An unexpected oxidation: NaK5Cl2(S2O6)2 revisited

The title compound, NaK5Cl2(S2O6)2 [systematic name: sodium penta-potassium dichloride bis-(di-thio-nate)], arose as an unexpected product from an organic synthesis that used di-thio-nite (S2O42-) ions as a reducing agent to destroy excess permanganate ions. Compared to the previous study [Stanley (1953 ▸). Acta Cryst.6, 187-196], the present tetra-gonal structure exhibits a root 2a × root 2a × c super-cell due to subtle changes in the orientations of the di-thio-nate anions. The structure can be visualized as a three-dimensional framework of [001] columns of alternating trans-NaO4Cl2 and KO4Cl2 octa-hedra cross-linked by the di-thio-nate ions with the inter-stices occupied by KO6Cl2 polyhedra to generate a densely packed three-dimensional framework. The asymmetric unit comprises two sodium ions (site symmetries 4 and -4, four potassium ions (site symmetries = -4, 4, 1 and 1), three chloride ions (site symmetries = 4, 4 and 2) and two half-di-thio-nate ions (all atoms on general positions). Both di-thio-nate ions are completed by crystallographic inversion symmetry. The crystal chosen for data collection was found to be rotationally twinned by 180° about the [100] axis in reciprocal space with a 0.6298 (13):0.3702 (13) domain ratio.