Synthesis and Characterization of the New Ternary Titanium Thiophosphate TiP₂S₇ and Comparison to Ti₄P₈S₂₉

Abstract

The synthesis of the new thiophosphate TiP2S7 succeeded from TiS2, P4S10, and elemental S in presence of Li2S or elemental Cu and additional S. The crystal structure [orthorhombic, Pbcn, a = 23.9895(13), b = 6.8308(4), c = 19.6295(6) Å, V = 1905.0(2) Å3, Z = 8, R1 = 2.78 %, wR2 = 6.35 % (all reflections)] consists of edge‐connected TiS6 octahedra and PS4 tetrahedra, which form corrugated layers. Each of these layers interpenetrates a second one to form double layers parallel to the bc plane. The highly anisotropic characteristics are macroscopically observed by the easy cleavage property. One S atom coordinating the Ti atom is partially replaced by a S2 dumbbell leading to a TiS5(S2) coordination. Including the dumbbell atoms the exact composition of the new compound is refined to TiP2S7.05. According to the crystal structure TiP2S7 shows two signals in 31P NMR spectra. Another known ternary thiophosphate with a very similar composition, Ti4P8S29, was reinvestigated with special consideration of the S/S2 occupational disorder, the composition was determined exactly to Ti4P8S28.68 and found to be different from the previously reported.