Table Of ContentComprehensive 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
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First edition 1973
Reprinted, with corrections, from Comprehensive Inorganic Chemistry, 1975
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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.
