CO2 Activation and Catalysis Driven by Iridium Complexes

Recent reports on homogeneous catalytic transformation of carbon dioxide by iridium complexes have prompted us to review the area. Progress on new iridium catalysts for carbon dioxide transformations should take into account the interaction of carbon dioxide with the iridium center, which seems to be governed by the oxidation state of iridium and the nature of the carbon dioxide molecule. Most examples of iridium catalyzed carbon dioxide reductions are based on Ir-III centers. These reactions take place through outer-sphere mechanisms, by means of nucleophilic attack on the carbon atom. In all the reported systems, the nucleophile is always a hydrido ligand coordinated to a Ir-III center. Future challenges on iridium catalyzed functionalization of carbon dioxide include the development of efficient electrophiles, compatible with the inclusion of appropriate nucleophiles, which would allow the preparation of value-added organic molecules using CO2 as C1 feedstock.