Synthesis of the new quaternary sulfides k₂y₄sn₂s₁₁ and balnags₃ (ln = er, y, gd) and the structures of k₂y₄sn₂s₁₁ and baerags₃

Several new quaternary sulfides, K₂Y₄Sn₂S₁₁ and BaLnAgS₃ (Ln = Er, Y, Gd), have been synthesized by the reaction of the constituent binary chalcogenides and elements at 1000°C. The crystal structures of K₂Y₄Sn₂S₁₁ and BaErAgS₃ have been determined by single-crystal X-ray diffraction techniques. Crystal data: K₂Y₄Sn₂S₁₁-space group D⁸_4h - P4/ncc, M = 1023.88, Z = 4, a = 8.587(1), c = 27.892(4) Å (T = 115 K), V = 2056.7(4) ų, R_w (F²) = 0.093 for 1965 observations and 48 variables, R(F) = 0.034 for 1319 observations having F²_o > 2σ(F²_o); BaEr AgS₃-space group C³_2h - C2/m, M = 508.65, Z = 4, a = 17.340(4), b = 4.014(1), c = 8.509(2) Å, β = 103.23(3)°, (T = 115 K), V = 576.5(2) ųR_w(F²) = 0.049 for 1404 observations and 48 variables, R(F) = 0.018 for 1299 observations having F²_o > 2σ(F²_o). In both structures the rare-earth atoms have octahedral coordination and the octahedra form slabs through edge- and corner-sharing. These slabs are separated by K⁺ or Ba²⁺ cations, and are crosslinked into three-dimensional frameworks by Sn₂S₆ units as edge-sharing SnS₄ tetrahedral pairs in K₂Y₄Sn₂S₁₁, and by Ag₂S₉ units as corner-sharing trigonal-bipyramidal AgS₅ pairs in BaEr AgS₃. From their powder diffraction patterns, BaYAgS₃ and Ba GdAgS₃ appear to be isostructural with BaErAgS₃.