Advances in

ORGANOMETALLIC CHEMISTRY
VOLUME 17

Catalysis and Organic Syntheses

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CONTRIBUTORS TO THIS VOLUME
B. BogdanoviC

N. Calderon
Gian Paolo Chiusoli
Denis Forster
Brian R. James
J. P. Lawrence
Christopher Masters
E. A. Ofstead

Roy L. Pruett
Giuseppe Salerno
John L. Speier
Aaron C. L. Su
Jiro Tsuji

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Advances in
Organ ometallic
Chemistry
EDITED BY

F. G. A. STONE

ROBERT WEST

DEPARTMENT OF INORGANIC CHEMISTRY

DEPARTMENT OF CHEMISTRY
UNIVERSITY OF WISCONSIN

THE UNIVERSITY

MADISON. WISCONSIN

BRISTOL. ENGLAND

Catalysis and Organic Syntheses
VOLUME 17

1979

-

ACADEMIC PRESS New York . San Francisco London
A Subsidiary of Harcourt Brace J o v a n o v i c h , Publishers


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COPYRIGHT
@ 1979, BY ACADEMIC
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ISBN 0-12-031 117-8
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79808182

9 8 7 6 5 4 3 2 1

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Contents
LIST OF CONTRIBUTORS
. .
PREFACE

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ix
xi

Hydroformylation


ROY L . PRUETT
I . Introduction

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I1 . Commercial Utilization .
111.
IV .
V.

VI .
VII .
VIII .
IX .

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Reaction Mechanism . . . . . .
Secondary Products and Reactions . .
Substrates . . . . . . . . . .
Catalyst Separation and Recycle . . .

Heterogeneous Catalysts . . . . .
Catalysts Other than Cobalt and Rhodium
Commercial Technology Trends . . .
References
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The Fischer-Tropsch Reaction

CHRISTOPHER MASTERS
I.
I1.

Introduction . . . . . . . . . . . . .
Fischer-Tropsch Related Organometallic Chemistry
.
I11. Possible Mechanisms for the Fischer-Tropsch Reaction
IV . New Technology . . . . . . . . . . . .
V . Summary . . . . . . . . . . . . . .
References
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61
66

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. . . . 100
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Selectivity Control in Nickel-Catalyzed Olefin Oligomerization

B . BOGDANOVIC
Introduction . . . . . . . . . . . .
Methods of Preparation and Some Features of Nickel
Active for the Oligomerization of Olefins and Related
I I 1 . Formation and Probable Structure of the Catalytically
. . . . . . . . . . . . .
Species
IV . Examples of Selectivity Control . . . . . .
References
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I.
I1.

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Catalysts
Reactions .
Active

. 105
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107

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Palladium-Catalyzed Reactions of Butadiene and Isoprene

JIRO TSUJI
I.

Comparison of Nickel- and Palladium-Catalyzed Reactions of
Butadiene . . . . . . . . . . . . . . . .
V

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. 141


Contents

vi

I1 . Catalytic Species . . . . . . . . . . . . . . .

111.
IV .
V.
VI .
VII .
VIII .
IX .
X.
XI .

Dimerization of Butadiene . . . . . . . . . . . .
Telomerization of Butadiene . . . . . . . . . . .
Dimerization and Telomerization of Isoprene . . . . . .
Cyclization Reactions . . . . . . . . . . . . .
Reactions of Carbon Dioxide . . . . . . . . . . .
Cooligomerization of Butadiene with Olefins . . . . . .
Oxidative Reactions of Butadiene with Pd*+ Salts . . . . .
Other Reactions . . . . . . . . . . . . . . .
Application of the Telomerization of Butadiene to Natural Product
Synthesis . . . . . . . . . . . . . . . . .

References
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146
148

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168
176
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. 182

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189

Synthetic Applications of Organonickel Complexes in Organic
Chemistry
GIAN PAOLO CHIUSOLI and GIUSEPPE SALERNO

I . Introduction . . . . . . . . . . . . . . . . . 195
I1. Carbon-Carbon Bond Formation . . . . . . . . . . . 198
I11. Formation of Bonds Other Than Carbon-Carbon . . . . . . 234
References
. . . . . . . . . . . . . . . . . 243

Mechanistic Pathways in the Catalytic Carbonylation of Methanol
by Rhodium and Iridium Complexes
DENIS FORSTER
I . Introduction . . . . . . . . . . . . . . . . .
I1. The Carbonylation of Methanol Catalyzed by Rhodium Complexes
in Solution
. . . . . . . . . . . . . . . . .
111. Supported Rhodium Carbonylation Catalysts for Methanol
Carbonylation . . . . . . . . . . . . . . . . .
IV . Iridium-Catalyzed Methanol Carbonylation . . . . . . . .
References
. . . . . . . . . . . . . . . . .

255

257
262
264
267

Catalytic Codimerization of Ethylene and Butadiene
AARON C . L . SU
I . Introduction . . . . .
The Rhodium Catalyst System

Ni-Based Catalyst System .
Co and Fe Catalyst System .
Pd-Based Catalyst System .
References
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I11.
IV .
V.

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269
271
291
309
315
3 16


Contents

vi i

Hydrogenation Reactions Catalyzed by Transition Metal
Complexes

BRIAN R . JAMES
I . Introduction . . . . . . . . . . . . . . . . .
Recent Studies of Catalyst Systems Discovered prior to 1971 . .
Asymmetric Hydrogenation . . . . . . . . . . . .
Supported Transition Metal Complexes as Catalysts . . . . .
Membrane Systems. Phase-Transfer Catalysts. Molten Salt Systems
Transition Metal Clusters Including Dimers . . . . . . . .
Hydrogenation of Aromatic Hydrocarbons . . . . . . . .

Photocatalysis
. . . . . . . . . . . . . . . .
Hydrogenase Systems . . . . . . . . . . . . . .
Hydrogen Transfer from Solvents . . . . . . . . . . .
Miscellaneous New Catalysts . . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . .
References
. . . . . . . . . . . . . . . . .

I1 .
111 .
IV .
V.
VI .
VII .
VIII .
IX .
X.
XI .
XI1 .

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319
321
338
361
367
368
376

378
380
381
383
388
390

Homogeneous Catalysis of Hydrosilation by Transition Metals

JOHN L . SPEIER
I.
I1 .
111 .

IV .
V.
VI .

Introduction
. . . . . . . . . . .
Chloroplatinic Acid as a Homogeneous Catalyst
Homogeneous Catalysis with Metals Other Than
Effects of the Structure of the Mane . . . .
Studies with Conjugated Dienes . . . . .
Hydrosilation of Acetylenes . . . . . .
References
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407

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Platinum . . . 428
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441

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Olefin Metathesis
N . CALDERON. J . P . LAWRENCE. and E . A . OFSTEAD
I . Introduction . . . . . . . . . . .
Origins of Carbene-Metal Complexes . . .
111 . Cyclopropanation
. . . . . . . . .
I V . Stereochemical Aspects of the Olefin Metathesis
V . Metathesis of Substrates Bearing Polar Groups .
VI . Conclusion
. . . . . . . . . . .
References
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I1 .

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Reaction .
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468
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SUBJECTINDEX

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493
CUMULATIVE
LIST OF CONTRIBUTORS
. . . . . . . . . . . . . . 507
CUM ULATI VE
LIST OF TITLES. . . . . . . . . . . . . . . . 509

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List of Contributors
Numbers in parentheses indicate the pages on which the authors’ contributions begin

B. BOGDANOVI~
(103, Max-Planck-Institut f i r Kohlenforschung,
Mulheim a. d. Ruhr, West Germany
N . CALDERON
(449), The Goodyear Tire and Rubber Company, Research
Division, Akron, Ohio 44316

GIAN PAOLO CHIUSOLI(195), Zstituto di Chimica
dell’ Universita, Via d’Azeglio 85, Parma, Italy

Organica


DENIS FORSTER(255), Corporate Research Laboratories, Monsanto
Company, St. Louis, Missouri 63166
BRIANR. JAMES (319), Department of Chemistry, University of British
Columbia, Vancouver, British Columbia, Canada
J. P. LAWRENCE
(449), The Goodyear Tire &Rubber Company, Research
Division, Akron, Ohio 44316

CHRISTOPHER
MASTERS*
(6 1), KoninklijkelShell-Laboratorium, Shell Research B.V., Amsterdam, The Netherlands
E . A. OFSTEAD(449), The Goodyear Tire and Rubber Company, Research Division, Akron, Ohio 44316

ROY L. PRUETT( l ) , Chemicals and Plastics Division, Union Carbide
Corporation, South Charleston, West Virginia
GIUSEPPE
SALERNO
(195), Istituto di Chimica Organica dell’ Universita,
Via d’Azeglio 85, Parma, Italy
JOHN L. SPEIER(407), Dow Corning Corporation, Midland, Michigan

AARONC. L. Su (269), Elastomer Chemicals Department, Pioneering
Division, Experimental Station, E. I . du Pont de Nemours and Company, Wilmington, Delaware 19898
JIRO TSUJI(141), Tokyo Institute of Technology, Meguro, Tokyo,
Japan 152

*Resent address: Shell Chemicals U . K . Ltd., Shell-Mex House, Strand, London, England WCZR ODX.
ix


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Preface
This volume of Advances in Organometallic Chemistry is concerned
exclusively with the involvement of metal compounds in catalysis and
organic synthesis. We have collected together ten chapters on these
topics so as to provide in one volume a survey of the growing importance
of organometallics in industrial processes and laboratory syntheses. It is
impossible to provide complete coverage of the subject within the confines of a single volume of necessarily limited length. Nevertheless, we
believe that our contributors have presented ample evidence of what
many regard as the most significant growth area of organometallic chemistry and one of vast technological importance.
Several articles on these topics have appeared in earlier volumes. For
the convenience of readers they are listed here. In addition, articles on
Ziegler-Natta catalysis and on organolithium compounds in diene polymerization are planned for the next volume of this serial publication.
The Olefin Metathesis Reaction
T. J. Katz, Vol. 16, p. 283-317
Supported Transition Metal Complexes as Catalysts
F. R. Hartley and P. N. Vezey, Vol. 15, p. 189-234
Activation of Alkanes by Transition Metal Compounds
D. E. Webster, Vol. 15, p. 147-188
Palladium-Catalyzed Organic Reactions
P. M. Henry, Vol. 13, p. 363-452
Organozinc Compounds in Synthesis
J. Furukawa and N. Kawabata, VoI. 12, p. 83-134

Boranes in Organic Chemistry
H. C. Brown, Vol. 11, p. 1-20
Recent Advances in Organothallium Chemistry
A. McKiUip and E. C. Taylor, Vol. 1 1 , p. 147-206
r-Allylnickel Intermediates in Organic Synthesis
P. Heimbach, P. W. Jolly, and G. Wilke, Vol. 8, p. 29-86
Catalysis by Cobalt Carbonyls
A. J. Chalk and J. F. Harrod, Vol. 6, p. 119-170
Olefin Oxidation with Palladium(I1) Catalyst in Solution
A. Aguild, Vol. 5. p. 321-352

F. G. A. STONE
ROBERTWEST

xi

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ADVANCES IN ORGANOMETALLIC CHEMISTRY, VOL 17

Hydroformylation
ROY L. PRUETT
Chemicals and Plastics Division
Union Carbide Corporation

South Charleston, West Virginia

I.
II.
111.
IV.

v

VI.
VII.
VIII.
IX.

Introduction . . . . . . . . . . . . . . .
Commercial Utilization . . . . . . . . . . . .
Reaction Mechanism . . . . . . . . . . . .
Secondary Products and Reactions . . . . . . . .
A. Isomer Problems . . . . . . . . . . . .
B. Alcohol Formation . . . . . . . . . . . .
. .
C. Alkane Formation . . . . . . . .
D. Ketone Formation . . . . . . . . . . . .
E. Olefin Isomerization . . . . . . . . . . .
. .
F. Other Secondary Reactions . . . . .
. .
Substrates
. . . . . . . . . . .
A. Acyclic Olefins . . . . . . . . . . . . .

. .
B. Cyclic Olefins . . . . . . . . .
C. a$-Unsaturated Aldehydes, Ketones, and Esters . .
D. Unsaturated Ethers and Alkenyl Esters . . . _ _
E. Conjugated Dienes . . . . . . . .
. .
Catalyst Separation and Recycle . . . . .
. .
. .
Heterogeneous Catalysts . . . . . . .
Catalysts Other Than Cobalt and Rhodium . . . . . .
Commercial Technology Trends . . . . .
. .
References
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I
INTRODUCTION
Hydroformylation is the general term applied to the reaction of an
olefin with carbon monoxide and hydrogen to form an aldehyde. Because
unsaturated hydrocarbons, especially C,-C, olefins, are important building blocks in the petrochemical industry, and because oxygenated products such as alcohols or acids are industrially important chemicals, the
hydroformylation reaction has been the subject of intensive investigation.
At the present time, about 8-10 billion pounds of aldehydes or derivatives
thereof are produced annually by hydroformylation of an olefin substrate,
with butyraldehyde from propylene being the largest single primary prod1

Copyright 01979 by Academic Press, Inc
All rights of reproduction in any form reserved.
ISBN 0-12-031 117-8

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2

ROY L. PRUETT

uct at a volume of about 6 billion pounds per year. The process is the
most important industrial synthesis which uses metal carbonyl catalysts

(I).
The hydroformylation reaction was discovered by Otto Roelen in 1938
(2, 3) while investigating the influence of olefins on the Fischer-Tropsch
reaction (I 1. Particularly in commercial publications, it has been termed
the “0x0” reaction; the more proper term, “hydroformylation,” was
proposed by Adkins ( 4 ) .
The reaction does not proceed in the absence of catalysts. As the
contemporary Fischer-Tropsch catalysts were heterogeneous, the first
hydroformylation catalyst was a solid (66% silica, 30% cobalt, 2% thorium oxide, and 2% magnesium oxide). Only later was the conclusion
reached and proved ( 5 ) that the actual catalytic species is homogeneous.
The hydroformylation reaction has been the subject of excellent reviews (for example 1 , 6-8); therefore, the object of this particular treatise
is not to provide comprehensive coverage of all aspects. The basic chemistry is presented, along with recent developments of interest as reported
in the literature, although not in chronological order. Stereochemical
studies (6) are included only when pertinent to another point under
consideration. Carbonylations or hydrocarboxylation reactions which
produce ketones, esters, acids, esters, or amides are not included (1).

Also not included is the so-called “Reppe” synthesis, which is represented by Eq. ( 1 ) .
RCH

=

CH,

+ 3C‘O + 2H,O + RCH,CH,CH,OH + 2C0,

(1)

II
COMMERCIAL UTILIZATION

The primary product of hydroformylation, as it is usually practiced,
consists of aldehydes with one more carbon atom than the olefin substrate.
RCH = CH,

+ CO + H, -+

RCH,CH,CHO

+ RCHCHO
I

(2)

CH,

These aldehydes can then be used to produce a variety of useful derivatives; the aldehydes themselves have minimum utility. The major derivatives are alcohols, formed either by direct hydrogenation [Eq. ( 3 ) ] , or

by an aldol condensation followed by hydrogenation [Eq. (4)].

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Hydroformylation
RCH,CHO

RCH,CHO

H*

OH

IBilbt,

(3)

RCH,CH,OH

I

~

I

-


R

(12

RCH,CH=CCHO

I

HzO

RCH,CHCHCHO

RCH,CH,CHCH,OH

(4)

I

R

R

As noted previously, the major alcohol of commerce produced by
hydroformylation is n-butanol, whose principal utility is found in solvent
applications. The major alcohol formed through the aldol sequence is 2ethylhexanol, again derived from propylene [Eq. (4),R = CH,CH,-1.
This alcohol is esterified with phthalic anhydride to form dioctyl phthalate
(DOP), the utility of which is for plasticizing polyvinyl chloride resins.
Processes have been described (9, 10) which combine the hydroformylation, aldol, and hydrogenation steps into a single process; however,
these have not gained widespread industrial usage at this time. Alcohols
of higher chain length, principally C,,-C,, , are utilized as detergents.

Other derivatives formed from the aldehydes are acids and amines,
produced by oxidation and reductive amination, respectively [Eqs. (51,
(611.
RCH,CHO
RCH,CHO

LO1

+ H, + NH, --+

RCH,COOH

(5)

RCH,CH,NH,

(6 )

The volume of usage for these materials is small, relative to alcohols.
The need for higher product specificity and milder reaction conditions
(see also Section IX) has led to extensive research in hydroformylation
technology. This research, as reported in technical journals, patent literature, and commercial practice has been primarily concerned with
catalysis by rhodium, in addition to the traditional cobalt, and with
catalyst modification by trialkyl or triaryl phosphines. These catalyst
systems form the basis for the major portion of the discussion in this
chapter; some other catalyst systems are discussed in Section VIII.
Rhodium has an activity lo4 times greater than that of cobalt (8).

111


REACTION MECHANISM

After it was recognized that the hydroformylation reaction is catalyzed
by a soluble species, HCo(CO), was proposed as the catalyst ( 1 1 ) . Sub-

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ROY L. PRUETT

4

sequent proposals regarding the mechanism were made by Wender et al.
(12), and Natta et al. (13, 14) made some important observations concerning the kinetics of the reaction. The first-order dependence on hydrogen pressure is balanced by an inverse first-order dependence on
carbon monoxide partial pressure. Therefore, the reaction rate is nearly
independent of total pressure. The reaction is first order in olefin and
first order in cobalt at higher carbon monoxide partial pressures.
Another important line of investigation concerned the ‘‘carbonyl insertion” reaction, which was best defined in manganese chemistry (15,
16) and extended to acylcobalt tetracarbonyls by Heck and Breslow. The
“insertion” may be through three-membered ring formation or by nucleophilic attack of an alkyl group on a coordinated CO group.
The mechanism offered by Heck and Breslow (17, 18) has been the
one most accepted as representing the probable reaction course. This is
outlined in Eqs. (7)-(11):

CH,CH,Co(CO),

+

CO


CH,CH,Co (CO),CH,CH,COCo(CO),

CH,CH,COCo(CO),

(9)
(10)

CH,CH,COCo(CO),

CH,CH,CHO

+

HCo(CO),

(1 1)

This scheme is shown with ethylene as the olefin substrate. If the olefin
is substituted, i.e., RCH-LH,, the possibility exists for the formation
of the isomers RCH,CH,CO(CO)~or RCH(CH,)Co(CO), in Eq. (8). These
isomers, which result from the insertion of olefin into the Co-H bond,
then produce the isomeric aldehydes RCH,CH,CHO and RCH(CH,)CHO.
The understanding of the factors which determine these pathways and
control the desired product, has been the motivation for much study.
For rhodium carbonyls, the reaction follows a similar pathway except
for the complication of equilibria involving the presumed intermediate
[HRh(CO),] (19). A similar equilibrium was postulated at an early date
by Natta et al. (14) in order to explain the half-order dependence on

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5

Hydroformylation

co
Rh4(C0)12

carbon monoxide at low partial pressures in the cobalt-catalyzed reaction
[Eqs. (W415)I.

The formation of multinuclear clusters is much more favorable for
rhodium than for cobalt. Additional evidence was obtained in comparative hydroformylation rate studies of 1-heptene and of cyclohexene at
75°C and 150 atm 1/1 H2/C0 (19). For the acyclic olefin the kinetics
followed the kinetic expression (except at low olefin):

But for the less reactive cyclic olefin, the expression became, with
RhJCO),, as the catalyst,
d(aidehyde)= k,bs[~y~lohe~ene][Rh]1~4[PH2]112[Prrr~o
dt

Both these results were explained in terms of the following reaction
sequence:
HRh(CO),

+

olefin


HRh(olefin)(CO),

(1)

RRh(CO),

lo

(2)

RCORh(CO),

RCORh(CO),

RCHO

RRh(CO),

+

HRh(CO),

(4)

For I-heptene, the rate-determining step was concluded to be the

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6


ROY L. PRUETT

hydrogenation of the acyl intermediate (3) to aldehyde and HRh(CO),
(1). The Rh,(CO),, which was added as catalyst was transformed after a
short induction period, the I-heptene reacted rapidly, and the acyl derivative, not Rh,(C0)12, was seen in high-pressure infrared spectra (19, 20).
In the case of cyclohexene, no change was noted in the initial spectrum
of Rh,(CO),, at temperatures below 100°C and not too long reaction
times. This agrees with the kinetic data in that the reaction of the olefin
with HRh(CO), is the rate-limiting step with this less reactive olefin, and
that the HRh(CO), is in equilibrium with Rh,(CO),,. At higher temperatures and/or longer reaction times, Rh,(CO)la was seen in the infrared
spectrum and the reaction was slower. The thermodynamically favored
cluster under these conditions is Rh,(CO),, , and the equilibrium would
be less favorable for formation of HRh(CO), .
Most hydroformylation investigations reported since 1960 have involved trialkyl or triarylphosphine complexes of cobalt and, more recently, of rhodium. Infrared studies of phosphine complex catalysts under
reaction conditions as well as simple metal carbonyl systems have provided substantial information about the postulated mechanisms. Spectra
of a cobalt I-octene system at 250 atm pressure and 150°C (21) contained
absorptions characteristic for the acyl intermediate C,H,,COCo(CO),
(2103 and 2002 cm-') and CO,(CO),. The amount of acyl species present
under these steady-state conditions increased with a change in the CO/
H, ratio in the order 3/1 > 1/1 > 1/3. This suggests that for this system
under these conditions, hydrogenolysis of the acyl cobalt species is a
rate-determining step.
However, when a less active olefin (e.g., diisobutylene or cyclohexene)
or a liganded system (Bu,P/Co = 2/1,80 atm CO/H2,19OOC) was used, the
hydrido species, e.g., HCo(CO),PBu, , predominated throughout the reaction. The author concluded that in slower systems, initial interaction
of the olefin with the hydrido species HCo(CO),L could be the ratedetermining step. These results are complementary to those discussed
(vide supra) for the rhodium carbonyl catalysis.
It should be noted that these results with the cobalt carbonyl phosphine
catalysts may not apply over a wide range of conditions. At milder

conditions of lower temperature and low catalyst concentration, the conversion of Co,(CO), to HCo(CO),PR, is only partially completed, even
with up to 5/1 ratios of P/Co (22).
In a different type of investigation, the individual steps of the hydroformylation of ethylene by HIr(CO),[P(iso-C,H,),] were characterized
by high-pressure infrared studies (23). This particular catalyst was chosen
because of its relative stability. The series of spectra in Figs. 1-3 show
the changes that occurred on treating HIr(CO),(P-i-Pr,) with 200 psi of
ethylene at 50°C (Fig. I), and on treating the resultant C2H,COIr(C0),)(P-

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--Hydroformylation

Hlr(CO)3P-i-Pr3

7

+ C2H,

---

2200

1600

2200

1600

2200


1600 cm-I

200 psi, 500 C

FIG. I . Infrared spectral changes during the reaction of HIr(CO)JP-i-Pr,and ethylene in
heptane. Reprinted with permission from J . Organometal. Chrm. 94.303 (1975). Copyright
by Elsevier Sequoia S. A.

--C,H,lr(CO),P-i-Pr,

+ CO

---

2200

1600

2200

1600

2200

1600 cm-’

200 psi, 500C

FIG.2. Infrared spectral changes during the reaction of C2H,Ir(CO),P-i-Pr3 and carbon

monoxide in heptane. Reprinted with permission from J . Organornetal. Chem. 94, 303
(1975). Copyright by Elsevier Sequoia S . A.

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--

8

ROY L. PRUETT

+ H,

C,H,COlr(CO),P-i-Pr,

1
1
1
1
1
1
1

2200

1600

-


2200

1600 ern-',

200 psi, 50’C

and
FIG. 3. Infrared spectral changes during the reaction of C2H5COIr(CO)3P-i-Pr3
hydrogen. Reprinted with permission fromJ. Organometal. Chem. 94,303 (1975). Copyright
by Elsevier Sequoia S. A.

i-Pr,) with 200 psi of H, at 50°C. All stages of the sequence HIr(CO),(PR),
+ HIr(CO),PR,
are spectroscopically isolated and shown to be actual intermediates. The
individual absorbances are given in Table I.
For the phosphine-substituted cobalt carbonyl hydroformylations, it is
probable that the mechanism follows the pathway of Heck and Breslow
(17, 18), although the possibility of an associative mechanism has been
raised (7). The increased stability of the HCo(CO),PR, complexes toward
loss of CO was cited.as being suggestive of a nondissociative pathway.
The studies of Wilkinson et al. during the late 1960’s(24-27) concerning

+ C,H,Ir(CO),(PR,) +-C,H,COIr(CO),PR, + C,H,CHO

TABLE I
INFRARED SPECTRA
OF IRIDIUMCOMPLEXES
(23)
HIr(CO)3(P-i-Pr3)
2038 m

1970 vs
1933 w

CZH5Ir(CO),(P-i-Pr3)
2030 m
2025 w
1957 s
1954 s
1920 vw

CZH5COIr(CO)3(P-i-Pr3)
2041 w
1978 s
1959 s
1671 m

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Hydroformylation

9

the triphenylphosphine-modified rhodium systems led them to propose
both dissociative and associative mechanisms, as outlined in Figs. 4 and
5. The complex HRh(CO),(PPh,), was selected as the key intermediate,
even though an equilibrium between several species may exist in solution
(28).
HRh(CO),(PPh,


11

-PPh3

HRh(CO)(PPh,),

)

+PPh$

=HRh(CO)z(PPh,)z
('0

J

-cn

-rm3Jr+Pph3

HRh(CO)(PPh,),

t

C(J

[HRh(CO),PPh,]

+(m

HRh(CO)(PPh,),


This selection was substantiated by the observation (29) that, if
HRh(CO)(PPh,), and HRh(CO),(PPh,), are present together in solution,
only the latter reacts with ethylene at 25°C and 1 atm, as shown by NMR
spectra.
By inspection of Figs. 4 and 5 it can be seen that the associative

H
rn3PL,,,'
Ph3P/

fast
co

Rh-CO
I
C
0

H

-3'

-

,\'co

Ph
Ph3P


IF

0

H
Ph3F3,kh 4

OCI'

C
0

11

11

0

Phgot,,
Ph3P'

R

fast

0

'

'Rh- co

I
C

0

FIG. 4. Dissociative mechanism for the rhodium-triphenylphosphine-catalyzed hydroformylation of olefins (24-27).

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ROY L. PRUETT

10

0

0

CHZCH~R
I

ph3P'l,/,,,l

co

/Ph-Co
c

pw


0

FIG. 5. Associative mechanism for the rhodium-triphenylphosphine-catalyzed hydroformylation of olefins (24-27).

pathway affords more steric hindrance to the coordinating olefin and
would be expected to provide preferential formation of the linear alkyl
rhodium intermediate. The associative mechanism is preferred at high
concentration of catalyst and triphenylphosphine.

IV
SECONDARY PRODUCTS AND REACTIONS
A. Isomer Problems

The principal product of the hydroformylation which is most desired
in industrial applications is a linear aldehyde. The unmodified, cobaltcatalyzed processes produce a mixture of linear and branched aldehydes,
the latter being mostly an a-methyl isomer. For the largest single application-propylene to butyraldehydes-the product composition has an
isomer ratio (ratio of percent linear to percent branched) of (2.54.0)/1.
The isobutyraldehyde cannot be used to make 2-ethylhexanol, and iso-

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Hydroformylation

11

butanol has less industrial value than n-butanol. Consequently, isomer
control of the hydroformylation is of tremendous economic importance
and has been the motivating force behind detailed investigations of the
mechanism, reaction parameters, and ligand effects.

For unmodified cobalt reactions, the most influential parameter is carbon monoxide partial pressure. This effect is demonstrated in Table 11.
(See also Section V,A, 1 .) Hydrogen pressure had a smaller effect (30).
Large discrepancies exist in the literature concerning the effect of temperature. At first, temperature was concluded to have a large effect on
the product isomer composition (31). Later work (32) showed that the
very high reaction rates obtained at high temperatures required vigorous
mixing to ensure against depletion of reactant gases in the liquid phase.
If depletion occurred, a condition of artificially low PCoresulted and low
isomer ratios were obtained. Under conditions of sufficient agitation,
temperature had an insignificant effect on isomer ratio.
The relative value of n-butyraldehyde and isobutyraldehyde is well
exemplified by the recent disclosure (33) of a process for decomposing
unwanted isobutyraldehyde back to the elements of propylene, carbon
monoxide, and hydrogen for recycling to make more n-butyraldehyde.

TABLE I1
EFFECTO F CARBON MONOXIDEPARTIAL PRESSURE ON
ISOMERIC DISTRIBUTION
O F THE HYDROFORMYLATION
PRODUCTS
OF OLEFINS
(30)a

Pro (atm)

Olefin
Propyleneb
Propyleneb
1-Buteneb
I-Butene*
cis-2-Buteneb

cis-2-Buteneb
I-Pentenec
1-Pentenec
2-Pentenec
2-Pentene
4-Methyl- 1-pentened
4-Methyl- I-pentened

2.5

90
2
140
2
138
1.7

90
1.7
93
2
150

Isomer ratio

1.6
4.4
1.1
3.7
1.1

2.4
1.3
4.5
1.3
3.1
1.4
8.1

Solvent, benzene or toluene; PHI, 80 atm; catalyst,
C%(CO)*.

Temperature 100°C.
Temperature 110°C.
Temperature 116°C.

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ROY L. PRUETT

12

B. Alcohol Formation

As normally practiced in a cobalt process, the aldehyde product contains about 10% alcohol, formed by subsequent hydrogenation. Marko
(34) reported that the hydrogenation is more sensitive to carbon monoxide
partial pressure than is the hydroformylation reaction and, in the region
between 32 and 210 atm, is inversely proportional to the square of the
partial pressure. The full kinetic expression for alcohol formation is
expressed by Eq. (17).

d[RoH1
-- k[RICHO][Co][PH,][PCOY
dt

The key steps in the hydrogenation, as stated by Marko, are given in
Eq. (18).
RCHO + HCo(C0)S e R C H S RCHsOCo(CO),
.1
HCo(C0)S
RCH,OCo(CO),

+ HZ+ RCHz0CoHz(CO)3+ RCH,OH + HCo(CO),

(18)

An alternate pathway for the hydrogenation has been suggested by
Aldridge and Jonassen (35):
H

I

R C S

e RCHOH

.1

HCo(CO),

I


HCacO),

RCH,OH

+ [Co,(CO),I

(19)

CO(CO),

A similar type of intermediate in the ruthenium-catalyzed hydroformylation was suggested by Wilkinson and co-workers (36).
While the 10% of alcohol normally produced during the cobalt hydroformylation is a usable and desired product, the product mixture in the
acidic medium forms acetals, and this presents problems in separation
and purification. This problem is circumvented if the reaction is modified
to produce all alcohols or all aldehydes (Section V,A).

C. Alkane Formation

Interception of the reaction sequence at the alkylcobalt carbonyl stage
before carbonyl insertion,” and hydrogenation of this intermediate,
produces an alkane. This undesired side reaction is only minor (1-3%) in
cobalt-catalyzed hydroformylation of a nonfunctional olefin, but may
become predominant with phenyl- or acyl-substituted olefins. Ethylbenzene has been obtained in >50% yield from styrene (37), and even more
alkane was obtained from a-methylstyrene (38).
“

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