Copper-catalyzed aerobic oxidative coupling of diaryl imines provides a route for conversion of ammonia to hydrazine. Here the present study uses experimental and density functional theory computational methods to investigate the mechanism of N–N bond formation, and the data support a mechanism involving bimolecular coupling of Cu-coordinated iminyl radicals. Computational analysis is extended to CuII-mediated C–C, N–N, and O–O coupling reactions involved in the formation of cyanogen (NC–CN) from HCN, 1,3-butadiyne from ethyne (i.e., Glaser coupling), hydrazine from ammonia, and hydrogen peroxide from water. The results reveal two different mechanistic pathways. Heteroatom ligands with an uncoordinated lone pair (iminyl, NH2, OH) undergo charge transfer to CuII, generating ligand-centered radicals that undergo facile bimolecular radical–radical coupling. Ligands lacking a lone pair (CN and CCH) form bridged binuclear diamond-core structures that undergo C–C coupling. This mechanistic bifurcation is rationalized by analysis of spin densities in key intermediates and transition states, as well as multiconfigurational calculations. Radical–radical coupling is especially favorable for N–N coupling owing to energetically favorable charge transfer in the intermediate and thermodynamically favorable product formation.
King, Daniel S., et al. "Divergent Bimetallic Mechanisms in Copper(II)-Mediated C–C, N–N, and O–O Oxidative Coupling Reactions." Journal of the American Chemical Society, vol. 146, no. 5, Jan. 2024. https://doi.org/10.1021/jacs.3c13649
King, Daniel S., Wang, Fei, Gerken, James B., Gaggioli, Carlo Alberto, Guzei, Ilia A., Kim, Yeon Jung, Stahl, Shannon S., & Gagliardi, Laura (2024). Divergent Bimetallic Mechanisms in Copper(II)-Mediated C–C, N–N, and O–O Oxidative Coupling Reactions. Journal of the American Chemical Society, 146(5). https://doi.org/10.1021/jacs.3c13649
King, Daniel S., Wang, Fei, Gerken, James B., et al., "Divergent Bimetallic Mechanisms in Copper(II)-Mediated C–C, N–N, and O–O Oxidative Coupling Reactions," Journal of the American Chemical Society 146, no. 5 (2024), https://doi.org/10.1021/jacs.3c13649
@article{osti_2348871,
author = {King, Daniel S. and Wang, Fei and Gerken, James B. and Gaggioli, Carlo Alberto and Guzei, Ilia A. and Kim, Yeon Jung and Stahl, Shannon S. and Gagliardi, Laura},
title = {Divergent Bimetallic Mechanisms in Copper(II)-Mediated C–C, N–N, and O–O Oxidative Coupling Reactions},
annote = {Copper-catalyzed aerobic oxidative coupling of diaryl imines provides a route for conversion of ammonia to hydrazine. Here the present study uses experimental and density functional theory computational methods to investigate the mechanism of N–N bond formation, and the data support a mechanism involving bimolecular coupling of Cu-coordinated iminyl radicals. Computational analysis is extended to CuII-mediated C–C, N–N, and O–O coupling reactions involved in the formation of cyanogen (NC–CN) from HCN, 1,3-butadiyne from ethyne (i.e., Glaser coupling), hydrazine from ammonia, and hydrogen peroxide from water. The results reveal two different mechanistic pathways. Heteroatom ligands with an uncoordinated lone pair (iminyl, NH2, OH) undergo charge transfer to CuII, generating ligand-centered radicals that undergo facile bimolecular radical–radical coupling. Ligands lacking a lone pair (CN and CCH) form bridged binuclear diamond-core structures that undergo C–C coupling. This mechanistic bifurcation is rationalized by analysis of spin densities in key intermediates and transition states, as well as multiconfigurational calculations. Radical–radical coupling is especially favorable for N–N coupling owing to energetically favorable charge transfer in the intermediate and thermodynamically favorable product formation.},
doi = {10.1021/jacs.3c13649},
url = {https://www.osti.gov/biblio/2348871},
journal = {Journal of the American Chemical Society},
issn = {ISSN 0002-7863},
number = {5},
volume = {146},
place = {United States},
publisher = {American Chemical Society (ACS)},
year = {2024},
month = {01}}
Univ. of Wisconsin, Madison, WI (United States); Energy Frontier Research Centers (EFRC) (United States). Catalyst Design for Decarbonization Center (CD4DC)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Contributing Organization:
University of Minnesota, Minnesota Supercomputing Institute
Grant/Contract Number:
FG02-05ER15690; SC0023383
OSTI ID:
2348871
Journal Information:
Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 5 Vol. 146; ISSN 0002-7863
Journal Article
·
Mon Dec 31 23:00:00 EST 1962
· Zhurnal Fizicheskoi Khimii (U.S.S.R.) For English translation see Russ. J. Phys. Chem. (Engl. Transl.)
·OSTI ID:4755277