New molybdenum(VI) catalysts for the epoxidation of cyclohexene: synthesis, reactivity and crystal structures

摘要

Compounds 1-6 of the type MoO2X2L2 (X = F, Cl, Br; L = OPMePh2, OPPh3) have been prepared in order to investigate the variation in catalytic activity with changes in electronic and steric properties. All six complexes catalyze the epoxidation of cyclohexene with tert-butylhydroperoxide, and the species with X = Cl and L = OPMePh2 (2) displays the best activity with 83% conversion and 90% selectivity in one hour at ambient atmosphere. These inexpensive and easily prepared dioxo catalysts are stable to air and water. Reactions of the dioxo compounds with H2O2 and t-BuOOH have also been carried out. The structures of MoO2F2(OPMePh2)(2) (1) and the product of its reaction with H2O2, MoO(O-2)(2)(OPMePh2)(2) (7) have been solved by single crystal X-ray diffraction. (C) 2004 Elsevier B.V. All rights reserved.