Iron-Mediated C-C Bond Formation via Reductive Coupling with Carbon Dioxide

Carbon dioxide functionalization is a potentially transformative method to enhance the sustainability of carbon-based commercial chemicals. The reductive functionalization of CO2 via C-C bond forming reactions is one route to deriving structurally diverse products from this renewable resource. Despite considerable advances in catalytic CO2 reduction into smaller molecular fragments, such as CO, there remains relatively few transition metal mediated processes to elaborate CO2 via reductive C-C bond functionalization. An investigation of iron(0) complexes capable of reductive coupling with CO2 to generate acrylate and oxalate are described here. A set of [(depe)(2)Fe] (depe = 1,2-bis(diethylphosphino)ethane) complexes were found to reductively functionalize CO2 with ethylene or a second molecule of CO2 to afford C-3 and C-2 products, respectively. Several factors influencing the stoichiometric yield of these transformations were examined including a deleterious CO2 disproportionation process which produces (depe)(2)Fe(CO) and (depe)(2)Fe(CO3). Additionally, an intermediate ironlactone complex in route to acrylate formation has been structurally characterized.