Macromolecular metal complexes of NbV as recoverable catalysts for selective and eco-compatible oxidation of organic sulfides in water

Department of Chemical Sciences, Tezpur University, Napaam, Tezpur-784 028, Assam, India

E-mail: nsi@tezu.ernet.in, nashreen.islam@rediffmail.com

Manuscript received 01 July 2018, accepted 18 July 2018

The activity of a pair of peroxoniobium(V) species immobilized on water soluble non-crosslinked polymers (WSP) formulated as, [Nb(O₂)₃(sulfonate)₂]-PSS [PSS = poly(sodium styrene sulfonate)] (catalyst 1) and [Nb₂(O₂)₆(carboxylate)₂]-PA [PA = poly(sodium acrylate)] (catalyst 2) as efficient and recyclable catalysts for selective sulfoxidation of a variety of organic thioethers with 30% H₂O₂ in water_, is described. A new polymer anchored macrocomplex (catalyst 1) has been synthesized from the reaction of sodium tetraperoxoniobate (NaNb) with 30% H₂O₂ and the macromolecular ligand poly(sodium styrene sulfonate) in an aqueous medium. The catalyst has been comprehensively characterized by spectral and other physicochemical techniques. Apart from being high-yielding and operationally simple, the additional important features which enhance the sustainability of the high yielding water-based oxidation protocol include chemoselectivity of the oxidation for sulfides and easy recyclability of the catalyst with consistent activity and selectivity for several cycles of oxidation.