catena-poly­[[[tetra­aqua­cobalt(II)]-μ-4,4′-bi­pyridine-κ2 N: N′] phthalate dihydrate].

A polymeric cobalt complex, {[Co(C10H8N2)(H2O)4](C8H4O4)·2H2O} n, was synthesized and its crystal structure has been determined by X-ray diffraction. The complex exhibits a polymeric structure consisting of six-coordinated CoII units linked via 4,4′-bi­pyridine (4,4′-bpy) to form a linear chain. The asymmetric unit contains only one half-mol­ecule of the bridging ligand and two coordinated water molecules, the CoII ion and the bridging ligand lying on a twofold rotation axis. Each cobalt(II) ion is in a distorted octahedral environment with a CoN2O4 core; 4,4′-bpy acts as a bridging ligand and four O atoms from coordinated water mol­ecules act as terminal ligands. The chains are linked to (which also lie on twofold axes) uncoordinated phthalate anions and water mol­ecules by extensive hydrogen bonds to form a three-dimensional supramolecular structure. [ABSTRACT FROM AUTHOR]