Synthesis and crystal structures of Li4-2xSr2+xB10S19 (x approximate to 0.27) and Na6B10S18. Two novel thioborates with highly polymeric macro-tetrahedral networks

Li4-2xSr2+xB10S19 (x approximate to 0.27) and Na6B10S18 were prepared from the reaction of strontium sulfide and lithium sulfide (sodium sulfide) with boron and sulfur at 700 degrees C in graphitized silica tubes. Li4-2xSr2+xB10S19 (x approximate to 0.270 crystallizes in the monoclinic space group P2(1)/c with a = 10.919(2) Angstrom, b = 13.590(3) Angstrom, c = 16.423(4) Angstrom, and beta = 90.48(2)degrees, Na6B10S18 in the tetragonal space group I4(1)/acd with a = 14.415(3) Angstrom, c = 26.137(4) Angstrom. Both structures contain supertetrahedral B10S20 units which are linked through tetrahedral corners to form a three-dimensional polymeric network in the case of Na6B10S18 and one-dimensional chains in the case of Li4-2xSr2+xB10S19 (x approximate to 0.27). All boron atoms are in tetrahedral BS4 coordination *B-S bond lengths vary from 1.879(5) to 1.951(5) Angstrom (1.875(10) to 1.987(9) Angstrom)). The strontium and lighium (sodium) cations are located within large channels formed by the anions.