Synthesis, crystal structure and catalytic activity of an oxo-diperoxo tungsten(VI) complex containing an oxazine ligand for selective oxidation of sulfides

Abstract

A novel oxo-diperoxo tungsten(VI) complex, [WO(O₂)₂(Hphox)], was prepared by reaction of WO₃ in H₂O₂ with an oxazine-type ligand, 2-(2′-hydroxylphenyl)oxazine (Hphox). The complex was characterized by FTIR, ¹H NMR and elemental analysis. The single-crystal X-ray diffraction studies revealed a seven-coordinate tungsten center with a distorted octahedral geometry. The [WO(O₂)₂(Hphox)] complex was applied as a catalyst in efficient and selective oxidation of sulfide to sulfoxide using 30% H₂O₂ or UHP (urea hydrogen peroxide) as oxidants. This catalyst showed excellent catalytic activities and high selectivities in producing a variety of aryl and alkyl sulfoxides under mild conditions. To get an insight into the mechanisms of oxidation of sulfides, the mechanistic studies were monitored by UV–Vis spectroscopy.

Graphical Abstract

Keywords:

• Oxo-diperoxo
• tungsten
• oxazine ligand
• oxidation of sulfides
• sulfoxide

Acknowledgements

M.B. thanks the Research Council of Sharif University of Technology for funding of this work.