Non-oxo vanadium(IV) complexes with acetylacetone 4-R-benzoylhydrazones

Abstract

Vanadium(IV) complexes of formula [V(acRbh)₂] with acetylacetone 4-R-benzoylhydrazones (H₂acRbh, R=H, Cl, OMe and NO₂) have been synthesized and characterized by elemental analysis, IR, UV–vis, and electron paramagnetic resonance (EPR) spectroscopic measurements. All the complexes are one-electron paramagnetic and show very similar axial EPR spectra in frozen solution. In dimethylformamide, the complexes display a V(IV)−V(III) redox couple in the E _1/2 range −0.16–−0.25 V (versus Ag/AgCl). Single crystal X-ray structures of [V(acHbh)₂] and [V(acClbh)₂] have been determined. The metal center in each complex is in a distorted trigonal prismatic N₂O₄ coordination sphere assembled by the enolate-O, the imine-N, and the iminolate-O donor acRbh²⁻.

Keywords:

• Non-oxo vanadium(IV)
• Aroylhydrazones
• Crystal structures
• Trigonal prism
• Physical properties

Acknowledgements

Financial support for this work has been received from the Department of Science and Technology (DST) (IYC Grant No. IR/S1/CF-01E/2011). K. Nagaraju and A. Sarkar thank the Council of Scientific and Industrial Research for research fellowships. We thank the DST and the University Grants Commission for the facilities provided under the FIST and the CAS programs, respectively.