Room‐Temperature Synthesis of Bismuth Clusters in Ionic Liquids and Crystal Growth of Bi₅(AlCl₄)₃

Abstract

Abstract The viability of Lewis‐acid ionic liquids for the synthesis of low‐valent bismuth compounds is demonstrated. At room temperature, elemental bismuth and bismuth(III) cations synproportionate in the ionic liquid [BMIM]Cl/AlCl 3 ([BMIM] + : 1‐ n ‐butyl‐3‐methylimidazolium) within minutes. The existence of bismuth polycations in the dark colored solution was proven by Raman spectroscopy. Dark‐red crystals of Bi 5 (AlCl 4 ) 3 were isolated from the ionic liquid and characterized by Raman spectroscopy and X‐ray crystallography (rhombohedral space‐group $R{\bar 3}c$ , a = 1187.1(2) pm, c = 3012.0(3) pm). The method allows the synthesis of bismuth cluster compounds under milder conditions than in high‐temperature melts and more conveniently and environmental friendly than in liquid SO 2 with strongly oxidizing, toxic agents like SbF 5 or AsF 5 .