SYNTHESIS, CRYSTAL-STRUCTURE AND THERMAL-BEHAVIOR OF CS1,5[RE3I3CL7,5(H2O)1,5]

Dark brown tetrahedra of Cs1,5[Re3I3Cl7,5(H2O)1,5] crystallize on slow cooling of a hot saturated solution of ReI3 and CsCl in conc. hydrochlorid acid. The crystal structure (cubic, P43mBAR (No. 215), a = 1241.06(3) pm, V(m) = 287.8(1) cm3mol-1, Z = 4, R = 0.067, R(w) = 0.037) is built up from isolated building units [Re3I3Cl7,5(H2O)1,5]1,5- with statistical distribution of chloride ions and water molecules in the in plane, terminal positions. Consistent with the result based on the X-ray analysis, the IR-spectrum shows one band for the OH stretching frequencies of the water molecules coordinated to the Re3 triangle at 3 240 cm-1. The anions are arranged in the fashion of a cubic closest packing with the cesium ions occupying all octahedral and one quarter of the tetrahedral interstices. Temperature-dependent Guinier-Simon photographs in connection with DTA/TG investigations reveal that Cs1,5[Re3I3Cl7,5(H2O)1,5] releases water at 190-degrees-C accompanied with a structural transition and the dehydration product decomposes at 370-degrees-C to Cs2ReCl6-xIx, Re3I3+yCl6-y and rhenium metal.