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.