| Summary: | The title double salt containing two distinct, differently protonated hexamolybdoplatinate(IV) polyanions, Na6[H5.5α-PtMo6O24][H4.5α-PtMo6O24]·29H2O, 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, {[H5.5α-PtMo6O24]; polyanion (A) and [H4.5α-PtMo6O24]; polyanion (B)}6−, can be rewritten as a set of real formula, viz. {[H6α-PtMo6O24]; polyanion (A). [H4α-PtMo6O24]; polyanion (B)}6− and {[H5α-PtMo6O24]; polyanion (A). [H5α-PtMo6O24]; polyanion (B)}6−. The polyanion pairs both form dimers of the same formula, viz. {[H10α-Pt2Mo12O48]}6− connected by seven interpolyanion O—H...O hydrogen bonds.
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