Ferromagnetically coupled heterodinuclear oxamido-bridged copper(II)-chromium(III) complexes

Four new mu-oxamido heterodinuclear complexes, [Cu(oxae)Cr(L)(2)](NO3)(3), where oxae denotes the N,N'-bis(2-aminoethyl)oxamido dianion and L represen ts 4,7-diphenyl-1,10-phenanthroline (Ph-2-phen), 5-chloro-1,10-phenanthroli ne (Cl-phen), 2,9-dimethyl-1,10-phenanthroline (Me-2-phen) and 4,4'-dimethy l-2,2'-bipyridine (Me-2-bpy), have been synthesized and characterized by el emental analyses, magnetic moments (at room temperature) and molar conducti vity measurements, and by spectroscopy (IR and electronic spectra). It is p roposed that these complexes have extended oxamido-bridged structures consi sting of planar copper(II) and octahedral chromium(III) ions. The cryomagne tic properties of [Cu(oxae)Cr(Me-2-bpy)(2)](NO3)(3) (1) and [Cu(oxae)Cr(Me- 2-phen)(2)](NO3)(3) (2) have been measured over the range 4.2-300 K. From l east-squares fit of the experimental data, based on the spin Hamiltonian, ( H) over cap = -2J (S) over cap(1).(S) over cap(2), the exchange integrals ( J) were evaluated as +19.8 cm(-1) for (1) and +21.5 cm(-1) for (2). The res ults have confirmed that the spin coupling between the adjacent copper(II) and chromium(III) ions through the oxamido-bridge in both complexes (1) and (2) is ferromagnetic.