Kristallstruktur und Schwingungsspektren der Caesium- und Kalium-Hexathiometadiphosphate Cs2P2S6 und K2P2S6

Crystal Structure and Vibration Spectra of Cs₂P₂S₆ and K₂P₂S₆ . Cs₂P₂S₆ and K₂P₂S₆ crystallize in the orthorhombic system, space group Immm, Z = 2 with the lattice constants . The compounds are isotypic to Tl₂P₂S₆. In the structure there are discrete P₂S₆^2? anions. Two PS₄ tetrahedra are connected by a common edge to hexathiometadiphosphate groups. The far infrared, infrared, and Raman spectra of these compounds are assigned on the basis of P₂S₆^2? units with D_2h symmetry in analogy to the isoelectronic Al₂Cl₆. The melting points are 440 ± 10°C for Cs₂P₂S₆ and 508 ± 10°C for K₂P₂S₆.