Na3Cr2P3S12 and K3Cr2P3S12:: Two new one-dimensional thiophosphate compounds with a novel structure

Two new alkali metal chromium thiophosphates, Na3Cr2P3S12 and K3Cr2P3S12, have been synthesized and their structure determined from single-crystal or powder X-ray diffraction analyses. These isostructural compounds, which exhibit a novel structural arrangement, crystallize in the monoclinic system (space group P2(1)/c) with the cell parameters a = 17.4076(10) Angstrom, b=11.1723(10) Angstrom, c=19.2502(11) Angstrom, beta=149.731(3)degrees (V= 1887.1(2) Angstrom(3), Z = 4) and a = 17.9690(14) Angstrom, b = 12.0607(5) Angstrom, c = 19.3109(16) Angstrom, beta = 150.008(3)degrees (V= 2091.98(16) Angstrom(3), Z= 4) for Na3Cr2P3S12 (I) and K3Cr2P3S12 (II), respectively. For (I), the single-crystal refinement led to R/R-w(F-2) = 0.0417/0.0650 (for 4125 independent reflections and 182 refined parameters). For (II), the Rietveld refinement led to R-p/R-wp = 0.0181/0.0233 (for 90 refined parameters). In both materials, the structures consist of (1)(infinity)[Cr2P3S12](3-) chains built upon two edge-sharing [CrS6] octahedra capped by two [PS4] tetrahedra defining isolated [Cr2P2S12](-8) entities. These entities are linked to each other through an extra [PS,] tetrahedral group. Magnetic measurements evidence antiferromagnetic coupling between Cr3+ cations. The charge balance of the phase is Mi(3)(I)Cr(2)(III)P(3)(V)S(12)(-II). (C) 2001 Elsevier Science.