Darstellung und Kristallstruktur von Cs2Sn3Se7, ein Cäsium-selenostannat(IV) mit fünffach koordiniertem Zinn / Preparation and Crystal Structure of Cs2Sn3Se7, a Cesium Selenostannate(IV) with Pentacoordinated Tin

Abstract

Methanolothermal reaction of Cs2CO3 with SnSe, in the presence of SnSe at 160 C and 13 bar yields the selenostannates(IV) Cs4Sn2Se6 and Cs,Sn3Se7. The structure of the latter phase was established by X-ray structural analysis. The crystal structure contains polyselenostannate(IV) sheet anions [Sn3Se7 2-]∞2, for which the basic elements are trigonal SnSe5-bipyramids. Six of the seven independent selenium atoms in the asymmetric unit are coordinated by two tin atoms, one by three atoms. Neighbouring anion sheets are so placed that channels are formed which contain two independent cesium cations; these display coordination numbers of, respectively, eight and seven.