Poly[bis­[μ(2)-(dimethyl­aza­nium­yl)methyl­enediphospho­nato]magnesium]

The title compound, [Mg(C(3)H(10)NO(6)P(2))(2)](n), synthesized by a hydro­thermal method, adopts a one-dimensional polymeric chain structure and is isotypic with the previously reported Cd complex based on the ligand N,N-dimethyl­amino­methane-1,1-diphospho­nic acid (H(4) L). The asymmetric unit contains one half Mg(2+) ion and one H(3) L (−) anion. The unique Mg(2+) ion lies on an inversion center and is octa­hedrally coordinated by O atoms from six phospho­nate groups of four different H(3) L (−) anions. Each H(3) L (−) anion, with one protonated N atom and two phospho­nate OH groups, serves as a tridentate ligand. Two of its six phospho­nate O atoms chelate to a Mg(2+) cation in a bidentate fashion, while a third O atom bridges to a neighbouring Mg(2+) ion. The inter­connection of Mg(2+) ions by the H(3) L (−)anions leads to the formation of a polymer chain along the a axis in which the adjacent Mg(2+) ions are doubly bridged by two equivalent H(3) L (−) anions. These discrete chains are further assembled into a three-dimensional supra­molecular network via O—H⋯O and N—H⋯O hydrogen bonds involving the non-coordin­ated phospho­nate O atoms and the protonated N atoms.