Poly[[diaqua[μ6‐(butane‐1,4‐diyldinitrilotetramethylene)tetraphosphonato]di‐μ2‐oxalato‐digadolinium(III)] tetra­hydrate]

The title compound, [Gd2(C8H22N2O12P4)(C2O4)2(H2O)2]·4H2O, was synthesized by the hydro­thermal method. It exhibits a pillar–layer structure, with the layers formed by GdIII ions inter­connected by the oxalate ions and the –NH(CH2PO3H)2 units of the tetra­phospho­nate dianions. The central organic groups of the tetra­phospho­nate ligands act as the pillars. Each oxalate ion bridges two GdIII ions and each tetra­phospho­nate ligand bridges six GdIII ions. Inversion centres are located at the mid-points of the central C—C bonds of both types of ligands.