Symmetric hydrogen bonding in dimethyl­ammonium hydrogen diphenyl­diphospho­nate.

In the title compound, C2H8N+·C12H11O5P2−, pairs of hydrogen diphenyl­diphospho­nate anions form dimers across a twofold axis, with two symmetric O⋯H⋯O hydrogen bonds [O⋯O = 2.406 (3) and 2.418 (3) Å]. The 12-membered ring thus formed has crystallographic 2 and quasi-222 symmetry. Cations on either side of the ring form N—H⋯O hydrogen bonds to the four extraannular O atoms, with N⋯O distances of 2.765 (2) and 2.748 (3) Å. [ABSTRACT FROM AUTHOR]