Kalium-Doppelsalze mit den gemischten Trisulfidometallat-Ionen [MoOS3]2- und [WOS3]2- / Potassium Double Salts with the Mixed Trisulfidometalate Ions [MoOS3]2- and [WOS3]2-

Abstract

In the course of the synthesis of mixed oxidosulfido molybdates and tungstates by passing H2S gas through solutions of the oxido metalates, several new salts containing the metalates [MOS3]2- besides further anions (halides X-, hydrosulfide SH- or thiosulfate S2O2- 3) were obtained as well-formed crystals. Their crystal structures have been determined using single crystal X-ray data. The salts containing SH- as the additional anion crystallize with a new structure type (orthorhombic, space group Pmn21, M=Mo=W, TM =20=-125 °C: a=957.7(2)/954.15(2), b=636.2(2)/636.19(1), c=812.4(2)/809.88(2) pm, Z =2, R1=0.0319=0.0185). The mixed sulfidomolybdate/ chloride K3[MoO1.25S2.75]Cl (orthorhombic, space group Pca21, a=1246.3(1), b=623.20(4), c=1230.44(8) pm, Z =4, R1=0.0472) is isotypic with the sulfidotungstate K3[WOS3]Cl, but contains 25% of the disulfido molybdate. The structures of the SH- and the Cl- salts are closely related: In both cases, the trisulfido metalates are overall coordinated by cuboctahedra of 12 K+ ions, and the small additional anions are centered in K+ octahedra. In this regard, the structures are both derivatives of the cubic perovskite (and thus the Cu3Au) type. This crystallographic group-subgroup relation is discussed in detail. Yellow hexagonal columns of the double salt K6[WOS3]2(S2O3) were obtained by the methanothermal decomposition of the disulfidotungstate K2[WO2S2]. It crystallizes with a new structure type (hexagonal, space group P63mc, a=983.78(8), c=1227.3(1) pm, Z =2, R1=0.0175). Like in the other mixed salts, the two crystallographically different [WOS3]2- anions exhibit an overall cuboctahedral coordination by 12 potassium cations. The smaller S2O2- 3 anions are surrounded by nine K+ ions arranged in the form of two flat facesharing octahedra. Again similar to the mixed halides and hydrosulfides, the two K polyhedra around the anions, here present in a 2 : 1 ratio, are arranged in a space-filling packing, in this case related to the ht- BaMnO3 (and thus the Ni3Ti) structure type. According to their ‘double salt’ character, the Mo/W-O and Mo/W-S distances and the intramolecular vibrational frequencies of the tetrahedral moieties of the title compounds are similar between them and those in the pure potassium trisulfido metalates. This further becomes apparent from the additive nature of their molar volumes, which correspond to the sum of the volumes of the simple salts KCl, KSH or K2(S2O3) and K2[MoOS3].