Dioxomolybdenum(VI) complexes with linear and tripodal tetradenate ligands: Synthesis, structures and their use as olefin epoxidation catalysts

A series of linear and tripodal tetradentate ligands containing an amine-bis(phenolate) core were synthesized by Mannich condensations. Treatment of these ligands with MoO2(acac)(2) (acac = acetylacetonate) in dichloromethane and methanol at room temperature gave the corresponding cis-dioxomolybdenum(VI) complexes in good yields. All these complexes were characterized by a wide range of spectroscopic methods (NMR, IR, and UV-Vis) and elemental analysis. The molecular structures of complexes MoO2(L-n) (n = 1-3,5) were confirmed by single-crystal X-ray diffraction analysis. The catalytic activities of all complexes towards the epoxidation of styrene by tert-butyl hydroperoxide have also been investigated. (C) 2012 Elsevier Ltd. All rights reserved.