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Formation of the complex between [Pd(en)Cl 2 ] (en = ethylenediamine) and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP, H 4 L) was studied by pH-potentiometry, UV–Vis spectrophotometry and 31 P NMR spectroscopy in aqueous solutions containing C KCl  = 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)] 2 L} 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)] 2 L} 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. [ABSTRACT FROM AUTHOR]

Acid–base properties of 2-pyrrolidine-1-hydroxymethane-1,1-diphosphonic acid were studied. Its structure was evaluated by single-crystal X-ray diffraction. Complexation of K 2 [PdCl 4 ] with 2-pyrrolidine-1-hydroxymethane-1,1-diphosphonic acid was studied by pH-potentiometry, UV–Vis, as well as by 31P, 13C and 1H NMR spectroscopy. • Acid–base properties of 2-pyrrolidine-1-hydroxymethane-1,1-diphosphonic acid were studied. • Structure of 2-pyrrolidine-1-hydroxymethane-1,1-diphosphonic acid was evaluated by single-crystal X-ray diffraction. • Interaction of K 2 [PdCl 4 ] with 2-pyrrolidine-1-hydroxymethane-1,1-diphosphonic acid was studied. • Formation constants were calculated for complexes Pd(II) with diphosphonic acid. • All complexes were characterized by UV–Vis and 31P, 13C and 1H NMR spectroscopy. The structure of the 2-pyrrolidine-l-hydroxymethane-l,l-diphosphonic acid (PyrHMDP, H 4 L) has been determined by X-ray crystallography. Formation of the complexes between K 2 [PdCl 4 ] and PyrHMDP was studied by pH-potentiometry, UV–Vis spectrophotometry and 31P, 13C and 1H NMR spectroscopy in aqueous solutions containing C KCl = 0.15 mol L−1, which corresponds to the concentration of chloride ions in intercellular fluid. The formation constants were calculated for the protonated forms of the PyrHMDP and for the [PdHLCl 2 ]3− and [PdLCl 2 ]4− complexes. The equilibrium concentration distribution diagram for the complexes of different composition was drawn using the formation constants of the Pd chloro-aqua complexes and the chloride concentration. In equimolar palladium complexes with PyrHMDP the ligand was coordinated in a bidentate manner via the nitrogen atom of the pyrrolidine ring and the oxygen atom of the phosphonic group forming a six-membered chelate ring. [ABSTRACT FROM AUTHOR]