The Bromine‐Rich Bromido Metallates [BMIm]2[SnBr6]·(Br2) and [MnBr(18‐crown‐6)]4[SnBr6]2·(Br2)4.5

Abstract

The bromine‐rich bromido metallates [BMIm]2[SnBr6]·(Br2) (1) and [MnBr(18‐crown‐6)]4[SnBr6]2·(Br2)4.5 (2) were prepared by the reaction of MgBr2 or MnBr2 with SnBr4, 18‐crown‐6, and elemental bromine in the ionic liquids [BMIm][N(Tf)2] and [MeBu3N][N(Tf)2] {BMIm: butyl methyl imidazolium, N(Tf)2: bis(trifluoromethylsulfonyl)amide}. This sequence of reactions was motivated by previous studies in the system ZnBr2/Br2/18‐crown‐6 and here expanded to divalent cations of comparable diameter (i.e., Zn2+ with 74 pm, Mg2+ with 65 pm; Mn2+ with 91 pm). In difference to Zn2+, however, totally different compounds and structures were obtained. [BMIm]2[SnBr6]·(Br2) contains zigzag chains of [SnBr6]2– anions and Br2 that are separated by [BMIm]+ cations. In [MnBr(18‐crown‐6)]4[SnBr6]2·(Br2)4.5 dibromine molecules are interconnected by [MnBr(18‐crown‐6)]+ cations to form two‐dimensional bromine layers. Thermogravimetry shows a remarkably high temperature of 250 °C for Br2 release. The Br–Br interactions were analyzed by Raman spectra and quantum chemical calculations, resulting in a reliable assignment of the observed vibrations and a calculation of the force constants.