Poly[tri-μ-aqua-di­aqua-μ-phosphono­formato-cobalt(II)sodium]

The title complex, [CoNa(CO₅P)(H₂O)₅]_n, was obtained by reacting sodium phosphono­formate with cobalt nitrate. The complex contains cobalt(II) and sodium ions, which are bridged by the O atoms of two aqua ligands. The Co^II ion is octahedrally coordinated by three phosphonoformato ligands (one bi- and the other monodentate) and by two O atoms from the bridging aqua ligands. The sodium cation is hexa­coordinated by six O atoms from four bridging and two terminal aqua ligands. The complex mol­ecules are linked to give a three-dimensional structure by phosphono­formate ligands bridging Co^II atoms and water mol­ecules establishing cobalt–sodium bridges. O—H...O hydrogen bonding between the aqua ligands and all O atoms of the phosphono­formato ligand and neighbouring aqua ligands help to consolidate the packing.