Hydrogen bonding and [pi]-[pi] stacking in the three-dimensional supra­molecular complex bis­(4,4'-bipyridinium) diaqua­dioxalatoferrate(II) bis(hydrogen oxalate)

The title compound, (C₁₀H₁₀N₂)₂[Fe(C₂O₄)₂(H₂O)₂](C₂HO₄)₂, appears to be a modular associate consisting of a complex anion containing bivalent Fe as the central atom, a bridging hydrogen oxalate anion and a diprotonated 4,4-bipyridine acting as the counter-cation. The Fe^II ion in the complex anion occupies a position on a centre of inversion. Its coordination environment is formed by six O atoms from two bidentate oxalate ligands, forming a basal plane, and two water mol­ecules approximately perpendicular to the plane, representing a distorted octa­hedral geometry. These three kinds of ions are connected by strong hydrogen bonds, with donor-acceptor distances (N...O and O...O) lying in the range 2.54-2.98 Å, and [pi]-[pi] stacking inter­actions between the 4,4'-bipyridinium cations, thus forming a three-dimensional supra­molecular structure.