Mesoporous silicas modified with dioxomolybdenum(VI) complexes: Synthesis and catalysis

The dioxomolybdenum(VI) fragment MoO2X2 has been confined within the ordere d mesopores of pure siliceous hexagonal MCM-41 and cubic MCM-48 molecular s ieves either by direct grafting (solvent impregnation) with MoO2X2(THF)(2) or by using a spacer ligand [L = NC(CH2)(2)Si-(OEt)(3)]. The materials have been characterised by elemental analysis, powder X-ray diffraction, N-2 ad sorption, IR spectroscopy, and magic-angle spinning NMR spectroscopy (C-13, Si-29). All catalysts, homogeneous and heterogenised, are active in the ep oxidation of cyclooctene with tert-butyl hydroperoxide.