Metal‐Free Electrochemical Reduction of Carbon Dioxide Mediated by Cyclic(Alkyl)(Amino) Carbenes

• Published in: Chemistry : a European journal Vol. 25; no. 24; pp. 6098 - 6101
• Main Authors: Lieske, Lauren E., Freeman, Lucas A., Wang, Guocang, Dickie, Diane A., Gilliard, Robert J., Machan, Charles W.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 26.04.2019
• Subjects: Adducts; Carbenes; Carbon cycle; Carbon dioxide; Carbon monoxide; Chemical reduction; Chemistry; Disproportionation; Electrochemistry; main group elements; Metals; Reagents; reduction; carbenes; carbon dioxide; electrochemistry; reduction; main group elements
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201900316

Carbenes are known to activate carbon dioxide to form zwitterionic adducts. Their inherent metal‐free redox activity remains understudied. Herein, we demonstrate that zwitterionic adducts of carbon dioxide formed with cyclic(alkyl)(amino) carbenes are not only redox active, but they can mediate the stoichiometric reductive disproportionation of carbon dioxide to carbon monoxide and carbonate. Infrared spectroelectrochemical experiments show that the reaction proceeds through an intermediate radical anion formed by one‐electron reduction, ultimately generating a ketene product and carbonate in the absence of additional organic or inorganic reagents. Caught in the middle: Carbenes activate carbon dioxide to form zwitterionic adducts. The zwitterionic adducts of carbon dioxide formed with cyclic(alkyl)(amino) carbenes (CAACs) are not only redox active, but they can mediate the stoichiometric reductive disproportionation of carbon dioxide to carbon monoxide and carbonate (see scheme).