Vanadyl heterosubstituted 1,3-β-diketonate complexes: Synthesis, characterization and catalytic applications for the selective oxidation and detoxification of sulfur compounds

Six novel Vanadyl heterocyclic/aromatic substituted 1,3-β-diketonates complexes containing bidentate ligands have been synthetized and their structures full characterized by single crystals X-ray analyses (complexes 1–3), EPR spectroscopy either in a glassy state (100 K) or as powder, FT-IR and UV-Vis analyses. The coordination environment of the complexes (a distorted octahedron) is formed by two chelate dianions in the equatorial plane in a cis-planar configuration. The catalytic activity of these new oxidovanadium(IV) complexes has been studied in the selective oxidation of a series of sulfur-containing substrates toward their corresponding sulfides and/or sulfones, using tert-butyl hydroperoxide as primary oxidant. The effects of oxidant to substrate molar ratio, catalyst amount, solvent and temperature have been studied. The high activity and selectivity showed by the complexes, prompted us to apply, successfully, the catalyst 4 in the challenging decontamination of the mustard gas simulants CEES and CEPS, towards their corresponding sulfoxide derivatives, under mild conditions. A rationale analysis on the main observed results in terms of substrate conversion yields and sulfoxides (or sulfones) selectivities, has been addressed.