Na5FeS4 – das erste Thioferrat(III) mit diskreten tetraedrischen Anionen

Na₅FeS₄ — the First Thioferrate(III) with Discrete Tetrahedral Anions Ruby red crystals of Na₅FeS₄ were obtained by reacting a stoichiometric mixture of Na₂S, Fe, and S at 970 K. The compound is orthorhombic, space group Pbca, with a = 11.947(5), b = 7.091(3), c = 21.54(1) Å, Z = 8. The crystal structure was determined from single crystal diffractometer data. The atomic arrangement – which corresponds to that of Na₅GaO₄ 1] – is characterized by discrete tetrahedral FeS₄] groups, separated from each other by Na⁺ cations. Measurements of the magnetic susceptibilities show coupling effects between Fe³⁺ ions below 28 K. At higher temperatures a Curie-Weiss behaviour indicates a high-spin-state of the Fe³⁺ ions. Relationships between the interatomic distances and the magnetic moments in alkali thioferrates are discussed.