Hexaaqua-cobalt(II) 3,3'-dicarb-oxy-biphenyl-4,4'-dicarboxyl-ate.

In the crystal structure of the title compound, [Co(H(2)O)(6)](C(16)H(8)O(8)), both the cation and anion are centrosymmetric. The Co cation displays a CoO(6) octa-hedral geometry formed by six water mol-ecules. In the anion, the two carboxyl groups are oriented at dihedral angles of 4.8 (5) and 10.4 (7)° with respect to the benzene ring. Very strong O-H⋯O hydrogen bonds between the protonated and deprotonated carboxylate groups occur. Neighbouring cations and anions are connected through O-H⋯O hydrogen bonds into a three-dimensional supra-molecular structure.