Syntheses, crystal structures, and solid state NMR investigations of K4M2P6S25 and K3M2P5S18 (M = Ti, Sn)

Reaction of K2S5 with P4S10 and Ti at 450degreesC results in the formation of K4Ti2P6S25, a new titanium thiophosphate, whose crystal structure was solved by single-crystal X-ray diffraction. The title compound crystallizes in the orthorhombic space group Fdd2, with the lattice constants a = 33.819(7), b = 35.508(7), and c = 6.251 (1) Angstrom (Z = 8). The structure contains a layered arrangement of crosslinked quasi-one-dimensional Ti2P6S254- chains. The K+ ions are situated between the layers. The Ti atoms within the chains are octahedrally coordinated by P2S74- and P2S94- ligands. Reaction of K2S with P4S10, S and Ti at 600 degreesC results in the formation of K3Ti2P5S18, a novel titanium thiophosphate, which crystallizes in the monoclinic space group C2/c, with a = 22.739(5), b = 6.058(1), c = 20.440(4) Angstrom, and beta = 105.41(3)degrees (Z = 4). The structure contains linear Ti2P5S183- chains with the K+ ions situated between the chains. The Ti atoms within the chains are octahedrally coordinated by PS43- and P2S74- ligands. Reaction of K2S with P4S10, S and Sn at 600 degreesC results in the formation of the isostructural compound K3SnP5S18, a novel tin thiophosphate, with the lattice parameters a = 23.303(7), b = 6.023(2), c = 20.888(6) Angstrom, and beta = 106.18 (2)degrees. The spectroscopic characteristics of the thiophosphate groups, in particular that of the novel P2S94- entity are examined by UV-VIS, FT-IR and P-31 one- and two-dimensional magic-angle spinning (MAS-) NMR studies. The NMR experiments illustrate the utility of double-quantum coherence techniques as a unique tool of site assignments based on P-31-P-31 spatial proximity, allowing a spectroscopic distinction of the P2S74- and the P2S94- groups can be differentiated based on their different chemical shift anisotropies. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.