Synthesis, Crystal Structure, and Thermal Properties of Na5[SnS4]Cl•13H2O

Reaction of Na2S with SnCl4 center dot 5H(2)O in aqueous alkaline sodium hydroxide solution leads to the formation of Na-5[SnS4]Cl center dot 13H(2)O (1). The compound crystallizes monoclinic in space group P2(1)/m with two formula units in the unit cell. In the crystal structure the Na+ cations are octahedrally coordinated and are linked into layers by bridging water molecules, mu(3) bridging Cl- anions and mu(1,1) bridging S atoms of [SnS4](4-) anions. Extended hydrogen bonding interactions generate a three-dimensional network. Investigations using differential thermoanalysis, thermogravimetry, and differential scanning calorimetry shows that upon heating in open crucibles the water can be removed leading to the formation of the anhydrate that is stable at room temperature and does not transform back into compound 1. Storage of the anhydrate in a desiccator over a water atmosphere leads first to formation of Na4SnS4 center dot 14H(2)O followed by crystallization of the title compound. After longer storage times NaCl appears as a second crystalline phase. If the thermal measurements are performed in a self-produced atmosphere, compound 1 transforms partly into Na4SnS4 center dot 14H(2)O with an increasing amount of this phase with increasing temperature. Synthetic investigations reveal that crystallization of compound 1 sensitively depends on the water content of acetone, which is used for precipitation of 1. Reacting Na4SnS4 center dot 14H(2)O directly with NaCl afforded formation of complex mixtures.