Low-melting imidazolium-based salts with the paramagnetic reineckate-analogue anion [Cr(NCS)4(bipy)]- (bipy = 2,2'-bipyridine): syntheses, properties, and structures.

In order to investigate the potential ionic liquid properties of Reineckate-analogue materials, four new salts, consisting of the heteroleptic [Cr(NCS)(4)(bipy)](-) complex anion and imidazolium-based cations A(+) = 1-ethyl-3-methylimidazolium, 1-n-butyl-3-methylimidazolium, pentamethylimidazolium, and 1,3-dimethyl-2,4,5-triphenylimidazolium, were investigated. Their structures were established by single-crystal X-ray diffraction. The compounds are paramagnetic with effective magnetic moments in the range of those expected by the number of unpaired spins of the chromium(III) ion. All melting points are above 100 °C, which prevents us from calling these compounds "ionic liquids". Nevertheless, they are low for salts of this constitution and may be useful for molten salt reactions. Cyclic voltammetry measurements show no reversible electron-transfer steps.