Redetermination of K(2)Mg(3)(OH)(2)(SO(4))(3)(H(2)O)(2) from single-crystal X-ray data revealing the correct hydrogen-atom positions

In comparison with the previous structure determination of K(2)Mg(3)(OH)(2)(SO(4))(3)(H(2)O)(2), dipotassium trimagnesium di­hydroxide tris­(sulfate) dihydrate, from laboratory powder X-ray diffraction data [Kubel & Cabaret-Lampin (2013 ▸). Z. Anorg. Allg. Chem. 639, 1782–1786], the present redetermination against CCD single-crystal data has allowed for the modelling of all non-H atoms with anisotropic displacement parameters. As well as higher accuracy and precision in terms of bond lengths and angles, the clear localization of the H-atom positions leads also to a reasonable hydrogen-bonding scheme for this hy­droxy hydrate. The structure consists of (100) sheets composed of corner- and edge-sharing [MgO(6)] octa­hedra and sulfate tetra­hedra. Adjacent sheets are linked by the potassium cations and a hydrogen bond of medium strength involving the water mol­ecule. The title compound is isotypic with its Co(II) and Mn(II) analogues: the three K(2) M (3)(OH)(2)(SO(4))(3)(H(2)O)(2) (M = Mg, Co, Mn) structures are qu­anti­tatively compared.