A2CuP3S9 (A = K, Rb), Cs2Cu2P2S6, and K3CuP2S7: New Phases from the Dissolution of Copper in Molten Polythiophosphate Fluxes

The reaction of Cu with a molten mixture of A2S/P2S5 (A = K, Rb, Cs) produced the quaternary compounds A2CuP3S9 (A = K, Rb) and Cs2Cu2P2S6. The reaction of Cu with a molten mixture of K2S/P2S5/S produced the quaternary compound K3CuP2S7. A2CuP3S9 (A = K, Rb); I, II, respectively) crystallizes in the space group P21/n (no. 14) for I:  a = 6.8331(6) A, b = 23.562(2) A, c = 9.5415(7) A, β = 100.242(7)°, Z = 4, V = 1511.8(4) A3, ρcalc = 2.298 g/cm3. Cs2Cu2P2S6 (III) crystallizes in the space group P21/c (no. 14) with a = 9.538(3) A, b = 12.793(4) A, c = 10.429(4) A, β = 103.76(2)°, Z = 4, V = 1236.1(7) A3, ρcalc = 3.478 g/cm3. K3CuP2S7 (IV) crystallizes in the space group P21/a (no. 14) with a = 13.113(5) A, b = 6.702(3) A, c = 15.141(7) A, β = 115.13(1)°, Z = 4, V = 1315(1) A3, ρcalc = 2.35 g/cm3. The structure of I−II consists of novel one-dimensional [CuP3S9]n2n- chains separated by A+ cations. The chains run along the crystallographic b-axis. The Cu+ cation is in tetrahedral coordination with the cyclic [...