Na_1.67Mn_2.17(MoO₄)₃

The title compound, disodium dimanganese(II) tris­[ortho­molybdate(VI)], was prepared by solid-state reactions. The structure can be described as being composed of Mn₂Mo₂O₁₄ double-chains that are inter­connected by corner-sharing with MoO₄ tetra­hedra, leading to a three-dimensional framework with channels propagating in [100] and [001] in which the Na⁺ counter-cations are located. One of these Na sites is located on an inversion centre, one is partially occupied [occupancy 0.341 (9)], and one is statistically occupied by Na and Mn in a ratio of 0.829 (5):0.171 (5). Na_1.67Mn_2.17(MoO₄)₃ is isotypic with structures of the Ag₂M₂(MoO₄)₃ (M = Zn, Mg, Co, Mn) family. A comparative structural description is provided between the structure of the title compound and those of related phases containing (MXO₈)_n chains (M = Mo, Mn and X = As) or M₂O₁₀ (M = Mo, Mn, Nb, V) dimers.

Non-centrosymmetric Rb₂Mn₂(MoO₄)₃

The title compound, dirubidium dimanganese(II) tris­(tetra­oxo­molyb­date), Rb₂Mn₂(MoO₄)₃, was prepared by solid-state reactions. The structure can be described as being composed of MnO₆ octa­hedra sharing corners with MoO₄ tetra­hedra. The three-dimensional framework contains cavities in which the rubidium ions are located. The Rb⁺ cations are within distorted nine- and 12-vertex polyhedra. The pairs of different Mn²⁺ and Rb⁺ cations are each located on threefold rotation axes.. Rb₂Mn₂(MoO₄)₃ is isotypic with compounds of the Cs₂M₂Mo₃O₁₂ (M = Ni, Fe) family. A comparative structural description is provided between the structure of the title compound and those of related phases. Differences with structures such as alluaudite are discussed.