Tris[hexaamminecobalt(III)] bis[trioxalatocobaltate(II)] chloride dodecahydrate

The title compound, [CoIII(NH3)6]3[CoII(C2O4)3]2Cl·12H2O, was synthesized under hydrothermal conditions. The asymmetric unit comprises two [Co(NH3)6]3+ cations, one located on a threefold axis and the other on a site of symmetry -3, a [Co(C2O4)3]4+ anion, located on a threefold axis, one sixth of a chloride anion [disordered over two sites, one threefold (site occupancy = 0.5) and the other -3 (site occupancy (0.25)] and two water molecules. Both CoIII centers are six-coordinated by NH3 molecules, forming [Co(NH3)6]3+ octahedra, with Co—N distances in the range 1.958 (2)–1.977 (3) Å. The title structure gives the first example of the [Co(C2O4)3]4− anion, with the distorted octahedral environment of CoII center formed by six O atoms from three oxalate residues. The Co—O bond lengths are 2.0817 (18) to 2.0979 (18) Å. Multiple N—H...O, N—H...Cl and O—H...O hydrogen bonds link the cations, anions and water molecules into a three-dimensional network