(LiI)2Li3SbS3: A mixed Alkali Metal Halide Thioantimonate with a novel Tetrahedron Network

(LiI)₂Li₃SbS₃ was prepared by solid‐state reaction of stoichiometric amounts of LiI, Li, Sb, and S in the ratio 2 : 3 : 1 : 3. The product is air and moisture sensitive. The crystal structure was determined from single crystals at room temperature. Colourless to pale yellow (LiI)₂Li₃SbS₃ crystallizes in the orthorhombic system, space group Pnnm (no. 58) with a = 10.436(1)Å, b = 13.509(1)Å, c = 7.530(1)Å, V = 1061.6(1)ų, and Z = 4 (data at 20 °C). The crystal structure of (LiI)₂Li₃SbS₃ is closely related to that of (CuI)₂Cu₃SbS₃ and (AgI)₂Ag₃SbS₃, at least for the positions of I, Sb, and S. Thus, iodine forms an eutactic arrangement which resembles the structure of hexagonal diamond. SbS₃]^3— units are embedded in this framework in a way that the sulphur atoms of two adjacent trigonal pyramids form distorted octahedral voids. The lithium ions are tetrahedrally coordinated and fully ordered within the anionic framework. The three‐dimensional connectivities in (LiI)₂Li₃SbS₃ are significantly different from the homologous copper and silver compound due to the bonding necessities of Li and slightly different radii of the monovalent cations. Thus, a novel three‐dimensional network of edge sharing tetrahedra is observed in (LiI)₂Li₃SbS₃. It exhibits strands of eight‐membered rings of edge sharing tetrahedra which are linked by common vertices and cross linked by double tetrahedra.