (2) 161 Ogliaro, F.(1 1) 15 Nomura, H. (7)78 Oglieve, K.E. (12) 142 Nomura, Y. (1 1) 300;(13) 468 Ogo,S.(11)12;(14)247 Nonaka, A. (13) 71 Ogoshi, S.(13) 144,505 Nonari, M. (13) 150 Ogura, K.(2) 167 Nordin, S.J.M. (1)373 Oh,M.(12)124, 191 Norlandcr, E.(1 1) 188;(13) 485 Oharcsian, G.(1) 9 Norman, N.C. (7)119;(14)161 OHare, D.(14) 167 Norman, T.(1) 249;(9)65 Ohe, K. (7)97;(8)92 Normant, J.F.(2)22;(3) 47 Ohf'f, A. (12)177 Nomby, P.-0. (1) 355,381-383, Ohff, M.(12)177;(13) 209 387;(13) 107, 118, 119 Ohishi, H.(13) 296 Norrman, K. (1) 9 Norton, J.R (6)6;(13)358;(14) Ohjno, K.(1) 32 Ohmori, K.(13)394 83 Ohno, H.(2)169 Norton, S.H.(1) 38;(2)76 Ohno, K.(1) 12 NOS^ H. (4)79 Ohsawa, K.(2)173 Novgorodova, M.N. (4) 140 Ohshiro, N.(12)I99 Novikov, Y.N. (10.1)54;(13) Ohta, K. (13)92 162 Oi, S. (8) 68 Nowak, I. (10.2)3 Ok, K.M.(12)124 Nowotny, M.(7)83;(14)10 Okada, N. (2)65 Noyori, R.(1)412;(13) 202 Okada, T.(I 1) 140 Nuber, B. (9)129;(1 1) 282;(13) Okada,Y. (13) 144,389,390 275;(14)86, 107 Okazaki, M.(9) 153;(1 1) 182, Nudelman, N.S. (1) 42 263,331 Niirnberg, 0.(12)132;(13) 335 Okazaki, R.(6)17,34 Nugay, T.(2)61 Oke, 0.(12)105 Ntiiiez, R.(5) 58 Okimura, H.(1 2) 5 1 Nunzi, F. (1) 3 1 1 Okuda, J. (4)47, 101, 110;(10.1) Nunzi, J.-M. (2)114 36;(14)20 Nuyken, 0.(12)218 Olbrich, F. (2) 147, 149 Nyce, G.W. (4)33 Nyulaszi, L. (1) 233;(7)8,42,45 Old, D.W. (8) 9

Niu, S. ( I ) 294,404;(12)89;(13)

Organometallic Chemistry

506

Oldfield, E. (1) 243 O'Leary, D.J. (8) 56 O'Leary, S.R (13) 305 Olejnik, M. (13) 353 Oliva, J.M. (1) 4 Olivan, M. (1) 306; (12) 224,235, 236

Olivares, R.C. (7) 117 Ollivier, J. (1) 384 Olmstead, M.M. (2) 222; (7) 73; (11) 238; (13) 109; (14) 170

Olofsson, K. (8) 132 Olsen, M . R (7) 108; (10.4) 23 Olsap, D.M. (9) 45 Olson, J.S. (1) 244 On&, L.H. (5) 29 Onak, T. (5) 11 Onaka, S. (1 1) 289 Oiiate, E. (1) 258,306; (12) 70, 73,235,236; (13) 430

O'Neil, LA. (1 1) 38 Ong, C.M. (6) 44,53 Ongania, K.-H. (2) 35; (14) 122 Onishi, M. (12) 35 Onitsuka, K. (12) 199 Ono, A. (13) 202 Ooi, T. (2) 10,85, 86 Opromolla, G. (2) 35 Oprunenko, Y.F. (1) 175 Orabona, I. (13) 153 Orchard, S.D.(9) 73, 80 Orchin, M. (10.4) 25 Ordinas, J.I. (13) 130 O'Reilly, R.K. (9) 14; (1 1) 86 Orejon, A. (1 1) 253 Orlandini, A. (3) 34 Ormsby, D.L.(5) 28 Oro, L.A. (11) 1, 198, 199,252, 253; (12) 99, 125, 128; (13) 101, 102,438,440; (14) 52 Orozco, M.(1) 19 Orpen, A.G. (1) 170; (2) 27, 188; (3) 40; (6) 26; (7) 119; (9) 81; (10.3) 36; (10.4) 3,4; (11) 50, 328; (12) 154; (1 3) 3 18,324, 435,509; (14) 161 Orsini, J. (13) 197 Ortin, Y. (10.4) 44; (13) 175 Ortmann, D.A. (12) 213 Qsada, M. (1 1) 222 Osada,T. (1) 28 Osakada,K. (1 3) 93; (14) 13 I O'Shaughnessy, P. (2) 50,53 Oshima, K. (2) 39; (13) 17 Osornio, Y.M. (1 1) 79 Qtero, A. (10.2) 1, 11, 12,27; (11) 254; (13) 140, 141,316,420; (14) 19

Otsa,

E. (3) 9

Ott, K.C. (11) 210 Otto, S . (13) 152 Overby, J.S. (14) 89 Overcast, J.D. (13) 148 Overman, L.E. (2) 162 Owcn, D.A. (13) 25 1 Owcn, P. (6) 16 Owuor, F.A. (14) 67 Oyefeso, A.O. (1) 232 Ozawa, F. (12) 188 Ozawa, Y. (11) 268 b k a r , S. (13) 49, 189, 190; (14) 148

Pacifico, C. (12) 171 Padilla-Tosta, M.E.(14) 193 Paffen, F.-J. (1) 157; (13) 276 Page, E.M. (1) 81 Page, N.A. (12) 62 Paget, T.J. (1) 170; (10.3) 36; (13) 3 18,323

Paik, S.J.(13) 178 Pailhous, I. (7) 18 Pais, A.A.C.C. (1) 369 Pajuelo, F. ( I ) 389; ( I 3) 116 Pakkanen, T.A. (1) 409; (9) 146; (1 1) 301

Pal, S.K. (14) 184 Palazzi, A. (12) 234 Pallin, V. (3) 7,9 Palma, P. (12) 12, 174, 180 Palmer, J.S. (2) 152; (14) 5 P h i e s , 0. (1) 256; (13) 210,220, 43 1

Pampaloni, G. (14) 87 Pan, G. (9) 60 Pan, Y.M.(1) 31; (13) 226 Panaro, S.A. (8) 57,61 Panchanatheswaran, K. (3) 37 Pancrazi, A. (2) 175 Panek, J. (1) 73; (8) 88 Pancque, M. (12) 97.98, 153, 228; (13) 98

Pang, W.-K. (8) 58 Panigati, M. (1 1) 65 Panitz, J.C. (1) 226 Panjabi, G. (11) 208,210 Panneerselvam, K. (1 1) 33 Pannell, K.H.(2) 142; (14) 201 Panov, D. (3) 6 Panunzi, A. (13) 112, 150, 151 Panyella, D. (13) 130, 13 1 Panzeri, W. (13) 201 Paoli, P. (1) 379; (12) 90; (13) 334

Papadopoulos, S. (6) 87

Papai, 1. (1) 3 13,323; (13) 106 Paquette, L.A. (14) 6 Pardo, T. (14) 193 Parente, V. ( I ) 28 Pares, J. (13) 48 1 Park, H . 4 . (6) 48 Park, J. (13) 526; (14) 174 Park, J.E. (6) 40, 79 Park, J.T. (6) 40,79; (13) 9 1 Park, J.W. (6) 49 Park, K.-L. (5) 67,71, 73 Park,Y.J. (13) 103 Park, Y.-L. (5) 71 Park, Y.S. (2) 17 Park, Y.W. (5) 74 Parker, D.G. (1 1) 144, 148; (12) 62

Parker, J.R. (10.2) 32; (13) 174 Parkin, D.(5) 2 Parkin, G. (6) 11,31; (10.1) 65, 66; (10.2) 16; (10.3) 21; (13) 163; (14) 77,92, 109 Parkinson, J.A. (5) 49 Parry, J.S. (2) 153 Parsons, S. (1) 296; (2) 68; (9) 47, 62, 109; (10.4) 34; (1 1) 125; (12) 145; (13) 47 Parthasamthi, V. (3) 37 Partridge, M.G.(1) 403 Parvez, M. (6) 5; (10.1) 68; (13) 169 Pary, Z. (14) 119 Paselli, A. (9) 155; (1 1) 312 Pasinszki, T. (1) 12 Pasquali, M. (1) 262 Pasynkiewicz, S. (1 1) 2 13; (1 3) 408; (14) 260 Patel, B.P. (1) 270 Patel, J . (12) 158 Patel, M.M.(13) 396 Pateman, G.E.(1 1) 77; (13) 352, 425 Paton, R.M. (2) 21 Patton, D.C.(1) 127 Patton, J.T. (4) 102; (13) 267 Paugam, R. ( I ) 384 Paul, F. (12) 61,71 Paulasaari, J.K. (13) 70 Pauson, P.L. (12) 117; (13) 363, 364, 366,379-38 1 Pavlcnko, N.1. (1 1) 307; (13) 445 Payen, A.J. (13) 234 Payne, B.R. (14) 167 Payne, C.K. (1) 210; (9) 24 Paz-Sandoval, M.A. (13) 78 Pearson, A.J. (13) 43 Pebler, J. (11) 83; (13) 344; (14) 184

Aulhor Index Peckham, T.J. (14) 162 Pedersen, B.(14) 144 Pederson, H.L. (14) 180 Pederson, M.R. (1) 127 Pellei, M. (6) 30;(13) 201 Pellinghelli, M.A. (10.2)12 Pellny, P.-M. (10.1)47-52;(13) 164, 165,280,281,312,439; (14)29,73 Pence, L.E. (1 1) 206 Penenory, A.B. (2)41 Peng, S.-M. (1) 230;(2) 177;(9) 74, 131;.(10.3)26,51;(11) 68,70,155,266,287;(12) 161;(13) 52, 143,441,442, 471,473-475;(14)96 Peng, 2.-H. (1) 396 Pennie, M.A. (13)425 Pennington, W.T.(13) 148 Penso, M.(2) 117 Peplow, M.A. (13) 1 1 Peppe, C.(1) 55; (6)93 PBralez, E. (1) 39,40 Perea, J.J.A. (2) 108 Pereira, M.M. (1) 369;(13) 213 Perera, J.R (1) 147;(14)200 Perez, G.E.(7)96 Perez, P.J.(12)97;(13) 98 Perez-Camacho, 0.(14)42 Perez-Carrerio, E.(1) 378,379; (12)90;(13)334 Perez-Torrente, J.J. (1 1) 252,253; (13)438,440;(14)52 Periasamy, M.(9)44;(13)384 Pericas, M.A. (9) 130;(13) 367, 368,385 Perin, G.(2)74 Peringer, P.(1 1) 247 Peris, E.(1) 235;(9) 16 Pejessy, A. (1) 169 Perkinson, J.L. (1) 250;(1 1) 76 Pernin, C.G.(4) 1 Perrin, J.L. (9)40,42,43;(1 1) 172, 174;(13) 359 Perron, P. (14) 154,215 Peny, J.K. (1) 328 Persoons, A. (12)68 Perutz, RN.(9)27,47;(10.4)34; (12) 145 Peruzzini, M. (10.4)39;(12)76, 229 Pesti, J.A. (2)84 Peter, M.(2) 141;(14)190 Peters, D.W.(6)80 Peters, F.(6) 29 Peters, R.(14)225 Peters, R.G.(14) 1 1 Peters, T.B. (12) 198

Petersen, J.L. (9)57;(12)215 Peterson, T.H.(2)37;(12)112 Pktillon, F.Y.(10.3)32;(13)346 Petri, S.H.A. (14) 108 Petrie, S.(1) 13 Petrini, M.(2) 87 Petrov, E.S.(4)140 Petrova, L. (14) 142 Petrovskaya, T.V.(4)61.66 Petrovskii, P.V.(5)54;(1 1) 307; (13)305,429,445 Petrukhina, M.A. (1I) 53 Petrusova, L.(14)3 1 Pctters, D.(1 1) 290 Pettig, S.J. (14)54 Pettinari, C.(6)30;(13) 201 Petz, W.(1) 241;(12)164 Peuchert, U.(10.1)44 Peukert, S.(8)122 Peulecke, N.(10.1)50;(13)280; (14)29 Peymann, T. (5) 15 Pfab, H.(13) 66,67 Pfaffen, F.4. (14)254 Pfaltz, A. (8)24 Pfeffer, M.(2)109;(12)36, 101, 158 Pfeiffer, D. (4)3.4 Pfeiffer, M. (1) 155 Pfister-Guillouzo, G. (1) 84,86 Pfitzner, A. (3) 16 Pfletschinger, A. (1) 165, 178; (13)291 Pflug, J. (10.1)35,45;(13) 170; (14)69 Pflum, D.A.(8)63 Phetmung, H. (2)27 Philipps, P. (13)79 Phillips, B.L. (1 1) 209 Phillips, G.N., Jr. (1) 244 Phillips, L.(14)30 Phillips, P. (7)59 Phillips, R.C. (2)91 Piaccnti, F. (1 1) 142 Pickardt, J. (12)186;(14)168 Pickett, N.L. (3)63;(6)84 Piquet, M. (12)53 Pie, G.(2)71 Piemontesi, F.(1) 345 Picrini, A.B. (I) 114 Pierloot, K.(1) 231;(7)66 Piers, W.E.(6)5,23;(10.1)68; (10.2)9;(13) 169;(14)58 Piet, J.J. (11) 163 Pietrass,T. (11) 210 Pietrowski, M.(1 1) 152 Pietrzykowski, A. (1 1) 213;(13) 408;(14)260,261

507 Pietzsch, C. (14)135 Pietzsch, H.-J. (9)82 Pignolct, L.H.(1 1) 325 Pigot, T.(1) 84 Pike, R.D.(1 I) 28 Pilloni, G.(12) 100 Pilo, L. (2)4 Pinado, G.J. (10.1)46;(13) 284 Pinho, P. (1) 41 1; (3) 61 Piniella, J.-F. (9) 130;(13)367, 368,385 Pinilla, E.(13) 521 Pink, M.(13)128 Pinkas, J. (3) 22;(6)54 Pinkerton, A.B. (8)80 Pinna, M.V.(2)210 Piotrowski, H.(13) 250 Piquet-Fad, V. (10.1)36 Pistolesi, L. (1 1) 142 Pittman, C.U.,Jr. (1) 100 Pizzano, A. (1) 283;(12)97;(13) 98 Planas, J.G. (12)28;(13)74 Plank, S.(7)57,58 Plath, M. (14)237,239 PIC, N.(2) 135 Plcicr, A.-K. (1 1) 133 Plcixats, R (1) 389;(13) 116 Plenio, H.(1) 1 1 Plesek, J. (5) 8 Pleune, B.(1) 139 Ploypradith, P. (2) 120 Plutino, M.R. (13) 152 Pldk, 2.(5)28,48 Poblet, J.-M. (1) 121,256,318; (13)431 Podkorytov, I.S.(9)3 1, 150;(1 1) 8,320 Poi!, A.J. (9)118, 124;(I 1) 168, 180;(1 3) 470 Piirschke, K.-R. (12)146 Pogrebnyakov, D.A.(1 1) 307; (13)445 Pohlman, M.(9)56 PolSck, M. (10.1)47,53,57;(13) 161,268,342,516;(14)203 Polborn, K.(3)16, 17;(7)33; (14)125 Poli, R.( I ) 136-139,156;(10.3) 10;(14)99, 101 Poliakoff, M. (13)27 Polikarpov, E.V.(1) 17 Polishchuk, 0.(7)25 Politzsch, W.(14)135 Polyakov, O.G.(2) 181;(9) 141 Pombeiro, A.J.L. (7)5; (10.4)6 Ponikwar, W.(6)75,94;(7)33, 81

508 Pons, M. (6) 18 Poole, A.D. (9) 127 Pope, S.J.A. (9)79,80 Popham, N.H. (13) 421;(14)68 l’opovic, Z.(6) 12 Poremba, P. (4)69 Porezag, D.V.(1) 127 Porschke, K.-R. (9) 137 Porta, F. (1 1) 65 Porter, J.R. (13)245 Porth, S.(13) 108 Posner, G.H. (2) 120 Potechin, V.V.(13) 149 Poujaud, N. (13)141 Poulard, C. (14)93 Poveda, M.L. (12)97,98,228; (13) 98 Powell, A.K. (10.1)26,61 Powell,D.R. (6) 14;(9) 157;(1 1) 51 Powell, H.R. (7)121;(1 1) 191 Power, M.P. (6)80 Power, P.P.(2) 192;(6)70,88; (7)69,73 Powers, D.E. (1) 288 Poui, G.(8) 131 Prabhakar, S.(14)220 Rraefcke, K.(12) 186 Rrashar, S.(10.2)27 ,Prater, M.E. (1 1) 206 Predien, G.(9)104;(1 1) 109 Pregosin, P.S. (13) 1 1 1, 196,525 Rreuss, F.(7)8 Prigge, J. (10.3)50 Prince, P.D. (13)5 1 1 Pringle, P.G. (12) 154 Pritchard, G.J. (2) 1 1 1 Pritchard, R.G.(2)68;(7) 106 Pritzkow, H.(1) 157,305;(2) 138;(11) 190,318;(13)44, 275,276,484,497;(14)254, 255 Probst, D.A. (8)52 Probst, J. (7)87 Prock, A. (12)144;(13) 232 Procopiou, P. (8)46 Procter, D.J. (2)3 Procter, M.J.(13) 36 Prokopchuk, E.M. (12)148 Prokopuk, N.(1 1) 78 Prosenc, M.-H. (1) 13 1 Proshar, S.(14) 19 Proust, A. (14)103 h i s , J.G. (12) 126 Psaro,R.(13)216 Pu, L. (3)59 Bucci, D.(12)168 Puddephatt, R.J. (2)223;(1 1)

Organomeiallic Chemistry Ramming, M. (1 3) 275 Ramon, D.J. (2)77 Ramondenc, Y.(2)71 Ramusino, M.C. (1)92 Ranaivonjatovo, H.(1) 97;(7)18, I9 Rancurel, C. (13) 128 Randaccio, L. (1) 285,301 Rankin, D.W.H. (1) 296 Rankin, J. (9)127 Rao, M. (3) 65 Rasmussen, T.(1) 355 Raston, C.L. (5) 3, 32,33;(6)87; (7)75 Rath, N.P. (5) 35;(12)116 Ratni, H.(9)55 Raubenheimer, H.G.(10.3)52 Qian, C.(4)46,52,56,57;(14) Rauccio, M. (11)313 15,23 Rauchfiiss, T.B.(14)259 Qian, Y.(4)42 Ray, C.D.(13) 324 Qu, B.(9)41 Raymond, C.C. (9)98;(1 1)74, Qualye, S.C.(14)238 80;(12)48;(1 3) 449 Q u a , Z.(13) 526;(14)174 Raymond, M.-N. (2)157, 158 Quannby, I.C.(14)106 Raper, C.M.(8)127 Quasdorf, J.-M. (9)138 Re,N. (1)301,304,311;(10.1) Quattrucci, I. (1)89 23;(I 0.2) 6;(10.3)28,55; Queguiner, G.(2)26, 135 (13)172 Quici, S.(8)13 1 Ready, J.M.(8) 118 Quindt, V.(14)127 Reardon, D.(10.2)4 Reau, R (7)27 Reboul, V. (13)255 Ra,C.S. (14)38 Reddmann, H. (4)149 Raabe, G.(14)225 Reddy, K.R. (2)177;(10.3)5,51; Rabe, G.W. (2) 133; (4)23.94 (12)161 Radetich, B.(13) 204 Reddy, N.D. (14)133 Radhakrishnan, U.(13)24 Redko, M. (2)91 Radius, U.(1) 246 Redmond, S.P. (1)249;(9)65 Radkov, E.V. (14)70 Redshaw, C.(6)46,47;(10.3)16, M o m , L.(1) 13; (7)63 17 Ragaini, F. (9) 103;(1 1) 136, 137 Reed, C.A.(1) 162;(5) 17 Rager, M.N. (14)245 Reed, D. (2)21;(5)49 Raghuraman, K. (14)146 Raithby, P.R (2)30, 152, 187;(7) Reek, J.N.H. (1) 385 Rees, W.S., Jr. (6)84 13, 120,121;(9)158; (1 1) 1, 46,56,191;(12)62;(13) 425, Reetz, M.T. (4) 137;(7)52;(1 1) 215;(13)208 426,437;(14)5 Regitz, M.(1)233;(7) 4,8,27 Raj, S.S.S.(1 1) 30,284 Rehder, D.(10.2)2;(13)315 Raja, R. (1 1) 45 Reibenspies, J.H. (1) 229,294;(9) Rajanbabu, T.V.(13) 204 61;(12)89;(14)202 Rajesh, T.(9)44;(13) 384 Rcich, H.J. (2)52, 102 Ramachandran, R. (9)124;(1 1) Reid, G.(9) 25,73, 79,80 180 Reid, S.M. (10.1)14 Ramirez, J.A. (14)193 Reider, P.J. (3) 56 Ramircz, L.R. (14)173 Reiger, A.L. (10.3)36 Ramirez, P. (10.3)40 Reiger, P.H.(10.3)36;(1 1) 189 Ramirez de Arellano, M.C.(9) Reina, R. (1 1) 3 1 1 158;(11) 46;(12)179, 182, Reinhold, J. (1) 133,219;(9) 4; 184;(13) 228 (11)17;(14)9 Ramirez-Solis, A. (1) 338

243,308,309,322;(12)148, 151, 157,170 Puerta, C. (13) 130 Pucrta, M.C. (12)10,57,58,74, 125 Pugin, R. (1 1) 42,43 Pumth, A.(1) 67;(6)72 Pun, V.K. (1 1) 15 1 Purpura, M. (2) 171 Pursiainen, J. (9) 146;(1 1) 301 Puttnat, M. (14)135 Putzer, M.A. (1) 291 Pye, C.C.(1) 340 Pyykko, P.(1) 63

Auihor lndex Reinhold, M.(1) 104; (6) 38 Reinhoudt, D.N. (2) 141; (14) 190, 197 Reising, J. (1) 284 Reisinger, C.P. (12) 6, 207 Reisky, M.(2) 48, 150; (12) 156, 167 ReiR, G.J. (13) 270 Rcisse, I. (3) 45 Reissmann, U.(4) 69 Reiter, R.C. (4) 64 Renard, C.(13) 251,271 Rendina, L.M.(12) 170 Renkema, K.B.(1) 398; (12) 33, 54; (13) 332 Rennenkamp, C. (6) 61 Rqat, H.(2) 61 Resconi, L. (1) 345 Reshetova, M.D.(14) 123 Rettig, S.J.(6) 5 ; (10.1) 37,39, 68; (10.2) 8,9; (10.3) 13-15, 29; (12) 63; (13) 50, 128, 167, 169 Retzow, S.(1) 36 Reumann, G. (6) 8 1,96 Reyes, M.(1 1) 146, 147 Reynolds, K.A. (12) 113 Reynolds, M.A. (9) 36 Rheingold, A.L. (2) 133; (4) 3,4, 94; (6) 68,85; (7)123; (8) 10; (10.3) 12; (11) 186,332,333; (12) 122, 169; (13) 37,39,85, 99,307; (14) 163,232 Rheinwald, G. (2) 186; (13) 417, 418,436,514; (14) 27 Rhine, W.E. (6) 57 Riahi, A. (13) 126 Riant, P. (4) 41; (7)39 Ribbing, C.(1) 208 Ricalton, A. (10.3) 33; (13) 240 Ricard, C.E.F. (13) 326 Ricard, L. (4) 41; (7) 36,3941, 53-56,68; (14) 75, 159 Ricart,S.(13) 481 Ricci, A. (2) 168 Ricci, J.S.(1) 89 Rice, C.R. (14) 161 Rice,D.A. (1) 81 Richard, P. (1) 139; (14) 93,99 Richards, A.F. (7)9, 16 Richards, C.J. (14) 177,256 Richards, R.L. (9) 25,66; (1 1) 82 Richardson, A.D. (1) 82,83 Richardson, N.A. (1) 78 Richeson, D.S.(10.2) 28 Richsenhein, H.(13) 191 Richter, R. (14) 136 Richter, U. (1) 133; (14) 9

509 Rickard, C.E.F. (1) 162; (12) 32 Ridge, D.P. (1) 405; (13) 54 Ride, J. (3) 35; (1 1) 237 Riedmiller, F. (I) 87 Rieger, A.L. (1) 170; (13) 318 Rieger, B.(14) 78 Rieger, P.H. (1) 170; (12) 118; (13) 318,324 Rieke, R.D. (3) 44 Riello, L. (12) 100 Rienmacker, C.M.(1) 95 Rienstra, C.M. (2) 182 Rienstra-Kirawfc, J.C.(1) 78 Riera, A. (9) 130; (13) 367,368, 385 Riera, V. (10.3) 57,58; (11) 314; (14) 114, 116 Riese, U. (11) 83 Rigby, J.H. (13) 15,233,234 Rigby, S.S.(13) 362 Rigo, P.(12) 226 Rigon, L. (7)19 Rijnberg, E.(3) 58 Riley, P.N. (10.2) 18,32; (13) 174 Ringelberg, S.N.(4) 103 Ringwald, M.(14) 63 Rink, B. (1 1) 57 Ripoche, I. (13) 300 Ritleng, V. (12) 36 Rizzoli, C.(1) 304; (10.1) 23; (10.2) 6; (10.3) 23,28,55; (13) 172 Robben, M.P. (1 1) 189 Robert, F.(13) 388 Roberto, D. (1 1) 85 Roberto-Neto, 0. (1) 1 Roberts, B.A. (7) 75 Roberts, RM.G. (14) 2 10 Roberts, RS.(8) 47 Roberts, S.M.(13) 209 Robertson, H.E.(1) 296 Robertson, S.M. (13) 381 Robinson, B.H.(9) 38; (1 1) 6, 185; (13) 519; (14) 181, 188 Robinson, G.H.(6) 76,77 Robinson, J.E. (8) 22,51 Robinson, L.A. (2) 16 Robinson, R.E. (8) 52 Robinson, W.T. (3) 37 Robirds, E.S.(6) 95 Rockwell, J.J. (5) 36 Roddick, D.M. (12) 106, 159; (13) 404 Rodebaugh, R. (1) 4 10 Rodewald, D. (1) 283 Rodger, P.J.A. (2) 40 Rodriguez, A. (10.2) 11,27; (I 1) 254; (13) 3 16,420; (14) 19,

178 Rodriguez, F. (1) 236 Rodriguez, M.A. (1) 236 Rodriguez-Fortea, A. (1) 94 Roe,C.(11) 153 Roe, D.C. (13) 94 Roe,J. (1 1) 153 Rohr, C.(13) 224 Rocrs, R.(13) 360 Rosch, N. (1) 145,220, 259,358, 359; (1 1) 16 Roesky, H.W. (3) 21,22; (6) 48, 51,54,61-63; (10.2) 5 Roesky, P.W. (1) 189,359; (4) 68; (6) 65 Rosler, R. (7) 85,87,90,95, 116 Roeves, G. (14) 135 Rogers, J.S. (10.1) 29,80 Rogers, L.M. (1) 26 Rogers, R.D.(1) 26; (14) 6 Rogge, W. (1) 70; (9) 128 Roh, J. (1 1) 166 Rohmer, M.M. (1) 121 Roidl, G.(1 1) 92; (13) 273,274, 454,480 Romiio, C.C. (1) 173; (13) 38,41; (14) 115 Romerosa, A. (10.4) 39; (12) 76, 229 Rominger, F. (1) 298; (8) 44; (12) 210,211; (13) 275,360 Rsmming, C. (1 0.3) 44 Roodt, A. (13) 152 Roper, W.R. (12) 32 Rosa, A. (1) 204,205 Rosa, P. (7) 53; (14) 75 Rosair, G.M.( 5 ) 51,52; (13) 191 Rosalez-Hoz, M.J.(14) 42 Rosdahl, J. (1) 163 Rose, E. (13) 251,271 Rose, J. (9) 144; (1 1) 275,276, 296 Rose, L. (1 1) 142 Rose-Munch, F. (13) 25 1,27 1 Rosenberg, D.M. (3) 44 Rosenberg, E. (1 1) 100,101,153, 165, 166 Rosenblum, D.B.(6) 78 Rosenpliinter, I. (6) 20 Rosenthal, U.(10.1) 47-52; (13) 164, 165,280,28 1,3 12,439; (14) 29,73 Rosi, M. (1) 280,281, 316; (13) 183 Rosini, G.P. (13) 182 Rossell, 0. (1 1) 31 1,315,316 Rossi, R.A. (2) 41; (10.4) 39 Rost, M.(13) 299

510 Rosta, E. (1) 130; (14) 43 ROSE&,S.(1) 159 Roth, G.(10.3) 47 Roth, W.R. (13) 303 Rothwell, I.P. (10.1) 3,4,7; (10.2) 15, 18,32; (13) 174 Rottlaender, M. (3) 11 Rouag, D. (1 1) 334 Rousseau, R. (1) 254; (12) 65; (13) 482 Roveda, C.(1 1) 85; (14) 191 Rovis, T. (8) 107 Rowlands, C.C.(10.3) 33; (13) 240 Rowley, M.(2) 110 Rowlings, R.B. (2) 128; (3) 4 Roy, B. (1 1) 153 Roy, S.(14) 220 Royo, B. (1) 173; (10.1) 64; (13) 38; (14) 41, 115 Royo, P. (10.1) 30,34,64; (10.2) 22; (10.3) 25; (14) 4 1 Rozhenko, A. (14) 3 Roznyatovsky, V.A. (1) 175 Ru, L. (3) 38 Ruba, E. (12) 225 Rubaylo, A.I. (1 1) 307; (13) 445 Rubin, Y. (13) 10 Rubio, C.(12) 182 Rubio, J. (1) 75 Ruble, J.C. (14) 81, 149, 175 Rubner, 0. (1) 206 Ruck, M. (5) 75,76 Rudd, G.E.A. (1 1) 297 Rudler, H. (1 0.4) 19 Riick-Bmun, K. (13) 19,61,62, 65 Rueda, A. (3) 40; (1 1) 328; (13) 434 Rueda, M.T.(10.3) 57; (14) 114, 116 Ruegger, H. (13) 200 Ruehmer, T. (4) 109 Ruffo, F. (12) 233; (13) 112, 150, 151, 153 Ruffolo, R. (1 3) 362 Rufiska, A. (9) I37 Ruhlandte-Senge, K. (3) 2 Ruhmer, T. (4) 107 Ruiz, A. (1) 256; (13) 210,213, 220,43 1 Ruiz, B.-M. (13) 411 'Ruiz, C. (1) 283; (12) 98 Ruiz, J. (13) 129; (14) 217,228 Ruiz, M.A. (10.3) 57,58; (14) 114, 116 Ruiz, M.J. (1 1) 254; (13) 420 Ruiz, N. (1) 306; (11) 147; (12)

Orgariometallic Chemistry 73,235,236 Ruiz, S.(2) 106 Ruiz-Bermejo, M. (13) 521 Ruiz-Molina, D. (14) 191 Rumrney, C.(1) 155 Rupert, P.R. (13) 148 Ruppli, U.(13) 272 Ruschewitz, U.(1 1) 232 Russell, C.A. (2) 152; (14) 5 Russell, D . R (7) 11 1; (1 1) 104; (14) 172 Russo, N. (1) 75 Ruth, N.P. (14) 48 Ruthe, F. (7) 20 Ruthefiord, D. (6) 4 1 Ryabov, A.D. (14) 123 Ryan, O.B.(1) 407; (12) 155 Rybakova, L.F.(4) 140 Rybtchinski, B. (12) 1, 107; (13) 26,95 Rychnovsky, S.D. (2) 107 Rycroft, D.S.(1 1) 220 Rykova, E.A. (1) 43 Rys,A.Z. (14) 110 Ryzhov, V.(1) 22,160 Saak, W.(1) 56,69; (6) 33.92 Sabat, M. (13) 179, 180,416; (14) 76 Sabo-Etienne, S.(1) 267,273; (12) 2 Sachs, M. (7) 84 Sacristin, J. (12) 195, 197; (13) 433 Sadekov, I.D. (9) 1 Sadighi, J.P. (8) 9 Sadorge, A. (14) 86,91 saeb5,s. (1) 100 Saeeng, R. (13) 392 Safionova, A.V. (4) 92 Sagawa,T. (12) 188 Sahakitpichan, P. (13) 297 Saillard, J.-Y. (1) 152,248,251; (7) 102; (9) 115; (11) 15, 18, 19, 102 Saitkulova, L.N. (1) 293; (3) 39; (1 1) 29 Saito, H.(10.3) 24; (13) 327 Saito, K. (14) 61 Saito, T. (1 1) 61 Sakaguchi, S.(4) 126, 130; (8) 93 Sakai, A. (2) 34 Sakai, S. (12) 137 Sakaki, S. (1) 107, 108,365,366, 380; (12) 136; (13) 115 Sakamoto, T.(2) 173; (3) 48 Sakamoto. Y.1121 188: (141 209 ,

\

I

I . ,

Sakanishi, S. (I 1) 297 Sakano, T. (14) 131 Sakarya, N. (1) 233; (7) 43,45 Sakata, G. (3) 52 Sakkoke, A. (13) 137 Sakuai, A. (1 1) 72 sakurada,1. (8) 91 Sakurai, A. (1 1) 292; (12) 50; ( I 3) 476 Sakurai, H.(2) 145; (14) 71 Salaneck, W.R. (1) 28 Salaiin, J. (1) 384 Salazar, V. (12) 98,228 Salcedo, R. (1) 24 Saldamli, S.(13) 189 Salliot, 1. (2) 135 Salmain, M. (9) 37 Salteris, C.S. (2) 122, 123 Salvini, A. (11) 141, 142 Salzer, A. (10.4) 22; (13) 272 Salzmann, R. (1) 243 Samoc, M. (12) 66 Sampanthar, J.T.(12) 95 Samuelson, A.G. (1 1) 227,228; (14) 184 Sanchez, F. (10.2) 26; (13) 218 Shchez, L. (1) 283 Sanchez, M. (7) 27 Sandee, A.J. (13) 219 Sander, L. (3) 12 Sanders, J.R. (14) 187 Sanders, L.K.(1) 243 Sandoe, E.J. ( 13) 25 1 Sankar, G. (1 1) 45 Sansoni, M. (1 1) 34 Sansores, L.E. (1) 24 Santi, S. (13) 423 Santini, C.(6) 30 Santos, F.E.(1) 359 Sanuclo, S.(13) 130 Sappa, E. (1 1) 67, 145; (13) 7 Sapunov, V.N. (1) 153 Sarakha, M. (9) 71 Smoca, C.(2) 218; (14) 152, 158 Sarsfield, M.J. (10.1) 11, 25 Sasaki, A. (12) 29 Sasaki, S. (7) 12 Sasaki,Y. (11) 127 Sashida, H. (2) 73 Sassian, M. (3) 8 SaRmannshausen, J. (10.1) 26-28, 61; (14) 74 Sat, Y.(8) 69 Sato, A. (13) 229 Sato, M. (14) 208,234 Sato, T. (8) 73 Sato,Y.(12)51 Satoh, H. (13) 395

Author Index Satou, T. (14) 209 Sattely, E.S.(8) 50 Saudan,C.M. (8) 101; (14) 233 Saura-Llamas, I. (13) 228 Saurenz, D. (14) 127 Sauvageot, P. (14) 86,91 Sava, X. (7) 41,54; (13) 523; (14) 159

Saveswam, K.(13) 426 Savignac, P. (2) 1 Sawitowski, T. (11) 42 Sayan, S. (4) 97 Sayers, S.F.(1) 267 Saygh, A.A. (13) 37 Scaccianoce, L. (9) 110; (1 1) 126 Scahnz, H.J. (5) 27 Scallorn, W.B. (13) 37 Scanlan,T.H. (12) 37,85; (13) 349,350

Schabel, A.B. (1 1) 325 Schaefer, H.F., III (1) 78; (6) 77 Schaer, M. (14) 127 Schafher, K. (13) 49 Schakei, M.(1) 240 Schalf, P. (14) 227 Schanz, H.-J. (5) 23; (12) 78,214, 2 16,220

Schanze, K.S.(10.3) 61 Schaper, F. (1) 13 1 Schattenmann, W.C.(12) 218 Schauer, C.K.(1) 250; (1 1) 76 Schauer, S.J.(6) 42,57 Schaumann, E. (2) 165 Schauss, D. (9) 56 Schautz, F. (1) 185; (4) 144 Schauwienold, A.-M. (4) 100; (14) 45

Schavenen, C.J. (14) 21 Schebaum, L.O.(6) 96 Scheck, P.A. (12) 49 Scheer, M. (1) 246; (7) 6; (1 1) 59; (14) 97

Scheffer, M.H. (7) 76,77 Schemer, B.(1 1) 247 Scheiring, T.(12) 150; (13) 23 1 Schell, A. (14) 137,213 Schenk, W.A. (1) 155; (10.4) 3 1 Scherer, O.J.(7) 4, 86; (1 1) 294 Scherer, W. (1) 359; (14) 144 Schertl, P. (14) 26 Schertz, T. (4) 64 Scheschkewitz, D. (1) 23; (2) 46 Schiemann, 0. (13) 344 Schier, A. (3) 35; (1 1) 237 Schiffer, T.J.(2) 98; (7) 23 Schifftin, D.J.(1 1) 38 Schimkowiak, J. (10.2) 5 Schimpf, M.R (6) 14

511

Schirmer, H. (13) 236 Schlegel, H.B. (1) 147; (4) 4; (14) 200

Schleyer, P.von R. (1) 23; (2) 46; (5) 24,27

Schmaelzlin, E.(14) 144 Schmalle, H.W.(1) 142,238; (10.4) 36,37

Schmalz, H . 4 . (1) 165,178; (13) 29 1

Schmid, G.(1 1) 42,43 Schmid, R.(12) 2 12,225; (13) 75-77,266,306

Schmidbaur, H.(1) 87; (1 1) 237 Schmidt, C. (2) 114 Schmidt, H.(13) 149,3 15 Schmidt, H . G . (3) 22; (6) 51,61, 63,65; (10.2) 5

Schmidt, M.U.(1 1) 291 Schmidt, 0. (1) 5; (7) 17,32 Schmidt, R. (1) 153 Schmidt, U. (7) 94 Schmitt, G. (7) 4 Schmitt, 0. (14) 127 Schmitz, A. (4) 137 Schmutzler, K.(4) 107. Schmutzler, R. (7) 118 Schnabel, R.C. (12) 106; (13) 404 Schneider, A.G. (1 1) 167 Schneider, J.J. (13) 59, 86,407; (14) 253

Schnepf, A. (1) 62; (6) 90; (7) 34 Schneusser, M. (7) 65 Schnkkel, H. (1) 62,67; (6) 72, 90; (7) 34, 104

Schobert, R. (10.4) 45; (13) 32, 66,67

Schoel, N.J. (14) 89 Schoeller, W.W. (1) 5; (7) 14, 17, 32,76; (14) 3

Schoneboom, J. (12) 2 13 Schijnecker, B. (13) 299 Schoil, M.(8) 41,42 Schollhammer, P. (10.3) 32; (13) 346

Schooler, P. (9) 109, 110; (1 1) 125, 126

Schore, N.E.(13) 378 Schormann, M. (10.2) 5 Schoss, J.D. (14) 6 Schottenberger, H.(13) 361; (14) 171

Schreckenbach, G. (1) 2 17 Schreiber, K.-A. (2) 48; (12) 156 Schreiner, P.R (1) I 15; (3) 47 Schrock, R.R (8) 49,50; (10.1) 12-18

Schrodi, Y. (10.1) 17

Schrkler, D. (1) 77,330,336 Schroeder, G.M.(8) 26 Schriider, M. (2) 200 Schroen, M. (8) 19 Schubcrt, U. (1 1) 3 19 Schulmeier. B.E.(13) 145 Schulte, P. (13)414 Schultz, R.H. (9) 15; (10.3) 8 Schulz, C.S. (12) 23 1; (13) 60 Schulz, H.G.(1) 42 Schulz, S. (6) 55,69; (7) 109 Schumann, H. (3) 18; (4) 10,32, 48,58,59,63,66, 100; (7) 93; (14) 45,46

Schunlann, S. (4) 8 Schuster, K.(1 1) 59 Schwarz, H.(1) 77,330,336 Schwarz, J. (12) 205,207 Schwarz, W. (3) 27; (7) 57,58 Schwarzc, D. (9) 89 Schweder, B. (10.1) 5 Schwcigcr, S.W. (10.2) 15 Schwenk, H.(6) 75 Schwerdtfeger, P. (1) 163; (7) 2 Schwieger, W. (4) 107 Scopelliti, R. (2) 129, 146; (3) 19, 30; (4) 75, 76; (10.1) 24; (10.2) 7; (10.3) 39 Scott, B.L. (4) 39,89; (5) 43; (9) 78, 83; (12) 147 Scott,R A . (13) 413 Scott, S.M. (14) 195 Scottow, A. (1) 266 Scowen, I.J. (1 1) 57,249; (14) 198 Screttas, C.G. (2) 114, 122, 123; (13) 211 Seaglc, P.(2) 161 Seco, M.(1 1) 31 1,315,316 Scconi, G. (2) 168 Scddon, K.R.(8) 135, 136 Seevogel, K.(9) 137; (12) 146 Segal, J.A. (6) 46 &gal&, G. (11) 315,316 Segerer, U. (14) 40 Seibel, C.A. (4) 38 Scidcl, S.W. (10.1) 17 Seidelmann, 0. (14) 136 Seifert, T.(3) 3, 16; (7) 33 Seiss-Brandl, U. (7) 30 Sejbal, J. (13) 133 Sekar, P. (14) 97 Sekiguchi, A. (2) 145 Selegue, J.P.(12) 119 Selke, R. (1) 3 10 Sella, A. (11) 63 Sellin, M.F.(9) 126 Selmi, M.(1) 262

Organometallic Chemistry

512 Selvakumar, K. (13) 111, 196 Semikolenova, N.V.(1) 103 Semmelmann, M. (1 1) 39 Senda, T. (8) 66,67 Sbn&chal-Tocquer, M . 4 . (13) 487

Sensato, F.R (1) 55; (6) 93 Senskey, M.D. (13) 479 Seo, H. (14) 212 Seok, W.K. (13) 178 Separovic, F. (14) 30 Seppelt, K. (1) 276; (1 1) 52 Sergeev, G.B. (1) 17 Serino, C. (2) 17 Serra, M.E.S. (13) 213 Serwatowski, J. (3) 23; (6) 67; (1 1) 246

Sethi, A. (8) 134 Setsune, J . 4 (13) 139 Severin, K.(14) 248 Sevin, A. (7) 50 Sewel, R. (1 1) 62 Seybert, G. (4) 11,78,115 Seyfetth, D. (2) 88 Sgamellotti, A. (1) 280,281,311, 316; (13) 183

Shade, J.E. (13) 37 Shadinger, S.C. (8) 38 Shafir, A. (6) 43; (10.1) 9 Sham,I.H.T. (1) 222; (9) 91 Shamov, G.A. (1) 402 Shang,I.-J. (1 1) 236 Shang, M.(1) 247; (6) 27; (1 1) 58,99, 183, 186,211,286; (14) 235 Shang, Z.F. (1) 3 1 Shapiro, P.J. (1) 57; (3) 15; (6) 68 Shapiro, T.A. (2) 120 Shapley, J.R. (9) 87, 15 1; (11) 288; (13) 348 Shapley, P.A. (12) 26 Sharma,D.C. (7) 46 Sharma, P. (7) 96 Sharma, S. (2) 142; (14) 201 Sharp, P.R. (1 1) 239 Sharpless, K.B. (8) 85-87,90 Shaughnessy, K.H. (14) 230 Shaver, A. (1 1) 108; (14) 1 10 Shedlow, A.M. (5) 26 Shelby, Q.D. (2) 38; (12) 45; (13) 46 Sheldon, R.A. (10.4) 9 Shen, B. (2) 174; (14) 53 Shen, F.-R.(4) 15 Shen, J. (1 1) 23 1 Shen, Q. (4) 19,20, 119 Shen, Y. (2) 20 Shephard, D.S.(1 1) 45

Sheppard, N. (13) 358 S h e d , N.(8) 127 Shi, X. (14) 67 Shibahara,T. (4) 116 Shibasaki, M. (8) 91 Shibata, K. (3) 50 Shido, T. (1 1) 222 Shieh, M. (1 1) 60,69 Shields, G.P. (13) 426 Shilai, M. (3) 48 Shim, I. (1) 118 Shimada, S. (1 1) 129 Shimamoto, K.-y. (13) 297 Shimazaki, Y. (2) 179 Shimizu, I. (12) 183 Shimizu, K.D. (13) 480 Shimizu, M. (3) 50 Shimoi, M. (I) 234; (9) 5 1; (14) 104

Shimon, L.J.W. (13) 95 Shimoyama, I. (9) 102; (1 1) 84 Shin, D. (12) 191 Shin, J.H. (10.1) 66; (10.2) 16; (10.3) 21; (14) 92, 109

Slun, J.M. (13) 103 Shin, K.S. (14) 204 Shinagawa, T. (13) 505 Shindo, M. (2) 6 Shinhmar, M.K. (10.4) 33 Shinohara, H. (1) 125 Shinokubo, H. (2) 39 Shintani, R. (8) 98 Shinyozu, T. (14) 209 Shiori, T. (2) 34 Shiota, Y. (1) 33 1,332 Shiotsuki, M. (13) 73,264 Shirai, M. (1 1) 321 Shiraishi, H. (4) 130 Shirawasa, N. (12) 2 1 Shiro, M. (7) 78; (12) 5 1 Shishido, T. (4) 136 Sku, L.-H. (13) 53 Sku,Y.-T. (9) 131; (11) 266; (13) 475

Shono, T. (3) 13 Shore, S.G.(6) 24; (1 1) 22 Shorokhov, D.J. (1) 84 Shriver, D.F. (9) 98; (1 1) 74,78, 80; (12) 48; (13) 449

Shubina, E.S.(1) 293; (3) 39; (1 1) 29

Shuegeral, G. (13) 266 Shukla, A.P. (2) 124 Shukri, K. (12) 39 Shur, V.B.(I) 293; (3) 39; (10.1) 54,55; (11) 151; (13) 162

Shusterman, A.J. (1) 101 Sibata, K. (3) 49

Sicock, P.J. (12) 203 Siebel, E.(2) 184 Siebert, W. (2) 138 Sicgbahn, P.E.M. (1) 393,395 Sielcr, J. (14) 40 Sicna, M.A. (10.3) 40 Sievers, H.L. (9) 138 Sievers, M.R. (4) 157 Sievert, M. (1) 44; (2) 126 Sikorski, W.H.(2) 52 Silk, T.V. (8) 96 Sillanpaa, R. (5) 47,58,59 Silveira, C.C. (2) 74 Silver, J. (14) 210 Silvcstru, A. (7) 95 Silvestru, C. (2) 132; (7) 70 Simanko, W. (13) 266 Simon, U. (1 1) 42,43 Simons, J. (1) 47,48,50 Simpson, J. (9) 38; (1 1) 6, 185; (13) 519; (14) 181, 188

Sinbandhit, S. (12) 231; (13) 60 Sinclair, D.J. (2) 67 Singh, A.J. (7) 96 Singleton, D.A. (13) 145 Sinn, E. (14) 193 Sinou, D. (8) 131 Siotsuki, M. (13) 192 Sirahama, H. (4) 124 Sirlin, C. (12) 36 Sironi, A. (9) 90; (1 1) 20,64,65 Sisak,A. (13) 88 Sita, L.R. (10.1) 8 Sitzmann, H. (7) 105; (14) 127 Sivacv, I.B. (5) 5 Six, C. (13) 79 Sizov, A.I. (4) 22,53, 54; (14) 13 Sjoberg, S. (5) 10; (13) 222 Sjovall, S. (12) 102, 103; (13) 221 Skalican, 2. (5) 5 1 SMitzky, D.J. (2) 107 Skancke, A. (7) 26 Skelton, B.W. (1) 252,255,286; (4) 90; (9) 108, 112, 154; (10.3) 31; (11) 23,90,91, 113, 115-122, 128,230,264; (12) 59,60,82, 158,206; (13) 356,402,443,452,458,459, 461467,477,478,520; (14) 100 Skibbe, V. (13) 49 Skowronska, A. (10.1) 74 Slcigh, C.J. (9) 30; (1 1) 9 Sloan,C.P. (2) 115 Slocum, D.W. (2) 134 Slowinski, F.(1 3) 277,278 Slugovc, C. (12) 225; (13) 75,77 Smail, S.J. (14) 157

Author Index Smart, B.A. (1) 296 Smawfield, D.J. (9)3 1, 150;(1 1) 8,320 Smernik, R.J. (12)84;(13)58 Smith, A.K. (9)29;(1 1) 35 Smith, B.(1) 244 Smith, D.W. (1) 290 Smith, J.D. (2)42,50;(3) 36;(4) 96 Smith, J.M. (12) 110 Smith, K. (2) 11, 1 1 1, 124 Smith, K.C. (13) 187 Smith, K.M.(1) 136, 138, 156; (10.3)10, 13 Smith, L. (5) 52 Smith, M.E.(12)82;(13) 520 Smith, M.R., I11 (6)3;(10.2) 17 Smith, R (11) 153,166 Smits, J.M.M. (12)120, 123;(13) 198,219 Smrcina, M. (13) 133 Snaith, R.(I) 25;(2)30,49,97; (6)66 Snapper, M.L.(8) 115;(13)245 Sneddon, L.G. (5) 26 Snee, P.T. (1) 210;(9) 24 Snegur, L.V.(14)216 Snieckus, V.(2)25 Snijders, J.G. (1) 204,205 Snyder, J.P. (1) 410 Sofield, C.D.(7)73 Soheili, S.(9)77 Sohlberg, K. (1) 405;(13)54 Sohn, Y.S.(13) 155 Soininen, E. (4)8 Sola, E.(12)99, 128;(13) 101, 102 Sol& M.(1) 360,376,408;(9)7; (13)33 Solan, G.A. (1 1) 77;(13) 352,425 Solano, S.(13)435 Solans, X.(14) 139 Solan, E.(1) 301,304;(2) 129, 146;(3) 19;(4)75,76;(10.1) 23,24;(10.2)6,7;(10.3)23, 28,39,55;(13)172 Soldin, P. (1) 16 Soldovzi, K.M.(12)212;(13)76 Soler, M.A. (13)375 Solling, T.I. (7)63 Solntsev, K.A. (5) 14,21;(9)142 Solomonov, B.N. (1) 402 Solov'ev, V.N.(1) 17 Son, S.U.(13) 178 Song, C.-P. (1 1) 329 Song, F.-Q.(4) 18 Song, H.(13)91 Song, J.-H. (14)229

Song, L.-C. (9) 94;(1 1) 259;(13) 29 Song, Y.-S. (4)7 Sonobe, H. (13) 393 Sonoda, M.(8) 72 Son& N.(2)79 Sordelli, L. (13)216 Sostero, S.(1 3) 200 Soto, J. (4)102;(14)193 Soulantica, K.(13)195 Soullez, D. (2)71 Sousa-Pedrares, A. (2)68 Sovago, J. (13) 397 Sow, B.H. (9) I 1 1; (11) 105 Sowa,T.(13)188 Sowden, R.J. (9)126 SPagna, R. (6)30 Spaniol, T.P. (4)101, 110;(10.1) 36;(14)20 Spannenberg, A. (10.1)47-52; (13) 164, 165,280,281,312, 439;(14)29,73 Speel, D.M. (1 1) 170 Speiser, B.(12)3 1; (14)206 Spek, A.L. (1) 240;(2)113,127; (7) 15,67;(10.3) 18-20,46; (12)77, 123, 181,209;(13) 72, 198,219 Spence, R.E.von H. (7)22;(10.1) 2,31 Spera, M.L.(13) 82,83 Spicer, M.D. (12)117;(13)363, 364,366,379,380 Spickermann, D.(14)253 Spiegler, M.(12) 109,205,207 Spies, T.(1) 56,71;(6)33,86 Spillner, E.(12)180 Spindler, F.(13)522;(14)179 Spingler, B.(1) 7;(2)43,45 Spiro, T.G. (1) 242 Spodine, E.(1 1) 25 Sprott, K.T.(8)59 Srebnik, M. (13) 302 Srinivas, G.N.(7)67 Sryker, J.M. (13) 279 Staeva, T.P. (2)182 sbm, u.(14)218 Stafstrom, S. (1) 28 Stahl, L. (1 3) 289 Stalke, D.(1) 155; (2)152, 180; (3)26;(4)69;(14)5 Stammlcr, A. (7) 77 Stammler, H . 4 . (6)8 1,96;(7) 14,76,77;(9)138;(14) 108 Stanciu, M. (7)95 Standar, Y.(10.3)52 Stang, M. (14)118 Stantzhellini. P.L. (1 11 5 Y

I

.

I

513 Stankevich, I.V. (1) 90, 146,293; (3) 39;(5) 54; (13)429 Stannek, J. (7)59,60 Staplcs, R.J. (8) 110 Starbuck, J. (14)161 Starikov, A.G. (1) 74 Starikova, Z.A. (14)216 Stark, J.L. (7) 102 Starkcy, G.W. (8) 13 Starks,D.F. (4) 152 Starnes. W.H.Jr. ( 1 1) 28 Starzcwski, K.A.O.(14)5 1 Stasko, D, (5) 17 Staufer, M . (1) 220 Stauffer, H.U.(4) 155 Stchedroff, M.J. (1 1) 164 Steck, R.(14)94 Stced, J.W. (7)74;(1 1) 71,97, 164;(12)38;(13) 265,351, 451,511 Steelc, B.R. (2) 123, 136 Stcffmut, P.(13) 522;(14)179 Stehle, N.(2) 17 Stehr, J. (4) 12 Stein, B. (1) 406 Stein, J. (13)413 Stein, T. (2)208;(13)419 Steinborn, D.(1 1) 221;(13) 149 Steiner, A. (2) 152;(3) 24;(9)29; (1 1) 35;(12)95;(14)5 Steinhuebel, D.P. (10.1)19-22 Steinmann, M.(12)31; (14)206 Stelck, D.S.(3) 15;(6)68 Steilfeldt, D.(4)9 Stelter, W.(4) 115 Stener, M. (1) 30,259;(1 1) 16 Stengel, T.(8)77 Stephan, D.W. (6)44,53,71;(7) 22; (10.1)2,31-33;(14)34 Stephen, S.C. (13) 133,412 Stephenson, G.R. ( I 3) 25 1,252 Sthpnicka, P.(10.1)47,53,56, 57;(13) 161, 164,313,342, 516;(14)203 Sterenberg, B.T. (1 1) 308,309, 322;(12)46 Stergiades, LA. (2)75 Stem, C.L. (1) 129;(4) 134;(1 1) 78;(13)267;(14)37 Sterzo, C.L. (13)25 Steudel, R.(14) 168 Stevens, A.M. (14)256 Stevens, E.D.(1 2) 78,214-216, 220 Stevenson, C.D. (4)64 Stewart, J.C.(7)22;(10.1)31,33 Stibr, B.(5)25,28,47,48 Stiriba, S.-E. (13)400

514 Suagera, R. (13) 266 Stirling, A. (1) 202 Suiirez, T. (1 1) 146, 147 Stoccoro, S.(2) 210; (12) 93 Suejda, S.A. (13) 114 Stocker, F.B. (2) 182 Suenaga, Y. (2) 203,206,207; Stkkigt, D. (1) 58; (6) 36 (13) 188,401,513 Stoeckli-Evans, H. (1) 25 1; (9) Siinkel, K. (2) 185; (9) 77; (10.4) 115; (1 1) 102, 107,302-306; 30; (12) 192; (13) 237,340, (13) 469 446 Stesser, G. (1) 62; (6) 90 S~S-Fink,G. (1) 25 1; (9) 1 15; Stoianova, D.S. (8) 53 (1 1) 102, 107,302-306; (13) Stolarzewicz, A. (2) 92 469 Stolz, B.M. (8) 63 Sugihara,T. (13) 389,390 Stone, F.G.A. (5) 53,55,56,60; (9) 85; (10.4) 43; (1 1) 98,297 Sugimeri, A. (14) 243 Sugimoto, K. (2) 203, 205-207; Storm Poulsen, C.(3) 53 (13) 401 Stowasser, R. (1) 155 Sugimoto, M. (1) 107, 108,365, Striifile, J. (13) 417 366, 380; (12) 136, 137; (13) Straka, M. (1) 63 115 Stramm,C.(9) 77 Sugimoto, T. (2) 65 Strassner, T. (1) 355,356 Sugioka, T. (1 1) 205 Straub, B.F. (2) 191; (13) 186 Sugiyama, T. (14) 243 Strauch, C. (10.2) 19 Suh, 1.-H. (6) 40,79; (13) 91 Strauch, H.C. (1) 134; (13) 173, Sulter, J.-P. (13) 128 287,288 Sumathi, R. (1) 1 19 Strauss, S.H. (1) 201; (2) 181; ( 5 ) 12, 14,20,21; (9) 8, 141, 142 Summers, D.A. (2) 201; (1 1) 54 Streib, W.E.(1) 299,398; (12) 33, Sun, C.C. (1) 120, 128 Sun, H.4. (6) 50 223 Sun, J. (2) 20; (4) 20,52,56,57; Streitweiser, A. (4) 152-154 (9) 70,75,94; (10.4) 46,47; Streubel, R. (7) 20 (1 1) 192,259,329,330; (13) Strieb, W.E. (13) 347 354,490,491,493,494; (14) Striejewske, W.S. (2) 178; (13) 15,23 185 Sun, W.-H. (2) 72; (1 1) 258; (14) Strissel, C.S. (4) 94 56 Stroble, S. (1) 100 Sun, Y.-L. (6) 58 Stromberg, S. (12) 163 Sunatsuki, Y. (10.4) 7 Strosser, G. (7) 34 Sundara Raj, S.S.(1 1) 30,284 Struchkov, Y.T. (5) 54; (13) 429 Sundermann, A. (7) 76; (14) 3 Strunina, E.V.(1) 43 Sung, K. (1) 3 Stryker, J. (10.1) 67; (14) 32 Sung Kwon, 0. (9) 43 Stuart, A.L. (14) 16 Suos, F.N.A. (13) 219 Stiier, W.(12) 222 Surpateanu, G. (1) 166 Stiirmer, R. (8) 1; (13) 205; (14) Sutton, D. (9) 86; (10.4) 28; (13) 63 181 Stufkens, D.J.(1) 253; (9) 121; Suzuki, A. (1) 327; (1 1) 112 (11) 160-163 Suzuki, H. (2) 195; (7) 78; (1 1) Stumpf, A. (13) 378; (14) 51 88; (12) 238 Stumpf, R. (10.1) 13, 14, 18 Suzuki, K. (13) 394 Sturla, S.J.(8) 35; (14) 36 Suzuki, N. (1 1) 138; (13) 422; Sturm, T. (14) 178 (14) 64 Stunner, R. (8) 95 Suzuki,T. (1) 388,39 1; (2) 32; Stutzmann, S. (7) 59,60 (13) 73, 117, 192,264 Styron, E.K. (6) 42 Suzuki, Y.(13) 403 (1 1) 196 SU,C.-Y. Svejda, S.A. (12) 139 Su, G. (1) 384 Svensson, M. (1) 382,386,387; Su, J. (6) 76,77 (12) 163; (13) 107 SU,M.-D. (1) 109-113,399-401; Svensson, P.H. (12) 103; (13) 222 (12) 87, 88 Svoboda, I. (10.4) 6 Suades, J. (13) 246

Organometallic Chemistry Swabey, J.W. (10.1) 2 Swamy, K.C.(14) 146 Swang, 0. (1) 407 Sweigert, D.A. (1 2) 165, 166; (13) 154 Sykes, A.G. (1 1) 255 Sylvester, G. (4) 109 Syutkina, O.P.(4) 140 Szabo, K.J.(1) 390; (13) 120, 127 Szafcrt, S. (10.4) 40.41 Szalontai, G. (13) 397 Szepes, L. (1) 130; (14) 43 Szewczyk, J. (14) 238,239 Sztiray, B. (1) 130; (14) 43 Sziics, E. (2) 116 Szymariska-Buzar, T. (9) 58,62; (1 3) 47,48 Taa, B. (14) 149 Tabellion, F. (7) 8 Taboada, S. (12) 97,98; (13) 98 Tabuchi, N. (14) 6 1 Tachibana, A. (1) 326 Taga, T. (2) 169 Tagge, C.D. (14) 47 Taguchi, T. (2) 32; (14) 61 Tahai, M. (1) 100 Taira, Z. (13) 263 Tijada, M.A. (1) 306; (12) 235, 236 Takahashi, M. (1) 116 Takahashi, S.(9) 35; ( I 1) 205; (12) 69, 199,232 Takahashi, T. (2) 72, 174; (10.1) 73; (13) 168; (14) 53,56,62 Takahashi, Y. (13) 92 Takai, S.(13) 382 Takaki, K. (4) 136 Takao, Y.(13) 139 Takara, S. (1 1) 12; (14) 247 Takata, T. (13) 63,294 Takats, J. (4) 72,73; (9) 116, 117; (12)41;(13)331 Takaya, Y. (8) 65-67 Takayama, T. (14) 208,234 Takcbayashi, M. (3) 13 Takeda,H.(ll) 13 Takeda, T. (13) 139 Takehara, K. (14) 209 Takehira, K. (4) 136 Takei, I. (8) 99; (14) 222 Takemoto, Y. (13) 296 Takemura, H. (14) 209 Takewara, E. (8) 93 Takimoto, H. (13) 93 Talarmin, J. (10.3) 32; (13) 346 Talzi, E.P. (1) 103

Author Index Tamam, Y. (3) 49 Tamm, M. (2) 144; (13) 30 Tamm, T. (1) 63 Tamura, Y. (3) 50 Tan, H. (10.4) 11 Tan, L. (3) 56 Tan, W. (1 1) 280 Tanabe, M. (4) 124 Tanaka, H. (2) 119 Tanaka, K. (3) 54 Tanaka, M. (4) 44; (1 1) 88, 129; (12) 238

Tanaka, R (12) 35, 188 Tanaka, T. (13) 296 Tanake, K. (13) 297 Tang, A.C. (1) 31,46 Tang, J. (2) 39 Tang, K. (1) 317; (9) 54; (13) 35 Tang, W.-D. (14) 231 Tang, Y. (9) 70,75; (10.4) 46,47 Tani, K. (10.2) 20; (12) 104; (13) 223,286

Tanimoto, M. (1 1) 150 Tannenbaum, R. (1 1) 184 Tantillo, D.J. (1) 164; (13) 235 Tarekeshwar, P. (1) 59 Tarlton, S.V. (11) 216; (13) 110 Tairraga, A. (14) 129 Tase,T. (11) 124 Tateiwa, J. (2) 209 Tatsumi, K. (1 1) 277-279,285 Taube, R (1) 352,353; (4) 109, 149; (12) 109; (13) 310,311

Tayama, E. (2) 10 Taylor, N.J. (13) 94, 199 Taylor, S.J. (8) 123 Tedesco, E.(1) 181; (9) 93; (13) 292

Tedrow, J.S.(8) 107 Teixidor, F. (5) 31, 37,42,47,48, 58,59

Tejeda, J. (10.2) 12 Tejel, C. (11) 198, 199 Tekkaya, A. (13) 189,190 Teldji, F. (13) 271 Temkin, O.N. (1) 43 Templeton, J.L. (10.3) 38; (13) 325

Teng, Q.W.(1) 3 1 Tedoro, M.L. (1) 244 Termaten, A. (7) 15; (12) 181 Terrem, P. (1 1) 254; (13) 420 Terroba, R (2) 221 Terzis, A. (2) 123 Tesmer, M. (1 1) 165 Tessier, C.A. (2) 83; (13) 8,479 Tetrick, S.M.(10.4) 29 TdafY, H.R. (10.4) 17

515

Teuben, J.H. (4) 103; (10.1) 6 Thal, C. (13) 253,255 Theopold, K.H. (10.3) 12; (13) 85 Thewalt, U. (10.1) 53; (13) 161, 268,342

Thiebaut, B.J.S. (13) 191 Thiel, W. (1) 76,201,221,226, 344; (2) 224; (3) 43; (7) 52; (9) 8, 1%(11)215;(13) 166; (14) 65 Thiele, S.K.-H. (10.1) 79 Thirupathi, N. (10.2) 28 Thiyagarajan, B. (6) 59

Thomas, A.A. (8) 87 Thomas, C.M. (1 1) 306 Thomas, E.J. (1) 117 Thomas, J.M. (1 1) 45 Thomas, K.RJ.(12) 173; (14) 169,219

Thomas, L.M. (9) 36 Thomas, R.C. (7) 74, 11$ (9) 50 Thomas,R.D. (2) 54 Thomas, R.L. (5) 38 Thompson, C. (10.3) 52; (13) 123 Thompson, D.M. (13) 176 Thompson, J.L. (2) 102 Thompson, R.C. (2) 201; (1 1) 54 Thorand, S. (2) 160 Thorn, M.G.(10.1) 3,4,7 Thornton-Pett, M. (10.1) 11,46, 60; (13) 284,524; (14) 155

Thottathil, J.K. (4) 138, 139 Thouvenot, R (14) 103 Tiainen, H. (6) 41 Tian, S. (4) 17, 132, 134 Tian, W. (1) 128 Tiekink, E.R.T.(12) 72 Tiezzi, E. (7) 112 Tikhonova, LA. (1) 293; (3) 39 Tilbmk, D.M.G. (13) 65 Tilley, T.D. (4) 80,8 1; (10.2) 30 Tillyer, R.D. (3) 56 Tilset, M.(10.3) 44; (12) 155 Tinkl, M.(2) 25 Tipton, A.A. (2) 178; (13) 185 Tiripicchio, A. (9) 59, 104; (1 1) 109; (12) 153, 171

Tislerova, I. (13) 133 Tius, M.A. (2) 75 To, T.H. (5) 29 Toader, D. (2) 13 Tobe, Y. (13) 10 Tobisch, S. (1) 352,353; (13) 3 10, 311

Tobisu, M. (8) 33; (1 1) 139 Tobita, H. (1 1) 182 Tocher, D.A. (13) 265 Toda, A. (2) 169

Toemqvist, R (4) 8 Tohier, M. (12) 23 1; (13) 60 Tok, O.L.(1) 115; (13) 305 Toke, L. (2) 116 Tokimitsu, T. (4) 1 1 I Tokitoh, N. (6) 17 Tokiwa, H. (1) 52 Tokunaga, M.( I 1) 13 1 Toledano, C.A. (14) 173 Tollari, S. (1 1) 137 Tomis, J. (1) 269 Tomas, M. (1) 263; (13) 434 Tomioka, K. (2) 6 Tomonou, M. (14) 209 Toniooka, K. (2) 18, 19 Tomuschat, P. (10.3) 4; (13) 16 Tonachini, G.(1) 34; (2) 63 Tone, S. (4) 111 Tong, Y.-X. (1 1) 196 Tooze, R.P. (13) 132 Toraman, G. (10.1) 24 Torkelson, J.R (12) 126, 130; (13) 406

Toro, A. (10.4) 28 Torraca, K.E. (10.3) 56,61 Torrent, M. (1) 360,376,408; (9) 7; (13) 33

T o m , R. (13) 521 Tomes, F. (13) 101 Toscano, M. (1) 75 Toscano, R.A. (7) 117; (1 1) 79 Toshiwara, D. (3) 13 Toskano, R.A. ( 14) 173 Touchard, D. (12) 53 Toupet, L. (1 1) 296 Tour, J.M. (2) 118 Toure, P. (13) 372 Tracy, H.J. (1) 89 Tran,N.T.(9) 157;(11)51 Tran, U. (5) 29 Trauner, D. (13) 108 Travaglia, M. (12) 187; (13) 138 Trebbe, R. (9) 137 Tregonning, R. (9) 110; (11) 126 Trcpanier, S.J. (12) 46 Trifonov, A.A. (4) 10,36,43,45, 62.63

Trifonova, O.A. (13) 238 Triller, M.U. (10.1) 6 1 Trinkaus, M. (5) 76 Trinquier, G. (1) 99 Tmka, T.M. (8) 4 1 Triisch, D.J.M. (1 1) 249; (14) 198 Trofimenko, S. (1) 286 Troin, Y. (13) 300 Trost, B.M.(8) 23,26, 80 Troung, T.U. (5) 29 Troutman, M.V. (8) 97; (14) 82,

516 84 Troyanov, S.I. (10.1) 55 Trudell, M.L. (8) 8 Trujillo, M.(12) 97, 122; (13) 98, 99 Trullinger, G.E. (1) 250; (1 1) 76 Tsagatakis, J.K. (1) 93 Tsai, C.-W. (10.4) 27 Tsai, K.-R.(1 1) 143,326 Tsai, M.-S. (13) 260 T m g , C.-W. (5) 18 Tschinkl, M. (3) 35,42; (6) 35 Tse, J.S. (1) 254; (12) 65; (13) 482 Tseng, H.-R. (2) 166 Tseng, T.-W. (1 1) 62 Tseng, W.4.(13) 143,473 Tsuji, T. (13) 410 Tsujimoto, T. (8) 72 Tsukioka, R (2) 119 Tsutsumi, K.(13) 144,505 Tuchagues, J.-P. (10.4) 7 Tuck, D.G.(1) 55; (6) 93 Tucker, J.H.R. (14) 189 Tudor, J. (14) 167 Tuinman, A.A. (1) 396 Tummolillo, G. (1 1) 137 TWg, S.-F.(1 1) 33 Tung, Y.-L. (13) 143 Tunge, J.A. (14) 83 Tunik, S.P.(9) 31, 150; (1 1) 8, 320 Turck, A. (2) 135 Turnbull, M.M. (14) 157 Turner, A.T. (13) 252 Turner, P.(12) 84; (13) 58 Turpin, J. (13) 228 Tuulments, A. (3) 6-9 Twamley, B. (6) 88; (7) 73; (1 1) 194; (13) 369 Tyler, D.J. (1) 287 Tyler, D.R. (14) 111 Tyrra, W.(7) 103

Uchimaru, Y.(1 1) 132 Uchiyama, M.(3) 48 Udachin, K.A. (1) 254; (1 1) 1 11; (12) 65; (13) 472,482

Uddin, J. (1) 69, 241,312; (12) 164; (13) 146 Uebelhart, P.(13) 238 IJemura, S.(7) 97; (8) 92,99; (14) 176,222 Ueng, C.-H. (1 1) 60 Uenoyama, S. (8) 14 Ueoka, M. (14) 176 Ueyama, N. (10.3) 24

Orgatrometallic Chemistry Uffing, C. (7) 104 Uggemd, E. (1) 405; (13) 54 Uguagliati, P. (13) 135, 136 Uhl, W. (1) 56,69,71; (6) 32,33, 83, 86,92

Ujaque, G. (1) 261,283,354 Ujjainwalla, F. (8) 79 Ullrich, D. (7) 4 Ulvenlund, S. ( I ) 163 Umani-Ronchi, A. (2) 163 Umeda, C.(8) 64 Umezawa-Vizzini, K. (12) 24; (13) 68

Ungvary, F. (1 3) 397 Uno, M.(9) 35; (12) 69 Unseld, D. (1) 142; (10.4) 37 Uozumi, Y. (13) 124 Uraev, A.I. (9) 1 Uniolabeitia, E.P. (3) 33; (1 1) 327; (12) 172

Uruichi, M. (1) 234; (9) 5 1 Usatov, A.V. (10. I ) 54; (13) 162 Uson, I. (3) 21; (6) 48,61 Ustynyuk, L.Y. (1) 397 Ustynyuk, N.A. (I) 175 Ustynyuk, Y.A. (1) 175,397; (13) 238 usugi, s. (2) 39 Uthmann, S. (7) 14 Uwatoko, Y.(2) 199 Vadecard, J. (1) 236 Vagedes, D. (6) 4 Vahrenkamp, H. (1 1) 165 Vairamani, M. (14) 220 Vaissermann, J. (13) 271; (14) 245

Valentini, M.(13) 111, 196 Valerga, P. (12) 10,57,58,74, 125, 180; (13) 130

Valerio, C. (12) 70; (14) 228 Valiullina, Z.S. (4) 150 Vallant, T. (13) 266 Vallorani, F. (6) 30 Valls, E. (1 1) 159 Vancso, G.J.(2) 141; (14) 190 van de Geijn, P.(1) 29 van der Boom, M.E.(12) 27,96, 108

Van der Maelen, J.F. (1 1) 3 14 van der Sluis, M.(7) 15; (12) 181 Vandervccr, D.G.(6) 84 van Eijkel, G.T.(1) 240 van Eldik, R.(12) 138 van Faassen, E.E. (I) 29 Van Gastel, F.(12) 42 van Gisbergen, S.J.A. (1) 204,205

van Haaten, R.J. (1) 385 Vanka, K.(1) 340 van Koppen, P.A.M. (1) 328 van Koten, G. (1) 29; (2) 127; (3) 58; (10.3) 18-20,46; (12) 77; (13) 72,418,504; (14) 27 van Leeuwen, P.W.N.M. (1) 385; (13) 131 van Lenthc, E. (1) 205,213,289 van Leur, M.(2) 127; (10.3) 19, 20 van Os,M.(2) 141; (14) 190 van Outersterp, J.W.M. (1) 253; (9) 121; (11) 160 Vanquickenborne, L.G.(1) 122, 182,231; (7) 66 van Santen, R.A. (1) 370,371; (10.1) 79 van Strijdonck, G.P.F. (1) 385 van ToI, M.F.H. (10.1) 79 van Veggel, F.C.J.M. (14) 197 van Vliet, M.C.A. (10.4) 9 van Wullen, C.(1) 214; (14) 57 Varga, V. (10.1) 57; (13) 516; (14) 203 Vargas, M.D.(1 1) 149 Varma, K.S. (6) 16 Vasama, K. (4) 8 Vasapollo, S. (4) 74 Vazquez, V. (11) 153, 166 VBzquez de Miguel, A. (10.3) 25 Veciana, J. (14) 191 Vedejs, E. (6) 14 Vedernikov, A.N. (1) 402 Vedsa, P.(3) 12 Vega, A. (1 1) 25 Vegas, A. (12) 174 Veghini, D. (14) 55 Veige, A S . (1) 176 Veige, S.(10.2) 29 Veiros, L.F. (1) 172-174,253, 305; (9) 121; (11) 160; (13) 38 Veith, M. (2) 151 Veldman, N. (2) 113 Vananzi, L.M. (13) 200 Ventelon, L. (14) 22 Venuti, M. (1) 30 Verbruggen, 1. (1) 93 Verdaguer, X.(9) 130; (13) 367 Vergoten, G. (1) 166 Verpeux, J.N. (13) 423 Vessieres, A. (9) 37 Veyama, N. (1 3) 327 Vicart, N. (10.1) 78 Vicente, J. (2) 211,213; (12) 182, 184; (13) 113,228 Vicic, D.A. (7) 94; (12) 121, 152

A u h r Index Vickers, D.M.(7)35 Vickery, J.C. (2)222;(1 1) 238 Vidal-Gancedo, J. (14) 191 Vigalok, A. (13) 95 Vignali, C.(9)104; (1 1) 109 Vij, A. (3) 15; (6)68;(14) 133 Vilar,R (1) 151;(11)216;(13) 110 Villa, M. (2) 163 Villacampa, M.D. (2)219;(11) 241;(14)185 Villani, C.(8) 128 Villieras, J. (2) 164 Villieras, M.(2) 164 Villiers, P.(2)71 Viiias, C. (5) 31,37,42,47,48, 58,59 Vincent, M.A. (1) 117 Vining, W.J. (1) 89 Vinson, N.A. (13)39 Visentin, F. (13)135,136 Visseaux, M. (4)46,71, 104 Vittal, J.J. (12) 170 Vizza, F.(13)216 Vladimir, V.I. (5) 5 Vlcek, A. (1) 207;(9)22,23 Vogel, K.M.(1) 242 Voges, M.H. (10.3)44 Vogler, A. (13)239 Vogt, D.(9)34;(13)504 Voigt, A. (14)97 Voith, M.(12) 145 Volatron, F. (7)51 Volden, H.V.(1) 84 Volken, R. (1 1) 201 Volland, M.A.O. (8) 44;(12)21 1 Vollhardt, K.P.C.(1) 143;(13) 502;(14) 117 Volpe, P.(1) 80 von Koblinski, C.(2) 143 von Matt, P. (8) 1 1 1 von Philipsborn, W. (1) 216 Vorontsov, E.V. (14)90 Vos, T.J. (8) 55 Vsetecka, V. (5) 19 Vyboishchikov, S.F.(1) 272 Vyskocil, S.(13) 133 Wachter, N.K.(13) 270 Wacker, A. (2) 138 Wada, E.(8) 114 Wada, K.(13)73,192,264 Wada, M. (14) 138 Wade, K.(5) 30,57 Wadepohl, H. (1) 157,305;(1 1) 2, 190,318;(13)276,484, 497;(14)254,255

517

Wagner, G. (14)144 Wagner, K. (10.3)33;(13) 240 Wagner, M.(6)29 Wakatsuki, Y.(4)35, 105, 106, 121, 123;(1 1) 123, 124, 131; (13) 422;(14)64 Walawalkar, M.G.(10.2)5;(1 1) 257 Walker, G.L.P. (10.3)17 Walker, T.G.(2) 102 Wallace, S.(1) 89 Walsh, J.C.(1) 164;(13)235 Walter, J.N. (9)69 Walters, M.L. (1 3) 34 Walters, S.J. (12)227 Walther, D. (1) 319;(10.1)5; (13) 338 Wan, H.(1 1) 326 Wan, H.-L. (11) 143 Wan& B.(7)67;(1 1) 268;(14) 186 Wang, C.H.(5) 19 Wang, C.J.(1) 329 W a g , C.-R. (1) 125 Wmg, D.-L. (1 1) 75 Wan& F.-C. (6)58,64 Wan& H.G. (4)27,29 Wang, H.M.J. (2)214 W a g , J. (2)99-101 W a g , J.-C. (1 1) 236 Wan& J.-Q. (5)44 Wan& L.-S. (1) 47-50 Wang, N.Q.(1) 199 Wang, Q.G. (1 1)323;(13)527; (14)182 Wang, Q.Y.(10.1)2;(10.2)4 Wang, R. (2) 143;(6)18; (12) 193;(13)354 W a g , S. (4)83,8547;(5) 61-63; (6)12, 15 W a g , S.-L. (9) 131;(10.3)34; (11) 193,266;(13)51,383, 475,488 W a g , T.-F. (10.4)27 Wang, W.D. (10.4)20 W a g , W.-L. (11) 187, 192,283, 295;(1 3) 489,490,496;(14) 130 Wang, x.(2)47;(5) 45 W a g , X.-R.(4)14 Wang, Y. (1) 33;(12)47,55,67; (13)40,81;(14)199,231 Wan& Y .G.(1) 45 Wang, Y.-P. (14)231 Wang, 2. (1)46;(2)84 W a g , Z.-X. (2)93,94;(9)96; (13)450 W a g , 2.-Y. (4)27-30

Warchhold, M.(14)248 Ward, A.J. (7) 110 Ward, D.L. (10.2)17 Warhurst, N.J.W. (13) 399 Waring, M.J. (8) 83 Warman, J.M. (1 1) 163 Warner, B.P. (14)1 1 Warshakoon, N.C.(13) 234 Wartchow, R. (1) 222;(9)91 Washedelder, RA.(8) 56 Washington, J. (9)116, 117;(12) 41;(13) 331 Wass, D.F. (10.3)1; (13) 28 Wasser, I.M.(13)502;(14)117 Wassersheid, P. (8) 133 Wasylishen, R.E.(2) 193, 194 Watanabe, J.-y. (13) 139 Watanabc, M.(8) 11; (14)208, 234 Watanabe, N.(8) 64 Watanabe, S.(8) 15 Watanabe, T.(13) 297 Watanabe, Y.(1 1) 12;(13)264; (14)247 Waterman, S.M. (9) 149, 152; (1 1) 270-274 Waters, J.M. (1 1) 169 Waters, M.L. (10.3)41 Watkin, J.G.(4)39,40,89 Watkins, C.L. (6)42;(7)67 Watson, E.J. (12) 165;(13) 154 Waugh, M.(12)37,85;(13)349, 350 Waymouth, R.M.(14)47 Wayner, D.D.M. (1) 254;(12)65; (13)482 Weakley, T.J.R. (12)115 Weber, B. (2)8;(14)213 Weber, L. (7) 14,76,77;(9) 138; (10.3)60 Weber, M. (1)344;(13)166;(14) 65 Weber, W.A. (1 1) 207,209,321 Weber, W.P. (13)70 Webemdorfer, B.(7)94;(12) 127, 131,213,222,237;(13) 89, 90,309 Webster, M. (7)114, 115 Weeber, A. (1) 131 Wegelius, E.(10.1)40 Wegner, G.L. (I) 87 W e h c h u l t e , R.J. (6)70 Wei, G. (1 1) 244 Wei, P. (6)77.95 Wei, X.-H. (2) 139;(14)60 Weidenbruch, M.(1) 96 Weigand, W.(10.4)30;(13) 237 Weigel, S. (1 1)294

518

Weimann, R. (4) 59, 100; (14) 45 Weinberger, D.A. (14) 232 Weingarten, U. (14) 46 Weinmann, S.(2) 208; (13) 419 Weiss, C.A. (13) 37 Weiss, J. (1) 64 Weissenbach, K. (10.3) 47 Weissensteiner, W. (14) 178 Weisshaar, J.C. (1) 334 Weissman, M. (12) 178 Welch, A.J. (5) 38,49, 51,52;

White, J.M. (13) 187 White, P.S.(1) 250; (10.3) 38;

(1 1) 76; (13) 96,325; (14) 240,258 Whitc, S. (12) 159 Whitehead, J. (1 1) 297 Whiteley, M.W. (13) 240 241 Whitener, G.D. (6) 43; (10.1) 9 Whitley, M.R. (10.3) 33 Whitmire, K.H.(7) 102 Whittaker, C. (1 1) 164 Whyman, R.(9) 31, 150; (11) 8, (13) 434 320 Welker, M.E. (13) 39 Weller, AS.(1) 247; (5) 1; (7) 29; Wibbeling, B. (1) 134; (10.2) 19; (13) 173 (11) 58 Wiberg, N. (6) 75,94 Weller, F.(1) 241; (12) 164 Wicht, D.K. (12) 169 Wells, R.L. (6) 85; (7) 123 Wick, D.D. (12) 113, 114 Weltar, A S . (14) 105 Welton, T. (8) 134; (1 1) 144, 148; Widauer, C.(7) 21 Widhalm, M. (13) 210 (12) s2 Widmair, R.(13) 302 Wen, T.-B. (1 1) 196 Wieneke, M. (3) 27 Wen, Y.-S. (9) 84; (10.4) 1.27; Wieser, U. (1) 131 (14) 169 Wieser-Jeunesse, C.(14) 223 Went, M.J. (1) 406 Wild, F. (1) 142; (10.4) 37 Werner, A. (13) 67 Wild, S.B.(7) 63 Werner, D. (1) 226 Wilkens, H. (7) 20 Werner, H.(7) 94; (12) 99, 127, Wilkens, M.J.(9) 3; (12) 14 131-133,213,222,237; (13) Willem, R. (1) 9 1,93 89,90,102,309,335 Willemsen, S.(13) 177 Wesemann, L.(5) 75,76 Weskamp, T. (1) 297; (8) 40; (12) Williams, B.S.(12) 141 Williams, D.J. (1) 151; (6) 46,47; 208,217,218 (10.3) 16; (12) 62,75 Wessel, H. (6) 48,61 Williams, E.F. (10.1) 25 Westcott, S.A. (13) 94, 199 Williams, J.M.J. (8) 20 Westerhausen, M. (3) 3, 16, 17, Williams, J.O. (6) 89 27; (7) 33, 81 Williams, V.C.(14) 58 Westlund, N.(2) 15,23,24 Williamson, A. (12) 32 Weston, J. (1) 27 Willimas, V.C. (6) 23 Wetzel, T.G.(1) 189; (4) 68 Willis, A.C. (13) 69 Weyerhausen, B. (10.3) 3; (12) 9; Willis, €3. (8) 133 (13) 21 Willis, M.C. (8) 108 Weyhermueller, T.(14) 124 Willis, P.A. (4) 155 Wheatley, A.E.H. (2) 30,49,97; Willner, H. (1) 222; (9) 91 (6) 66 Wheatley, N. (10.3) 6; (12) 3; (13) Wilson, C.J.(1) 287 Wilson, D.J.(7) 7,8; (10.1) 72 6; (14) 215 Wilson, D.R.(1 3) 267 Wheeler, J.L. (9) 45 Wilson, F.X.(2) 23,24 Whitby, R.J. (10.1) 77,78 White, A.H. (1) 252,255,286; (4) Wilson, S.R (14) 259 Wilson, 2.(1) 100 90; (9) 108, 112, 154; (10.3) Wilton-Ely, J.D.E.T. (7) 3; (12) 31;(11)23,90,91, 113, 11575,79,80 122, 128,230,264; (12) 59, Windisch, H.(4) 109 60,82, 158,206; (13) 356, Windmiilltr, B.(12) 132; (13) 335 402,443,452,458,459,461Winfield, J.M. (1 1) 220 467,477,478,520; (14) 100 White, A.J.P. (1) 151; (6) 46,47; Wingerter, S.(2) 180; (3) 26 (10.3) 16; (12) 62, 75 Winkler, J.D.(8) 60 Winkler, K. (1) 3 18 White, D.P. (1) 232

Orgartometallic Chemistry Winter, C.H. (1) 147; (4) 3,4; (14) 200

Winter, M.J. (12) 227 Winter, P. (13) 323 Wintcr, R.F. (12) 83 Wircko, F. (9) 72 Wirschun, W.G. (8) 115 Wistuba, T. (1) 325 Wit, J.B.M. (I) 240 Witt, E. (12) 167 Witte, P.T. (13) 285 Wittkc, 0. (10.4) 28 Witulski, B. (8) 77 Wocadlo, S. (10.1) 26,61 WGrle, M. (13) 11I, 196,522; (14) 179

Woerpel, K.A. (2) 155 Woisctschlagcr, O.E.(10.4) 30; (13) 237

Wojcicki, A. (1) 183; (12) 190; (13) 157

Wojciechowska, M. (1 1) 152 Wojdelski, M. (1) 243 Wojicik, M.(5) 10 Wolczanski, P.T. (1) 176; (10.2) 29

Wolf, J. (7) 94; (12) 132,222, 237; (13) 335

Wolf, M.O. (12) 63 Wolfart, V. (13) 275 Wolfe, J.P. (8) 5,9 Wolff, S.K. (1) 289 Wolmershiuser, G. (7) 4,86, 105; (11)294;(14) 127

Won, G. (12) 124,191; (13) 103 Wong, K. (8) 70 Wong, K.M.-C. (2) 189; (10.4) 35,38; (11) 224; (13) 447

Wong, K.-Y.(12) 64 Wong, R.C.S. (1 1) 55 Wong, T.-H. (1) 60.6 1 Wong, W.-T. (9) 26, 122, 123, 147, 148; (1 1) 89,93-95, 103, 154, 156, 158, 176-179, 181, 261,280,28 1,298,299,3 10, 317; (12) 56; (13) 428,455457,5 18 Wong, W.-Y. (1 1) 156 Wong, Y.-L. (10.3) 22 Wonnemann, J. (10.1)41 Woo, T.K.(1) 350 Wood, J.A. (7) 120 Wood, J.L. (8) 63 Woodford, J.N. (5) 19 Woods, A.D. (7) 13 Woolf, J. (8) 134 Worrall, J.M. (13) 64 Wortmann, R. -(1) 154

Author Index Wrackmeyer, B. (5) 23,27,68-70; (7) 37; (1 1) 282; (14) 107, 160,210,218 Wright, A.C. (6) 89 Wright, C.A. (9) 15 1; (1 1) 288 Wright, D.S.(2) 152; (7) 120; (14) 5 Wright, L.J. (12) 32 Wright, L.L. (13) 148 Wright, T.G. (1) 16 Wrobleski, A.D. (8) 59 WU, C.-Y. (9) 99; (1 1) 8 1 Wu, G. (6) 15 Wu, 1.Y. (2) 208; (13) 365,419 Wu, L.P. (2) 203,205,207; (13) 188,513 Wu, M.H.(8) 120 Wu, Q. (6) 12 Wu, Q.G. (6) 15 WU, Q.-J. (14) 130 WU, S.-L. (1 1) 192,330; (13) 490 Wu, X. (9) 111; (1 1) 105 WU,Y.-D. (1) 396 Wu, Y.J. (3) 38 WU,Y.-R. (10.3) 34; (13) 51 WU,Y.-T. (13) 236 Wu, Z. (4) 6 Wu, 2.4. (4) 15 Wiirthwein, E.U.(1) 35; (2) 60 Wulff, W.D. (10.3) 41; (13) 34 Wurst, K.(2) 35; (10.3) 54; (1 1) 247; (13) 361; (14) 122,171 Wuzik, A. (1) 155 Wyatt, P. (2) 27

Xi, R.(1 1) 268 Xi, 2.(2) 174; (14) 62 Xia, A. (1 1) 239 Xia, H.P.(12) 56 Xiang, K.(12) 230 Xiang, Y. (1) 14 Xiao, J. (8) 137 Xie, S. (2) 120 Xie, Y. (6) 77 Xie, 2.(1) 162; (4) 3 1,82-87; (5) 18,6146

Ximba, B.J. (4) 4 Xin, X. (1 1) 30,280,283 Xin, X.-L. (1 1) 3 1 Xin, X.-Q. (1 1) 281,284 Xiong, C.(4) 118, 122,125 Xu, F. (11) 258 Xu, G. (6) 2 Xu, L. (8) 137; (1 1) 127 XU,P.-P. (1 1) 143 Xu, S.(14) 186 Xu, W.(7) 22; (10.1) 2,31

x.

xu, (1) 199 Xu,Y. (11)212

Xu,Z. (1) 268 Xue, F. (4) 18,31; (5) 18; (10.3) 22; (12) 92

Xue, M.(4) 119 Xue, 2. (1) 303,3%; (9) 5; (12) 20 1

Yamto, K.J. (12) 160 Yadsgar, S. (13) 372 Yagupolski, Y.L. (7) 103 Yajima, T. (2) 209 Yaknjazhanski, S. (14) 42 Yam, V.W.-W. (2) 189; (10.3) 59; (10.4) 35,38; (1 1) 41,49, 223,224,229; (12) 5; (1 3) 447,508 Yamabe, T. (1) 327,33 1,332 Yamada, M.(2) 10 Yamada, Y. (1 1) 289 Yamagah,T. (12) 104; (13) 223 Yamaguchi, I. (14) 131 Yamaguchi, M. (13) 389,390 Yamaguchi, T. (14) 138 Yamaguchi, Y.(13) 422; (14) 64 Yamakawa, M. (1) 4 12 Yamamoto, A. (12) 183 Yamamoto, J.H. (1 1) 262 Yamamoto, K. (2) 18 Yamamoto, M.(4) 99 Yamamoto, T. (13) 93,225; (1 4) 131 Yamamoto, Y. (8) 78; (13) 24, 125; (14) 153 Yamasaki, I. (1) 380 Yamasaki, M. (12) 51 Yamasaki, S.(8) 91 Yamashita, K.(1) 106 Yamashita, M. (1 1) 289; (12) 5 1 Yamashita, N. (3) 13 Yamauchi, M.(8) 73 Yamauchi, 0. (2) 179 Yamazaki, A. (10.1) 73; (13) 168 Yamazaki, H.(13) 403 Yamazaki, S.(13) 263 Yan, c. (5) 66 Yan, H.(5) 68-70 Yan, L.-F. (6) 58 Yan, M.(8) 70 Yanagase, A. (4) 111 Ymg, C.-N. (1) 120, 158, 160; (12) 56 Yang, H.(1) 210; (9) 3,24; (12) 14; (13) 217 Yang, H.-Y. (1 1) 60 Yan& K.-H. (1) 61

519 Yang, L. (8) 70; (10.4) 2 Yang, L.-M. (2) 166 Ymg, 0.-B. (1 1) 321 Yang, Q. (4) 82,8447; (5) 62-66 Yang, S.Y. (1 1) 258 Yang, Y. (3) 22; (6) 54 Yanovsky, A.I. (5) 54; (9) 150; (11) 320; (13)429; (14) 216

Yao, H. (4) 26 Yao, X.-L. (14) 130 Yaouanc, J.J. (14) 196 Yap, G.P.A. (2) 125; (4) 74,77; (10.2) 4,28; (1 1) 186; (12) 151, 169; (13) 85 Yasin, S.A. (2) 14 Yasuda, G. (4) 99,113,114 Yasuda, €4. (4) 44,95, 117, 124 Yasuc, T. (14) 104 Yasui, M.(13) 63 Yates, B.F. (1) 3 12 Yates, S.A. (1) 287 Ye, J.S. (12) 56 Ye, S.(1) 329 Yeh, M.-C. (13) 260 Yeh, W.-Y. (9) 99; (1 1) 68,70, 81; (13) 441,442,471; (14) 96 Yei, M. (8) 52 Yeo, S.P.(14) 15 1 Ywton, J.S.(9) 48; (12) 91; (14) 25 1 Yeung, Y.4. (13) 244 Yi, C.S.(9) 100; (12) 23 Yi, M.P.Y. (10.3) 59 Yi, S.S.(1) 334 Yi, X.-D. (1 1) 143 Yih, K.-H. (13) 40 Yin, J. (2) 84; (13) 45 Yin, X. (10.3) 27; (10.4) 24 Yin, Y.-Q. (11) 187, 192,265, 295,329,330; (13) 489-496 Yoda, c . (4) 35 Yoder, J.C. (4) 60; (13) 158 Yokoyama, H.(2) 179 Yoneda, E.(1 1) 205 Yoneda, Y.4. (14) 183 Yoshifuji, M. (7) 12 Yoshikawa, A. (10.4) I 1 Yoshikawa, N. (13) 296 Yoshimatsu, M. (2) 65 Yoshizawa, K.(1) 327,331,332 You, T. (13) 204 YOU,X.-2. (6) 50 Young, B. (8) 116 Young, G.B. (13) 226 Young, V.G.,Jr. (1) 299; (3) 20; (6) 5, 82; (7) 10; (10.1) 68; (10.2) 31; (10.3) 14; (12) 223;

520 (13) 169; (14) 70 Youngs, W.J. (2) 83; (13) 8,479 Younus, M. (1) 151; (12) 62 Yoza, K. (13) 391 Yu, C.-H. (13) 53 Yu, H.-B. (3) 59 Yu, J.Y. (1 1) 258 Yu, K.(1 1) 280 Yu, K.-B. (1 1) 31,258 Yu, K.-L. (11) 49; (13) 508 Yu, P. (3) 21 Yu, Q. (1) 67; (6) 72 Yu, X.-Y.(1 1) 196 Yu, Y.-Q. (4) 15 Yuan, F. (4) 19,20 Yuan, M. (4) 118, 122, 125 Yuan, Y. (1 1) 326 Yudanov, I.V. (1) 358,359 Yudenfreund, J. (1) 8; (6) 37 Yuge, M. (9) 35; (12) 69 Yuki, M. (9) 153; (1 1) 182,263, 33 1 Yun, C.S. (8) 12 Yun, Y.K. (13) 298 Yunusov, S.M.(1 1) 15 1 Yus, M. (2) 7,70, 77, 104, 106 Yuzefovich, M.(3) 3 1

Zaari, F. (2) 158 Zabel, M. (1) 154 Zablocka, M. (10.1) 74,75; (14) 66 Zacchini, S. (9) 155; (1 1) 312, 313

Zachara, J. (3) 23; (6) 60; (11) 21, 246; (13) 353,448 Zagarian, D. (12) 193 Zahl, A. (12) 138 Zahn, S.K. (8) 28 Zaitseva, N.N. (9) 108; (1 1) 90, 91, 113, 121, 128; (13) 356, 458,459,467 Zakharov, 1.1. (1) 103 Zakharov, V.A. (1) 103 Zilis, S. (1) 207; (9) 23 Zalkin, A. (4) 153, 154 Zanello, P. (1) 3 17; (2) 35; (9) 54, 140, 145; (1 I) 36,47,319, 334; (13) 35; (14) 135,253

Zangrando, E. (12) 187; (13) 138 Zanobini, F. (12) 76,229 Zanotti, V. (12) 234 Zanousek, 2.(5) 19 Zaragozi, R.J. (1) 37 Zarbin, A.J.G. (1 1) 149 Zargarian, D. (13) 104 Zauche, T.H.(10.4) 15 Zaworotko, M.J. (10.1) 38,39; (13) 167; (14) 54,79 Zdanovich, V.I. (13) 517 Zehnder, M. (1) 7; (13) 498 Zenneck, U. (7) 30,37 Zenoni, M. (2) 117 Zgiereski, M.Z.(1) 242 Zhan, T. (13) 289 Zhang, C.Y. (2) 118; (8) 8 Zhang, H. (1) 128; (2) 47; (4) 26, 88; (5) 45 Zhang, H.-X. (1 1) 196 Zhang, J. (1 1) 187, 192,265,295, 329; (I 3) 489-496 Z h g , L.-B.(4) 5,49 Zhang, L.-X. (4) 2,5 Zhang, P. (4) 29 Zhang, Q. (1 1) 30 Zhang, Q.-F. (1 1) 284 Zhang, Q.N. (1) 199 Zhang, S. (4) 96; (12) 64 Zhang, S.-W. (11) 205; (12) 232; (1 3) 264 Zhang, T. (1) 264; (1 1) 218,324 Zhang, W. (4) 13, 14,55; (14) 183 Zhang, (3) 10 Zhang, X. (3) 57; (8) 71; (12) 165, 166; (13) 154 Zhang, Y.-H. (1 I) 329 Zhang, Z. (9) 116, 117; (12) 41; (13) 331 Zhang, Z.-Y. (4) 18 Zhang, Z.-Z. (1 1) 323 Zhao, A. (1 1) 207 Zhao, G. (13) 527; (14) 182 Zhao, H.(13) 450 Zhao,Q. (6) 50 Zhao, X.H. (1) 3 1 Zhao, Z. (14) 192 Zheleznova, T.A. (4) 92 Zheng, C. (4) 88 Zheng, H. (1 1) 280

w.-c.

Organontetallic Chemistry Zheng, J. (14) 163 Zheng, X. (1) 46; (6) 20 Zheng, X.-F. (3) 59 Zheng, Z. (3) 5 Zhil'tsov, S.F. (4) 92, 93 Zhou, G.-D. (2) 202; (1 1) 233; (13) 512

Zhou, M.(1) 190-197,203,321, 322; (4) 156; (9) 12,20

Zhou, X. (4) 5 1; (1 1) 23 1; (14) 186

Zhou, X . 4 . (4) 2,5,7,49; (9) 96 Zhou, Z.-Y. (2) 139; (4) 83; (5) 61; (9) 96; (14) 60

Zhu, B. (13) 354 Zhu, D.(2) 212; (4) 88; (6) 1 Zhu, N. (1 1) 40 Zhu, S. (1) 38; (2) 76 Zhu, S.S. (8) 49 Zhu, Y. (3) 38; (1 1) 283; (12) 63; (14) 130

Zhu, Y .H. ( 13) 29 Zhu, Z. (10.4) 15 Zhuang, B. (9) 60 Zhuang, S. (4) 26 Zie, W. (14) 186 Ziegeweid, M. (14) 30 Ziegler, M.L.(13) 289 Ziegler, T. (1) 94,289,340,341, 348-351,360; (12) 16, 134; (13) 56 Zietzke, K. (4) 100; (14) 45 Ziller, J.W. (4) 23,33,34,38,61, 67,91; (14) 4, 17, 18 Zimmermann, B. (8) 29 Zimniak, A. (1 1) 21; (13) 353, 448 Zinn, A.A. (3) 28 Ziolek, M. (10.2) 3 Zoller, J.P. (10.4) 18 Zora, M.(14) 148 Zoricak, P. (10.1) 2 Zou, G. (4) 57; (14) 23 Zsolnai, L. (13) 44,4 17 Zubieta, I. (2) 183 Zucca, A. (2) 210; (12) 93 Zuccaccia, C. (12) 187; (13) 138, 153 Zuckerman, R.L. (10.1) 71