Hexa­aqua­bis­[3,5-bis­(hy­droxy­imino)-1-methyl-2,4,6-trioxo­cyclo­hexa­nido-κ2 N 3,O 4]barium tetrahydrate

In the title compound, [Ba(C7H5N2O5)2(H2O)6]·4H2O, the Ba(2+) cation lies on a twofold rotation axis and is ten-coordinated by two 3,5-bis-(hy-droxy-imino)-1-methyl-2,4,6-trioxo-cyclo-hexa-n-ide oxo O atoms [Ba-O = 2.8715 (17) Å], two hy-droxy-imino N atoms [Ba-N = 3.036 (2) Å], and six water mol-ecules [Ba-O = 2.847 (2), 2.848 (2), and 2.880 (2) Å]. The 3,5-bis-(hy-droxy-imino)-1-methyl-2,4,6-trioxo-cyclo-hexa-nide monoanions act in a bidentate chelating manner, coordinating through an N atom of the non-deprotonated hy-droxy-imino group and an O atom of the neighboring oxo group. Two lattice water mol-ecules are located in the cavities of the framework and are involved in hydrogen bonding to O atoms of one of the coordinating water mol-ecules and the O atom of a keto group of the ligand. As a result, a three-dimensional network is formed.