Thermodynamics of complexation of magnesium and calcium ions with dichloromethylenediphosphonate

Thermodynamic parameters for the complexation of CA 2+ and Mg 2+ ions by dichloromethylenediphosphonate (clodronate) ligand were obtained by potentiometric and calorimetric techniques. The measurements were conducted at an ionic strength of 0.10 M [(CH 3) 4NCl]) and at 25°C. The potentiometric data were consistent with a model involving the presence of ML 2−MHL − and M 2L species (L = tetranegative clodronate anion). The enthalpies of formation of the ML 2− and MHL − complexes were obtained from calorimetric data. Attempts to determine the enthalpies of formation of the M 2L species were unsuccessful due to the limited solubilities of these species.