Surface Organometallic Chemistry: Hydrogenation of Ethylene with and Os3(CO)10(μ-H)(μ-OPh). Evidence for Cluster Catalysis

Article abstract of DOI:10.1021/ja00217a015

The silica-supported cluster (1) efficiently catalyzes the hydrogenation of ethylene under mild reaction conditions; the reaction is zero order in ethylene and first order in hydrogen.The reaction kinetics as well as volumetric and IR studies of the interaction of 1 with C2H4, H2, and CO indicate a mechanism involving the intact triosmium framework in all the elementary steps conforming the catalytic cycle.The facile <*> interconversion of surface-oxygen ligands provides the appropriate energy balance for cluster catalysis without fragmentation.The reactivity of the molecular analogue Os3(CO)10(μ-H)(μ-OPh) (2) toward C2H4 and H2 has also been studied by IR and NMR spectroscopy, and the data are in agreement with the proposed hydrogenation cycle for 1.However, in contrast with 1, 2 is quickly transformed in solution under catalytic conditions with loss of phenol and formation of H2Os3(CO)10 and H4Os4(CO)12.This difference of behavior indicates the stabilizing influence of the silica support.