Crystal structure of poly[μ-aqua-bis(μ3-2-methylpropanoato-κ4 O:O,O':O')dipotassium].

The structure of the title compound, [K2(C4H7O2)2(H2O)] n , is composed of stacked sandwiches, which are formed by cation-oxygen bilayers surrounded by methyl-ethyl hydro-phobic chains. These sandwiches are held together by van der Waals inter-actions between the methyl-ethyl groups. The methyl-ethyl groups are disordered over two positions with occupancies 0.801 (3):0.199 (3). The potassium cations are coordinated by seven O atoms, which form an irregular polyhedron. There is a water mol-ecule, the oxygen atom of which is situated in a special position on a twofold axis (Wyckoff position 4e). The water H atoms are involved in Owater-H⋯Ocarbox-yl hydrogen bonds of moderate strength. These hydrogen bonds are situated within the cation-oxygen, i.e. hydro-philic, bilayer.