Synthesis, X-Ray Crystal Structures and Catalytic Epoxidation of Oxidovanadium(V) Complexes with Aroylhydrazone and Ethyl Maltolate Ligands

Two oxidovanadium(V) complexes, [(VOLL)-L-1] (1) and [(VOLL)-L-2] (2) (L = ethyl maltolate), derived from the aroylhydrazones 4-bromo-N'-(2-hydroxy-5-methylbenzylidene)benzohydrazide (H2L1) and N'-(3,5-dibromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H2L2), respectively, have been synthesized and characterized by elemental analysis, infrared and electronic spectroscopy. Structures of the complexes were further confirmed by single crystal X-ray determination. The V atoms in the complexes are coordinated by the ONO donor atoms of the aroylhydrazone ligand, ONO donor atoms of the ethyl maltolate ligand, and one oxido O atom, forming octahedral coordination. The complexes function as effective olefin epoxidation catalysts with hydrogen peroxide as terminal oxidant and sodium hydrogen carbonate as a co-catalyst.