ISOLATED [M6S14] UNITS IN TERNARY SULFIDE S OF TECHNETIUM AND RHENIUM

We have successfully prepared the ternary sulfides Rb10Tc6S14, Cs10Tc6 S14, Rb10Re6S14, and Cs10Re6S14 by heating alkali carbonate with eleme ntal technetium or rhenium in a hydrogen stream charged with sulfur. S tructural investigations on single crystals revealed that these compou nds crystallize in the space group Fm3mBAR. [M6S14] cluster units (M c orresponds to Tc, Re) are found as the characteristic structural featu res, in which regular M6 octahedra are coordinated by sulfur atoms ove r their eight faces and six vertices. Other than in the case of the pr eviously investigated ternary technetium and rhenium chalcogenides, th ese units are not linked to one another, but occur as isolated complex anions which form a cubic close packed array. The alkali ions, whose sites are partly statistically occupied, are found on the corners, the edges and the longer face diagonals of a rhombic dodecahedron surroun ding each of these units. The dodecahedra share all their faces with o ne another. The diamagnetic behaviour which was measured on Cs10Tc6S14 in the temperature range from 10 to 295 K is in accordance with a 24- electron-configuration of the regular M6 octahedra.