Alkyl Ligands Written with Prof. Jack R Norton

Alkyl Ligands (Written with Prof. Jack R. Norton) 

Transition metal-methyl bonds tend to be stronger than those of higher alkyl ligands. For example, the U-C bond in (Cp ),U-CH, (Cp =T -Me3SiC5HJ is 49 kcal/mol, but the 

The strength of cobalt-carbon bonds has been extensively investigated because of the presence of a Co-C bond in coenzyme Bj. Reported cobalt-alkyl bond dissociation energies range from 17 to 37 kcal/mol in complexes of the type Co(N -macrocyde)R, with and without axial bases. Much of the variation in Co-C bond energy appears to result from steric factors. Indeed, structural data reveal a steric influence on the length of the Co-C bond.  

The homolysis of the Co-C bond of neopentylcobalamin in aqueous solution has been examined with particular care. These studies showed that AH for this homolysis is 28.3(2) kcal/moP kinetic studies in ethylene glycol and corrections for solvent cage effects indicate that the Co-neopentyl bond strength is 28(2) kcal/mol, in this medium and is probably similar in other media. The Rh-C bond is stronger. The Rh-C bond in (porphyrin)Rh-CH3 is 57 kcal/mol and in (porphyrin)Rh-C2H5 is 50 kcal/mol. 

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