Hexa-aqua-nickel(II) bis-[tri-aqua-μ3-oxalato-di-μ-oxalato-bariumchromate(III)] tetra-hydrate.

Abstract

The title compound, [Ni(H2O)6][BaCr(C2O4)3(H2O)3]2·4H2O, was obtained in the form of single crystals from the slow evaporation of an aqueous mixture of {Ba6(H2O)17[Cr(C2O4)3]4}·7H2O and NiSO4·6H2O in the molar ratio 1:4. Its structure is made up of corrugated anionic (101) layers of formula [BaCr(C2O4)3(H2O)3] n n - that leave voids accommodating the charge-compensating cations, [Ni(H2O)6]2+ (point group symmetry ), as well as the water mol-ecules of crystallization. The anionic layers are built from the connection of barium and chromium atoms through bridging oxalate ligands. The CrIII atom is hexa-coordinated by O atoms of three oxalate ligands while the BaII atom is tenfold coordinated by three O atoms of water mol-ecules and seven O atoms of four oxalate ligands. Each NiII atom sits on an inversion center and is coordinated by six water mol-ecules. One of the uncoordinated water mol-ecules is disordered over two sites, with a refined occupancy ratio of 0.51 (5):0.49 (5). In the crystal, extensive O-H⋯O hydrogen-bonding inter-actions link the anionic layers, the charge-balancing cations as well as the water mol-ecules of crystallization into a three-dimensional supra-molecular network.