NaAg(2)Mo(3)O(9)AsO(4).

The title compound, sodium disilver arsenatotrimolybdate, Na(0.93 (1))Ag(2.07 (1))Mo(3)AsO(13), was prepared by a solid-state reaction. In the crystal structure, isolated AsO(4) tetra-hedra share corners with groups of three edge-sharing MoO(6) octa-hedra. This arrangement leads to the formation of anionic (1) (∞)Mo(3)AsO(13) ribbons extending parallel to [100]. The three metal sites show occupational disorder by Ag(I) and Na(I) cations, each with a different Ag:Na ratio. The metal cations are situated in the space between the ribbons and are surrounded by terminal O atoms of the ribbons in the form of distorted MO(7) polyhedra (M = Ag, Na) for distances < 3.0 Å. The title compound shows weak ionic conductivity. Structural relationships between different compounds in the quaternary systems M-Sb-P-O, M-Nb-P-O and M-Mo-As-O (M is Ag or an alkali metal) are also discussed.