Zoledronate complexes. I. Poly[[mu2-aqua[mu3-1-hydroxy-2-(1H,3H-imidazol-3-ium-1-yl)ethylidenediphosphonato]potassium(I)] monohydrate].

The title compound, {[K(C(5)H(9)N(2)O(7)P(2))(H(2)O)].H(2)O}(n), is polymeric and consists of layers parallel to (001) interconnected by hydrogen-bonding and pi-pi interactions. The K(+) cation is eightfold coordinated in a KO(8) environment by O atoms from three different chelating zoledronate units and two coordinated water molecules. The zoledronate group presents its usual zwitterionic character, with negative charges in the singly protonated phosphonate groups and a positive charge at the protonated imidazole N atom. The anion binds to three different K(+) cations in a (so far unreported) triply chelating manner. Intra- and interplanar interactions are enhanced by a variety of hydrogen bonds involving all available O-H and N-H donors. A strong imidazole-phosphonate C-H...O interaction is present in the structure.