Reactivity of Aqueous Fe(IV) in Hydride and Hydrogen Atom Transfer Reactions

Pestovsky, Oleg; Bakač, Andreja

doi:10.1021/ja0457112

Cited by 269 publications

(265 citation statements)

References 52 publications

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“…Some authors (38)(39)(40)(41) , have developed techniques to determine selectively the presence of [FeO] 2+ or •OH based on the reactivity again a substrate ( Figure 5). (15) .…”

Section: Fe(iv) and Singlet Oxygen In Fenton Reactionmentioning

confidence: 99%

Fenton Reaction Driven by Iron Ligands

Salgado

Melín

Contreras

et al. 2013

J. Chil. Chem. Soc.

107

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One of the most important sources of reactive oxygen species (ROS) in biological systems is the Fenton reaction. In this, the Fe 2+ or Fe 3+ reacts with H 2 O 2 to produce ROS as the hydroxyl radical (•OH), superoxide radical (O 2 •-) and singlet oxygen ( 1 O 2 ). The main ROS, responsible for the high oxidizing power of the Fenton reaction, is not clear. Some authors claim that the principal reactive species is •OH, while others propose a ferryl specie (Fe 4+ or [FeO] 2+ ) (1,2) . Recently, have been proposed that the kind of reaction species produced depends mainly of pH and the iron composition of the coordination sphere. This is highlighted for Fe 3+ , because in mono and (some) bis-complexes Fe 3+ is reduced to Fe 2+ and there are some positions occupied by water or hydroxide ligands, readily to be exchanged by H 2 O 2 . On the other hand, in tris-complexes there are not any positions occupied by water or hydroxide, avoiding the formation of peroxo-complexes, necessary for Fenton or Fenton like reaction.The 1,2-dihydroxybenzenes (DHBs) have been described as modulators of Fenton reaction. The DHBs driven Fenton reaction have been used for environmental applications as an advanced oxidation process. Furthermore, these systems participate in different biological process, as the wood biodegradation by fungi and oxidative stress in neurodegenerative diseases.In this review, the effect of 1,2-dihydroxybenzenes on the activated species production by the Fenton and Fenton like reaction will be discussed and its participation in different systems.

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“…Some authors (38)(39)(40)(41) , have developed techniques to determine selectively the presence of [FeO] 2+ or •OH based on the reactivity again a substrate ( Figure 5). (15) .…”

Section: Fe(iv) and Singlet Oxygen In Fenton Reactionmentioning

confidence: 99%

Fenton Reaction Driven by Iron Ligands

Salgado

Melín

Contreras

et al. 2013

J. Chil. Chem. Soc.

107

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“…DFT calculations [38,64] and first-principles molecular dynamics [64][65][66] 2+ with O 3 in acidic aqueous solution, and it has been found to be stable over a period of about 10 seconds. [67][68][69] To date, this is the only known synthetic S = 2 ferryl complex. Buda et al [38,41] and Louwerse and Baerends [46] presented detailed analyses of the electronic structure of this complex and of the factors governing its reactivity in hydrogen abstraction from methane and methanol.…”

Section: Introductionmentioning

confidence: 99%

The Role of Equatorial and Axial Ligands in Promoting the Activity of Non‐Heme Oxidoiron(IV) Catalysts in Alkane Hydroxylation

2007

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Keywords: Density functional calculations / Fenton reaction / Alkanes / Hydroxylation / High-valent oxidoiron(IV) systems / Push effectThe key electronic structural feature of the FeO 2+ moiety, which determines its activity as an alkane hydroxylation catalyst, is the presence of low-lying acceptor orbitals, namely the 3σ* 3d z 2-2p z antibonding orbital. Both the energetic position of this orbital and the spin state of the system (which in turn also affects the 3σ* energy) depend on the surrounding ligands. We present results of density functional theory (DFT) calculations performed on a series of gas-phase complexes of2+ by substitution of ligand water molecules with L = NH 3 , CH 3 CN, H 2 S and BF 3 . The calculations reveal that the high-spin (quintet) state is favoured by the weaker σ-donating equatorial ligands, which is consistent with the literature. The high-spin configuration is more reactive because of significant exchange stabilisation of the crucial 3σ*Ȇ orbital. Once the

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“…Much less is known regarding the reactivity of synthetic quintet oxidoiron compounds, and at present pentaaqua oxidoiron [FeO(H 2 O) 5 ] 2+ , which was obtained by reaction of O 3 and aqueous Fe II , [34][35][36] is the only compound from this category which has been fully characterised chemically and spectroscopically. This species was found to be stable over a period of about 10 seconds, and to behave as a strong oxidant acting in both one-electron hydrogen abstractions and two-electron oxidations of alcohols to ketones.…”

Section: Introductionmentioning

confidence: 99%

“…This species was found to be stable over a period of about 10 seconds, and to behave as a strong oxidant acting in both one-electron hydrogen abstractions and two-electron oxidations of alcohols to ketones. [35] [FeO(H 2 O) 5 ] 2+ has also been proposed as a possible active species in organic reactions catalysed by the Fenton reagent, aqueous H 2 O 2 /Fe II . [8,25,[37][38][39][40][41] We have recently presented a study of the relation between reactivity, spin state and electronic structure of oxido-Fe IV complexes derived from [FeO(H 2 O) 5 ]…”

Section: Introductionmentioning

confidence: 99%

The EDTA Complex of Oxidoiron(IV) as Realisation of an Optimal Ligand Environment for High Activity of FeO²⁺

Bernasconi

Baerends

2008

Eur J Inorg Chem

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A prerequisite for the high activity of the FeO2+ moiety as a hydroxylation agent is that its ligand environment stabilizes the 3σ*↑LUMO, which dominates the reactivity of this system. Features in the ligand environment that promote the reactivity of FeO2+ are: weak equatorial ligand field to obtain a quintet ground state that stabilizes the unoccupied 3σ*↑; weak axial ligand field to stabilize the 3σ*↑; a positive overall charge to lower the 3σ*↑. Generalised gradient‐corrected Density Functional Theory (DFT) calculations for the series of oxidoiron compounds of composition [FeO·EDTAHn](n–2)+, with n = 0, 1, 2, 3, 4, show that in particular the complex with n = 4 (charge +2) realises such an environment. Hypothetically, these species may appear as intermediates in the degradation of EDTA and related organics in aerated aqueous FeII/EDTA solutions. A strong dependence of the C–H activation properties in the hydroxylation of methane on the overall charge of yielding the lowest C–H dissociation barriers. In the n = 4 case, C–H dissociation occurs with anactivation energy of ca. 7 kJ mol–1, which is below the value computed for the corresponding reaction catalysed by [FeO(H2O)5]2+ (23 kJ mol–1). This enhanced catalytic activity is explained by EDTAHn(2–n)– satisfying the listed requirements for an effective ligand, in particular by the very weak axial coordination by the EDTA nitrogen atoms due to large Fe–N distances.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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Reactivity of Aqueous Fe(IV) in Hydride and Hydrogen Atom Transfer Reactions

Cited by 269 publications

References 52 publications

Fenton Reaction Driven by Iron Ligands

Fenton Reaction Driven by Iron Ligands

The Role of Equatorial and Axial Ligands in Promoting the Activity of Non‐Heme Oxidoiron(IV) Catalysts in Alkane Hydroxylation

The EDTA Complex of Oxidoiron(IV) as Realisation of an Optimal Ligand Environment for High Activity of FeO²⁺

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Reactivity of Aqueous Fe(IV) in Hydride and Hydrogen Atom Transfer Reactions

Cited by 269 publications

References 52 publications

Fenton Reaction Driven by Iron Ligands

Fenton Reaction Driven by Iron Ligands

The Role of Equatorial and Axial Ligands in Promoting the Activity of Non‐Heme Oxidoiron(IV) Catalysts in Alkane Hydroxylation

The EDTA Complex of Oxidoiron(IV) as Realisation of an Optimal Ligand Environment for High Activity of FeO2+

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The EDTA Complex of Oxidoiron(IV) as Realisation of an Optimal Ligand Environment for High Activity of FeO²⁺