New strontium polysulfides, SrS3, and Sr2(OH)2S4.10H2O, obtained by the high-pressure treatment of a Sr-S mixture

A new polymorph of SrS(3) was obtained by a reaction of SrS and S with an atomic ratio of Sr:S = 1:5 under a pressure of 5 GPa at 1200 degrees C. It crystallized in a tetragonal unit cell with a = 6.708(1) A, c = 3.942(1) A, and V = 177.36(6) A(3). It was isotypic with BaS(3), and contained S3(2-) polysulfide ions. The product obtained from the high-pressure synthesis contained an amorphous component. It was highly deliquescent and formed a yellowish solution. A new layered polysulfide, Sr(2)(OH)(2)S(4).10H(2)O, crystallized in the solution. The sulfide belonged to a triclinic space group of P (No. 2) with lattice constants of a = 5.9107(5) A, b = 7.8682(6) A, c = 9.4134(6) A, alpha = 75.639(6) degrees, beta = 73.824(3) degrees, gamma = 71.639(3) degrees, V = 392.83(5) A(3), and Z = 1. Each Sr ion was coordinated with one OH ligand and eight H(2)O ligands. Six H(2)O ligands out of the eight were bridging ligands to form two-dimensional Sr(2)(OH)(2)(H(2)O)(10)(2+)]( infinity ) cationic layers, between which S4(2-) tetrapolysulfide ions were situated. The S4(2-) anion had a coplanar configuration with a dihedral angle of 180.0 degrees. The stability of S4(2-) anions having different conformations was discussed from a viewpoint of ab initio MO calculations on changing the dihedral angles of S4(2-).