BONDING PROPERTIES OF COPPER(II) N-CHROMOPHORES - PREPARATION, STRUCTURE, AND SPECTROSCOPIC PROPERTIES OF ETHYLENEDIAMINE-COPPER(II) COMPLEXES - MOLECULAR-STRUCTURE OF [CU(ETHYLENEDIAMINE)-(PYRIDINE)2(CLO4)2]

Ethylenediaminecopper(II) Perchlorate complexes of the [Cu(ethylenediamine)L2(ClO4)2] type, where L = imidazole, N-methylimidazole, 2-methylimidazole, 4-methylimidazole, and pyridine, have been prepared and characterized by elemental analyses, and electronic, vibrational, and e.p.r. spectroscopic measurements. The molecular structure of [Cu(ethylenediamine)(pyridine)2(ClO4)2] has been determined by three-dimensional X-ray diffraction data. The Cu(II) ion is coordinated by one ethylenediamine and two pyridine ligands forming an equatorial plane, and by two perchlorate anions located on the z axis. The pyridine ligands incline at 54.9-degrees to the CuN4 plane suggesting virtually no pi-interaction in the complex. Similar structures with a CuN4 coordination plane are proposed for other complexes based on the spectroscopic data. The bonding properties of these complexes are elucidated and discussed with reference to the electronic structures deduced from Gaussian analyses of their LF spectra.