Synthesis and Structural Characterization of the Alkali Thiophosphates Na 2 P 2 S 6 , Na 4 P 2 S 6 , K 4 P 2 S 6 , and Rb 4 P 2 S 6

Four compounds in the ternary systems Na‐P‐S, K‐P‐S, and Rb‐P‐S, Na 2 P 2 S 6 , Na 4 P 2 S 6 , K 4 P 2 S 6 , and Rb 4 P 2 S 6 were prepared and structurally characterized using single‐crystal X‐ray diffraction. Na 2 P 2 S 6 crystallizes in the monoclinic space group P 2 1 / m (no. 11) with a = 6.6752(3) Å, b = 7.7968(4) Å, c = 9.0379(4) Å, and β = 90.151(1)° in a new structure type that can be described as a distorted Tl 2 P 2 S 6 structure.The monoclinic structure of Na 4 P 2 S 6 [space group C 2/ m , no. 12, a = 6.725(2) Å, b = 11.222(2) Å, c = 7.542(2) Å, and β = 107.03(3)°] is a stuffed variant of the FePS 3 structure. K 4 P 2 S 6 and Rb 4 P 2 S 6 are isotypic and crystallize in the K 4 P 2 Se 6 structure type [space group P 2 1 / c , no. 14, a = 13.243(3) / 13.538(3), b = 11.946(2) / 12.310(3), c = 8.396(2) / 8.751(2) Å, and β = 91.44(3) / 92.46(3)° for K 4 P 2 S 6 / Rb 4 P 2 S 6 ].