Copper(II) complexes of asymmetrical and symmetrical acyclic pentadentate (N5) mono-Schiff-base ligands.: The X-ray structure of [Cu(ppe-py)](ClO4)2

In the presence of copper(II) ion, two asymmetrical tripodal tetraamine ligands N{(CH2)(3)NH2}{(CH2)(2)NH2}(2) (pee), N{(CH2)(3)NH2}(2) {(CH2)(2)NH2} (ppe) an one symmetrical ligand, N{(CH2)(3)NH2}(3) (tpt), were condensed with 2-acetylpyridine. In EtO-H2O solutions the reaction stops after the first condensation stage, and complexes of acyclic pentadentate(N-5) mono-Schiff-base ligands were obtained. With asymmetrical tetraamines there are two possible condensation sites: the primary amine of the propylene, or the ethylene chain. The X-ray structure analysis of one complex, [Cu(ppe-py)] (ClO4)(2), indicates that condensation with 2-acetylpyridine in this case occurs at the propylene chain and the geometry around the copper ion is trigonal-bipyramidal.