Darstellung und Kristallstruktur von Na2Sn2Se5 Ein neues Chalkogenostannat(IV) mit schichtförmigen Komplexanionen

Preparation and Crystal Structure of Na₂Sn₂Se₅ A Novel Chalcogenostannate(IV) with Layered Complex Anions Na₂Sn₂Se₅ was obtained from a stoichiometric mixture of Na₂Se, Sn, and Se powders through a solid state reaction at 450 °C. It crystallizes orthorhombic, space group Pbca with a = 13.952(6) Å, b = 12.602(2) Å, c = 11.524(2) Å; Z = 8 and undergoes peritectic decomposition at 471(2) °C. The crystal structure was determined at ambient temperature from diffractometer data (MoKα‐radiation) and refined to a conventional R of 0.040 (1490 F_o's, 83 variables). Na₂Sn₂Se₅ is characterized by layered complex anions running parallel to (100) which are built up by SnSe₄ tetrahedra sharing common corners. The mean Sn–Se bond length calculates as 2.252(2) Å. The Na⁺ cations are coordinated to 6 or 7 Se in irregular configurations. The crystal structure can be described as a stacking of distorted c. p. 3⁶ chalcogen layers and mixed square 4⁴ alkali‐chalcogen layers.