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Hydroxylation of Aromatics by H 2 O 2 Catalyzed by Mononuclear Non-heme Iron Complexes: Role of Triazole Hemilability in Substrate-Induced Bifurcation of the H 2 O 2 Activation Mechanism
Rieske dioxygenases are metalloenzymes capable of achieving cis-dihydroxylation of aromatics under mild conditions using O and a source of electrons. The intermediate responsible for this reactivity is proposed to be a cis-Fe (O)(OH) moiety. Molecular models allow the generation of a Fe (OOH) specie...
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Published in: | Chemistry : a European journal 2020-01, Vol.26 (3), p.659-668 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Rieske dioxygenases are metalloenzymes capable of achieving cis-dihydroxylation of aromatics under mild conditions using O
and a source of electrons. The intermediate responsible for this reactivity is proposed to be a cis-Fe
(O)(OH) moiety. Molecular models allow the generation of a Fe
(OOH) species with H
O
, to yield a Fe
(O)(OH) species with tetradentate ligands, or {Fe
(O); OH
} pairs with pentadentate ones. We have designed a new pentadentate ligand, mtL
, bearing a labile triazole, to generate an "in-between" situation. Two iron complexes, [(mtL
)FeCl](PF
) and [(mtL
)Fe(OTf)
]), were obtained and their reactivity towards aromatic substrates was studied in the presence of H
O
. Spectroscopic and kinetic studies reflect that triazole is bound at the Fe
state, but decoordinates in the Fe
(OOH). The resulting [(mtL
)Fe
(OOH)(MeCN)]
then lies on a bifurcated decay pathway (end-on homolytic vs. side-on heterolytic) depending on the addition of aromatic substrate: in the absence of substrate, it is proposed to follow a side-on pathway leading to a putative (N
)Fe
(O)(OH), while in the presence of aromatics it switches to an end-on homolytic pathway yielding a {(N
)Fe
(O); OH
} reactive species, through recoordination of triazole. This switch significantly impacts the reaction regioselectivity. |
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ISSN: | 0947-6539 1521-3765 |
DOI: | 10.1002/chem.201903239 |