PHOTOCHEMICAL GRAFTING OF METAL-CARBONYL CLUSTERS TO INORGANIC OXIDES

Supported metal carbonyl clusters have attracted much attention in the preparation of catalysts containing highly dispersed metals on inorganic oxide supports. Typically such systems are formed by thermal activation until the cluster reacts with the surface hydroxyls. As a new approach, the photochemical grafting of metal carbonyl clusters to the surface of silica has been investigated by DRS uv-visible, FT-ir and ion exchange methods. It had been demonstrated that Fe3(CO)12 can not be grafted to silica by thermal activation. However Fe3(CO)12 physisorbed on silica was cleanly converted to the surface bound trinuclear hydrido anion cluster, HFe3(CO)11-, by room temperature irradiation at 450 nm. Os3(CO)12 physisorbed on silica was converted by XeF excimer laser irradiation (351 nm) at room temperature to the surface attached species HOs3(CO)10-OSi≡. KrF excimer laser irradiation (248 nm) at room temperature led to a mixture of the attached trinuclear osmium cluster along with the attached mononuclear osmium carbonyl. KrF excimer laser irradiation at 173 K produced only the mononuclear species. These results have demonstrated the utility of a photochemical approach for the selective attachment of metal carbonyl clusters to the surface of inorganic oxides. © 1990 Pergamon Press plc.