Structure cristalline de type alluaudite K(0.4)Na(3.6)Co(MoO(4))(3)

A new triple molybdate, potassium sodium cobalt tris­(molybdate), K(0.4)Na(3.6)Co(MoO(4))(3), was synthesized using solid-state reactions. The Co(2+) and one Na(+) cation are located at the same general site, each with occupancy 0.5. Another site (site symmetry 2) is occupied by Na(+) and K(+) cations, with occupancies of 0.597 (7) and 0.402 (6), respectively. The other two Na(+) cations and one of the two Mo atoms lie on special positions (site symmetries -1, 2 and 2, respectively). The structure is characterized by M (2)O(10) (M = Co/Na) dimers, which are linked by MoO(4) tetra­hedra, forming infinite layers. The latter are connected firstly by insertion of one type of MoO(4) tetra­hedra and secondly by sharing corners with the other type of MoO(4) tetra­hedra. This results in an open three-dimensional framework with the cavities occupied by the Na(+) and K(+) cations. The structure is isotypic with Na(3)In(2)As(3)O(12) and Na(3)In(2)P(3)O(12). A comparison is made with structures such as K(2)Co(2)(MoO(4))(3) and β-NaFe(2)(MoO(4))(3) and their differences are discussed.