Two new thiophosphates with interlocked structures: AgTi2(PS4)(3) and Ag2NbTi3P6S25

The crystal structures of AgTi2(PS4)(3) and Ag2NbTi3P6S25 were determined f rom single-crystal X-ray diffraction data. AgTi2 (PS4)(3) crystallizes in t he orthorhombic system, spare group Ccc2 (no. 37), a = 34.691(4) Angstrom, b = 20.018(2) Angstrom, and c = 11.576(2) Angstrom, V = 8039(4) Angstrom(3) , Z = 16. The structural skeleton is built up from TiS6 octahedra and PS4 t etrahedra linked to each other by edges. It exhibits very wide tunnels alon g the c asis, Ag2NbTi3P6S25 crystallizes in the orthorhombic system, space group Pccn (no. 56), a = 22.609(2) Angstrom, b = 27.694(2) Angstrom, and c = 11.589(1) Angstrom, V = 7256(4) Angstrom(3), Z = 8. The structure is made of edge-sharing TiS6 octahedra, PS4 tetrahedra, P2S6 bitetrahedra, and Nb2 S8+4 tetracapped trigonal biprisms. The Nb2S8 entity includes two disulfide anions (S-2)(2-) and an Nb-IV-Nb-IV bond. The formula of the compound can be written as (Ag4Nb2Ti6IV)-Nb-I-Ti-IV (P2S6)(2-)(PS4)(10)(3-)(S-2)(2)(2-). Each of the two structures presents two interlocked sublattices of polyhed ra chains linked together by bridging S-Ag-S bonds. For AgTi2(PS4)(3) the i onic conductivity measured along [001] is in agreement with a strong deloca lization of Ag+ ions in the wide tunnels (C) 2000 Academic Press.