Cobalt complexes with α-amino acid ligands catalyze the incorporation of CO2 into cyclic carbonates

Arguably one of the largest research areas involving carbon dioxide (CO₂) fixation is the coupling of CO₂ to epoxides to form cyclic carbonates and polycarbonates. In this sense, there is an ever-increasing demand for the development of higher-performing catalytic systems that could counterbalance sustainability and energy efficiency in the production of cyclic carbonates. The use of abundant first-row transition metals combined with naturally occurring amino acids may be an ideal catalytic platform to fulfill this demand. Nevertheless, detailed information on the interactions between metal centers and natural products as catalysts in this transformation is lacking. Here a series of Co(III) amino acid catalysts operating in a binary system showed outstanding performance for the coupling reaction of epoxides and CO₂. Nine new complexes of the type trans(N)-[Co(aa)₂(bipy)]Cl (aa: ala, asp, lys, met, phe, pro, ser, tyr, and val) were used to explore the structure-activity relationship influenced by the complex outer coordination sphere, and its effect on the catalytic activity in the coupling reaction of CO₂ and epoxides.

Nickel-Catalyzed Selective Decarbonylation of α-Amino Acid Thioester: Aminomethylation of Mercaptans

The nickel-catalyzed aminomethylation of mercaptans has been disclosed that offers efficient and expedient access to synthesize α-aminosulfides. The intramolecular fragment coupling shows excellent chemoselectivity. This transformation shows good functional-group compatibility, tolerates a wide range of electron-withdrawing, electron-neutral, and electron-donating substituents in this process, and can serve as a powerful synthetic tool for the synthesis of α-aminosulfides at a gram scale. Thus, the newly developed methodology enables a facile route for C-S bond formation in a straightforward fashion.

Delocalized electron effect on single metal sites in ultrathin conjugated microporous polymer nanosheets for boosting CO2 cycloaddition

CO2 cycloaddition with epoxides at low temperature and pressure has been broadly recognized as an ambitious but challenging goal, which requires the catalysts to have precisely controlled Lewis acid sites. Here, we demonstrate that both stereochemical environment and oxidation state of single cobalt active sites in cobalt tetraaminophthalocyanine [CoPc(NH2)4] are finely tuned via molecular engineering with 2,5-di-tert-butyl-1,4-benzoquinone (DTBBQ). Notably, DTBBQ incorporation not only enables formation of 5-nm-thick conjugated microporous polymer (CMP) nanosheets due to the steric hindrance effect of tert-butyl groups but also makes isolated cobalt sites with high oxidation state due to the presence of delocalized electron-withdrawing effect of alkene groups in DTBBQ via conjugated skeleton. Notably, when used as heterogeneous catalysts for CO2 cycloaddition with different epoxides, single cobalt active sites on the ultrathin CMP nanosheets exhibit unprecedentedly high activity and excellent stability under mild reaction conditions.

Highly active dinuclear cobalt complexes for solvent-free cycloaddition of CO2 to epoxides at ambient pressure

Dinuclear Co-based catalysts are used for the coupling reaction of epoxides and CO₂ in the presence of a cocatalyst.

Cobalt amino-bis(phenolate) complexes for coupling and copolymerization of epoxides with carbon dioxide

Electron-withdrawing groups on phenolate donors enhance polycarbonate production from CO₂ and cyclohexene oxide by Co(ii) amino-bis(phenolate) complexes.

Stable Fe(iii) phenoxyimines as selective and robust CO2/epoxide coupling catalysts

Air- and moisture-stable Fe(iii)-phenoxyimine complexes catalyse CO₂ coupling reactions with a range of epoxides to selectively form cyclic carbonates.

New ionic cobalt(iii) complexes based on the N,N-bis(2-pyrazinecarboxamide)-1,2-benzene ligand: application to the formation of organic carbonates from epoxides and CO2

New cobalt(iii) complexes based onN,N-bis(2-pyrazine-carboxamide)-1,2-benzene were tested as catalysts for the coupling of propylene- and cyclohexene oxide with CO₂.