Vanadium(V) complexes with hydrazone and benzohydroxamate ligands: synthesis, structures and catalytic epoxidation

Abstract

Two structurally similar vanadium(V) complexes, [VOL¹L] (1) and [VOL²L] (2), where L¹ is the dianionic form of N′-(3,5-dibromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide, L² is the dianionic form of N′-(3,5-dibromo-2-hydroxybenzylidene)nicotinohydrazide, and L is benzohydroxamate, were prepared and characterized by elemental analysis, infrared spectra, and single crystal X-ray diffraction. 1 crystallizes in the monoclinic space group P2₁/c, with unit cell dimensions a = 12.0262(7), b = 16.5629(9), c = 12.3449(8) Å, β = 105.160(2)°, V = 2373.4(2) ų, Z = 4, R₁ = 0.0376, wR₂ = 0.0844, GOOF = 1.058; 2 crystallizes in the monoclinic space group P2₁/c, with unit cell dimensions a = 10.6439(7), b = 16.1968(9), c = 13.1108(8) Å, β = 104.180(2)°, V = 2191.4(2) ų, Z = 4, R₁ = 0.0521, wR₂ = 0.1142, GOOF = 1.018. X-ray analysis indicates that vanadium in the complexes are coordinated by phenolate oxygen, imino nitrogen, and enolate oxygen of the hydrazone, two oxygens of the benzohydroxamate, and one oxo, generating octahedral coordination. Oxidations of olefins with the complexes as catalysts were evaluated. The complexes showed effective catalytic efficiency in oxidation of several aliphatic and aromatic substrates under mild conditions, using tert-butyl hydrogen peroxide as oxidant.

Graphical Abstract

Keywords:

• Hydrazone ligand
• Vanadium complex
• Crystal structure
• Catalytic epoxidation

Acknowledgement

The author greatly acknowledges Jingchu University of Technology for financial support.