RATIONAL PREPARATION OF CATALYTIC ACTIVE-SITES USING ATTACHED OXIDE CLUSTERS

Oxide clusters such as [n-Bu(4)N](2)[{(eta(3)-C4H7)(2)Rh}(2) (V4O12)], [(MCP*)(4)V6O19] (M=Rh, Ir), and [(MCP*)(4)Mo4O16] (M=Rhl Ir) were attached on a silica surface as a molecular model for oxide catalysts and supported metal catalysts. The structure and electronic state of the attached clusters were investigated by EXAFS, FT-LR, XPS, TPD, and FT-Raman spectroscopies. Kinetic studies of catalytic reactions such as hydroformylation, oxidation, hydration, and metathesis were carried out; Coordination unsaturated sites appeared upon evacuation of attached vanadium oxide clusters or the photo-reduction of attached molybdenum oxide cluster under CO, which were characterized on a molecular level. The kinetic study related to the cluster structure revealed that the coordinatively unsaturated sites produced by the thermal evacuation or the photo-reduction were catalytically active for selective propene oxidation and metathesis reactions. This study showed that attached oxide clusters were promising model, which can be well characterized on a molecular level, of oxide catalysts and/or supported metal catalysts.