Oxovanadium and dioxomolybdenum complexes: synthesis, crystal structure, spectroscopic characterization and applications as homogeneous catalysts in sulfoxidation

Abstract

New oxovanadium and dioxomolybdenum Schiff base complexes, [VO(L)(OCH₃)]_n and [MoO₂(L)(CH₃OH)], were synthesized by treating an ONO donor Schiff base (H₂L) derived by condensation of 3-ethoxysalicylaldehyde and nicotinic hydrazide with oxo and dioxo acetylacetonate salts of vanadium and molybdenum (VO(acac)₂ and MoO₂(acac)₂), respectively. The synthesized ligand and complexes were characterized by FTIR, multinuclear (¹H, ¹³C) NMR, elemental and single crystal X-ray diffraction analysis. In both complexes, the geometry around the central metal ions was distorted octahedral as revealed by diffraction studies. Theoretical calculations of the synthesized compounds were carried out by DFT at B3LYP/Def2-TZVP level of theory, which showed good correlation with the experimental results. Moreover, the catalytic efficiency of both complexes was investigated by oxidizing aryl and alkyl sulfides in the presence of 30% H₂O₂ in ethanol.

Graphical Abstract

Keywords:

• Oxovanadium(V)
• dioxomolybdenum(VI)
• tridentate Schiff base
• homogeneous catalysis
• sulfoxidation

Acknowledgement

We gratefully acknowledge practical support of this study by Ardakan University and Payame Noor University.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability

Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC 2045556 and 2044074 for the vanadium and molybdenum complexes, respectively. Copies of this information may be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html or from the Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax: [phone]; E-mail: [email protected]).