Titanium-germoxy precursor route to germanium-modified epoxidation catalysts with enhanced activity

The complex Ti[OGeⁱPr₃]₄ (1), prepared via the reaction of Ti(OⁱPr)₄ with ⁱPr ₃GeOH, represents a useful structural and spectroscopic model for titanium-germanium species dispersed onto silica. This precursor was used to introduce site-isolated Ti(IV) centers onto the surface of a mesoporous SBA15 support via the thermolytic molecular precursor method. The local environments of the supported materials (TiGe₃SBA15 and calcined TiGe ₃SBA15-O₂) were studied by various spectroscopic methods, including X-ray absorption spectroscopy. These materials are active catalysts for the epoxidation of cyclic and terminal olefins with alkyl hydroperoxides under anhydrous conditions. Compared to catalysts synthesized from siloxide-only precursors, the new catalysts produce 2-3 times more product after 9 h under identical reaction conditions for the epoxidations of cyclohexene and 1-octene. The new materials did not significantly leach under reaction conditions.