Dioxo and oxo-peroxo molybdenum(VI) complexes bearing salicylidene 2-picoloyl hydrazone: Structures and catalytic performances

Molybdenum complexes bearing a salicylidene 2-picoloyl hydrazone ligand have been synthesized and characterized. The salicylidene 2-picoloyl hydrazone ligand (H2sal-phz) was prepared by reaction of picoloyl hydrazine with salicylaldehyde. Reaction of H2sal-phz with MoO2(acac)2 generates the dioxo molybdenum complex MoO2(sal-phz)(CH3OH). Treatment of MoO3 in the presence of H2O2 with H2sal-phz produces the oxo-peroxo molybdenum(VI) complex MoO(O2)(sal-phz)(CH3OH). The new compounds were characterized by 1H NMR and IR spectroscopies, and elemental analysis. The complexes were also characterized by single crystal X-ray diffraction crystallography. The complexes were evaluated for epoxidation catalysis with tert-butyl hydroperoxide (tert-BuOOH). The MoO2(sal-phz)(CH3OH) complex exhibited high catalytic activity for the epoxidation of olefins, whereas the peroxo analogue is inert to reaction with olefins, thus ruling out the peroxide compound as the intermediate responsible in the [MoO2(sal-phz)(CH3OH)]-catalyzed epoxidation with tert-BuOOH.

MoO2(sal-phz)(CH3OH) and MoO(O2)(sal-phz)(CH3OH) have been synthesized and studied as catalysts for the epoxidation of olefins. The MoO2(sal-phz)(CH3OH) complex exhibits high catalytic activity for the epoxidation of olefins, whereas the peroxo analogue is inert to the reaction. The lack of reactivity of the peroxo complex rules out the peroxo species as the intermediate responsible for oxygen transfer in the reaction pathway.Figure optionsDownload as PowerPoint slide