Heteroligand o-Semiquinonato Cobalt Complexes of 3-Cyano and 3-Nitroformazans

The synthesis of four heteroligand o‐semiquinonate cobalt complexes of bidentate 3‐cyano‐ and 3‐nitroformazans is described. All complexes are characterized by single‐crystal X‐ray diffraction and magnetic susceptibility measurements. The square‐planar mono‐o‐semiquinonato‐formazanate cobalt(II) complexes demonstrate diamagnetic properties due to strong intramolecular antiferromagnetic metal–ligand exchange. Magnetic properties of the six‐coordinated bis‐o‐semiquinonato‐formazanate cobalt(III) complexes indicate the domination of antiferromagnetic exchange interactions between unpaired electrons of o‐semiquinonato ligands, and the inclusion of electron‐withdrawing cyano and nitro groups at R³ position of formazanate ligand leads to an increase of the energy of this exchange interaction.