Tetra-μ-aqua-octaaqua-bis(μ-4-chloro-pyridine-2,6-dicarboxyl-ato)bis-(4-chloro-pyridine-2,6-dicarboxyl-ato)tri-cobalt(II)disodium(I) bis-[triaqua-bis(4-chloro-pyridine-2,6-dicarboxyl-ato)cobalt(II)] hexa-hydrate.

The title compound, [Co(3)Na(2)(C(7)H(2)ClNO(4))(4)(H(2)O)(12)][Co(C(7)H(2)ClNO(4))(H(2)O)(3)](2)·6H(2)O, consists of a centrosymmetric dimer of [Co(II)(dipicCl)(2)](2-) complex dianions [dipicCl is 4-chloro-pyridine-2,6-dicarboxyl-ate] bridged by an [Na(2)Co(II)(H(2)O)(12)](4+) tetra-cationic cluster, two independent [Co(dipicCl)(H(2)O)(3)] complexes, and six water mol-ecules of crystallization. The metals are all six-coordinate with distorted octahedral geometries. The [Co(II)(dipicCl)(H(2)O)(3)] complexes are neutral, with one tridentate ligand and three water molecules. The [Co(II)(dipicCl)(2)](2-) complexes each have two tridentate ligands. The [Na(2)Co(II)(H(2)O)(12)](4+) cluster has a central Co(II) ion which is coordinated to six water molecules and lies on a crystallographic inversion center. Four of the water molecules bridge to two sodium ions, each of which have three other water molecules coordinated along with an O atom from the [Co(II)(dipicCl)(2)](2-) complex. In the crystal structure, the various units are linked by O-H⋯O hydrogen bonds, forming a three-dimensional network. Two water molecules are disordered equally over two positions.