Crystal structure of poly[diaqua(mu-2-carboxyacetato-kappa O-3,O ':O '')(2-carboxyacetato-kappa O)di-mu-chlorido-dicobalt(II)]

The asymmetric unit of the title polymer, [Co-2(C3H3O4)(2)Cl-2(H2O)(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 Co2Cl2 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 center dot center dot center dot Cl and O-H-water center dot center dot center dot O hydrogen bonds are present. Adjacent layers are linked through O-H center dot center dot center dot O=C hydrogen bonds involving the carboxylic acid OH and carbonyl groups.