Hexaaquanickel(II) bis[triaqua-μ₃-oxalato-di-μ-oxalato-bariumchromate(III)] tetrahydrate

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 \overline{1}), as well as the water molecules of crystallization. The anionic layers are built from the connection of barium and chromium atoms through bridging oxalate ligands. The CrIII atom is hexacoordinated by O atoms of three oxalate ligands while the BaII atom is tenfold coordinated by three O atoms of water molecules and seven O atoms of four oxalate ligands. Each NiII atom sits on an inversion center and is coordinated by six water molecules. One of the uncoordinated water molecules 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 interactions link the anionic layers, the charge-balancing cations as well as the water molecules of crystallization into a three-dimensional supramolecular network.

Two isostructural oxalato-bridged dimetallic heptanuclear [BaII3MIII4] complexes (M = Cr; Fe) associated with 3-aminopyridinium cations: Synthesis, crystal structure and magnetic properties

“…In the three-dimensional anionic network formed by bimetallic heptanuclear units, [Ba3(H2O)5M III 4(C2O4)12] 6-, the M•••M distances are in the range 6.670-7.329 Å. These values are slightly smaller than those in the oxalato-bridged dimetallic trinuclear complexes C4[M II Cr2(C2O4)6(H2O)2]•nH2O (C + = 4-aminopyridinium; M 2+ = Mn 2+ ; Co 2+ )[28] In the two compounds, the overall Ba-O distances range from 2.770 to 2.986 Å and are in the expected range for barium oxalate complexes[12,13,29,30]. In the crystal, intermolecular N-H•••O and O-H•••O hydrogen bonds link the anions and 3aminopyridinium cations and lattice water molecules into three-dimensional framework (Table…”