Oxidative dehydrogenation of an amine group of a macrocyclic ligand in the coordination sphere of a CuII complex

Abstract

The spontaneous oxidation of an amine group to an imine has been observed experimentally in an octa-aza macrocyclic dinucleating ligand LH₄ coordinated to Cu^II. The reaction is bimolecular and spontaneous in which amine groups of one macrocycle are oxidised and the Cu^II centres of a second macrocyclic complex are reduced. No additional oxidating or external base agents are required. DFT calculations are carried out to compare the reaction with that recently reported for a ligand coordinated to an Fe^III centre, but which requires an external base as proton acceptor. The computational results show that the copper and iron catalysed amine to imine reactions proceed via different mechanisms.