Activity of Mo(II) allylic complexes supported in MCM-41 as oxidation catalysts precursors

[Mo(η3-C3H5)X(CO)2(NCCH3)2] (X = Br, 1a; X = Cl, 1b) complexes reacted with the bidentate ligand RNC(Ph)–C(Ph)NR, R = (CH2)2CH3 (DAB, 2) affording [Mo(η3-C3H5)X(CO)2(DAB)] (X = Br, 4a; X = Cl, 4b), which were characterized by elemental analysis, FTIR and 1H and 13C NMR spectroscopy. The modified silylated ligand RNC(Ph)C(Ph)NR, R = (CH2)3Si(OCH2CH3)3 (DAB–Si, 3), was used to immobilize the two complexes in MCM-41 (MCM) mesoporous silica. The new materials were characterized by powder X-ray diffraction, N2 adsorption analysis, FTIR and 29Si and 13C CPMAS solid state NMR spectroscopy. Both the materials and the complexes were tested in the oxidation of cyclooctene and styrene and behaved as active catalyst precursors for cyclooctene and styrene epoxidation with TBHP (t-butylhydroperoxide), leading selectively to epoxides with high conversions and TOFs. Although the homogeneous systems reach 100% conversion of cyclooctene and slightly less for styrene, the loss of catalytic activity in the heterogeneous systems is small, with a 98% conversion of styrene achieved by the chloride containing material.