Complexation of dichloro(ethylenediamine)palladium(II) with 1-hydroxyethylidene-1,1-diphosphonic acid

Complexation of [Pd(en)Cl2] with 1-hydroxyethylidene-1,1-diphosphonic acid (L) was studied by pH-potentiometry, UV–Vis and NMR spectroscopy. The binuclear complex {[Pd(en)]2L} was isolated and its structure was determined by single-crystal X-ray diffraction and 31P NMR spectroscopy. [Display omitted] •Interaction of [Pd(en)Cl2] with 1-hydroxyethylidene-1,1-diphosphonic acid was studied.•Formation constants were calculated for complexes [Pd(en)Cl2] with diphosphonic acid.•All complexes were characterized by UV–Vis and 31P NMR spectroscopy.•The structure of the binuclear complex was determined by single-crystal X-ray diffraction. Formation of the complex between [Pd(en)Cl2] (en = ethylenediamine) and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP, H4L) was studied by pH-potentiometry, UV–Vis spectrophotometry and 31P NMR spectroscopy in aqueous solutions containing CKCl = 0.15 mol L−1 and 0.004 mol L−1, which corresponds to the concentration of chloride ions in intercellular and intracellular fluids. The formation constants were calculated for [Pd(en)HL]−, [Pd(en)L]2− and {[Pd(en)]2L} complexes. In combination with data reported in the literature, they were used for deriving distribution curves for the corresponding aqua-, hydroxo- and chloro-substituted complexes of the [Pd(en)]2+ moiety. The binuclear complex {[Pd(en)]2L} was synthesized and characterized by elemental analysis and NMR spectroscopy. The structure of this complex in which the HEDP bridges two [Pd(en)]2+ moieties has been determined by X-ray crystallography.