Schiff base complexes of Ni, Co, Cr, Cd and Zn supported on magnetic nanoparticles: As efficient and recyclable catalysts for the oxidation of sulfides and oxidative coupling of thiols

Oxidation of sulfides to sulfoxides and oxidative coupling of thiols into their corresponding disulfides were carried out using hydrogen peroxide (H2O2) as oxidizing agent in the presence of immobilized Ni, Co, Cr, Zn or Cd complexes on Fe3O4 magnetic nanoparticles (M-Salen-MNPs) as stable, heterogeneous, efficient and magnetically recoverable nanocatalysts under mild reaction conditions. These supported complexes were characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). A variety of aromatic and aliphatic sulfides and thiols with different functional groups were successfully oxidized with short reaction times in good to excellent yields. Recovery of the catalyst is easily achieved by magnetic decantation and reused for several consecutive runs without significant loss of its catalytic efficiency. (C) 2015 Elsevier B.V. All rights reserved.