Crystal structure of poly[μ(2)-aqua-aqua­(μ(2)-4-nitro-2,5,6-trioxo-1,2,5,6-tetra­hydro­pyridin-3-olato)hemi-μ(4)-oxalato-barium(II)]

In the title coordination polymer, [Ba(C(5)HN(2)O(6))(C(2)O(4))(0.5)(H(2)O)(2)](n), the tenfold coordination of the Ba centre consists of four O atoms from the two 4-nitro-2,5,6-trioxo-1,2,5,6-tetra­hydro­pyridin-3-olate (L) anions, three O atoms of two oxalate anions and three water mol­ecules. The Ba—O bond lengths fall in the range 2.698 (3)–2.978 (3) Å. The L ligand chelates two Ba atoms related by a screw axis, leading to formation of fused five- and six-membered chelate rings. Due to the bridging function of the ligands and water mol­ecules, the complex monomers are connected into polymeric two-dimensional layers parallel to the bc plane. Inter­molecular O—H⋯O hydrogen bonds link these layers into a three-dimensional supra­molecular framework.