NHC-Containing Manganese(I) Electrocatalysts for the Two-Electron Reduction of CO2


  • Research at UGA was supported by the National Science Foundation (NSF), Grant CHE-1054286. Research at Princeton was supported by funding from the DOD-MURI program under AFOSR Award FA9550-10-1-057 and the NSF under grant CHE-1308652. T.W.S. acknowledges the NSF for a graduate research fellowship. We thank Dr. Pingrong Wei for assistance in the acquisition and refinement of X-ray structures, and Dr. Todd Harrop for the use of an infrared spectrometer. NHC=N-heterocyclic carbene.


The synthesis and characterization of the first catalytic manganese N-heterocyclic carbene complexes are reported: MnBr(N-methyl-N′-2-pyridylbenzimidazol-2-ylidine)(CO)3 and MnBr(N-methyl-N′-2-pyridylimidazol-2-ylidine)(CO)3. Both new species mediate the reduction of CO2 to CO following two-electron reduction of the MnI center, as observed with preparative scale electrolysis and verified with 13CO2. The two-electron reduction of these species occurs at a single potential, rather than in two sequential steps separated by hundreds of millivolts, as is the case for previously reported MnBr(2,2′-bipyridine)(CO)3. Catalytic current enhancement is observed at voltages similar to MnBr(2,2′-bipyridine)(CO)3.