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

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]