Disodium tris-(dioxidomolybdenum) bis-(diarsenate).

The asymmetric unit of the title compound, Na(2)(MoO(2))(3)(As(2)O(7))(2), is composed of two cyclic MoAs(2)O(11) units and an MoO(6) corner-sharing octa-hedron. The anionic framework can be decomposed into two types of layers, viz. MoO(2)As(2)O(7) and Mo(2)As(2)O(14), 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).