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

Abstract

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)2Fe] (depe = 1,2-bis­(diethylphosphino)­ethane) complexes were found to reductively functionalize CO2 with ethylene or a second molecule of CO2 to afford C3 and C2 products, respectively. Several factors influencing the stoichiometric yield of these transformations were examined including a deleterious CO2 disproportionation process which produces (depe)2Fe­(CO) and (depe)2Fe­(CO3). Additionally, an intermediate iron–lactone complex in route to acrylate formation has been structurally characterized.

Divergent CO2 Activation by Tuning the Lewis Acid in Iron‐Based Bimetallic Systems

“…We decided to use the Fe 0 fragment [(depe) 2 Fe] as a metallic Lewis base because its corresponding CO 2 adduct ( 1 ) is readily accessible [17a] and exhibits a rich carbon dioxide functionalization chemistry [17b,c] . Besides, Szymczak and co‐workers used the latter to investigate the activation of dinitrogen by push‐pull interactions [18] .…”

Molecular Catalysts for the Reductive Homocoupling of CO2 towards C2+ Compounds

“…A more recently reported Fe 0 system of the type [(depe) 2 Fe] (depe=1,2‐bis(diethylphosphino)ethane) afforded oxalate in 98 % yield in the presence of 2 equiv KC 8 in THF at 45 °C (Figure 3B8) [31] . Control experiments using KC 8 only or other Fe‐based complexes resulted in lower oxalate yields, thereby demonstrating that the [(depe) 2 Fe 0 ] species plays a key role in the reductive CO 2 coupling.…”

Recent developments on the transformation of CO2utilising ligand cooperation and related strategies

“…Multiple type 2 CO2 activation on cerium-pyrazole complex Carmona and co-workers have described the use of an iridium complex containing a pyridylidene ligand in addition to a hydrotris(pyrazolyl)borate co-ligand (Scheme 19). Exposure to CO2 led to the formation of a carbamate complex (75). In this case, the AB unit corresponds to C-N (within the pyridylidene ligand) and the nitrogen atom acts as the nucleophile where the The Mann research group reported a cyclometallated iridium(III) complex where the AB atom bridge corresponds to a hydrazino (H2N-NH2) ligand (Scheme 20).…”

“…Bernskoetter and co-workers recently reported the synthesis of Fe(0) complex 50 containing a coordinated alkene, which promoted CO 2 fixation leading to the formation of the stable ferralactone 51 (Scheme 13). 75 The authors also prepared a Fe(0) complex containing coordinated CO 2 instead of an alkene. The use of KC 8 as a reducing agent in the presence of CO 2 (1.5 atm) led to the stoichiometric formation of acrylate salts.…”

“…Carmona and co-workers described the use of an iridium complex containing a pyridylidene ligand in addition to a hydrotris( pyrazolyl)borate co-ligand (Scheme 19). Exposure to CO 2 led to the formation of a carbamate complex (75). In this case, the AB unit corresponds to C-N (within the pyridylidene ligand) and the nitrogen atom acts as the nucleophile where the final product is the result of CO 2 activation involving a 2-atom bridge (CvN) between the metal and the ligand.…”