Metal grafted mesoporous silica catalysts combine the advantages of both homogeneous and heterogeneous catalysts and have gained tremendous importance over the last two decades. As a result, such catalysts continue to be an active area of intense research. Particular attention has been given to the preparation of Ti (IV) grafted silica catalysts due to the high catalytic activity for olefin epoxidation. Several Ti (IV) precursors have been previously reported to generate such systems. However, there is a lack of literature report on the use of Ti (IV) aryloxide complexes as precursors for grafting. This deficiency is notable due to the successful utilization of aryloxides as homogeneous catalysts in various industrially significant chemical conversions. In this report, we employed 2, 6 di-substituted aryloxides as ligands to synthesize well-defined monomeric and dinuclear Ti (IV) precursors. The synthesis and characterization of these complexes using single crystal X-ray diffraction, FT-IR and NMR spectroscopy and elemental analysis have been performed. With rational variation of the steric bulk around the phenyl rings as well as increasing the electrophilicity of the metal center via the use of ancillary guanidine ligands, the coordination environment and Lewis acidity of the metal center in these complexes are simultaneously tuned making them suitable candidates as molecular precursors for the one-step direct grafting of SiO2. The silica grafting and evaluation of these complexes as olefin epoxidation catalysts will additionally be reported.

Tuning the metal coordination environment of Titanium aryloxide molecular precursors for application as grafted mesoporous silica catalysts for olefin epoxidation

246th National Meeting (2013)

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