Hexaaquabis[3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanido- κ2N3,O4]barium tetrahydrate

In the title compound, [Ba(C7H5N2O 5)2(H2O)6]·4H2O, the Ba2+ cation lies on a twofold rotation axis and is ten-coordinated by two 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide oxo O atoms [Ba - O = 2.8715(17)Å], two hydroxyimino N atoms [Ba - N = 3.036(2)Å], and six water molecules [Ba - O = 2.847(2), 2.848(2), and 2.880(2)Å]. The 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide monoanions act in a bidentate chelating manner, coordinating through an N atom of the non-deprotonated hydroxyimino group and an O atom of the neighboring oxo group. Two lattice water molecules are located in the cavities of the framework and are involved in hydrogen bonding to O atoms of one of the coordinating water molecules and the O atom of a keto group of the ligand. As a result, a three-dimensional network is formed.