THE QUADRUPLE CHAINS OF SBO6 OCTAHEDRA IN SB2TE2O9 - AN EXAMPLE OF LOW EXTENT OF AGGREGATION OF PENTAVALENT ANTIMONY POLYHEDRA

Single crystals of Sb2Te2O9 have been grown by transport methods, and the crystal structure determined by X-ray single-crystal techniques. The results have been confirmed by a neutron powder diffraction refinement. The compound crystallizes in the monoclinic system, space group P2(1)/c, Z = 8, with unit-cell parameters a = 21.79(1), b = 4.849(1), c = 14.574(9) angstrom and beta = 109.21(3)-degrees. The structure consists of infinite quadruple chains of vertex-sharing SbVO6 octahedra, running along the b axis, bridged by (Te6O26)infinity strings parallel to the [001] direction and by isolated Te2O10 groups. The Te(IV) is five- and six-co-ordinated by oxygen, in very irregular environments making room for the free electron pairs. This structure is discussed in the framework of other pentavalent antimony complex oxides and contrasted with those of the known oxides in the M2O5-TeO2 (M = V, Nb or Ta) systems.