PREPARATION, CRYSTAL-STRUCTURE AND LI-7 NMR OF LI6+2X[B10S18]SX(X ALMOST-EQUAL-TO 2)

Li6+2x[B10S18]Sx (x≈2), a novel thioborate-sulfide double salt, was prepared from the elements by reaction at 750° C in a graphitized sealed tube, and single crystals were obtained by annealing at 550-500°C. The crystal structure (space group C2/c, a=20.996(5), b=21.157(4), c=16.197(5) A ̊, β= 128.53(1) °) contains a well-defined polymeric thioborate network of composition position [B10S186-]n consisting of a system of edge-sharing [B10S16S 4 2] adamantanoid macro-tetrahedra. Two rigid symmetry-related interpenetrating networks of this kind form large channels in which a strongly disordered system of lithium and sulfide ions (10Li+ and 2 S2- per formula unit) is observed. The dynamic behaviour of the lithium ions in the crystalline compound was investigated from the temperature and frequency dependence of the 7Li NMR spectra. © 1990.