Pd-PVP-Fe (palladium-poly(N-vinylpyrrolidone)-iron) catalyzed S-arylation of thiols with aryl halides in aqueous media

Abstract

Pd-PVP-Fe (palladium-poly(N-vinylpyrrolidone)-iron) nano catalyst catalyzes selective C–S cross-coupling (S-arylation) reactions of thiols with aryl halides and avoids the formation of S–S (disulfide) homocoupling byproducts. The reactions were carried out in aqueous media using only 0.23mol% palladium with high selectivity and short reaction time. The effects of the Pd0 and Fe0 moieties on the C–S cross-coupling reaction mechanism, yield, and selectivity were investigated. The yield and selectivity can be controlled by adjusting the order of adding the reactants and catalyst into the reaction medium. The X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) microscopy, energy dispersive X-ray (EDX) spectroscopy, and thermal gravimetric analysis (TGA) tools were used to characterize the catalyst. The C–S cross-coupling reaction process could be repeated up to six times without losing effectiveness. The metals leaching of Pd-PVP-Fe nanocatalyst after reusing cycles were investigated by atomic absorption spectroscopic (AAS) and EDX spectroscopy. The nature of Pd metal after the first run of the C–S cross-coupling reaction was studied by UV–vis spectrophotometry. The morphology of bimetallic nanocatalyst after the first run of the C–S cross-coupling reaction was investigated by SEM, EBSD, and EDX microscopy.