title: Poly[[hexa-aqua-(μ(3)-2,2'-bipyridine-4,4',6,6'-tetra-carboxyl-ato-κ(6)O(4):N,O(6),O(6'),N':O(4'))dinickel(II)] dihydrate].
abstract: 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 octa-hedral environments (one by two N atoms from a bipyridine unit, two O atoms from two water mol-ecules and two O atoms from two carboxyl-ate groups, and the second by four O atoms from four water mol-ecules and two O atoms from two carboxyl-ate 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.
authors.affiliation: State Key Lab. Base of Novel Functional Materials and Preparation Science, Institute of Solid Materials Chemistry, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211,  People's Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Ke-Wei
authors.initials: KW
authors.lastname: Lei
authors.forename: Dong-Guo
authors.initials: DG
authors.lastname: Xia