Efficient Epoxidation of Olefins by Silica Supported Dioxidomolybdenum(VI) Coordination Compounds.

Molybdenum coordination compounds, [MoO2L1(CH3OH)] (1) and [MoO2L2(CH3OH)]0.5(CH3OH) (2), were obtained by the reaction of molybdenum trioxide with ONO-donor ligands [H2L1 = (E)-4-amino-N'-(5-bromo-2-hydroxybenzylidene)benzohydrazide and H2L2 = (E)-4-amino-N'-(2-hydroxynaphthalen-1-yl)methylene)benzohydrazide]. The structures of 1 and 2 were determined by single crystal X-ray analysis and they further characterized by elemental analysis (carbon, hydrogen and nitrogen) and spectroscopic methods such as FT-IR, UV–Vis and NMR analyses. According to the structural analyses, a free amine functionality (Ph-NH2) was present in the structure of compounds 1 and 2. Therefore, compounds 1 and 2 were supported on the surface of functionalized silica gel by amidification reaction. The obtained supported catalysts (Si-Mo-1 and Si-Mo-2) were characterized by XPS, XRD, EDX, DRS, TGA and FT-IR analyses. The obtained supported catalysts (Si-Mo-1 and Si-Mo-2) were tested in the epoxidation of olefins using aqueous TBHP oxidant. Some effective parameters on the selectivity and activity of Si-Mo-1 and Si-Mo-2 like the effect of the concentration of catalyst and oxidant, temperature and solvent were studied. The supported catalysts were easily recovered from the mixture of the reaction by filtration and the recovered catalysts were also characterized by various analyses. The results indicated that the supported catalysts (Si-Mo-1 and Si-Mo-2) are selective and effective catalysts for epoxidation of olefins. [ABSTRACT FROM AUTHOR]