Crystal structures and spectroscopic properties of palladium complexes isolated from Pd–EDTA solutions

Two complexes were isolated from aqueous Pd(NO3)2–Na2H2EDTA solutions and studied by single crystal X-ray diffraction, IR/Raman spectroscopy, and photoelectron spectroscopy. The first complex, Pd(Hkpda)2 (kpda = ketopiperazinediacetate dianion, C8H10N2O5), forms yellow parallelepipeds during slow evaporation of Pd(NO3)2–Na2H2EDTA solution at 25 °C, and is a result of EDTA oxidation. The second one, [Pd(μ-H2EDTA)]2 · 2NaNO3 · 7.5H2O, with two EDTA molecules acting as bridges between two palladium atoms, forms yellow bipyramides during fast evaporation at 60 °C. In both complexes, the palladium atoms adopt a planar trans-geometry by bonding to two nitrogen and two oxygen atoms of two ligand molecules.