Hidden radical reactivity of the [FeO]2+ group in the H-abstraction from methane: DFT and CASPT2 supported mechanism by the example of model iron (hydro)oxide species

Kovalskii, Viktor Yu.; Shubin, A. A.; Chen, Y.; Ovchinnikov, Dmitry A.; Ruzankin, Sergey Ph.; Hasegawa, Jun‐ya; Zilberberg, Igor L.; Parmon, Valentin N.

doi:10.1016/j.cplett.2017.05.002

Cited by 11 publications

(6 citation statements)

References 26 publications

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“…Some authors also reported that a stable nonradical (and so lower activity) terminal oxygen center may possess radical-like reactivity toward C−H/C�C bond activation due to a low-lying excited radicaloid oxyl state. 49 Our results are consistent with the above since methanol production at a higher temperature in Fe-MOR/8.4 (second step mass spectrometry signal evolution) corresponds to its appearance in Fe-MOR/14.6 containing Fe(III)−OH sites as a major species. The Fe(III)− OH sites were previously confirmed as the sites highly active in NO oxidation at room temperature [Figure 1D].…”

Section: ■ Results and Discussionsupporting

confidence: 92%

Oxygen Splitting and Methane Oxidation over Fe-Mordenite: Insight by the Operando 2D COS UV–Vis–NIR–IR Approach

Tarach,

Sobalska,

Held

et al. 2024

J. Phys. Chem. C

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Activation of molecular oxygen and subsequent oxidation of methane over Fe sites in mordenite zeolites with different content of framework Al atoms were studied in the continuous regime at low temperatures. For this purpose, reactivity tests of methane oxidation by molecular oxygen over iron mordenite zeolites were combined with an operando 2D COS UV−vis−NIR−IR study to analyze the reaction pathway. The transmission spectra in the visible−NIR−IR range of investigated iron mordenites revealed the structural changes of Fe(II) after O 2 treatment and the formation of the spectral features typical for α-O stabilized on iron. Mass spectrometry analysis of gaseous products of the simultaneous interaction of methane and oxygen with iron mordenite revealed the formation of methanol, water, carbon monoxide, and carbon dioxide. Moreover, operando 2D COS UV−vis−NIR−IR also evidenced the presence of formaldehyde, formate, carbon dioxide, and carbon monoxide as products of subsequent methanol oxidation. The differences in the reaction pathway of methane oxidation over Fe-mordenite compared to Fe-ferrierite and Fe-*BEA catalysts reflect unique properties of mordenite topology providing isolated α-oxygens in individual mordenite pockets, although formed by splitting of molecular oxygen by two cooperating iron ions and the nature of adsorption sites in the mordenite matrix.

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Section: ■ Results and Discussionsupporting

confidence: 92%

Oxygen Splitting and Methane Oxidation over Fe-Mordenite: Insight by the Operando 2D COS UV–Vis–NIR–IR Approach

Tarach,

Sobalska,

Held

et al. 2024

J. Phys. Chem. C

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“…The hydroxylation reaction mechanisms, although thoroughly investigated at the DFT level, [188] have not been verified with multireference methods. Only hydrogen abstraction reactions by a few small models (e. g. FeO + and FeO(OH) 2 ) were considered [54,192] . Studies using multireference methods can provide two‐fold benefits.…”

Section: Spin State Energetics In Metalloproteinsmentioning

confidence: 99%

“…Only hydrogen abstraction reactions by a few small models (e. g. FeO + and FeO(OH) 2 ) were considered. [54,192] Studies using multireference methods can provide two-fold benefits. First, they are certainly more accurate than DFT.…”

Section: Spin State Energetics In Metalloproteinsmentioning

confidence: 99%

Ab Initio Methods in First‐Row Transition Metal Chemistry

Feldt

Phung

2022

Eur J Inorg Chem

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Molecules containing 3d transition metals (TMs) are usually associated with versatile reactivity, partly due to their complicated electronic structures involving multiple close‐lying spin states. An accurate description of different electronic states is notoriously difficult and still a challenge for computational methodologies. Density functional theory, although repeatedly shown to give less reliable results for near‐degeneracy problems, remains the workhorse to explore the reactivity of TM complexes. Ab initio wavefunction theory has been lagging behind due to its high computational cost. However, tremendous efforts have been put to improve their applicability over the past few years, particularly local coupled cluster and low‐scaling multireference methods. In this mini‐review, we highlight major advancements of these ab initio techniques and discuss their recent applications in the calculations of spin state energetics of first‐row TM complexes, ranging from spin crossover compounds and metalloproteins to biomimetic complexes capable of activating C−H bonds.

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“…The only way to arrange such an approach of water molecule is to adsorb it first on the neighboring metal cation (Figure 4(A)) to avoid undesired interaction with hydroxyl group on Fe1. When oxyl oxygen in the HOFe IV O• moiety abstracts proton from adsorbed water molecule, two hydroxyl groups appear on metal sites (Figure 4(C)), rather than the FeOH moiety and free OH radical as it might be expected for the water oxidation route by analogy with the abstraction of hydrogen from methane on oxyl oxygen producing methyl radical [21]. Therefore, the low barrier process (9 kcal/mol) has to be assigned to the dissociative adsorption or hydroxylation.…”

Section: Resultsmentioning

confidence: 99%

The Fe^IVO• oxyl unit as a key intermediate in water oxidation on the Fe^IIIhydroxide: DFT predictions

Shubin

Kovalskii

Ruzankin

et al. 2021

Int J of Quantum Chemistry

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The O O coupling process in water oxidation on the gamma FeOOH hydroxide catalyst is simulated by means of density functional theory using model iron cubane cluster Fe 4 O 4 (OH) 4. A key reactive intermediate is proposed to be the HO Fe IV O• oxyl unit with terminal oxo radical. The "initial" vertex Fe III (OH) moiety forms this intermediate at the calculated overpotential of 0.93 V by adding one water molecule and withdrawing two proton-electron pairs. The O O coupling goes via water nucleophilic attack on the oxyl oxygen to form the O O bond with a remarkably low barrier of 11 kcal/mol. This process is far more effective than alternative scenario based on direct interaction of two ferryl Fe IV O sites (with estimated barrier of 36 kcal/mol) and is comparable with the coupling between terminal oxo center and three-coordinated lattice oxo center (12 kcal/mol barrier). The process of hydroxylation of terminal oxygen inhibits the O O coupling. Nevertheless, being more effective for ferryl oxygen, the hydroxylation in fact enhances selectivity of the O O coupling initiated by the oxyl oxygen.

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Hidden radical reactivity of the [FeO]2+ group in the H-abstraction from methane: DFT and CASPT2 supported mechanism by the example of model iron (hydro)oxide species

Cited by 11 publications

References 26 publications

Oxygen Splitting and Methane Oxidation over Fe-Mordenite: Insight by the Operando 2D COS UV–Vis–NIR–IR Approach

Oxygen Splitting and Methane Oxidation over Fe-Mordenite: Insight by the Operando 2D COS UV–Vis–NIR–IR Approach

Ab Initio Methods in First‐Row Transition Metal Chemistry

The Fe^IVO• oxyl unit as a key intermediate in water oxidation on the Fe^IIIhydroxide: DFT predictions

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Hidden radical reactivity of the [FeO]2+ group in the H-abstraction from methane: DFT and CASPT2 supported mechanism by the example of model iron (hydro)oxide species

Cited by 11 publications

References 26 publications

Oxygen Splitting and Methane Oxidation over Fe-Mordenite: Insight by the Operando 2D COS UV–Vis–NIR–IR Approach

Oxygen Splitting and Methane Oxidation over Fe-Mordenite: Insight by the Operando 2D COS UV–Vis–NIR–IR Approach

Ab Initio Methods in First‐Row Transition Metal Chemistry

The FeIVO• oxyl unit as a key intermediate in water oxidation on the FeIIIhydroxide: DFT predictions

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The Fe^IVO• oxyl unit as a key intermediate in water oxidation on the Fe^IIIhydroxide: DFT predictions