About selenidostannates. I. Synthesis, structure, and properties of [Sn2Se6](4-), [Sn4Se10](4-) and [Sn3Se7](2-)

Abstract

The selenidostannates [(C4H9)(2)NH2](4)Sn2Se6 . H2O (I), [(C4H9)(2)NH2](4)Sn4Se10 . 2H(2)O (II) und [(C3H7)(3)NH](2)Sn3Se7 (III) were prepared by hydrothermal syntheses from the elements and the amines. I crystallizes in the monoclinic spacegroup P2(1)/n (a = 1262.9(3) pm, b = 1851.3(4) pm, c = 2305.2(4) pm, beta = 104.13(3)degrees and Z = 4). The [Sn2Se6](4-) anion consists of two edge-sharing tetrahedra. II crystallizes in the orthorhombic spacegroup Pna2(1) (a = 2080.3(4) pm, b = 1308.2(3) pm, c = 2263.5(5) pm and Z = 4). The anion is formed from four SnSe4 tetrahedra which are joined by common corners to the adamantane cage [Sn4Se10](4-). III crystallizes in the orthorhombic spacegroup Pbcn (a = 1371.1(3) pm, b = 2285.4(5) pm, c = 2194.7(4) pm and Z = 8). The anion is a chain, built from edge-sharing [Sn3Se5Se4/2](2-) units, in which two corner sharing tetrahedra are connected to a trigonal bipyramid by an edge of one and a corner of the other tetrahedron. The results of the TG/DSC measurements and of temperature dependent X-ray diffractograms reveal that I and II decompose at first by release of minor quantities of triethylammonium to compounds with layer structure and larger cell dimensions. At still higher temperature the rest of triethylammonium and H2Se is evolved, leaving SnSe2 and Se in the bulk. The former decomposes partially at the highest temperature to SnSe. In the measurements of III the complex intermediate compound was not observed. III decomposes directly to SnSe2.