Two novel supramolecular structures of Evans–Showell type polyoxometalate for heterogeneous and efficient catalytic conversion of different sulfides

Abstract

Selective oxidation reactions of sulfides have been attracting chemists from different fields due to the wide applications of the products. In this work, two hybrid compounds of Evans–Showell type polyoxometalate, [Co(bpy)₃]₂[Co₂Mo₁₀O₃₈H₄]·6H₂O (1) and [Cu₃(bpy)₃(H₂O)₆][Co₂Mo₁₀O₃₈H₄]·5H₂O (2) (bpy = 2,2′-bipyridine), were designed to catalyze the oxidation of various sulfides. Their corresponding structures were determined by Fourier-Transform Infrared-Spectroscopy (FT-IR), X-ray diffraction (single-crystal and powder), and elemental mapping analysis, exhibiting three-dimensional supramolecular structures formed through extensive hydrogen bonding interactions. Compound 1, in the model reaction of selective oxidation of methyl phenyl sulfide (MPS) to methyl phenyl sulfoxide (MPSO), achieved complete conversion within 35 min and exhibited a dramatically higher turnover frequency (TOF) compared to those of the other various precursors. Compound 2 also exhibited excellent catalytic properties within 60 min, despite the significant difference in the three-dimensional stacking pattern from that of 1. Besides, more generally, both compounds showed satisfactory catalytic performance for different sulfide substrates. Finally, their excellent structural stability and recyclability under working conditions were confirmed using different tests.