Heterogenization of [Ti(η 5-C 5HMe 4)Cl 3] on to MCM-41 and organomodified MCM-41 to form epoxidation catalyst

Abstract

This paper describes the heterogenization of a tetramethylmonocyclopentadienyl titanium (IV) trichloride complex, [Ti(η 5-C 5HMe 4)Cl 3] onto mesoporous MCM-41. Its immobilization has been performed via a straightforward grafting process of the organometallic precursor in the pores of an MCM-41 host material and by reaction with previously organomodified MCM-41 material with a hydroxyl triazine based compound. Applying all-silica MCM-41 hosts, stable and heterogeneous liquid-phase epoxidation catalysts are obtained. Powder X-ray diffraction and nitrogen adsorption–desorption analysis indicated that the structural integrity of the support has been preserved during the titanium complex immobilization. These materials have been also extensively characterized using diffuse reflectance UV–vis, 13C and 28Si MAS NMR and FT-IR spectroscopy. With these techniques the strong adsorption of the intact catalytic complex within an all-silica MCM-41 host is demonstrated. These materials have been tested as catalyst for the epoxidation of aliphatic and aromatic alkenes with TBHP as oxidant exhibiting a significant selectivity toward the epoxide with negligible leaching of titanium species. The conversion values are moderated, being the olefin trend reactivity 1-octene > cyclohexene > styrene.