Bond cleavage carbon-cobalt

B12 and related organocobalt chemistry formation and cleavage of cobalt-carbon bonds. P. J. Toscano and L. G. Marzillo, Prog. Inorg. Chem., 1984, 31,105-204 (677). 

Fig. 28. Routes of cobalt-carbon bond cleavage showing possible electronic arrangements of the resulting spin labeled derivative...

Chemistry Formation and Cleavage of Cobalt Carbon Bonds. 31 105... 

The first step of the reduction by cobalt(II) chloride and NaBH4 involves the production of cobalt hydride species which is capable of exchanging hydrogen ligands with the medium. The second step is a hydrometallation reaction followed by a reductive cleavage of the carbon-cobalt bond. The hydrocobaltation seems to be reversible, as indicated by deuterium label incorporation93. 

The dehydration and deamination reactions appear to operate in a parallel fashion and will be considered together. Schrauzer and Silbert propose a base-catalyzed cleavage of the carbon-cobalt bond in the B12-catalyzed diol dehydration reaction as shown in Fig. 17 (81), based on demonstrated lability of the beta hydrogens in alkyl cobaloximes with electronegative groups in this position. 

The stereochemical course of the cleavage of cobalt-carbon bonds in alkyl... 

A widely accepted mechanism of coenzyme Bir dependent rearrangements encompasses, as the initial step, the homolytic cleavage of the carbon-cobalt bond to generate the 5 -deoxyadenosyl radical. The thermodynamic and kinetic aspects of this and related processes involving the homolysis of transition metal-carbon bonds are discussed. 

Mechanistically, alcohol carbonylation reactions catalyzed by the HCo(CO)4/ Co(CO)4 system appear to be governed by several features which are unique to this system. In particular, the high inherent acidity of the HCo(CO)4 species (45), coupled with the nucleophilicity of the conjugate base (55), is responsible for the activation of the substrate and formation of the alkyl-cobalt bond. In addition, the facility of homolytic cleavage of cobalt-carbon bonds (46, 47) may be responsible for the complications in selectivity not normally observed with other systems. 

The first step in this reaction scheme involves the homolytic cleavage of the carbon-cobalt bond of the coenzyme to cob(II)alamin and a 5 -deoxyadenosyl radical. This intermediate (I) is responsible for the spectral... 

Free Energy Profile for Cobalt-Carbon Bond Cleavage and H-atom Transfer Steps 1487... 

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