Synthesis in molten alkali metal polythiophosphate fluxes. The new quaternary bismuth and antimony thiophosphates ABiP₂S₇ (A = K, Rb), A₃M(PS₄)₂ (A = K, Rb, Cs; M = Sb, Bi), Cs₃Bi₂(PS₄)₃, and Na_0.16Bi_1.28P₂S₆

We used the molten alkali metal polychalcogenide flux method to prepare the new compounds ABiP₂S₇ (A = K, Rb), A₃M(PS₄)₂ (A = K, Rb, Cs; M = Sb, Bi), Cs₃Bi₂(PS₄)₃, and Na_0.16Bi_1.28P₂S₆. KBiP₂S₇ crystallizes in the monoclinic space group P2₁/c with a = 9.500(3) Å, b = 12.303(4) Å, c = 9.097(3) Å, β = 90.59(3)^○, V = 1063 ų, at 23°C. D_calc = 3.34 g cm^-3, μ = 184.85 cm^-1, 2θ_max = 50^○ Mo Kα. Data with I>3σ-(I) 1672, R/Rw(%) = 2.8/3.1. K₃Bi(PS₄)₂ crystallizes in the orthorhombic space group P2₁2₁2₁ with a = 23.894(8)(3) Å, b = 6.799(3) Å, c = 9.049(2) Å, V = 1470 ų, at -60°C. D_calc = 2.91 g cm^-3, μ = 140.8 cm^-1, 2θ_max = 50^○. Data with I>3σ(I) 1745, R/Rw(%) = 5.5/6.0. Cs₃Bi₂(PS₄)₃ crystallizes in the monoclinic space group P2₁/c with a = 18.091(5) Å, b = 6.791(2) Å, c = 18.723(3) Å, β = 97.95(2)^○, V = 2278 ų, at 23°C. D_calc = 3.77 g cm^-3, μ = 213.3 cm^-1, 2θ_max = 50^○. Data with I>3σ(I) 2623, R/Rw(%) = 7.0/9.0. Na_0.16Bi_1.28P₂S₆ crystallizes in the monoclinic space group F2₁/n with a = 6.554(2) Å, b = 7.297(2) Å, c = 9.371(1) Å, β = 92.04(2)^○, V = 447.8 ų, at 23°C. D_calc = 3.73 g cm^-3, μ = 236.2 cm^-1, 2θ_max = 50^○. Data with I>3σ(I) 892, R/Rw(%) = 7.7/8.5. The structural diversity in this family of compounds ranges from the one-dimensional non-centrosymmetric chains of A₃M(PS₄)₂ and the layered compounds, ABiP₂S₇ and Cs₃Bi₂(PS₄)₂, to the dense three-dimensional framework of Na_0.16Bi_1.28P₂S₆. KBiP₂S₇ is a layered solid with a complex new structure type, where corrugated layers are separated by eight-coordinate K⁺ ions. It contains a [P₂S₇]^4- ligand in a complicated coordination mode. The structure of K₃Bi(PS₄)₂ is assembled from one-dimensional, helical [Bi(PS₄)₂]^3n-_n chains running along the crystallographic b-axis. The chain structure features two interesting binding modes for a tetrahedral [PS₄]^3- ligand. The structure of Cs₃Bi₂(PS₄)₃ has layers containing the same one-dimensional helical chains observed in K₃Bi(PS₄)₂. However, the PS₄ unit acts as a bridge to a Bi₂(PS₄)₂ dimeric unit. This unit is linked to another chain via a second bridging PS₄ ligand to form sheets that are parallel to the [101] crystallographic plane. The structure of Na_0.16Bi_1.28P₂S₆ is three dimensional but consists of layers of P₂S₆ groups in the a-b plane separated by a single layer of Bi³⁺ ions. The ethane-like [P₂S₆]^4- ligand chelates to eight Bi atoms in a very convoluted fashion. Positional disorder was found between Na and Bi ions in one crystallographic site. Their synthesis, structural characterization, optical absorption and thermal properties are reported.