Monopotassium monosodium hexa-hydrogen α-hexa-molybdoplatinate(IV) undeca-hydrate.

The title compound, KNa[H(6)PtMo(6)O(24)]·11H(2)O, contains a discrete hexa-molybdoplatinate(IV) [H(6)PtMo(6)O(24)](2-) poly-anion (1 symmetry), which has the highest level of protonation. Five O atoms of the central PtO(6) octa-hedron (μ(3)-atoms, Oc) and one O atom of an outer edge-sharing MoO(6) octa-hedron (O bridging μ(2)-atom, Ob) are protonated. The polyanions are connected by almost linear O-H⋯O hydrogen bonds between protonated and unprotonated Ob atoms. Further consolidation of the crystal structure is accomplished by extensive O-H⋯O hydrogen bonding involving the uncoordinated water mol-ecules. The two independent K(+) cations are equally disordered about a twofold rotation axis.