catena-Poly[[(acetato-κ2O,O′)triaquabarium(II)]-μ3-acetato-κ4O:O,O′:O′]

The present form of barium acetate, formulated as [Ba(C2H3O2)2(H2O)3] n , is the largest reported hydrate of the salt and this leads to a distinct structural behaviour setting it apart from the rest of the family. The compound is a linear polymer with a nine-coordinate Ba(Oaqua)3(Oacetate)6 mono-mer unit. The non-H part of the structure is ordered according to C2/m symmetry, while the disordered water H atoms only abide by this symmetry in a statistical sense. Each mol-ecule is halved by a mirror plane bis-ecting the Ba centre, one water mol-ecule and one acetate ligand, while containing the other acetate ligand. The chains are inter-connected by a disordered water-water/acetate O - H⋯O hydrogen-bonding network involving all water H atoms. The structure and stability of this phase are compared with the other known acetates of barium which differ in the degree of hydration. © 2008 International Union of Crystallography.