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 H(2)sal-phz with MoO2(acac)(2) generates the dioxo molybdenum complex MoO2(sal-phz)(CH3OH). Treatment of MoO2 in the presence of H2O2 with H(2)sal-phz produces the oxo-peroxo molybdenum(VI) complex MoO(O-2)(sal-phz)(CH3OH). The new compounds were characterized by H-1 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. (C) 2013 Elsevier Ltd. All rights reserved.