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

Abstract

Six alkoxohexavanadate-based Cu- or Co-POVs [Cu(dpa)(acac)(H2O)]2[V6O13(OMe)6] (1), [Cu(phen)(acac)(MeOH)]2[V6O13(OMe)6] (2), [Co(dpa)(acac)2]2[V6O13(OMe)6]·2MeOH (3), [Co(phen)(acac)2]2[V6O13(OMe)6] (4), [Cu(dpa)(acac)]2[VIV2VV4O12(OMe)7] (5), and [Cu(dpa)(acac)(MeOH)]2[VIV2VV4O11(OMe)8] (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 [V6O12(OMe)7]2- 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 H2O2 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.