Rational Synthesis, Structures and Properties of the Ionic Liquid Binary Iodine-Bromine Octahalide Series [In Br8-n ]2- (n=0, 2, 3, 4).

A series of octanuclear iodine-bromine interhalides [In Br8-n ]2- (n=0, 2, 3, 4) were prepared systematically in two steps. Firstly, addition of a dihalogen (Br2 or IBr) to the triaminocyclopropenium bromide salt [C3 (NEt2 )3 ]Br forms the corresponding trihalide salt with Br3 - or IBr2 - anions, respectively. Secondly, addition to Br3 - of half an equivalent of Br2 gives the octabromine polyhalide [Br8 ]2- , whereas addition to IBr2 - of half an equivalent of Br2 , IBr or I2 gives the corresponding interhalides: [I2 Br6 ]2- , [I3 Br5 ]2- , and [I4 Br4 ]2- , respectively. The four octahalides were characterized by X-ray crystallography, computational studies, Raman and Far-IR spectroscopies, as well as by TGA and melting point. All of the salts were found to be ionic liquids.