Solubility Behaviour of TiCl4, ZrCl4, and HfCl4 in Chloroaluminate Ionic Liquids

The solubility of NbCl5, TaCl5, TiCl4, ZrCl4, and HfCl4 in neutral [BMIM][AlCl4] (BMIM = 1‐butyl‐3‐methylimidazolium) was determined. While TiCl4 was immiscible with the neutral ionic liquid, 0.80 molar equivalents of ZrCl4 and stoichiometric amounts of HfCl4 dissolved in the melt at ambient temperature. The crystal structures and the unit cell parameters of [BMIM]2[Ti2Cl10], [BMIM]2[Zr2Cl10], and [PhNMe3][Hf2Cl9] were determined. [BMIM]2[Ti2Cl10], and [BMIM]2[Zr2Cl10] were crystallised from basic chloroaluminate melts. With a trimethylanilinium cation, [PhNMe3][Hf2Cl9] crystallised from an equimolar composition of PhNMe3Cl, AlCl3, and HfCl4. Obviously, HfCl4 ed a chloride ligand from [AlCl4]– to give highly Lewis acidic [Al2Cl7]– anions.