Neue Chalcogenophosphate: KBaPS 4 , KBaPSe 4 und Ba 3 PO 4 PSe 4 / New Chalcogenophosphates: KBaPS 4 , KBaPSe 4 , and Ba 3 PO 4 PSe 4

Colourless single crystals of KBaPS 4 (a = 11.587(2), b = 6.700(1), c = 10.118(2) Å ), and pale orange ones of KBaPSe 4 (a = 11.972(2), b = 6.973(1), c = 10.388(2) Å ) were obtained by reactions of Ba 3 (PS 4 ) 2 and Ba 3 (PSe 4 ) 2 , respectively, with KCl (790 °C; 30 h). The isotypic compounds crystallize with a slightly modified TlEuPS 4 type structure (Pnma, Z = 4); that is, the characteristic units are distorted discrete PX 4 tetrahedra (X: S, Se) interconnected by K + and Ba 2+ . However, due to the strong distortion of the trigonal X 6 prisms along [001] the coordination numbers increase from 8 to 9 for the barium atoms and from 8 to 11 for the potassium atoms. Orange crystals of Ba 3 PO 4 PSe 4 (a= 6.779(1), b =7.108(1), c =12.727(3)Å ; α = 82.45(3)°, β =78.88(3)°, γ =81.34(3)°) resulted as a by-product of the synthesis of Ba 3 (PSe 4 ) 2 . The compound crystallizes in a new type of structure (P1̅; Z = 2) and is the first chalcogenophosphate with discrete PO 4 and PSe 4 tetrahedra. The coordination polyhedra of the barium atoms are formed by both chalcogen atoms