Synthesis and Magnetic Studies of μ‐Oxamido‐Bridged Cu(II)–Cr(III) and Cu(II)–Fe(III) Heterobinuclear Complexes

Abstract Two new μ‐oxamido‐bridged heterobinuclear complexes have been synthesized and identified as [Cu(dmoxae)Cr(bpy)2](ClO4)3 (1) and [Cu(dmoxae)Fe(bpy)2](ClO4)3 (2), where dmoxae denotes N, N′‐bis[2‐(dimethylamino)ethyl]oxamido dianion and bpy represents 2,2′‐bipyridine. The two complexes have not yet been isolated in crystalline form suitable for x‐ray structure analysis, but based on elemental analyses, IR, ESR and electronic spectra studies, and molar conductivity measurements, the complexes are proposed to have an extended oxamido‐bridged structure consisting of planar copper(II) and octahedral chromium(III) or iron(III) ions. The two heterobinuclear complexes were further characterized by variable‐temperature magnetic susceptibility (4.2–300 K) measurements and the magnetic data have also been used to deduce the indicated heterobinuclear structure. The results derived from the least‐squares fit of the experimental data have confirmed that the adjacent copper(II) and chromium(III) ions in complex (1) are ferromagnetically coupled through the oxamido‐bridge with the exchange integral J (Cu–Cr) = +16.5 cm−1, while intramolecular antiferromagnetic coupling is detected between the copper(II) and iron(III) ions through the oxamido‐bridge in complex (2) with the exchange integral J (Cu–Fe) = −18.9 cm−1, on the basis of the spin‐Hamiltonian operator, Hˆ = − 2J Sˆ Cu Sˆ M (M = Cr and Fe). The influence of electronic‐structural variations of the metal ions on the nature of spin‐exchange interaction between the paramagnetic centers is also discussed.