Crystal structure of poly[[hexa­aqua­tris­(μ-3,6-di­oxo­cyclo­hexa-1,4-diene-1,4-diolato)dierbium(III)] octa­deca­hydrate]

The title lanthanide complex, [Er(2)(C(6)H(2)O(4))(3)(H(2)O)(6)]·18H(2)O, is isostructural with its La, Gd, Yb and Lu analogues. The Er(3+) ion, located on a threefold rotation axis, is nine-coordinated in a distorted tricapped trigonal–prismatic geometry, which is completed by six oxygen atoms from three dhbq(2−) ligands and three oxygen atoms from coordinated water mol­ecules. Each dhbq(2−) ligand acts in a μ(2)-bis­(bidentate) bridging mode to connect two Er(3+) ions to form honeycomb (6,3) two-dimensional sheets extending in the ab plane, having an Er⋯Er separation of 8.7261 (2) Å. In the crystal, extensive O—H⋯O hydrogen-bonding inter­actions involving the coordinated water mol­ecules and the water mol­ecules of crystallization, as well as the oxygen atoms of the dhbq(2−) ligands, generate an overall three-dimensional supra­molecular network.