Pr3S2Cl2[AsS3]: A Praseodymium(III) Sulfide Chloride Thioarsenate(III) with Double Chains of Condensed [SPr4]10+ Tetrahedra

Abstract

AbstractSingle crystals of Pr3S2Cl2[AsS3] were obtained by reacting praseodymium sesquisulfide and trichloride with arsenic and sulfur (molar ratio: 7:4:6:9) in torch‐sealed evacuated silica ampoules at 850 °C for a week and subsequent slow cooling to room temperature. The transparent, pale yellowish green platelets crystallize monoclinically (Pr3S2Cl2[AsS3]: a = 2190.96(9) pm, b = 685.49(3) pm, c = 701.87(3) pm, β = 98.752(3)°) in the non‐centrosymmetric space group Cc with Z = 4. The crystal structure of Pr3S2Cl2[AsS3] comprises three crystallographically different Pr3+ cations. (Pr1)3+ and (Pr2)3+ exhibit bicapped trigonal prismatic environments of five sulfur and three chlorine atoms (C.N. = 8) each, whereas only seven sulfur atoms arranged as capped trigonal prism (C.N. = 7) are present in the case of (Pr3)3+. Two of the five crystallographically different sulfur atoms (S1 and S2) are coordinated by four Pr3+ cations, each in the shape of slightly distorted [SPr4]10+ tetrahedra (d(S–Pr) = 278–294 pm). Hence, the crystal structure of Pr3S2Cl2[AsS3] contains double chains with the composition 1∞{[S2Pr3]5+}, consisting of two parallel edge‐fused chains of anti‐SiS2‐analogous single strands 1∞{[SPr2]4+}, formed by trans‐edge sharing [SPr4]10+ tetrahedra. The arrangement of the 1∞{[S2Pr3]5+} double chains running along [001] can be described as a hexagonal rod‐packing. Chloride anions (Cl1 and Cl2) as well as the isolated, ψ1‐tetrahedral thioarsenate(III) groups [AsS3]3– (d(As–S) = 228–229 pm) consisting of three sulfur atoms (S3, S4, and S5) and an As3+ cation carrying a stereochemically active non‐bonding electron pair take care of the three‐dimensional interconnection and the charge balance of the 1∞{[S2Pr3]5+} double chains. All lone pairs at the As3+ cations of the [AsS3]3– pyramids point in the same direction parallel to the c axis of the acentric crystal structure of Pr3S2Cl2[AsS3].