Bond dissociation ligand effect

Table 1.2 indicates that alloying platinum with tin led to important changes in the product distribution an increase in the AA chemical yield and a decrease in the AAL and CO2 chemical yields. The presence of tin seems to allow, at lower potentials, the activation of water molecules and the oxidation of AAL species into AA. In the same manner, the amount of CO2 decreased, which can be explained by the need for several adjacent platinum atoms (three or four) to realize the dissociative adsorption of ethanol into CO species, via breaking the C-C bond. In the presence of tin, dilution of platinum atoms can limit this reaction. The effect of tin, in addition to the activation of water molecules, may be related to some electronic effects (ligand effects) on the CO oxidation reaction [38]. 

Ng, F. T. T., Rempel, G. L., and Halpem, J., 1982, Ligand effects on transition-metal alkyl bond-dissociation energies, J. Am. Chem. Soc. 104 621n623. 

In view of the coordination pattern in protein-bound methylcobalamin (see below), the thermodynamic studies on the effect of the coordination of the dimethylbenzimidazole base to the a-side of the cobalt center on the homolytic and heterolytic (Co/3-C)-bond dissociation energy in (4) (thermodynamic effect of the trans ligand or trans influence ) were extended to corresponding investigations with Co/3-methyl-imidazolylcobamides, such as (9), where imidazole replaces the dimethylbenzimidazole these studies showed this change of the nature of the axial base to have little effect on the two relevant bond-dissociation energies of the corresponding methylcobamide. ... 

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