Dioxomolybdenum(VI) complexes of hydrazone phenolate ligands - syntheses and activities in catalytic oxidation reactions

The new cis-dioxomolybdenum (VI) complexes [MoO2(L2)(H2O)] (2) and [MoO2(L3)(H2O)] (3) containing the tridentate hydrazone-based ligands (H2L2 = N'-(3,5-di-tert-butyl-2-hydroxybenzylidene)-4-methylbenzohydrazide H2L3 N'-(2-hydroxybenzylidene)-2-(hydroxyimino)propanehydrazide) have been synthesized characterized via IR, 1H 13C NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction analysis. catalytic activities of 2 3, analogous known complex [MoO2(L1)(H2O)] (1) (H2L1 N'-(2-hydroxybenzylidene)-4-methylbenzohydrazide) evaluated for various oxidation reactions, viz. oxygen atom transfer from dimethyl sulfoxide to triphenylphosphine, sulfoxidation methyl-p-tolylsulfide or epoxidation different alkenes using tert-butyl hydroperoxide as terminal oxidant. were found be comparable all three complexes, but 1 3 showed better performances than 2, which contains a more sterically demanding ligand other two complexes.