AbstractFourμ‐ oxamido heterodinuclear complexes, [Cu (oxae) Cr (L)2] (NO3)3, where oxae denotes theN, N'bis (2‐aminoethyl) oxamido dianion and L represents 1,10‐phenanthroline (phen); 5‐nitro‐1,10‐phenanthroline (NO2‐phen); 5‐methyl‐1, 10‐phenanthroline (Me‐phen) and 2, 2′‐bipyridine (bpy), have been synthesized and characterized by elemental analyses, magnetic moments (at room temperature) and molar conductivity measurements and spectroscopy. It is proposed that these complexes have extended oxamido‐bridged structures consisting of a copper (II) ion and a chromium (III) ion, which have a square planar environment and octahedral environment, respectively. The cryomagnetic properties of the [Cu(oxae)Cr(bpy)2(NO3)3(1) and [Cu(oxae)Cr(phen)2](NO3)3(2) complexes have been measured over the range of 4.2–300 K. The leastsquares fit of the experimental data based on the spin Hamiltonian, Ĥ = ‐2JŜ1·Ŝ2, the exchange integrals (J) were evaluated as +36.9 cm−1for 1 and +35.8 cm−1for 2. The reds have connived that the spin coupling between the adjacent copper (II) and chromium (III) ions through oxamido