title: Intramolecular iron-mediated C-H bond heterolysis with an assist of pendant base in a [FeFe]-hydrogenase model.
abstract: Although many metalloenzymes containing iron play a prominent role in biological C-H activation processes, to date iron-mediated C(sp(3))-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 Fe(II)-[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.
authors.affiliation: State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT) , Dalian 116024, People's Republic of China.
authors.forename: Dehua
authors.initials: D
authors.lastname: Zheng
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Mei
authors.initials: M
authors.lastname: Wang
authors.forename: Shengda
authors.initials: S
authors.lastname: Ding
authors.forename: Chengbing
authors.initials: C
authors.lastname: Ma
authors.forename: Marcetta Y
authors.initials: MY
authors.lastname: Darensbourg
authors.forename: Michael B
authors.initials: MB
authors.lastname: Hall
authors.forename: Licheng
authors.initials: L
authors.lastname: Sun
mesh_terms: D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism*; D058085:Iron Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D011789:Quantum Theory
chemical_list: D058085:Iron Compounds; D007506:Iron-Sulfur Proteins; C118830:iron hydrogenase; D006864:Hydrogenase