Molecular structures of copper(II) and iron(III) chloro complexes with di- and monoprotonated N-(pyrid-2-ylmethyl)ethylenediamine-N,N',N'-triacetate (H(2)pedta(-); Hpedta(2-))

The molecular structures of two complexes of di- and monoprotonated N-(pyrid-2-ylmethyl)ethylenediamine-N,N',N'-triacetate (pedta(3-)) with Cu-II and Fe-III as central atoms have been determined by single crystal X-ray diffraction methods. Both complexes have a distorted octahedral coordination with H(2)pedta(-) and Hpedta(2-) as pentadentate ligands and a chloride ion occupying the sixth coordination site. The different oxidation states of the central atoms result in a completely different coordination behaviour of the carboxyl groups. In both complexes one of the -CH2-COOH groups is uncoordinated. In the Fe-III complex, the central atom is coordinated by the hydroxylic O atoms of the deprotonated carboxyl groups. Contrary to this in the Cu-II complex, the central atom is coordinated by the carbonylic O atoms. One of the coordinated carboxyl groups is protonated and the other is deprotonated. All protonated carboxyl groups in both complexes form intermolecular hydrogen bonds.