Synthesis and Crystal Structure of the Cesium Silver ­Permanganate Cs₃Ag[MnO₄]₄

After successful syntheses and structural refinements of the already known permanganates of cesium (Cs[MnO4]) and silver (Ag[MnO4]) we started to blend aqueous solutions of both components in various molar ratios. From crystallization experiments of these mixtures only three species of crystals with different chemical compositions were obtained: tricesium monosilver tetrakispermanganate (Cs3Ag[MnO4]4) and, depending upon the respective ratio, either additional silver permanganate or surplus cesium permanganate, namely. The new title compound crystallizes in the orthorhombic space group Pnnm (no. 58) with two formula units per unit cell and cell dimensions of a = 764.53(4), b = 1883.57(9) and c = 584.34(3) pm. The crystal structure of Cs3Ag[MnO4]4 consists of two crystallographically distinguishable cesium cations. (Cs1)+ is surrounded by fourteen oxygen atoms constructing a slightly distorted bicapped hexagonal prism. These polyhedra are connected through edge-sharing with two other polyhedra of this kind to form chains along [001]. The chains are linked to each other via sixfold coordinated Ag+ cations (d(Ag–O) = 238–246 pm), arranged in such a manner that they link three oxygen atoms of two cesium polyhedra, leading to a two-dimensional layer spreading out parallel to the (001) plane. Together with the two crystallographically different tetrahedral oxomanganate(VII) anions [MnO4]– (d(Mn–O) = 161–162 pm) the other kind of cesium cations ((Cs2)+ with CN = 13) finally connect these layers three-dimensionally.