Oxychloridoselenites(iv) with cubane-derived anions and stepwise chlorine-to-oxygen exchange

Abstract

The novel oxychloridoselenites(IV) [BMIm][Se₃Cl₁₃] (1), [BMIm][Se₄Cl₁₅O] (2), [BMIm]₂[Se₄Cl₁₄O₂] (3), [BMPyr]₂[Se₄Cl₁₄O₂] (4), [BMPyr]₂[Se₆Cl₁₈O₄] (5), [BMIm]₂[SeCl₄O] (6), [BMPyr]₂[Se₂Cl₆O₂] (7), and [BMPyr]₂[Se₆Cl₁₄O₆] (8) are prepared by ionic-liquid-based synthesis. Accordingly, SeCl₄, SeO₂ (1–6), and/or SeOCl₂ (7,8) as the starting materials are reacted in [BMIm]Cl or [BMPyr]Cl as ionic liquid (BMIm: 1-butyl-3-methylimidazolium, BMPyr: 1-butyl-1-methylpyrrolidinium; partially with AlCl₃ in addition). Generally, the composition and structure of title compounds can be derived from the tetrameric, heterocubane-type (SeCl₄)₄ as the initial building unit. Thus, chlorine is successively exchanged by oxygen from 1 to 8. Moreover, the four edge-sharing (SeCl₆) octahedra in (SeCl₄)₄ are increasingly dismantled, ending with a [SeCl₄O]²⁻ anion as a single pseudo-octahedron in 6. Based on the weakly coordinating ionic liquid, it is possible to selectively obtain the different species via synthesis near room temperature (20–80 °C). The oxychloridoselenite anions [Se₄Cl₁₅O]⁻, [Se₄Cl₁₄O₂]²⁻, [Se₆Cl₁₈O₄]²⁻, and [Se₆Cl₁₄O₆]²⁻ are obtained for the first time. The title compounds are characterized by X-ray structure analysis based on single crystals and powders as well as by infrared spectroscopy and thermal analysis.