Dioxomolybdenum(VI) Epoxidation Catalyst Supported on Mesoporous Silica Containing Phosphane Oxide Groups

A new mesoporous hybrid material (denoted LP-TEPPPO-Mo) has been prepared by tethering [MoO2Cl2] onto mesoporous silica previously functionalised with phosphane oxide spacer ligands. The LP-TEPPPO-Mo material was tested in the liquid-phase epoxidation of olefins [cis-cyclooctene, (R)-(+)-limonene, trans-2-octene and 1-octene] with tBuOOH, at 55 degrees C, and without a co-solvent, giving at least 90% selectivity to the corresponding epoxide at 36-77% conversion: in the case of limonene, regioselectivity favours the epoxidation of the endocyclic double bond, giving mainly 1,2-epoxy-p-menth-8-ene. The catalytic system based on a liquid-liquid biphasic system containing the homogeneous complex [MoCl2(O)(2)[OP(CH2CH3)(Ph)(2)}(2)] dissolved in the ionic liquid 1-butyl-4-methylpyridinium tetrafluoroborate leads to lower epoxide selectivity (91% at 64 % conversion) in the reaction of cyclooctene in comparison to that observed for LPTEPPPO-Mo (100 % at 87 % conversion). The reused solid-liquid and liquid-liquid biphasic catalytic systems show partial loss of catalytic activity.