Direct Benzene Hydroxylation with Dioxygen Induced by Copper Complexes: Uncovering the Active Species by DFT Calculations

Borrego, Elena; Tiessler-Sala, Laura; Lázaro, Jesús; Caballero, Ana; Pérez, Pedro J.; Lledós, Agustí

doi:10.1021/acs.organomet.2c00202

Cited by 5 publications

(4 citation statements)

References 48 publications

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“…This unreactivity of qnt 20 toward the oxidation of benzene could be attributed to the lack of oxyl character of the oxygen atom. In the copper complex studied by Lledós et al, the oxygen atom possesses a spin density of 1.18 e/Å 3 , 63 whereas this value for the analogous oxygen in qnt 20 is only 0.094 e/Å 3 .…”

Section: Resultsmentioning

confidence: 93%

“…Lledós and co-workers recently computationally demonstrated that a Cu II (μ–O • )(μ–OH)Cu II complex is capable of oxidizing benzene into phenol in a stoichiometric reaction via the oxygen-rebound mechanism as well as a σ-complex mechanism ( Scheme 2 a). 63 The σ-complex mechanism begins with the attack of an oxyl species on the π system of benzene, leading to the formation of a σ complex. In a subsequent step, a proton shuttle facilitates the transfer of a proton from the ipso carbon to the oxygen, producing phenol.…”

Section: Resultsmentioning

confidence: 99%

“…Scheme 2. Hydroxylation of Benzene into Phenol by a Cu II (μ−O • )(μ−OH)Cu II Complex via Two Different Mechanisms Reported by Lledoś et al63 …”

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confidence: 95%

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DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H₂O₂

Farshadfar,

Laasonen

2024

Inorg. Chem.

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Introduction of oxygen into aromatic C−H bonds is intriguing from both fundamental and practical perspectives. Although the 3d metal-catalyzed hydroxylation of arenes by H 2 O 2 has been developed by several prominent researchers, a definitive mechanism for these crucial transformations remains elusive. Herein, density functional theory calculations were used to shed light on the mechanism of the established hydroxylation reaction of benzene with H 2 O 2 , catalyzed by [Ni II (tepa)] 2+ (tepa = tris[2-(pyridin-2-yl)ethyl]amine). Dinickel(III) bis(μ-oxo) species have been proposed as the key intermediate responsible for the benzene hydroxylation reaction. Our findings indicate that while the dinickel dioxygen species can be generated as a stable structure, it cannot serve as an active catalyst in this transformation. The calculations allowed us to unveil an unprecedented mechanism composed of six main steps as follows: (i) deprotonation of coordinated H 2 O 2 , (ii) oxidative addition, (iii) water elimination, (iv) benzene addition, (v) ketone generation, and (vi) tautomerization and regeneration of the active catalyst. Addition of benzene to oxygen, which occurs via a radical mechanism, turns out to be the rate-determining step in the overall reaction. This study demonstrates the critical role of Ni-oxyl species in such transformations, highlighting how the unpaired spin density value on oxygen and positive charges on the Ni−O • complex affect the activation barrier for benzene addition.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

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DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H₂O₂

Farshadfar,

Laasonen

2024

Inorg. Chem.

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“…[14] Examples of triplet-triplet energy transfer using water as solvent are rare and not well established in organic synthesis. [15] Micelles have been presented as suitable nanoreactors for carrying out a wide range of reactions, [16] particularly transitionmetal-catalysed [17] or cascade type [18] reactions. The array of disclosed works on micellar catalysis demonstrates that micelles not only offer solubility in water, as a more benign solvent, [19] but might also offer additional advantages which are unique and tuneable by careful selection of the employed catalysts, reactants [20] and amphiphiles.…”

Section: Introductionmentioning

confidence: 99%

Facilitating [2+2] Photocycloadditions by Promoting Oxygen Tolerance and Substrate Activation in Water

Kürschner

Brüss

Næsborg

2023

Chemistry A European J

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Micellar photocatalysis has been used to overcome oxygen quenching and enable a [2 + 2] photocycloaddition through triplet-energy transfer in water under aerobic conditions. The cheap and commercially available self-assembling sodium dodecyl sulfate (SDS) micelles were found to increase the oxygen tolerance of a typically oxygen-sensitive reaction. Furthermore, the use of the micellar solution was found to activate α,β-unsaturated carbonyl compounds to energy transfer and allow [2 + 2] photocycloadditions to take place. Our preliminary studies of micellar effects on energytransfer-based reactions demonstrate the reaction between α,β-unsaturated carbonyl compounds and activated alkenes in a mixture of SDS, water and [Ru(bpy) 3 ](PF 6 ) 2 .[a] J.

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Orbital Analysis Captures the Existence of a Mixed‐Valent Cu^III−O−Cu^II Active‐Site and its Role in Water‐Assisted Aliphatic Hydroxylation

Arora,

Rawal,

Gupta

2024

Chemistry A European J

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The Cu−O−Cu core has been proposed as a potential site for methane oxidation in particulate methane monooxygenase. In this work, we used density functional theory (DFT) to design a mixed‐valent CuIII−O−CuII species from an experimentally known peroxo‐dicopper complex supported by N‐donor ligands containing phenolic groups. We found that the transfer of two‐protons and two‐electrons from phenolic groups to peroxo‐dicopper core takes places, which results to the formation of a bis‐μ‐hydroxo‐dicopper core. The bis‐μ‐hydroxo‐dicopper core converts to a mixed‐valent CuIII−O−CuII core with the removal of a water molecule. The orbital and spin density analyses unravel the mixed‐valent nature of CuIII−O−CuII. We further investigated the reactivity of this mixed‐valent core for aliphatic C−H hydroxylation. Our study unveiled that mixed‐valent CuIII−O−CuII core follows a hydrogen atom transfer mechanism for C−H activation. An in‐situ generated water molecule plays an important role in C−H hydroxylation by acting as a proton transfer bridge between carbon and oxygen. Furthermore, to assess the relevance of a mixed‐valent CuIII−O−CuII core, we investigated aliphatic C−H activation by a symmetrical CuII−O−CuII core. DFT results show that the mixed‐valent CuIII−O−CuII core is more reactive toward the C−H bond than the symmetrical CuII−O−CuII core.

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Direct Benzene Hydroxylation with Dioxygen Induced by Copper Complexes: Uncovering the Active Species by DFT Calculations

Cited by 5 publications

References 48 publications

DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H₂O₂

DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H₂O₂

Facilitating [2+2] Photocycloadditions by Promoting Oxygen Tolerance and Substrate Activation in Water

Orbital Analysis Captures the Existence of a Mixed‐Valent Cu^III−O−Cu^II Active‐Site and its Role in Water‐Assisted Aliphatic Hydroxylation

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Direct Benzene Hydroxylation with Dioxygen Induced by Copper Complexes: Uncovering the Active Species by DFT Calculations

Cited by 5 publications

References 48 publications

DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H2O2

DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H2O2

Facilitating [2+2] Photocycloadditions by Promoting Oxygen Tolerance and Substrate Activation in Water

Orbital Analysis Captures the Existence of a Mixed‐Valent CuIII−O−CuII Active‐Site and its Role in Water‐Assisted Aliphatic Hydroxylation

Contact Info

Product

Resources

About

DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H₂O₂

DFT Mechanistic Investigation into Ni(II)-Catalyzed Hydroxylation of Benzene to Phenol by H₂O₂

Orbital Analysis Captures the Existence of a Mixed‐Valent Cu^III−O−Cu^II Active‐Site and its Role in Water‐Assisted Aliphatic Hydroxylation