Double salt crystal structure of hexa­sodium hemiundeca­hydrogen α-hexa­molybdoplatinate(IV) heminona­hydrogen α-hexa­molybdoplatinate(IV) nona­cosa­hydrate: di­hydrogen disordered-mixture double salt

The title double salt containing two distinct, differently protonated hexa­molybdoplatinate(IV) polyanions, Na(6)[H(5.5) α-PtMo(6)O(24)][H(4.5) α-PtMo(6)O(24)]·29H(2)O, has been synthesized by a hydro­thermal reaction at ca pH 1.80. The positions of the H atoms in the polyanions were established from difference Fourier maps and confirmed by the inter­polyanion hydrogen bonds, bond-distance elongation, and bond-valence sum (BVS) calculations. The fractional numbers of H atoms in each polyanion are required for charge balance and in order to avoid unrealistically short H⋯H distances in the inter­polyanion hydrogen bonds. Considering the disorder, the refined formula of the title polyanion, {[H(5.5) α-PtMo(6)O(24)]; polyanion (A) and [H(4.5) α-PtMo(6)O(24)]; polyanion (B)}(6−), can be rewritten as a set of real formula, viz. {[H(6) α-PtMo(6)O(24)]; polyanion (A). [H(4) α-PtMo(6)O(24)]; polyanion (B)}(6−) and {[H(5) α-PtMo(6)O(24)]; polyanion (A). [H(5) α-PtMo(6)O(24)]; polyanion (B)}(6−). The polyanion pairs both form dimers of the same formula, viz. {[H(10) α-Pt2Mo(12)O(48)]}(6−) connected by seven inter­polyanion O—H⋯O hydrogen bonds.