Die Selenostannate(IV) [enH2]2[Sn2Se6] · 1/2 en 1 und [enH2][Sn3Se7] · 1/2en 2 wurden durch methanolothermale Reaktion von SnSe2 mit Ethylendiamin (en) (160°C, 13 bar) in Anwesenheit von Se bzw. BaSe dargestellt. Das Anion [Sn2Se6]4− in 1 besteht aus zwei kantenverknüpften SnSe4‐Tetraedern und weist kristallographische Ci‐Symmetrie auf. Im Kristallgitter von 2 liegen schichtartige Polyanionen [Sn3Se72] ∞2 vor, die trigonale SnSe5‐Bipyramiden als Baueinheiten aufweisen. Die drei symmetrieunabhängigen Zinnatome sind jeweils über SnSeSnBrücken miteinander verknüpft, so daß Sn3Se10‐Einheiten entstehen. Die methanolothermale Umsetzung von SnSe2 mit en allein liefert die kantenverknüpfte Kettenstruktur [2 SnSe2 · en]∞ 3, in der die Zinnatome jeweils von vier Selenatomen koordiniert sind. Jedes zweite Zinnatom wird zusätzlich von einem en‐Molekül koordiniert und weist somit eine verzerrte oktaedrische Geometrie auf. Die restlichen Zinnatome sind tetraedrisch von Se‐Atomen umgeben.
The selenostannate(IV) Cs4Sn2Se6 has been prepared by methanolothermal reaction of Cs2CO3 with SnSe2 at 160°C and 13 bar. The [Sn2Se6]4— anions contain two edge-bridged SnSe4 tetrahedra and display crystallographic C2h symmetry. The bridging Sn—Se distances of 2.587(1) are markedly longer than the terminal Sn—Se distances of 2.447(1) and 2.452(2) Å.
The cesium polyselenide mentioned in the title is prepared by methanolothermal synthesis from Cs2CO3 and Se (1:4, 160 °C, 13 bar; 88% yield based on Se).
The cesium polyselenide Cs4Se16 has been prepared by the methanolothermal reaction of Cs2CO3 and Se at 160 °C and 13 bar. [Se16]4- fragments may be regarded as containing an Se6 ring with Cs symmetry and two Se5 chains related by the crystallographic mirror plane. Se4 of the sixmembered ring, which displays a square planar geometry, participates in two relatively long Se4—Se5 bonds [2.989(4) A] to individual chains. The trans-sited Se4—Se3 bonds [2.425(4) A] are markedly longer than the remaining Se—Se bonds in the Se6 ring [2.344(4), 2.356(4) A]. Further Se—Se interactions of length 3.132(4) and 3.346(4) Å are observed between individual [Se16]4- fragments.
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 [Sn3Se72-]∞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.
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