CHEMISORPTION OF FORMATE AND ACETATE ON CLUSTER-MODELS OF RH AND BIMETALLIC RHSN CLUSTERS

Density functional theory has been applied to the study of the interaction of the formate and acetate species with pure rhodium and bimetallic rhodium-tin model clusters. The calculated equilibrium parameters (optimized geometries, harmonic frequencies and atomic charges) suggest that the internal structure of the formate (and acetate) species is not influenced significantly, however, the metal-formate (and metal-acetate) bond is weakened in the presence of tin atoms. This effect is rationalized in terms of perturbation theory of orbital interaction. In light of our results, a possible explanation is given for the improved selectivity of a RnSn bimetallic catalyst for the hydrogenation of ethyl acetate to ethanol.