A metathesis model for ester hydrogeation by a ruthenium octahedral complex using DFT calculations -

Abstract

Electronic structure DFT method had been used to investigate the mechanism of ester hydrogenation by a known octahedral ruthenium hydride catalyst having a PNN pincer type ligand. Our results identified a direct low-energy reaction path connecting the ester and the octahedral ruthenium hydride with an octahedral ruthenium alkoxide and an aldehyde. This path represents a novel ion-pair metathesis mode in which a hydride and an alkoxide are exchanged between a metal and an acyl group in an outer sphere mode. A related path is computed for the reaction of a carboxamide. The given reaction path provides a new perspective to understanding the mechanism of the given catalyst that is radically different from the generally accepted metal-ligand cooperation mechanism invoking a formation and reaction of a hemiacetal. The calculations are also used to identify new complexes that may be used to support the proposed mechanism experimentally.