The synthesis and crystal structures of novel antimony compounds: A4Sb 4O 8( X4O 12) ( A:K, Rb, Cs, Tl; X =Si, Ge)

Abstract

A series of A 4Sb 4O 8( X 4O 12) compounds ( A =K, Rb, Cs, Tl; X =Si, Ge) have been prepared either by solid-state reaction or via a sol-gel route. Single crystals of the cesium compounds have been isolated and their structure determined by X-ray diffraction. Cs 4Sb 4O 8(Si 4O 12) crystallizes in the tetragonal system, space group P4 2/ mmc with a = 7.172(1)Å, c = 19.645(2)Å, Z = 2. The structure was determined from 557 reflections collected on a Nonius CAD4 diffractometer using the Mo Kα radiation. The final R index and weighted R w index are 0.026 and 0.024, respectively. The structure is built up from planes of cross-linked chains of corner-sharing SbO 6 octahedra, linked together via corner-sharing by four-membered Si 4O 12 single rings. This three-dimensional arrangement delimits intercrossing tunnels wherein Cs cations are situated. Cs 4Sb 4O 8(Ge 4O 12) crystallizes in the tetragonal system, space group I4 122 with a = 10.241(1)Å, c = 40.073(6)Å, Z = 8. Its structure was determined from 1303 reflections and refined to R = 0.034 and R w = 0.035. It appears as a slightly distorted form of the silicate analogue.