Two Ce³⁺-Substituted Selenotungstates Regulated by N, N-Dimethylethanolamine and Dimethylamine Hydrochloride

Two multi-Ce³⁺-substituted selenotungstates (STs), [HDMEA][H₂N(CH₃)₂]₄H₃Na₄[Ce₂(H₂O)₆(DMEA)W₄O₉(α-SeW₉O₃₃)₃]·26H₂O (1) and [H₂N(CH₃)₂]₁₀H₄Na₁₀[Ce₂W₄O₉(H₂O)₇(α-SeW₉O₃₃)₃]₂·63H₂O (2), were prepared by the one-pot approach of sodium tungstate, sodium selenite, and lanthanide nitrate in an acidic water solution in the presence of N, N-dimethylethanolamine (DMEA) or dimethylamine hydrochloride (DMAHC). 1 was obained in the presence of DMEA, whereas 2 was synthesized in the presence of DMAHC. The trimeric polyoxoanion of 1 contains an unusual V-shaped [Se₃W₂₉O₁₀₃]^20- group embracing a prominent heterometal oxide fragment, [Ce₂(H₂O)₆(DMEA)W₂O₅]⁸⁺, and the hexameric polyoxoanion of 2 is constructed from two equivalent trimeric [Ce₂W₄O₉(H₂O)₇(SeW₉O₃₃)₃]₂^24- subunits through two -O-W-O-Ce-O- linkages. The most worthy of attention is that the polyoxoanion of 1 can be approximatively viewed as a half of the polyoxoanion of 2 because of the coordination and blocking effect of DMEA. The stability of 1 and 2 in different water pH values was studied by electrospray ionization mass spectroscopy (ESI-MS), and the results manifest that 1 and 2 are stable in pH = 3.5-7.5 and 3.5-7.0, respectively. The oxidation reactions of aromatic sulfides catalyzed by H₂O₂ were studied when 1 or 2 worked as a catalyst, and experimental results reveal that 1 or 2 can serve as available catalysts for the oxidation of aromatic sulfides under mild conditions.