Square-pyramidal copper(II) chelate complexes of edta-type and related ligands forming six-membered rings. Crystal structure of magnesium (ethylenediamine- N, N, N′-tri-3-propionato- N′-3-propionate)copper(II) decahydrate, Mg[Cu(edtp)]·10H 2O

Abstract

Two square-pyramidal complexes, Mg[Cu(edtp)]·10H 2O ( 1) (edtp=ethylenediamine- N, N, N′, N′-tetra-3-propionate ion, acting as a pentadentate) and Mg[Cu(ed3p)] 2·6H 2O ( 2) (ed3p=ethylenediamine- N, N, N′-tri-3-propionate ion) have been prepared and characterized. A square-pyramidal geometry was established crystallographically for the complex Mg[Cu(edtp)]·10H 2O ( 1). The Cu(II) ion in the complex anion is displaced by 0.195 Å from the plane of the four in-plane (2N and 2O) ligand atoms towards the apical oxygen atom of the β-alaninate (R) ring (CuO ax=2.173 Å). The conformations of the chelate rings are those usually expected for these kinds of chelates (a five-membered diamine (E) ring in a twist(λ) conformation, two β-alaninate (G 1 and G 2) rings in a distorted twist-chair and one β-alaninate (R) ring in a distorted twist-boat conformation). The structural data correlating the square-pyramidal stereochemistry are discussed with reference to those obtained for related complexes. Electronic absorption and reflectance spectra are discussed in comparison with those of related complexes of known structures. IR data (carboxylate region) are also reported.