Degrés d'oxydation métalliques et ligands redox non innocents De Charybde en Scylla

The notion of the oxidation state in coordination complexes is subtle and deserves great attention. Thus, the ideas of formal oxidation state and spectroscopic oxidation state are opposed and depending upon the ligand of the coordination complex, they can be very similar or very different. This allows introducing a novel concept, very popular at the moment in coordination chemistry, the concept of redox non-innocent ligands. They are guilty as they do not easily allow defining the oxidation state of the metal center. However, for the development of potential applications, it is very important to precisely define the electronic density localization in order to draw a link between the redox properties of the coordination complexes and their physical properties and/or their potential reactivity. This article proposes several examples of these molecules with unusual electronic structure with transition metals but also with lanthanides.