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

摘要

New binuclear complexes of the type [(Ni(Medpt)NO_3)_2ox] (1) (Medpt = 3,3'-diamino-N-methyl-dipropylamine, H_2ox = oxalic acid), [(Ni(dach)_2)_2ox]NO_3 centre dot 2H_2O (2) (dach = trans-1,2-diaminocyclohexane), [(Cu(Medpt))_2ox]X_2 centre dot yH_2O (X = NO_3, y = 2 2/3 (3); X = ClO_4, y = 0 (4)) and [(Zn(dach)_2)_2ox](ClO_4)_2 centre dot 2H_2O (5) have been prepared and characterized by IR and UV-Vis spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between six-coordinated (N_3O_3 or N_4O_2) Ni(II) (compounds 1 or 2), five-coordinated (N_3O_2) Cu(II) (compounds 3 and 4) or six-coordinated (N_4O_2) Zn(II) (compound 5). The crystal structure of [(Cu(Medpt))_2ox](NO_3)_2 centre dot 2 2/3 H_2O (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_1S_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.