Erik Fischer

Ammonium 1-hydroxy-2-(2-pyridinio)ethane-1,1-diyldiphosphonate dihydrate and potassium 1-hydroxy-2-(2-pyridinio)ethane-1,1-diyldiphosphonate dihydrate.

The crystal structures of the title compounds, ammonium risedronate dihydrate, NH4+.C7H10NO7P2-.2H2O, (I), and potassium risedronate dihydrate, K+.C7H10NO7P2-.2H2O, (II), have been determined from single-crystal X-ray data collected at 120 K. Compound (I) forms a three-dimensional hydrogen-bonded network which connects the ammonium and risedronate ions and the water molecules. In compound (II), the K+ ions are seven-coordinated in a capped distorted trigonal prism. The coordination polyhedra form chains by corner-sharing, and these chains are connected by phosphonate groups into layers in the ac plane. The layers are stacked and connected by hydrogen bonds in the b direction. The risedronate conformation is determined by intramolecular interactions fine-tuned by crystal packing effects. All H-atom donors in both structures are involved in hydrogen bonding, with D...A distances between 2.510 (2) and 3.009 (2) A.

Sodium 3-ammonio-1-hydroxy­propyl­idene-1,1-bisphospho­nate monohydrate

The title compound, sodium pamidronate monohydrate, Na+·C3H10NO7P{}_{2}^{\,- }·H2O, crystallizes in sheets in the ab plane through Na—O coordination and hydrogen bonding to the pamidronate zwitterion. The neutral sheets are connected through hydrogen bonding, including the water molecule in the c direction.