The K2nCoMo2+nO7+4n family of structures, with n = 2, 3 or 5.

The compounds K(4)CoMo(4)O(15) (tetrapotassium cobalt tetramolybdate), K(6)CoMo(5)O(19) (hexapotassium cobalt pentamolybdate) and K(10)CoMo(7)O(27) (decapotassium cobalt heptamolybdate) belong to a series of compounds with closely related crystal structures. In K(4)CoMo(4)O(15), the Co atom and one of the two unique Mo atoms are at sites with threefold symmetry; two of the three unique K atoms lie at sites with 3 symmetry. K(6)CoMo(5)O(19) crystallizes in a new monoclinic structure type. Each [CoO(6)] octahedron is surrounded by one face-sharing [MoO(6)] octahedron and six corner-sharing [MoO(4)] tetrahedra. All three compounds have this structural unit in common, but differ in the degree of connectivity between these units. They form layers in K(4)CoMo(4)O(15) and zigzag chains in K(6)CoMo(5)O(19), both by sharing [MoO(4)] tetrahedra. In K(10)CoMo(7)O(27), the structural units are isolated from each other.