The asymmetric unit of the inorganic–organic hybrid salt, poly[aqua[μ4-bis(2-methyllactato)borato]rubidium], [Rb(C8H12BO6)(H2O)]n, comprises a rubidium cation, a bis(2-methyllactato)borate anion, and a water molecule of crystallization. The rubidium cation is pseudo-octahedrally coordinated by five O atoms from four bis(2-methyllactato)borate ligands and by a water molecule. The presence of four coordinating O atoms within the anion lead to the formation of a polymeric three-dimensional framework structure that is consolidated by additional O—H...O hydrogen-bonding interactions.
