Crystal structure of hepta-guanidinium nona-hydrogen bis-[α-hexa-molybdoplatinate(IV)] hepta-hydrate.

The title compound, (CH6N3)7H9[PtMo6O24]2·7H2O, containing the well-known Anderson-type heteropolyoxomolybdate, was obtained by recrystallization of its powdered guanidinium salt. The protonated O atoms in the polyanion were confirmed by electron-density maps, inter-polyanion hydrogen bonds and bond-valance sums (BVS). The {[H4.5PtMo6O24]2}(7-) polyanion is the same as that already characterized in K7[H4.5PtMo6O24]2·11H2O [space group P-1; Lee & Joo (2010 ▶). Acta Cryst. E66, i8-i9]. The heteropolyanions form inversion-generated dimers, {[H4.5PtMo6O24]2}(7-), held together by each of the four μ3-O-H⋯μ1-O, two μ2-O-H⋯μ2-O hydrogen bonds and one centrosymmetric μ3-O-H-μ3-O hydrogen bond. The H atom of the centrosymmetric hydrogen bond is located on an inversion centre. One guanidinium ion and one water mol-ecule are equally disordered about a twofold rotation axis.