Alkyl Migration Reactions

Reaction of [Mn(R)(CO)j] with neutral nucleophiles is by far the most widely studied type of reaction for [Mn(R)(CO)s] compounds. The reaction usually involves addition of the neutral neucleophile, L, and is accompanied by CO insertion/alkyl migration to form an acyl species [Eq. (29)]. L is usually a tertiary phosphine (PR3), an alkylated amine (RNH2), or free carbon monoxide. Besides being a carbon-carbon bond forming reaction of fundamental importance, alkyl migration reactions of transition metal alkyl species have direct relevance to catalysis, especially for the 0X0 or hydroformylation process (2), the Monsanto acetic acid synthesis (2), and the synthesis of ethylene glycol (94). 

Cotton and co-workers 107,114) investigated the reactions of a series of substituted benzyl manganesepentacarbonyl compounds, [Mn(CH2C6H4X)(CO)s] with PR3 [Eq. (30)] in order to probe the steric and electronic effects of X on the alkyl migration reaction. The rate data were analyzed in terms of the reaction pathway proposed in Scheme 8. In the majority of cases there was no detectable contribution from the ki pathway. The rate constant, obs (effectively kt), was found to increase signifi-... 

Alkyl rheniumpentacarbonyl species are known to be reluctant to undergo alkyl migration reactions (43)-, third row i/-block transition metals (i.e., 5d) are usually less inclined to undergo alkyl migration than the 3d... 

The mechanism of alkyl migration [reaction (a)], is now generally accepted for alkyl and aryl complexes of transition metals. Experiments indicating an insertion mechanism have... 

An extended Huckel study of the alkyl migration reaction indicates the cyclic transition state depicted in 23. A small change in this transition state... 

M. Brookhart et al. - Implication of Three-Center, Two-Electron M-H-C Bonding for Related Alkyl Migration Reactions Design and Study of an Ethylene Polymerization Catalyst, /. Am. Chem. Soc. 107, 1443,1985 Mechanism of Rh(III) Catalyzed Methyl Acrylate Dimerization, ibid. 114,4437,1992. 

J.P. Collman et al. - Disodium Tetracarbonylferrate - A Transition Metal Analog of a Grignard Reagent, Acc. Chem. Res. 8, 342, 1975 Lewis Acid Catalyzed [RFe(CO)4] Alkyl Migration Reactions. A Mechanistic Investigation,... 

An extensive kinetic study of the carbonyl insertion, or alkyl migration, reaction... 

Metal carbonyl acyl complexes have been an important class of organometal-lic compound because of the fundamental need to understand the structure and bonding of metal-carbon linkages and the chemistry of organic functional groups that are attached to metal moieties via carbon-donor atoms. These compounds have played a particulariy important role in our understanding of alkyl-migration reactions and other types of liquid transformations. 

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