Schiff base Mn(iii) and Co(ii) complexes coated on Co nanoparticles: an efficient and recyclable magnetic nanocatalyst for H2O2 oxidation of sulfides to sulfoxides

Abstract

In this paper, an effective and selective heterogeneous catalyst was produced by immobilization of manganese and cobalt Schiff base-complexes on Co magnetite nanoparticles (MNP). The catalysts Co@SiO₂[(EtO)₃Si–L³]/M (M = Mn(III) and Co(II)) were synthesized using Co@SiO₂ core–shell nanoparticles and amino-functionalized Co@SiO₂. The Schiff base ligand Co@SiO₂[(EtO)₃Si–L³] was synthesized by reacting Co@SiO₂ core–shell nanoparticles with 2-hydroxy 1-naphthaldehyde for the synthesis of Co@SiO₂[(EtO)₃Si–L³]/M. The catalysts were characterized by several techniques, such as FT-IR, TEM, XRD, TGA and VSM. The catalytic activities of the prepared catalysts were studied by oxidation of sulfides to the sulfoxides under different conditions. These catalysts can be easily recovered and reused in at least seven sequential cycles without considerable leaching and loss of reactivity.