Synthesis and Characterization of (μ-Oxalato)nickel(II), Copper(II) and Zinc(II) Complexes with Chelating Polyamines

Abstract

New binuclear complexes of the type [(Ni(aep)2)2ox](ClO4)2 (1) (aep = 2-(2-aminoethyl)pyridine, H2ox = oxalic acid), [(Ni(ept)H2O)2ox](NO3)2 (2), (ept = N-(2-aminoethyl)-1,3-diaminopropane), [(Cu(aep)H2O)2ox](ClO4)2 (3), [(Cu(ept))2ox](NO3)2·H2O (4) and [(Zn(L))2ox](ClO4)2·nH2O (L = ept, n = 0 (5); L = N,N'-bis(3-aminopropyl)-1,2-diaminoethane (3,2,3-tet), n = 4 (6)) have been prepared and studied by IR and UV-VIS spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between six-coordinate (N4O2 or N3O3) Ni(II) (compounds 1 and 2), (N2O3 or N3O2) Cu(II) (compounds 3 and 4) or (N3O2 or N4O2) Zn(II) (compounds 5 and 6). The crystal structure of [(Cu(aep)H2O)2ox](ClO4)2 (3) has been determined by single-crystal X-ray analysis. The copper atom is coordinated by two oxygen atoms of the oxalato ligand, two nitrogen atoms belonging to aep and one oxygen atom of water in a square-pyramidal arrangement. The intermetallic distance of Cu(1)-Cu(1a) is 5.204(2) Å. The temperature dependence of magnetic susceptibilities (94-298 K) was measured for 1 and 3. Magnetochemical measurements show that metal ions in these compounds are antiferromagnetically coupled, J = -17 and -160 cm-1 (H = -2JS1S2) for 1 and 3, respectively.