Syntheses and characterization of four novel monooxovanadium(v) hydrazone complexes with hydroxamate or alkoxide ligand

Abstract

Four novel monooxovanadium(V) hydrazone complexes, [VOL 1(Hshi)] (1), [VOL 1(bz)] (2), [VOL 2(bz)]·CH 2Cl 2 (3), and [VOL 2(OCH 3)(CH 3OH)]·CH 3OH (4) (H 2L 1=salicylaldehyde benzoylhydrazone, H 2L 2=o-vanillin benzoylhydrazone, H 2shi=salicylhydroxamic acid, Hbz=benzohydroxamic acid), were prepared and characterized by IR, Raman, UV, 1H NMR spectra, cyclic voltammetry measurements and X-ray diffraction. The geometry around the vanadium atoms is a distorted VO(ONO)(OO) octahedron in complexes 1, 2 and 3, while the geometry is a distorted VO(ONO)(O)(O) octahedron in 4. The VO bond distance is 1.574(4), 1.593(5), 1.594(4) and 1.577(4) Å for complexes 1, 2, 3 and 4, respectively. In complexes 1, 2 and 3, the O, N, O atoms of a tridentate hydrazone ligand and one oxime oxygen atom of a bidentate hydroxamate ligand are coordinated to the vanadium(V) atom, forming an equatorial plane. In complexes 1, 2 and 3, the axial position trans to the oxo group is occupied by the carbonyl oxygen atom of the hydroxamate ligand, but not by the oxime oxygen atom. The bond distances in the equatorial plane in the title complexes follow the order: alkoxide oxygen<phenoxide oxygen, oxime oxygen<enolic oxygen<imine nitrogen. The complexes 1, 2 and 3 represent the first structural examples of vanadium complexes containing both hydrazone and hydroxamate ligands.