Speciation of chloroindate(III) ionic liquids

A range of chloroindate(III) ionic liquid systems was prepared by mixing of 1-alkyl-3-methylimidazolium chloride with indium(III) chloride in various ratios, expressed as the mol fraction of indium(III) chloride, chi(InCl3). For chi(InCl3) <= 0.50, the products were liquids, whereas for chi(InCl3) > 0.50, the products were biphasic (suspensions of a solid in an ionic liquid). Speciation of these chloroindate(III) systems was carried out using a wide range of techniques: differential scanning calorimetry (DSC), polarised optical microscopy (POM), liquid-state and solid-state In-115 NMR spectroscopy, X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS). Ionic liquids prepared using an excess of the organic chloride (chi(InCl3) < 0.5) contained [InCl6](3-), [InCl5](2-) and [InCl4](-) anions, in proportions dependent on the chi(InCl3) value. Equimolar mixtures yielded single compounds: 1-alkyl-3-methylimidazolium tetrachloroindates(III). Systems containing an excess of indium(III) chloride (chi(InCl3) > 0.5) contained indium(III) chloride powder suspended in a neutral tetrachloroindate ionic liquid.