Poly[[hexa­aqua­(μ(3)-2,2′-bipyridine-4,4′,6,6′-tetra­carboxyl­ato-κ(6) O (4):N,O (6),O (6′),N′:O (4′))dinickel(II)] dihydrate]

In the title complex, {[Ni(2)(C(14)H(4)N(2)O(8))(H(2)O)(6)]·2H(2)O}(n), the two Ni(II) atoms are located in different special positions (one on a twofold rotation axis and the second on a centre of symmetry) and have different distorted octa­hedral environments (one by two N atoms from a bipyridine unit, two O atoms from two water mol­ecules and two O atoms from two carboxyl­ate groups, and the second by four O atoms from four water mol­ecules and two O atoms from two carboxyl­ate groups). Thus, the environments of the Ni(II) atoms may be denoted as NiN(2)O(4) and NiO(6). In the crystal, there exists an extensive network of classical O—H⋯O hydrogen bonds.