New mononuclear dioxidomolybdenum(VI) complexes with hydrazone ligands: Synthesis, crystal structures and catalytic performance

Abstract Three new dioxomolybdenum (VI) complexes, [MoO 2 L 1 (MeOH)] ( 1 ), [MoO 2 L 2 (MeOH)] ( 2 ) and [MoO 2 L 3 (H 2 O)]·EtOH ( 3 ), where L 1 , L 2 and L 3 are the dianionic form of N′-(2-hydroxybenzylidene)-3-methylbenzohydrazide, 4-bromo-N′-(2-hydroxybenzylidene)benzohydrazide and 2-bromo-N′-(2-hydroxy benzylidene)benzohydrazide, respectively, have been prepared and characterized by IR, UV–Vis and NMR spectra, as well as single crystal X-ray diffraction. The Mo atoms in the complexes are in octahedral coordination, with the ONO donor set of the hydrazone ligands, O atoms of the solvents, and two oxo groups. Crystals of the complexes are stabilized by hydrogen bonds of types O H⋯N and O H⋯O. Moreover, the catalytic properties of complexes 1 – 3 are compared in cyclohexane oxidation. It was found that sebacic acid and FeCl 3 could promote the catalytic activities of the complexes.