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

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/AlCl3 ([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(AlCl4)(3) were isolated from the ionic liquid and characterized by Raman spectroscopy and X-ray crystallography (rhombohedral space-group R (3) over barc, 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 SO2 with strongly oxidizing, toxic agents like SbF5 or AsF5.