1419075-07-2Relevant articles and documents
Hydroxylation of Aromatics by H2O2 Catalyzed by Mononuclear Non-heme Iron Complexes: Role of Triazole Hemilability in Substrate-Induced Bifurcation of the H2O2 Activation Mechanism
Rebilly, Jean-No?l,Zhang, Wenli,Herrero, Christian,Dridi, Hachem,Sénéchal-David, Katell,Guillot, Régis,Banse, Frédéric
, p. 659 - 668 (2020)
Rieske dioxygenases are metalloenzymes capable of achieving cis-dihydroxylation of aromatics under mild conditions using O2 and a source of electrons. The intermediate responsible for this reactivity is proposed to be a cis-FeV(O)(OH) moiety. Molecular models allow the generation of a FeIII(OOH) species with H2O2, to yield a FeV(O)(OH) species with tetradentate ligands, or {FeIV(O); OH.} pairs with pentadentate ones. We have designed a new pentadentate ligand, mtL42, bearing a labile triazole, to generate an “in-between” situation. Two iron complexes, [(mtL42)FeCl](PF6) and [(mtL42)Fe(OTf)2]), were obtained and their reactivity towards aromatic substrates was studied in the presence of H2O2. Spectroscopic and kinetic studies reflect that triazole is bound at the FeII state, but decoordinates in the FeIII(OOH). The resulting [(mtL42)FeIII(OOH)(MeCN)]2+ 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 (N4)FeV(O)(OH), while in the presence of aromatics it switches to an end-on homolytic pathway yielding a {(N5)FeIV(O); OH.} reactive species, through recoordination of triazole. This switch significantly impacts the reaction regioselectivity.
Iron coordination chemistry with new ligands containing triazole and pyridine moieties. comparison of the coordination ability of the N-donors
Ségaud, Nathalie,Rebilly, Jean-No?l,Sénéchal-David, Katell,Guillot, Régis,Billon, Laurianne,Baltaze, Jean-Pierre,Farjon, Jonathan,Reinaud, Olivia,Banse, Frédéric
supporting information, p. 691 - 700 (2013/03/13)
We report the synthesis, characterization, and solution chemistry of a series of new FeII complexes based on the tetradentate ligand N-methyl-N,N′-bis(2-pyridyl-methyl)-1,2-diaminoethane or the pentadentate ones N,N′,N′-tris(2-pyridyl-methyl)-1,2-diaminoethane and N,N′,N′-tris(2-pyridyl-methyl)-1,3-diaminopropane, modified by propynyl or methoxyphenyltriazolyl groups on the amino functions. Six of these complexes are characterized by X-ray crystallography. In particular, two of them exhibit an hexadentate coordination environment around FeII with two amino, three pyridyl, and one triazolyl groups. UV-visible and cyclic voltammetry experiments of acetonitrile solutions of the complexes allow to deduce accurately the structure of all FeII species in equilibrium. The stability of the complexes could be ranked as follows: [L5Fe II-py]2+ > [L5FeII-Cl] + > [L5FeII-triazolyl]2+ > [L5FeII-(NCMe)]2+, where L5 designates a pentadentate coordination sphere composed of the two amines of ethanediamine and three pyridines. For complexes based on propanediamine, the hierarchy determined is [L5FeII-Cl]+ > [L5FeII(OTf)]+ > [L5Fe II-(NCMe)]2+, and no ligand exchange could be evidenced for [L5FeII-triazolyl]2+. Reactivity of the [L5FeII-triazolyl]2+ complexes with hydrogen peroxide and PhIO is similar to the one of the parent complexes that lack this peculiar group, that is, generation of FeIII(OOH) and Fe IV(O), respectively. Accordingly, the ability of these complexes at catalyzing the oxidation of small organic molecules by these oxidants follows the tendencies of their previously reported counterparts. Noteworthy is the remarkable cyclooctene epoxidation activity by these complexes in the presence of PhIO.
