Intramolecular Iron-Mediated C–H Bond Heterolysis with an Assist of Pendant Base in a [FeFe]-Hydrogenase Model
- 7 October 2014
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 136 (48) , 16817-16823
Abstract
Although many metalloenzymes containing iron play a prominent role in biological C–H activation processes, to date iron-mediated C(sp3)–H heterolysis has not been reported for synthetic models of Fe/S-metalloenzymes. In contrast, ample precedent has established that nature’s design for reversible hydrogen activation by the diiron hydrogenase ([FeFe]-H2ase) active site involves multiple irons, sulfur bridges, a redox switch, and a pendant amine base, in an intricate arrangement to perform H–H heterolytic cleavage. In response to whether this strategy might be extended to C–H activation, we report that a [FeFe]-H2ase model demonstrates iron-mediated intramolecular C–H heterolytic cleavage via an agostic C–H interaction, with proton removal by a nearby pendant amine, affording FeII–[Fe′II–CH–S] three-membered-ring products, which can be reduced back to 1 by Cp2Co in the presence of HBF4. The function of the pendant base as a proton shuttle was confirmed by the crystal structures of the N-protonated intermediate and the final deprotonated product in comparison with that of a similar but pendant-amine-free complex that does not show evidence of C–H activation. The mechanism of the process was backed up by DFT calculations.Keywords
Funding Information
- Division of Chemistry (CHE-1266097, CHE-1300787)
- Welch Foundation (A-0648, A-0924)
- Energimyndigheten
- Ministry of Education of the People's Republic of China (20130041110024)
- Ministry of Science and Technology of the People's Republic of China (2014CB239402)
- Knut och Alice Wallenbergs Stiftelse
- National Natural Science Foundation of China (21101057, 21120102036, 21373040, 91233201)
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