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Directing a Non‐Heme Iron(III)‐Hydroperoxide Species on a Trifurcated Reactivity Pathway
Author(s) -
Wegeberg Christina,
Lauritsen Frants R.,
Frandsen Cathrine,
Mørup Steen,
Browne Wesley R.,
McKenzie Christine J.
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201704615
Subject(s) - heme , reactivity (psychology) , chemistry , biochemistry , medicine , enzyme , pathology , alternative medicine
The reactivity of [Fe III (tpena)] 2+ (tpena= N , N , N′ ‐tris(2‐pyridylmethyl)ethylenediamine‐ N ′‐acetate) as a catalyst for oxidation reactions depends on its ratio to the terminal oxidant H 2 O 2 and presence or absence of sacrificial substrates. The outcome can be switched between: 1) catalysed H 2 O 2 disproportionation, 2) selective catalytic oxidation of methanol or benzyl alcohol to the corresponding aldehyde, or 3) oxidative decomposition of the tpena ligand. A common mechanism is proposed involving homolytic O−O cleavage in the detected transient purple low‐spin ( S = 1 / 2 ) [(tpenaH)Fe III O−OH] 2+ . The resultant iron(IV) oxo and hydroxyl radical both participate in controllable hydrogen‐atom transfer (HAT) reactions. Consistent with the presence of a weaker σ‐donor carboxylate ligand, the most pronounced difference in the spectroscopic properties of [Fe(OOH)(tpenaH)] 2+ and its conjugate base, [Fe(OO)(tpenaH)] + , compared to non‐heme iron(III) peroxide analogues supported by neutral multidentate N‐only ligands, are slightly blue‐shifted maxima of the visible absorption band assigned to ligand‐to‐metal charge‐transfer (LMCT) transitions and, corroborating this, lower Fe III /Fe II redox potentials for the pro‐catalysts.