A novel protonated hexatungstoplatinate(IV), Na5.5[H2.5PtW6O24]·17H2O

The novel protonated hemiundecasodium hemipenta­hydrogen hexatungstoplatinate(IV) heptadecahydrate, Na5.5[H2.5PtW6O24]·17H2O, crystallizes in the triclinic system in space group P\overline 1. The protonated O atoms were identified by considering three factors: inter-polyanion hydrogen bonds, elongation of W—O(H) bond distances, and bond angles of W—O(H)—W. The [H2.5(PtW6O24)]5.5− polyanion has no inversion symmetry, and it forms a dimer, viz. [H5(PtW6O24)2]11−, via five strong hydrogen bonds.