Crystal structure of poly[di­aqua­(μ-2-carb­oxy­acetato-κ(3) O,O′:O′′)(2-carb­oxy­acetato-κO)di-μ-chlorido-dicobalt(II)]

The asymmetric unit of the title polymer, [Co(2)(C(3)H(3)O(4))(2)Cl(2)(H(2)O)(2)](n), comprises one Co(II) atom, one water mol­ecule, one singly deprotonated malonic acid mol­ecule (HMal(−); systematic name 2-carb­oxy­acetate) and one Cl(−) anion. The Co(II) atom is octa­hedrally coordinated by the O atom of a water mol­ecule, by one terminally bound carboxyl­ate O atom of an HMal(−) anion and by two O atoms of a chelating HMal(−) anion, as well as by two Cl(−) anions. The Cl(−) anions bridge two Co(II) atoms, forming a centrosymmetric Co(2)Cl(2) core. Each malonate ligand is involved in the formation of six-membered chelate rings involving one Co(II) atom of the dinuclear unit and at the same time is coordinating to another Co(II) atom of a neighbouring dinuclear unit in a bridging mode. The combination of chelating and bridging coordination modes leads to the formation of a two-dimensional coordination polymer extending parallel to (001). Within a layer, O—H(water)⋯Cl and O—H(water)⋯O hydrogen bonds are present. Adjacent layers are linked through O—H⋯O=C hydrogen bonds involving the carb­oxy­lic acid OH and carbonyl groups.