Die Lanthanid(III)-ortho-Thiophosphate(V) vomTypM[PS4] (M= La–Nd, Sm, Gd–Er): Synthese, Kristallstruktur und 31P-NMR-Untersuchungen / The M[PS4]-Type Lanthanide(III) ortho-Thiophosphates(V) (M = La–Nd, Sm, Gd–Er): Synthesis, Crystal Structure, and 31P NMR Investigations

Abstract

Single crystals of the lanthanide(III) thiophosphates(V) with the composition M[PS4] (M = La-Nd, Sm, Gd-Er) are formed within seven days at 950 °C by oxidation of the lanthanide metals and red phosphorus with sulfur (molar ratio: 1 : 1 : 4) in evacuated silica tubes without using any flux to avoid the entrapment of e. g. alkali metal cations. Their crystal structure (tetragonal, I41/acd, Z = 16; e. g. La[PS4]: a = 1098,97(5); c = 1953,26(9) pm and Er[PS4]: a = 1062,41(5); c = 1892,38(9) pm for the borderline representatives discussed here) is built up by a distorted cubic closest packing of discrete [PS4]3− tetrahedra (d(P5+-S2−) = 203 - 204 pm; ∢(S-P-S) = 107 - 116°) where the M3+ cations are situated in one half of the tetrahedral interstices, the same way as S2− in the Pt2+ arrangement of the cooperite-type PtS structure. Therefore an eightfold sulfur coordination for both crystallographically independent M3+ cations results in the shape of a trigonal dodecahedron. The 31P-MAS-NMR spectra of La[PS4], Nd[PS4], Gd[PS4], and Er[PS4] are reported and discussed