Formation of titanium tert-butylperoxo intermediate from cubic silicon-titanium complex with tert-butyl hydroperoxide and its reactivity for olefin epoxidation

Abstract

Epoxidation of olefins by tert-butyl hydroperoxide (TBHP) was effectively catalyzed by a cubic silicon-titanium mu-oxo-complex, which is obtained from a bulky silanetriol and titanium alkoxides. The stoichiometric reaction of the complex with TBHP in the absence of olefin formed a novel complex as white solid. The comparison of this product with analogous complexes in H-1 and C-13 NMR spectra indicated that the titanium tert-butylperoxo complex; this kind of intermediate is considered to be active for epoxidation in titanium-based catalysts, was first isolated. This titanium peroxo complex reacted with cyclohexene to produce cyclohexene oxide without additional oxidant accompanying the formation of titanium tert-butoxide. All pathways of the catalytic cycle of the epoxidation using titanium catalysts were verified experimentally. (C) 2002 Elsevier Science Ltd. All rights reserved.