Disodium tris­(dioxidomolybdenum) bis­(diarsenate)

The asymmetric unit of the title compound, Na₂(MoO₂)₃(As₂O₇)₂, is composed of two cyclic MoAs₂O₁₁ units and an MoO₆ corner-sharing octa­hedron. The anionic framework can be decomposed into two types of layers, viz. MoO₂As₂O₇ and Mo₂As₂O₁₄, which use mixed Mo-O-As and As-O-Mo bridges to achieve a new three-dimensional structure with two types of large channels in which the Na⁺ cations are located. Two O atoms are disordered and are located in two positions close to their initial positions with occupancy ratios of 0.612 (17):0.388 (17) and 0.703 (12):0.298 (12).

Na₂MoO₂As₂O₇

Disodium molybdenum dioxide diarsenate, Na₂MoO₂As₂O₇, has been synthesized by a solid-state reaction. The structure is built up from MoAs₂O₁₂ linear units sharing corners to form a three-dimensional framework containing tunnels running along the a-axis direction in which the Na⁺ cations are located. In this framework, the As^V atoms are tetra­hedrally coordinated and form an As₂O₇ group. The Mo^VI atom is displaced from the center of an octa­hedron of O atoms. Two Na⁺ cations are disordered about inversion centres. Structural relationships between different compounds: A₂MoO₂As₂O₇ (A = K, Rb), AMOP₂O₇ (A = Na, K, Rb; M = Mo, Nb) and MoP₂O₇ are discussed.