The Binary Iodine-Chlorine Octahalide Series [In Cl8-n ]2- (n=3, 3.6, 4).

The octanuclear iodine-chlorine interhalides [I4 Cl4 ]2- and [I3 Cl5 ]2- were prepared in two steps. Firstly, addition of ICl to the triaminocyclopropenium chloride salt [C3 (NEt2 )3 ]Cl forms the trihalide ICl2 - salt, secondly, addition of half an equivalent of I2 or ICl, respectively, gave the desired products upon crystallization at low temperature. The non-stoichiometric octahalide [I3.6 Cl4.4 ]2- was obtained after heating a CH2 Cl2 solution of the ICl2 - salt to reflux for 2 hours followed crystallization. [I4 Cl4 ]2- is best described as two ICl2 - anions bridged by I2 , whereas [I3 Cl5 ]2- is best described as an [I2 Cl3 ]- pentahalide with a weak halogen bond to an ICl2 - trihalide. The octahalides were characterized by X-ray crystallography, computational studies, Raman and Far-IR spectroscopies, as well as by TGA and melting point.