Titanium–Germoxy Precursor Route to Germanium-Modified Epoxidation Catalysts with Enhanced Activity

The complex Ti[OGe i Pr 3 ] 4 ( 1 ), prepared via the reaction of Ti(O i Pr) 4 with i Pr 3 GeOH, 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 ( TiGe 3 SBA15 and calcined TiGe 3 SBA15-O 2 ) 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.