Atmospheric Oxygen Influence on the Chemical Transformations of 4,5-Dimethyl-1,2-Phenylenediamine in the Reactions with Copper(II) Pivalate

The one-pot synthesis of the Cu(II) complex with hard to access symmetric bis-azoligand is carried out by the reaction of 4,5-dimethyl-1,2-phenylenediamine (Dmpda) with the [Cu2(Piv)4(HPiv)2] complex (Piv is the pivalate anion) in the presence of atmospheric oxygen. The amine form of the ligand takes place and the bis-diiminosemiquinone biradical redox form of the ligand does not take place in the [CuLazo] complex as unambiguously shown by the data of X-ray structure analysis (CIF files CCDC nos. 1877582 (I · DMF) and 1877583 (II), ESR spectroscopy, SQUID magnetometry, and electrochemical and quantum chemical studies. The coordination polymer [Cu2(Piv)4(Dmpda)]n in which the Dmpda molecules perform the bridging function is formed in the same reaction mixture under reduced air pressure.