Synthesis, crystal structure and magnetic properties of novel copper(II)-nickel(II) complexes of macrocyclic oxamides

Three novel oxamido-bridged heterobinuclear copper(II)-nickel(II) complexes derived from macrocyclic oxamido compounds have been synthesized and characterized by IR, ESR and electronic spectra. They are of the formula [(CuL¹)Ni(pmtn)(NCS)]ClO₄ (1), [Cu(L²)Ni(pmtn)(NCS)]ClO₄ (2) and [(CuL³)Ni(pmtn)(NCS)]ClO₄ (3), where H₂L¹ = 2,3-dioxo-5,6:14,15-dibenzo-7,13-bis (ethoxycarbonyl)-1,4,8,12-tetraazacyclopentadeca-7,12-diene, H₂L² = 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis (ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene and H₂L³ =2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12- bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, respectively. The crystal structure of 2 has been determined by X-ray crystallography. The nickel(II) ion is pseudo-octahedrally coordinated and the copper(II) ion is in a distorted square-pyramidal environment. The temperature dependence of the magnetic susceptibility for 1 and 2 has been analyzed using the Hamiltonian Ĥ = -2JŜ₁·Ŝ₂, leading to J= -47.5 and -47.2 cm^-1, for 1 and 2, respectively.