Synthesis and characterization of binuclear μ-oxalato nickel(II), copper(II) and zinc(II) complexes with 3,3′-diamino-N-methyl-dipropylamine or trans-1,2-diaminocyclohexane

New binuclear complexes of the type [(Ni(Medpt)NO3)(2)ox] (1) (Medpt=3,3'-diamino-N-methyl-dipropylamine, H(2)ox=oxalic acid), [(Ni(dach)(2))(2)ox]NO3. 2H(2)O (2) (dach=trans-1,2-diaminocyclohexane), [(Cu(Medpt))(2)ox]X-2. yH(2)O (X=NO3, y=2 2/3 (3); X=ClO4, y=0 (4)) and [(Zn(dach)(2))(2)ox](ClO4)(2). 2H(2)O (5) have been prepared and characterized by IR and UV-Vis spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between six-coordinated (N3O3 or N4O2) Ni(II) (compounds 1 or 2), five-coordinated (N3O2) Cu(II) (compounds 3 and 4) or six-coordinated (N4O2) Zn(II) (compound 5). The crystal structure of [(Cu(Medpt))(2)ox](NO3)(2). 2 2/3 H2O (3) has been determined by single-crystal X-ray analysis. The structure of (3) consists of centrosymmetric binuclear cations [(Medpt)Cu(ox)Cu(Medpt)](2+), nitrate anions and water molecules of crystallization. The copper atom is five-coordinated by two oxalate-oxygen and three Medpt-nitrogen atoms, in a hybrid arrangement between trigonal-bipyramidal and square-pyramidal. The temperature dependence of magnetic susceptibility (1.8-300 K) was measured for compounds 1-4. Magnetochemical measurements show that Ni(II) complexes are antiferromagnetically coupled, J=-29.4 (1) and -32.7 cm(-1) (2) (H=-JS(1)S(2)) while the Cu(II) complexes present a very weak coupling, J=-2.6 (3) and +1.9 cm(-1) (4), being antiferro- and ferromagnetic in nature. (C) 1999 Elsevier Science Ltd. All rights reserved.