Die Kristallstrukturen von Hexachalcogeno‐Hypodiphosphaten des Magnesiums und Zinks

Crystal Structures of Hexachalcogeno‐Hypodiphosphates of Magnesium and Zinc Five chalcogeno‐hypodiphosphates were synthesized and investigated by single crystal X‐ray methods. Mg₂P₂S₆ (C2/m; a = 6.085(1), b = 10.560(2), c = 6.835(1)Å, β = 106.97(3)°; Z = 2) crystallizes with the Fe₂P₂S₆ type structure, whereas Mg₂P₂Se₆ (a = 6.404(1), c = 20.194(4)Å) and Zn₂P₂Se₆ (a = 6.290(3), c = 19.93(2)Å) build up the Fe₂P₂Se₆ type (R3; Z = 3). The structures are characterized by closest packings of sulfur (selenium) with Mg²⁺ (Zn²⁺) ions and P₂ pairs in half the octahedra — analogous to the CdCl₂ and CdI₂ type, respectively. In Mg₂P₂S₆ half the Mg²⁺ ions can be substituted by Ag⁺ ions resulting in Ag₂MgP₂S₆ (C2/n; a = 6.364(1), b = 10.975(2), c = 13.999(3)Å, β = 108.29(3)°; Z = 4). In this compound the Ag⁺ ions are disordered and located in the octahedra originally occupied by Mg²⁺ ions. In Mg₂P₂Se₆ an analogous substitution by K⁺ ions leads to the compound K₂MgP₂Se₆ (P2₁/n; a = 6.546(1), b = 12.724(3), c = 7.599(2)Å, β = 103.02(3)°; Z = 2) with K₂FeP₂S₆ type structure. The structure is characterized by columns of alternating face‐sharing Se octahedra (centered by Mg) and trigonal antiprisms (centered by P₂ pairs) along 100]. The columns are interconnected by inserted K⁺ ions.