Poly[bis[μ2-(dimethylazaniumyl)methylenediphosphonato]magnesium

Abstract

The title compound, [Mg(C3H10NO6P2)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 (H4 L). The asymmetric unit contains one half Mg2+ ion and one H3 L − anion. The unique Mg2+ ion lies on an inversion center and is octa­hedrally coordinated by O atoms from six phospho­nate groups of four different H3 L − anions. Each H3 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 Mg2+ cation in a bidentate fashion, while a third O atom bridges to a neighbouring Mg2+ ion. The inter­connection of Mg2+ ions by the H3 L −anions leads to the formation of a polymer chain along the a axis in which the adjacent Mg2+ ions are doubly bridged by two equivalent H3 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.