RHENIUM SELENIDETELLURIDES RE2SEXTE5-X - THE STRUCTURE OF RE6SE8TE7

Well-crystallized rhenium selenidetellurides of the Re2Te5-type structure were prepared from the elements in evacuated sealed quartz glas tubes at 1130 K within 14 d. The orthorhombic lattice parameters of the phases shrink with increasing selenium content from a = 1304.9(1) - 1255.8(2) pm, b = 1297.5(1)-1260.0(2)pm, and c = 1425.1(1)-1408.2(1)pm. The phase width ends at composition Re2Se2,7Te2,3. An X-ray structure analysis of a crystal of composition Re6Se8Te7 was performed. Selenium and tellurium atoms differ structurally completely: Whereas the selenium atoms are separated within distorted octahedral [Re6Se8] clusters, the tellurium atoms form homonuclear bonded bicyclic [Te(Te-3)(2)] units. They also link the clusters which are arranged according to the motif of a cubic closest packing.