Darstellung und Kristallstruktur der Alkalithiochromate (III), ACr5S8 (A ≙ Cs,Rb und K)

Preparation and Crystal Structure of the Alkali Thiochromates (III), ACr₅S₈ (A ? Cs, Rb und K) The alkali thiochromates (III), ACr₅S₈ (A ? Cs, Rb und K), can be obtained by the reaction of chromium powder with the corresponding alkali metal carbonate in a current of dry hydrogensulfide at about 1320 K. X-ray investigations on single crystals revealed that the compounds crystallize isotypic in the space group C2/m (No. 12), z = 2. Chromium is surrounded by six sulphur atoms in form of an octahedron. These sulphur octahedrons are sharing edges and partly faces, building up a frame with tubes which contain the alkali metal ions in a linear arrangement. Remarkable is the very short cesium-cesium distance of 346 pm, in CsCr₅S₈.