Cover illustration: View of the triaquahexakis(2-betaine-O:O')-3-oxo-triiron(III) bis(tetrachloromanganate) cation. Displacement ellipsoids are drawn at the 50% probability level. See Ramos Silva, Matos Beja, Paixão, Alte da Veiga & Martin-Gil [Acta Cryst. (2001), C57, 542-545].
β-RbSb crystallizes with the LiAs structure type. As in the α phase (NaP type), Sb− forms approximate 41 helical chains (21 crystallographic symmetry), with Sb—Sb distances of 2.838 (1) and 2.862 (1) Å. In contrast to the α phase, the helices have different chirality.
The antimonide oxide Ba3Sb2O consists of discrete [Sb2]4− and O2− anions, and crystallizes with a new structure type. The Sb—Sb distances are comparable to those known from electron-precise zintl phases and the tetrahedral coordination of the O2− anion is also observed in some other Ba-rich metallide oxides.
The anion of the title compound has the α-Keggin structure, with a central tetrahedrally coordinated BIII atom surrounded by four groups of three edge-sharing octahedra (W3O13 subunits) which are linked in turn to each other and to the central BO4 tetrahedron by shared O atoms at the vertices.
KSbO(Ge0.32Si0.68)O4 is isomorphic with KTP, i.e. KTiOPO4. It contains mixed (Ge/Si)O4 tetrahedra with the same distribution in each independent tetrahedron and split potassium-cation positions. The crystal is paraelectric (space group Pnan) at room temperature.