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The title compound, K[Cr(C2O4)2(H2O)2], was crystallized from an aqueous solution. It is the first member without uncoordinated water molecules of formula Am[ M(C2O4)2(H2O)2]· xH2O, where A = monovalent cation, m = 1 or 2, M = metal(II) or metal(III), x≥ 0. The crystal packing is governed by electrostatic and coordinative inter­actions, and inter­molecular hydrogen bonds help to stabilize the packing. The coordination of the Cr sites is quasi-octa­hedral, and the K ions are eight-coordinated by O atoms of oxalate ligands, forming strongly distorted square anti­prisms. [ABSTRACT FROM AUTHOR]

In the title compound, [Co(C2H6N4O2)3]2(C2O4)(SO4)212H2O, the Co3+ ion adopts a distorted octahedral coordination involving six imino N atoms of three bidentate oxamide dioxime ligands. The oxalate ion is centrosymmetric. The bulk structure is consolidated by a network of O—H...O and N—H...O hydrogen bonds, interconnecting the building blocks in such a manner that the framework delineates infinite channels parallel to [100]. The 12 water molecules are lodged inside the channels, six of them being O—H...O and N—H...O bonded to the ionic species, whilst the other six, located along the central axis of the channel, form infinite cyclohexameric water tapes. Two of the water molecules are disordered over two sites, in 0.786 (7):0.214 (7) and 0.637 (8):0.363 (8) ratios. [ABSTRACT FROM AUTHOR]