Poly[[aqua­(μ-4,4′-bipyridyl-κ(2) N:N′)bis­(μ-formato-κ(2) O:O′)iron(II)] tetra­hydrate]

In the title compound, {[Fe(CHO(2))(2)(C(10)H(8)N(2))(H(2)O)]·4H(2)O}(n), the Fe(II) ion is coordinated by two 4,4′-bipyridyl (4,4′-bpy) ligands, three formate ligands and one water molecule. The slightly distorted octahedral FeN(2)O(4) coordination results from the N atoms of two bridging 4,4′-bpy ligands, the O atoms of two bridging HCOO(−) anions of anti–anti mode, all in trans positions around the metal centre, and the O atoms of one terminal HCOO(−) anion and of one water molecule. The bridging formate ligands link the metal ions into chains that are further connected via 4,4′-bpy ligands into a framework structure. The three-dimensional structure is stabilized by extensive O—H⋯O hydrogen bonding. The crystals were twinned containing a 0.84:0.16 racemate.