Molybdenum-MCM-41 silica as heterogeneous catalyst for olefin epoxidation

MCM-41-supported molybdenum/bis-dithiocarbamate complex can be efficiently utilized, after treatment with tert-butylhydroperoxide (TBHP), for the epoxidation of alkenes under solventless conditions. The treatment with TBHP allows the formation of the real catalyst through oxidative decomposition of the complex affording well dispersed Mo(VI) species grafted onto the silica surface through the silanol groups. Experimental results, catalytic efficiency and spectroscopy data, allow to advance some hypotheses on the molybdenum-grafted catalyst formation. The grafted catalyst can be reused several times in the model epoxidation of cyclohexene affording the epoxide with very good yield; only during the first run a modest molybdenum leaching is observed. Both cyclic and linear alkenes can be epoxidized in good to excellent yields and selectivities.