Controllable Synthesis of Lindqvist Alkoxopolyoxovanadate Clusters as Heterogeneous Catalysts for Sulfoxidation of Sulfides.

Six alkoxohexavanadate-based Cu- or Co-POVs [Cu(dpa)(acac)(HO)][VO(OMe)] (1), [Cu(phen)(acac)(MeOH)][VO(OMe)] (2), [Co(dpa)(acac)][VO(OMe)]·2MeOH (3), [Co(phen)(acac)][VO(OMe)] (4), [Cu(dpa)(acac)][VVO(OMe)] (5), and [Cu(dpa)(acac)(MeOH)][VVO(OMe)] (6) (POV = polyoxovanadate; dpa = 2,2'-dipyridine amine; phen = 1,10-phenanthroline; acac = acetylacetone anion) have been synthesized by controlling the reaction conditions and characterized by single-crystal X-ray diffraction and powder X-ray diffraction analyses, FT-IR spectroscopy, element analyses, and X-ray photoelectron spectroscopy. In compounds 1-4 and 6, Cu or Co complexes and alkoxohexavanadate anions are assembled through electrostatic interactions. Differently, in compound 5, seven-methoxo-substituted Lindqvist-type [VO(OMe)] are bridged to Cu complex via terminal O atoms by coordination bonds. All compounds 1-6 exhibit excellent heterogeneous catalytic performance in oxidative desulfurization and CEES ((2-chloroethyl) ethyl sulfide, a sulfur mustard simulant) abatement with HO as oxidant. Among them, the catalytic activity of 6 [conv. of DBT (dibenzothiophene) up to 100% in 6 h; conv. of CEES reached 100% and selectivity of CEESO ((2-chloroethyl) ethyl sulfoxide) up to 85% after 4 h] outperforms others and can be reused without losing its activity.