New molybdenum (VI) catalyst for the epoxidation of alkenes and oxidation of sulfides: An experimental and theoretical study

The preparation and catalytic activity of molybdenum(VI) dioxido complex [MoO2L(C2H5OH)] (L = N′-[1-(2-hydroxynaphthyl)ethylidene]-2-hydroxy benzohydrazide) are reported. The reaction of the respective benzohydrazide ligand and the Mo(VI) dioxido precursor, [MoO2(acac)] (acac = acetylacetonate), in ethanol afforded the [MoO2L(C2H5OH)] complex. Structure of the complex was unequivocally established by single-crystal X-ray crystallography. The X-ray structure of complex reveals a six coordinate molybdenum center with a distorted octahedral geometry. By using the AIM analysis, topological properties of the electron density were analyzed to define the bond path between atoms. The AIM calculations indicate that the ligand H2L coordinates to the molybdenum ion in the enol-enamine form (not keto-amine). An insight in the electronic structure of the complex was also obtained by using the density functional theory (DFT). The [MoO2L(C2H5OH)] complex was successfully applied as a catalyst in both, the epoxidation of olefins with tert-butyl hydroperoxide (TBHP) and the oxidation of sulfides with urea hydrogen peroxide (UHP), to form the corresponding sulfoxides.