Comprehensive Inorganic Chemistry EDITORIAL BOARD J. C. BAILAR JR., Orbana H. J. EMELfiUS, F.R.S., Cambridge tSIR RONALD NYHOLM, F.R.S., London A. F. TROTMAN-DICKENSON, Cardiff {Executive Editor) ORGANO-TRANSITION METAL COMPOUNDS AND RELATED ASPECTS OF HOMOGENEOUS CATALYSIS B. L. Shaw and N. I. Tucker Chapter 53 of Comprehensive Inorganic Chemistry PERGAMON PRESS OXFORD . NEW YORK . TORONTO SYDNEY . PARIS . BRAUNSCHWEIG Pergamon Press Offices: U.K. Pergamon Press Ltd., Headington Hill Hall, Oxford, OX3 OBW, England U.S.A. Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, New York 10523, U.S.A. CANADA Pergamon of Canada Ltd., 207 Queen's Quay West, Toronto 1, Canada AUSTRALIA Pergamon Press (Aust.) Pty. Ltd., 19a Boundary Street, Rushcutters Bay, N.S.W. 2011, Australia FRANCE Pergamon Press SARL, 24 rue des Ecoles, 75240 Paris, Cedex 05, France WEST GERMANY Pergamon Press GmbH, D-3300 Braunschweig, Postfach 2923, Burgplatz 1, West Germany Copyright © Pergamon Press 1973 All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means: electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers First edition 1973 Reprinted, with corrections, from Comprehensive Inorganic Chemistry, 1975 Library of Congress Catalog Card No. 77-189736 Printed in Great Britain by A. Wheaton & Co, Exeter ISBN 0 08 018872 9 (Hard cover) ISBN 0 08 018871 0 (Flexicover) PREFACE The excellent reception that has been accorded to Compre hensive Inorganic Chemistry since the simultaneous publication of the five volumes of the complete work has been accompanied by the plea that sections should be made available in a form that would enable specialists to purchase copies for their own use. To meet this demand the publishers have decided to issue selected chapters and groups of chapters as separate editions. These chapters will, apart from the corrections of misprints and the addition of prefatory material and individual indices, appear just as they did in the main work. Extensive revision would delay publication and greatly raise the cost, so limiting the circulation of these definitive reviews. A. F. TROTMAN-DICKENSON Executive Editor vii 53. 0RGAN0-TRANSITI0N METAL COMPOUNDS AND RELATED ASPECTS OF HOMOGENEOUS CATALYSIS B. L. SHAW and N. I. TUCKER The University of Leeds LIST OF ABBREVIATIONS acac acetylacetonato · Et ethyl Bu n-butyl Me methyl Bu' t-butyl NBD norbornadiene COD 1,5-cyclo-octa-1,5-diene Ph phenyl COT cyclo-octatetraene Pr n-propyl Cp cyclopentadienyl Pr» isopropyl diphos Ph2PCH2CH2PPh2 py pyridine dipy dipyridyl INTRODUCTION The field of organo-transition metal chemistry is one of the largest and most active areas of modern chemistry; yet before 1951 it was relatively unimportant. The field is an old one since Zeise's salt, K[PtCl3(C2H4)]H 0, was known in 1830 and a few alkyl derivatives 2 of gold and platinum have been known since the early 1900s. The discovery of ferrocene (dicyclopentadienyliron) in 1951 and Ziegler-Natta catalysis about the same time, prompted much more interest in the field. Soon after the synthesis of ferrocene, many other metals were shown to form stable cyclopentadienyl- and later arene-derivatives. The discovery of ways of stabilizing transition metal-carbon σ-bonds followed a little later. Although the existence of π-allylic complexes was not established until as recently as 1960, this is now an important area of transition metal chemistry. The field of olefin, polyolefin and acetylene complexes, relatively small in 1960, is now very large indeed. More recent still has been the discovery of carbene, benzyne, carbide and other unusual complexes. In this account of the chemistry of organo-transition metal complexes the compounds are classified mainly from the number of carbon atoms which are actually bonded to the metal and to each other. For example, section 1 deals with alkyl, aryl, ethynyl, acyl and carbene complexes (one carbon atom); section 2 with olefin and chelating diolefin (e.g. cyclo-octa-l,5-diene) complexes and complexes formed from acetylene; section 3 with π-allylic complexes; section 4 with conjugated diolefinic complexes, e.g. containing buta diene or cyclobutadiene; section 5 with cyclopentadienyls; section 6 with arene complexes; 781 782 ORGANO-TRANSITION METAL COMPOUNDS: B. L. SHAW AND N. I. TUCKER and section 7 with tropylium complexes. In section 8 are discussed complexes formed from cyclo-octatetraene or azulene even though fewer than eight carbon atoms are bonded to a metal atom; carbollide complexes are also discussed in this section. The uses of organo-transition metal complexes as homogeneous catalysts and as intermediates in organic syntheses are discussed in the appropriate section. Such aspects of organo-metallic chemistry are currently of great interest and importance. For an excellent and full account of organo-transition metal complexes the reader is recommended to refer to the book by Green1. This gives many hundreds of references up to 1967. The book by Pauson2 serves as an introductory text. There are also many articles on organo-transition metal compounds and related topics in the review journals. 1. ALKYLS, ARYLS, ACETYLIDES, FLUOROCARBON COMPLEXES, CARBIDES 1.1. ALKYLS AND ARYLS3 4 1.1.1. Preparations and General 1.1.1a. Using Alkylating or Arylating Reagents This is the most commonly used method of synthesis and generally consists of replacing a halide ligand on the transition metal by an alkyl or aryl group, leaving the other ligands unaffected. Organolithium reagents are more reactive than Grignard reagents in this replace ment, but frequently either may be used5. Examples: mesityl MgBr /ra/w-NiBr(PEtPh) > /ra/i.y-Ni(mesityl)(PEtPh) 2 2 2 2 2 2 PhMgBr CrCl · 3THF > CrPh · 3THF 3 3 c/j-PtCl (PEt ) \ phLi f cw-PtPh(PEt) 2 3 2 2 32 /ra/w-PtCl(PEt)J \/raAw-PtPh(PEt) 2 32 2 32 MeMgCl PtCl (chelating diolefin) > PtMe (chelating diolefin) 2 2 MeLi TiClCp > TiMe Cp 2 2 2 2 2TiCl + Al Cl Me > 2TiClMe + 2AlCl 4 2 2 4 3 3 FeI(CO)Cp + HgPh > FePh(CO)Cp 2 2 2 Sometimes the alkyl or aryl group may be generated from a transition metal complex6, e.g. Ph Ph N^N\/C1 NaCo(CO)^ fN\ ), + CO Pd o(CO + o NaMn(CO) reacts similarly. 5 1 M. L. H. Green, Organometallic Compounds, Vol. 2, The Transition Elements, Methuen (1968). 2 P. L. Pauson, Organometallic Chemistry, Edward Arnold, London (1967). 3 I. I. Kritskaya, Russian Chem. Rev. 35 (1966) 167. 4 G. W. Parshall and J. J. Mrowca, Advances Organomet. Chem. 7 (1968) 157. 5 J. Chatt and B. L. Shaw, /. Chem. Soc. A (1960) 1718. 6 R. F. Heck, /. Am. Chem. Soc. 90 (1968) 313. 782 ORGANO-TRANSITION METAL COMPOUNDS: B. L. SHAW AND N. I. TUCKER and section 7 with tropylium complexes. In section 8 are discussed complexes formed from cyclo-octatetraene or azulene even though fewer than eight carbon atoms are bonded to a metal atom; carbollide complexes are also discussed in this section. The uses of organo-transition metal complexes as homogeneous catalysts and as intermediates in organic syntheses are discussed in the appropriate section. Such aspects of organo-metallic chemistry are currently of great interest and importance. For an excellent and full account of organo-transition metal complexes the reader is recommended to refer to the book by Green1. This gives many hundreds of references up to 1967. The book by Pauson2 serves as an introductory text. There are also many articles on organo-transition metal compounds and related topics in the review journals. 1. ALKYLS, ARYLS, ACETYLIDES, FLUOROCARBON COMPLEXES, CARBIDES 1.1. ALKYLS AND ARYLS3 4 1.1.1. Preparations and General 1.1.1a. Using Alkylating or Arylating Reagents This is the most commonly used method of synthesis and generally consists of replacing a halide ligand on the transition metal by an alkyl or aryl group, leaving the other ligands unaffected. Organolithium reagents are more reactive than Grignard reagents in this replace ment, but frequently either may be used5. Examples: mesityl MgBr /ra/w-NiBr(PEtPh) > /ra/i.y-Ni(mesityl)(PEtPh) 2 2 2 2 2 2 PhMgBr CrCl · 3THF > CrPh · 3THF 3 3 c/j-PtCl (PEt ) \ phLi f cw-PtPh(PEt) 2 3 2 2 32 /ra/w-PtCl(PEt)J \/raAw-PtPh(PEt) 2 32 2 32 MeMgCl PtCl (chelating diolefin) > PtMe (chelating diolefin) 2 2 MeLi TiClCp > TiMe Cp 2 2 2 2 2TiCl + Al Cl Me > 2TiClMe + 2AlCl 4 2 2 4 3 3 FeI(CO)Cp + HgPh > FePh(CO)Cp 2 2 2 Sometimes the alkyl or aryl group may be generated from a transition metal complex6, e.g. Ph Ph N^N\/C1 NaCo(CO)^ fN\ ), + CO Pd o(CO + o NaMn(CO) reacts similarly. 5 1 M. L. H. Green, Organometallic Compounds, Vol. 2, The Transition Elements, Methuen (1968). 2 P. L. Pauson, Organometallic Chemistry, Edward Arnold, London (1967). 3 I. I. Kritskaya, Russian Chem. Rev. 35 (1966) 167. 4 G. W. Parshall and J. J. Mrowca, Advances Organomet. Chem. 7 (1968) 157. 5 J. Chatt and B. L. Shaw, /. Chem. Soc. A (1960) 1718. 6 R. F. Heck, /. Am. Chem. Soc. 90 (1968) 313. ALKYLS AND ARYLS 783 It is possible to effect only partial replacement of the halogens PtCl +HgMe -> [PtClMe ] 4 2 3 4 NbCl + ZnMe -> NbCl Me 5 2 2 3 /rfl/ij-RuCl2(diphos)2 + AlR6 -> cw-RuClR(diphos) 2 2 (R = Me, Et or Ph) However, for alkyl- or aryl-platinum(II) or alkyl—iridium(III) complexes it is usually better to replace all the halogens and then to cleave them selectively using halogen acid or halogen7, e.g. LiMe, I2 I2 IrClL > IrMeL -► IrIMeL -> IrIMeL (L = PMePh) 3 3 3 3 2 3 2 3 2 Triphenylphosphine has also been used as an arylating agent,.e.g. Pd(PPh3)4 and PdCb when heated together in dimethyl sulphoxide at 130° give a 90% yield of trans- PdClPh(PPh )2, together with a diphenylphosphide-bridged species. 3 1.1.1b. From Organic Halides and Complex Metal Anions Metal carbonyls can frequently be reduced to anions which will react with alkyl halides to give alkyl-metal carbonyls73·7b. Usually the anion is prepared in situ, e.g. Na/Hg Mel Mn(CO)io > Na[Mn(CO) ] ► MnMe(CO) 2 5 5 Na/Hg RX [Mo(CO)Cp] > Na[Mo(CO) Cp] > MoR(CO) Cp (R = alkyl) 3 2 3 3 BrCH2C:CH [Fe(CO)Cp] -> Na[Fe(CO)Cp] '—> Fe(CH CiCH)(CO) Cp « 2 2 2 2 2 A semiquantitative study of the reaction of complex metal anions with alkyl halides gives the order of nucleophilicity to be [Fe(CO) Cp]- > [Ru(CO) Cp]- > [Ni(CO)Cp]" > 2 2 [Re(CO) ]- > [W(CO) Cp]- > [Mn(CQ) ]- > [Mo(CO) Cp]- > [Cr(C0^ Cp]- > 5 3 5 3 3 [Co(CO) ]" > [Cr(CN)(CO) ]- > [MoCN(CO) ]' > [WCN(CO) ]-. 4 5 5 5 The method may be used to synthesize aryl- or vinyl-metal complexes, but the reactions may be sluggish and the yields low. Onium compounds may be used in place of halides, e.g. [Fe(CO)Cp]- + Ph S+BF4 -> FePh(CO)Cp 2 3 2 1.1.1c. Additions to Coordinated Olefins and Other Insertion Reactions In its most commonly occurring form this- reaction involves the addition of a metal- ligand bond across a coordinated olefin or acetylene, i.e. either an olefin (acetylene) insertion reaction or a nucleophilic attack on a coordinated olefin, i.e. either _ M = metal M C C X x _ anionic ligand (nucleophile) i B. L. Shaw and A. C. Smithies, J. Chem. Soc. (1967) 1047. 7a R. B. King, Advances Organomet. Chem. 2 (1964) 157. 7b F. Calderazzo, R. Ercoli and G. Natta, in Organic Syntheses Via Metal Carbonyls, Vol. 1 (eds. 1. Wender and P. Pino), Interscience, New York (1968), p. 4. » P. W. Jolly and R. Pettit, J. Organomet. Chem. 12 (1968) 491. C.I.C. Vol. 4-BB 784 ORGANO-TRANSITION METAL COMPOUNDS: B. L. SHAW AND N. I. TUCKER It is likely that insertion gives a cw-addition across the double (or triple) bond and that nucleophilic attack gives a trans-addition. Also in this class of reaction is the insertion of methylene formed from diazomethane: MnH(CO) + CH N -* MnMe(CO) 5 2 2 5 IrCl(CO)(PPh)2 + CHN2 -> IrCHCl(CO)(PPh)2 3 2 2 3 Diazoacetic ester reacts similarly to give compounds containing the grouping MCHCOOEt 2 (M = metal). Examples of insertions of olefins or acetylenes into metal-hydrogen bonds to give alkyls include the following: C2H4 PtHCl(PEt) ^Ζί PtClEt(PEt ) 32 32 heat This reaction is reversible and catalysed by stannous chloride in the presence of which equilibrium is reached in 30 min at 1 atm/25°. On heating the dideuterio compound PtCl(CDCH)(PEt3)2, however, a mixture of deuterioethylenes, PtHCl(PEt) and 2 3 3 2 PtDCl(PEt3) is produced9. This suggests that the reversible insertion step occurs several 2 times before coordinated ethylene leaves the complex. An unusual synthesis of alkyl- platinum complexes occurs when lithium tetrachloroplatinate(II) is heated with olefins such as oct-1-ene in a formic acid/dimethylformamide mixture. The n-octyl complex PtCl(C8Hi )CODMF is formed, presumably by addition of a platinum hydride species 7 across the double bond. Other olefins react similarly. Examples of hydrides of other metals adding to olefins or acetylenes to give alkyls10 are summarized below: HCl RhCl(PPh) —> RhHCl (PPh ) 33 2 3 2 /cH^CHz \. HC-CH RhClEt(PPh) RhCl(CH :CH )(PPh) 2 32 2 2 32 MnH(CO) + CH :CHCH:CH -* CH CH :CHCH Mn(CO) 5 2 2 3 2 5 Addition of pyridine and acrylonitrile to rhodium trichloride in ethanol gives RhCl{CH(CN)Me}py3, formed presumably by addition of a rhodium hydride species to 2 the double bond of acrylonitrile. Ethylene oxide gives a 0-hydroxyethyl complex with CoH(CO) : 4 CoH(CO) + CH CH -► Co(CHCHOH)(CO) 4 2 2 2 2 4 O From the hydridoiridium(III) complex IrHCl(Me SO) and the chalcone PhCOCH :CHPh 2 2 3 in isopropanol, the chelate alkyl complex [1.1.1] is formed. The structure has been proved O IrCl(MeSO) 2 2 2 [1.1.1] 9 J. Chatt, R. S. Coffey, A. Gough and D. T. Thompson, /. Chem. Soc. A (1968) 190. 10 M. C. Baird, J. T. Mague, J. A. Osborn and G. Wilkinson, J. Chem. Soc. A (1967) 1347. 785 ALKYLS AND ARYLS by X-ray diffraction. This alkyl complex is an intermediate in the catalysed reduction of the chalcone by isopropanol in the presence of the iridium hydride. Attack by bromine on an o-allylphenyldiphenylphosphine derivative of gold(I) bromide [1.1.2] gives a chelated alkyl derivative of gold(HI) [1.1.3]. /OH 2C^H I Ori2 CH2CH ^Br Br O >-PPh2AuBr 2 o P/ \ Ph Br 2 [1.1.2] [1.1.3] Treatment of the dimethyl(o-allylphenyl)arsine complex of platinum(II) [1.1.4] with bromine followed by ethanol gives the alkyl-platinum(IV) complex [1.1.5], the structure of which has been determined by X-ray diffraction11. A remarkable skeletal rearrangement from allyl to isoalkyl occurs, probably during the ethanol treatment. ^\/CH CH:CH 2 2 Me,As o AsMe /Br 7 (l)Br2 m Br^ C]iCH. CH,OEt Xpt\ (2)EtOH ^Pt Br^ I ^Br Br As.Me2 AsMe 2 ^CH, CH:CH 7 [1.1.4] [1.1.5] An example of addition across an acetylenic bond to give a vinylic complex [1.1.6] occurs when acetylenic amines of the type Me2NCRiR2C;CR3 are treated with palladium chloride in methanol12: R 3 ci C\ / PdCl + Me NCRiR C i CR Pd 2 2 2 3 V R^ N R2 Me, [1.1.6] Chelating dienes coordinated to palladium(II) or platinum(II) are susceptible to attack by nucleophiles, forming a metal-carbon σ-bond, i.e. MeO OMe 11 M. A. Bennett, G. J. Erskine, J. Lewis, R. Mason, R. S. Nyholm, G. B. Robertson and A. D. C. Towl, Chem. Commun. (1966) 395. 12 T. Yukawa and S. Tsutsumi, Inorg. Chem. 7 (1968) 1458.