Heterogenized catalysts for olefin hydroformylation containing cobalt and palladium-cobalt complexes anchored on phosphinated SiO 2:a 13C solid-state NMR study

Abstract

13C solid-state NMR technique with high-power H decoupling was employed to study heterogenized hydroformylation catalysts containing the anchored complexes of general composition  SiP 2Co 2(CO) 6.6 and  SiP 2PdCo 2(CO) 7.8 (where  SiP 2 is the diphosphine ligand covalently bonded to a silica surface). The data on the content and state of complexed CO are compared with those obtained earlier by IR. The values of chemical shift anisotropy provide information on the molecular motion of anchored metal carbonyl fragments. Evidence is presented for the fast restricted motion of these fragments which is not typical for the supported metal crystallites. The interaction of CO, H 2, and ethylene with the anchored Co and PdCo carbonyl complexes were studied to identify the species which might act as intermediates in hydroformylation reaction. During these studies, the resonances attributed tentatively to π-bonded ethylene and surface propionyls were observed. Based on the data obtained, we discuss the mechanism of action of Co and PdCo catalysts, as well as the reasons of the observed PdCo synergism.