Die Lanthanid(III)-ortho-Thiophosphate(V) vom Typ M[PS4] (M = La-Nd, Sm, Gd-Er) : Synthese, Kristallstruktur und 31P-NMR-Untersuchungen

Single crystals of the lanthanide(III) thiophosphates(V) with the composition M[PS 4 ] (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, I4 1 /acd, Z = 16; e.g. La[PS 4 ]: a = 1098,97(5); c = 1953,26(9) pm and Er[PS 4 ]: 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 [PS 4 ] 3- tetrahedra (d(P 5+ -S 2- ) = 203-204 pm; <(S-P-S) = 107 - 116°) where the M 3+ cations are situated in one half of the tetrahedral interstices, the same way as S 2- in the Pt 2+ arrangement of the cooperite-type PtS structure. Therefore an eightfold sulfur coordination for both crystallographically independent M 3+ cations results in the shape of a trigonal dodecahedron. The 31 P-MAS-NMR spectra of La[PS 4 ], Nd[PS 4 ], Gd[PS 4 ], and Er[PS 4 ] are reported and discussed.