Two New Thiophosphates with Interlocked Structures: AgTi2(PS4)3 and Ag2NbTi3P6S25

The crystal structures of AgTi2(PS4)3 and Ag2NbTi3P6S25 were determined from single-crystal X-ray diffraction data. AgTi2 (PS4)3 crystallizes in the orthorhombic system, space group Ccc2 (no. 37), a=34.691(4) ?, b=20.018(2) ?, and c=11.576(2) ?, V=8039(4) ?3, Z=16. The structural skeleton is built up from TiS6 octahedra and PS4 tetrahedra linked to each other by edges. It exhibits very wide tunnels along the c axis. Ag2NbTi3P6S25 crystallizes in the orthorhombic system, space group Pccn (no. 56), a=22.609(2) ?, b=27.694(2) ?, and c=11.589(1) ?, V=7256(4) ?3, Z=8. The structure is made of edge-sharing TiS6 octahedra, PS4 tetrahedra, P2S6 bitetrahedra, and Nb2S8+4 tetracapped trigonal biprisms. The Nb2S8 entity includes two disulfide anions (S2)2- and an NbIV–NbIV bond. The formula of the compound can be written as AgI4NbIV2TiIV6(P2S6)2(PS4)3-10(S2)2-2. Each of the two structures presents two interlocked sublattices of polyhedra chains linked together by bridging S–Ag–S bonds. For AgTi2(PS4)3 the ionic conductivity measured along [001] is in agreement with a strong delocalization of Ag+ ions in the wide tunnels.