Direct Dynamics Trajectories Reveal Nonstatistical Coordination Intermediates and Demonstrate that σ and π-Coordination Are Not Required for Rhenium(I)-Mediated Ethylene C–H Activation

Ye, Bo; Schouten, Anna O.; Ess, Daniel H.

doi:10.1021/jacs.1c01709

Cited by 21 publications

(21 citation statements)

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“…For example, in the C–H activation between methane and [Cp*(PMe 3 )Ir III (CH 3 )] + , as well as the β-hydrogen transfer for [Cp*Rh III (Et)(ethylene)] + , despite a fully characterized intermediate on each of the DFT potential energy landscapes direct dynamics simulations revealed that the intermediate is either sometimes or always skipped due to dynamical coupling of multiple reaction steps through dynamic matching or the lack of IVR. We also discovered dynamic effects, specifically dynamical pathway branching, in the reaction between Tp(NO)(PR 3 )W and benzene as well as Cp(PMe 3 ) 2 Re and ethylene . Related organometallic dynamic effects were reported for hydrogenation reaction steps of (Cl)(CO)(PH 3 )Ru II (H)(H 2 )(C 2 H 4 ), Rh-carbenoid C–H bond insertion, and Au/Ag arene C–H functionalization .…”

Section: Resultsmentioning

confidence: 74%

“…We also discovered dynamic effects, specifically dynamical pathway branching, in the reaction between Tp(NO)(PR 3 )W and benzene 40 as well as Cp(PMe 3 ) 2 Re and ethylene. 41 Related organometallic dynamic effects were reported for hydrogenation reaction steps of (Cl 42 Rh-carbenoid C−H bond insertion, 43 and Au/Ag arene C−H functionalization. 44 There are also recent reports of dynamic effects for Ru geminal hydroboration, 45 Fe Diels− Alder reactions, 46 Fe arene amination, 47 and Pd transmetalation.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination during Au- and Pd-Catalyzed Diol Cyclizations

2021

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Au and Pd complexes have emerged as highly effective π-bond cyclization catalysts to construct heterocycles. These cyclization reactions are generally proposed to proceed through multistep addition–elimination mechanisms involving Au– or Pd–alkyl intermediates. For Au- and Pd-catalyzed allylic diol cyclizations, while the density functional theory (DFT) potential energy surface landscapes show a stepwise sequence of alkoxylation π-addition, proton transfer, and water elimination, quasiclassical direct dynamics simulations reveal dynamical mechanisms that depend on the metal center. For Au, trajectories reveal that after π-addition the Au–alkyl intermediate is always skipped because addition is dynamically coupled with proton transfer and water elimination. In contrast, for Pd catalysis, due to differences in the potential energy landscape shape, only about half of trajectories show Pd–alkyl intermediate skipping. The other half of the trajectories show the traditional two-step mechanism with the intervening Pd–alkyl intermediate. Overall, this work reveals that interpretation of a DFT potential energy landscape can be insufficient to understand catalytic intermediates and mechanisms and that atomic momenta through dynamics simulations are needed to determine if an intermediate is genuinely part of a catalytic cycle.

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Section: Resultsmentioning

confidence: 74%

Section: ■ Results and Discussionmentioning

confidence: 99%

Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination during Au- and Pd-Catalyzed Diol Cyclizations

2021

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“…Figure 11 shows a potential-energy landscape and the structures located with static DFT calculations. 2 From an ethylene σ-coordination structure, there is branching with two pathways, one pathway leading to the Re vinyl hydride and the other leading to the Re(η 2 -ethylene) π-complex. While these two pathways possibly explain the reaction selectivity, CCSD(T) calculations showed that a transition-state theory approach did not match the experimental selectivity.…”

Section: Making Non-irc Connectionsmentioning

confidence: 99%

“…Quasiclassical direct dynamics trajectories provided a more reasonable selectivity model and revealed dynamically connected reaction pathways. 2 For this reaction, trajectories were initiated at both transition-state structures as well as structures identified using metadynamics simulations. Trajectories resulted in direct formation of either the Re vinyl hydride I or to the πcomplex II.…”

Section: Making Non-irc Connectionsmentioning

confidence: 99%

Quasiclassical Direct Dynamics Trajectory Simulations of Organometallic Reactions

Ess

2021

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Homogeneous metal-mediated organometallic reactions represent a very large and diverse reaction class. Density functional theory calculations are now routinely carried out and reported for analyzing organometallic mechanisms and reaction pathways. While density functional theory calculations are extremely powerful to understand the energy and structure of organometallic reactions, there are several assumptions in their use and interpretation to define reaction mechanisms and to analyze reaction selectivity. Almost always it is assumed that potential energy structures calculated with density functional theory adequately describe mechanisms and selectivity within the framework of statistical theories, for example, transition state theory and RRKM theory. However, these static structures and corresponding energy landscapes do not provide atomic motion information during reactions that could reveal nonstatistical intermediates without complete intramolecular vibrational redistribution and nonintrinsic reaction coordinate (non-IRC) pathways. While nonstatistical intermediates and non-IRC reaction pathways are now relatively well established for organic reactions, these dynamic effects have heretofore been highly underexplored in organometallic reactions. Through a series of quasiclassical density functional theory direct dynamics trajectory studies, my group has recently demonstrated that dynamic effects occur in a variety of fundamental organometallic reactions, especially bond activation reactions. For example, in the C−H activation reaction between methane and [Cp*(PMe 3 )Ir III (CH 3 )] + , while the density functional theory energy landscape showed a two-step oxidative cleavage and reductive coupling mechanism, trajectories revealed a mixture of this two-step mechanism and a dynamic onestep mechanism that skipped the [Cp*(PMe 3 )Ir V (H)(CH 3 ) 2 ] + intermediate. This study also showed that despite a methane σcomplex being located on the density functional theory surface before oxidative cleavage and after reductive coupling, this intermediate is always skipped and should not be considered an intermediate during reactive trajectories. For non-IRC reaction pathways, quasiclassical direct dynamics trajectories showed that for the isomerization of [Tp(NO)(PMe 3 )W(η 2 -benzene)] to [Tp(NO)(PMe 3 )W(H)(Ph)], there are many dynamic reaction pathway connections due to a relatively flat energy landscape and π coordination is not necessary for C−H bond activation through oxidative cleavage. Trajectories also showed that dynamic effects are important in selectivity for ethylene C−H activation versus π coordination in reaction with Cp(PMe 3 ) 2 Re, and trajectories provide a more quantitative model of selectivity than transition state theory. Quasiclassical trajectories examining Au-catalyzed monoallylic diol cyclizations showed dynamic coupling of several reaction steps that include alkoxylation π bond addition, proton shuttling, and water elimination reaction steps. Over...

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“…The reactivity of energetically non-equilibrated intermediates (kinetically activated, "hot" intermediates) has received significant attention recently. 24,26 It has been shown that dynamic effects and the amount of excess energy and how it is distributed can control the reactivity of intermediates in solution, 27,28 in organometallic reactions 29,30 and in enzymes. [31][32][33] Here we show that the high chemoselectivity in metal-oxo mediated alkene oxidation by iron porphyrin-type catalysts is a consequence of the radical's dynamic behavior in its kinetically (vibrational) activated state.…”

Section: Introductionmentioning

confidence: 99%

Enzymatic control over reactive intermediates enables direct oxidation of alkenes to carbonyls by a P450 iron-oxo species

Soler

Gergel

Hammer

et al. 2022

Preprint

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The oxidation of alkenes by high-valent iron-oxo active species normally leads to the formation of the corresponding epoxides. Rarely, carbonyl compounds are observed as a side product of the reaction. However, the selective formation of carbonyl compounds from alkenes using iron-oxo species and small molecule catalysts has not yet been achieved. Recently, a new P450-based enzyme (aMOx) has been engineered through laboratory directed evolution to directly oxidize styrenes to their corresponding aldehydes. This transformation uses an enzymatic iron-oxo species as catalytic oxidant and generates aldehydes with high activity and selectivity while suppressing epoxidation. Here, we combine extensive computational modelling together with experimental mechanistic investigations to study the reaction mechanism and unravel the molecular basis behind the selectivity achieved by the laboratory evolved aMOx enzyme. We found that alkene epoxidation and carbonyl formation pathways diverge from a common covalent radical intermediate generated after the first C–O bond formation. Although both pathways are accessible and very similar in energy, intrinsic dynamic effects determine the strong preference for epoxidation. We discovered that aMOx overrides these intrinsic dynamic preferences by controlling the accessible conformations of the covalent radical intermediate. This disfavors epoxidation and facilitates the formation of a key carbocation intermediate that generates the aldehyde product through a fast 1,2-hydride migration. Computations predicted that the hydride migration is stereoselective due to the conformational control over the intermediate species when formed in the enzyme active site. These predictions were corroborated by experiments using deuterated styrene substrates, which proved that the hydride migration is cis- and enantioselective. Our results demonstrate that directed evolution tailored a highly specific active site that imposes strong steric control over key fleeting biocatalytic intermediates, which is essential for accessing the carbonyl forming pathway and preventing competing epoxidation.

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Direct Dynamics Trajectories Reveal Nonstatistical Coordination Intermediates and Demonstrate that σ and π-Coordination Are Not Required for Rhenium(I)-Mediated Ethylene C–H Activation

Cited by 21 publications

References 74 publications

Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination during Au- and Pd-Catalyzed Diol Cyclizations

Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination during Au- and Pd-Catalyzed Diol Cyclizations

Quasiclassical Direct Dynamics Trajectory Simulations of Organometallic Reactions

Enzymatic control over reactive intermediates enables direct oxidation of alkenes to carbonyls by a P450 iron-oxo species

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