The preparation and characterisation of metal complexes of a new binucleating ligand having two different coordination sites

Abstract

A new ligand, referred to as H 4aapen, has been prepared; it is the ethylenediamine Schiff base derivative of o-acetoacetylphenol and has one site with two nitrogen and two oxygen atoms (N 2O 2) and a second site with four oxygen atoms (O 2O 2) two central oxygens being common to both sites. A series of mono-nuclear complexes have been prepared from this ligand in order to investigate the coordination selectivity of the two compartments. In Ni(H 2aapen) the nickel(II) is in the N 2O 2 site, while in UO 2(H 2aapen)(H 2O) and Li 2[UO 2(aapen)(H 2O)]H 2O the uranyl ions are in the O 2O 2 site. Positional isomers can be prepared with copper(II): one having the copper in the O 2O 2 site and the other with copper in the N 2O 2 one. The mononuclear complexes were used as ligands to prepare the binuclear complexes MM′(aapen) (M = Ni 2+, Cu 2+, UO 2+ 2; M′ = Ni 2+, Cu 2+). These complexes were characterized on the basis of the analytical data, mass, ir, uv spectra and magnetic moments at room temperature.