CuClCu₂TeS₃:  Synthesis, Structure Determination, and Raman Spectroscopic Characterization of a New Zincblende Derivative^†

Pure black CuClCu₂TeS₃ was prepared by reaction of stoichiometric amounts of CuCl, Cu, Te, and S in evacuated silica ampules. The crystal structure was determined from single crystals at room temperature. The compound crystallizes in the rhombohedral system, space group R3m with a = 7.361(1) Å and c = 10.401(1) Å (hexagonal setting), and Z = 3. Structural considerations and group-subgroup relationships show that CuClCu₂TeS₃ can be regarded as a new ordered zincblende derivative. In this material copper and sulfur are four-coordinate. By contrast tellurium has a trigonal pyramidal coordination and chlorine is located in a trigonal planar surrounding. Raman spectra are dominated by stretching modes of thiometalate ions [TeS₃]^2- at ν_asym = 359 cm^-1 and ν_sym = 336 cm^-1, respectively. DTA measurements reveal a peritectic decomposition of CuClCu₂TeS₃ at 448 °C.