Carbon dioxide reduction with homogenous early transition metal complexes: Opportunities and challenges for developing CO2 catalysis

The field of carbon dioxide reduction by homogeneous early transition complexes (groups 3–7) is reviewed. Many reactions with CO2 have been studied with late transition metal complexes (groups 8–10), and significant progress has been made in developing active and selective homogeneous catalysts for CO2 reduction with late metals. However, one major drawback of these systems is that they generally only produce the 2e− reduction products CO or formate. In comparison, early transition metal complexes have been neglected for the development of CO2reduction catalysts. Stoichiometric and catalytic reductions of CO2 to methanol and similar products have been observed with early transition metal complexes, and highly active catalysts may be developed based on early transition metal complexes that could reduce CO2 to liquid fuels such as methanol or to hydrocarbons such as methane