The new cesium praseodymium thiophosphate Cs3Pr5[PS4](6)

Transparent platelet-shaped green single crystals of the title compound were obtained by the reaction of cesium bromide, praseodymium, sulfur, and red phosphorus in the molar ratio 1:2:8:2 with an excess of CsBr as flux in evacuated silica ampoules at 950 degreesC for fourteen days. Cs3Pr5[PS4](6) crystallizes monoclinically in the space group C2/c (a = 1627.78(7), b = 1315.09(6), c = 2110.45(9)pm, beta = 103.276(5)degrees; Z = 4). Its crystal structure is different from all the other alkali-metal containing ortho-thiophosphates of the lanthanides, since it is not possible to formulate a layer containing the praseodymium centered sulfur polyhedra ([PrS8](13-), d(Pr- S) = 286 - 307 pm) and the isolated [PS4](3-) tetrahedra (d(P-S) = 202 - 207 pm, not less than(S-P-S) - 104 - 106degrees). All these tetrahedra are edge-sharing with the metal polyhedra to build up a framework instead. The coordination sphere of the half occupied (Cs2)(+) cations (CN = 10 + 2) can be described as two six-membered sulfur rings in chair conformation containing a cesium-pair in the middle. In contrast the (Cs1)(+) cations are surrounded in the not unusual configuration of tetracapped trigonal prisms (CN = 10, better 10 + 2 as well).