The asymmetric unit of the title organic–inorganic hybrid salt poly[aquabis[μ3-bis(2-methyllactato)borato]dipotassium], [K(C8H12BO6)(H2O)0.5]n, consists of one bis(2-methyllactato)borate anion, one potassium cation and one water molecule that shows half occupancy due to disorder around a twofold rotation axis. The potassium cation is pseudo-octahedrally coordinated by five O atoms of four symmetry-related bis(2-methyllactato)borate ligands and by the half-occupied water molecule. O—H...O hydrogen bonds between the water molecule and one of the borate O atoms of the bis(2-methyllactato)borate ligand are present in the crystal structure.
