Statistical analysis of C–H activation by oxo complexes supports diverse thermodynamic control over reactivity

Schneider, Joseph; Goetz, McKenna K.; Anderson, John S.

doi:10.1039/d0sc06058e

Cited by 43 publications

(75 citation statements)

References 106 publications

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“…Although strong Brønsted-Evans-Polanyi (BEP) relations between reaction energies and barrier heights have been invoked 68,71 , we observe these to only hold for HAT and not for oxo formation, consistent with prior work 68,73,116 (Supporting Information Figures S41 and S42).…”

Section: Catalytic Cycles Of Pareto Optimal Catalystssupporting

confidence: 85%

New Strategies for Direct Methane-to-Methanol Conversion from Active Learning Exploration of 16 Million Catalysts

Nandy

Duan

Conrad

et al. 2022

Preprint

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Despite decades of effort, no earth abundant homogeneous catalysts have been discovered that can selectively oxidize methane to methanol. We exploit active learning to simultaneously optimize methane activation and methanol release calculated with machine learning (ML)-accelerated density functional theory (DFT) in a space of 16M candidate catalysts with novel macrocycles. By constructing these macrocycles from fragments inspired by synthesized compounds, we ensure synthetic realism in our computational search. Our large-scale search reveals that low spin Fe(II) compounds paired with strong field (e.g. P or S-coordinating) ligands have the best energetic tradeoff between hydrogen atom transfer (HAT) and methanol release. This observation is distinct from prior efforts that have focused on high spin Fe(II) with weak field ligands. By decoupling equatorial and axial ligand effects, we determine that negatively charged axial ligands are critical for more rapid release of methanol and, higher valency metals (i.e., M(III) vs M(II)) are unlikely to be suitable for methanol release. With full characterization of barrier heights, we confirmed that optimizing for HAT did not lead to large oxo formation barriers. Energetic span analysis revealed designs for an intermediate spin Mn(II) catalyst and a low spin Fe(II) catalyst that would lead to good turnover frequencies. This active learning approach is expected to be beneficial for search of large catalyst spaces where no prior designs have been identified and where linear scaling relationships between reaction energies or barriers may be limited or unknown.

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Section: Catalytic Cycles Of Pareto Optimal Catalystssupporting

confidence: 85%

New Strategies for Direct Methane-to-Methanol Conversion from Active Learning Exploration of 16 Million Catalysts

Nandy

Duan

Conrad

et al. 2022

Preprint

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“…Anderson's model, adapted to the prediction of relative HAA barriers, is defined as follows: 28 ∆∆𝐺 ≠ = 0.31 × ∆∆𝐺 0 + 0.07 × ∆∆𝐺 0,𝑃𝑇1 + 0.12 × ∆∆𝐺 0,𝐸𝑇1…”

Section: Most Of the Points Of The Mayer Set Inmentioning

confidence: 99%

“…1). Recently, Anderson experimentally investigated correlations between thermodynamics and second-order rate constants k2 for a set of H-atom abstraction reactions involving one Co III O acceptor and four organic H-atom donors, 28 while Borovik performed a similar experimental study on a set of H-atom abstraction reactions between one Mn IV O acceptor and ten organic H-atom donors. 29 In both studies, they ascertained the importance of off-diagonal terms from the thermocycle of Scheme 1, following our study on asynchronicity.…”

Section: Introductionmentioning

confidence: 99%

“…To further elaborate the importance of frustration σ in reactivity as compared to two other thermodynamic components -asynchronicity and ∆𝐺 0 , let us now consider six sets of metal-oxo mediated HAA reactions taken from literature (four sets are experimental and named according to the corresponding authors: Anderson, 28 Borovik, 29 Tolman, 31 Mayer 32 and two remaining are computational studied earlier by us: TMC 24 The fact that frustration has an effect on ∆𝐺 ≠ implies that it also must have an effect on the character of the TS as well. For the TMC set, we demonstrated in ref.…”

Section: Introductionmentioning

confidence: 99%

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H-atom Abstraction Reactivity through the Lens of Asynchronicity and Frustration with their Counter-Acting Effects on Barriers

Maldonado-Domínguez

Srnec

2022

Preprint

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Hydrogen atom abstraction (HAA) is central to life and its importance in synthetic chemistry continues to grow. Enzymes rely on HAA to trigger life-sustaining reaction cascades, and greener synthetic routes are attainable by in situ capture of the carbon-centered radicals generated by HAA. Despite the potential of HAA for the diversification of molecular complexity and the late-stage functionalization of bioactive compounds, readily applicable and reliable models translating experimentally or computationally accessible thermodynamic quantities into relative free energy barriers are missing. In this work, we discovered a complete thermodynamic basis for the description of HAA reactivity, which consists of three components. Besides, the traditional linear free energy relationship and the recently introduced factor of asynchronicity (Srnec et al, PNAS 2018, 115, E10287-E10294), we present the third thermodynamic component of H-atom abstraction reactions – factor of frustration that arises from the dissimilarity of the species competing over a hydrogen atom in their overall ability to acquire electron and proton. Incorporating these non-classical descriptors into a Marcus-type model, the approach herein presented allows nearly quantitative prediction of relative barriers in six sets of metal-oxo-mediated HAA reactions, outperforming existing methods even in a stringent test with >200 computational HAA reactions.

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“…This overall observation is satisfyingly consistent with a recent statistical analysis on the rates of reaction of a broad family of transition metal-oxo complexes from our group. 94 Interestingly, however, the model provides a more nuanced picture of this trend. When either DepthPT or DepthET becomes small, the reaction becomes more sensitive to this lower depth, as illustrated by the decreased curvature of the upper-left and bottom right corners of Figure 7A.…”

Section: Simulations Support Trends With Off-diagonal Thermodynamic Valuesmentioning

confidence: 99%

Reconciling Imbalanced Transition State Effects with Nonadiabatic CPET Reactions

Schneider

Goetz

Anderson

2021

Preprint

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Recently there have been several experimental demonstrations of how concerted proton electron transfer (CPET) reaction rates are affected by off-main-diagonal energies, namely the stepwise thermodynamic parameters ΔG°PT and ΔG°ET. Semi-classical structure-activity relationships have been invoked to rationalize these asynchronous linear free energy relation-ships despite the widely acknowledged importance of quantum effects such as nonadiabaticity and tunneling in CPET reactions. Here we report variable temperature kinetic isotope effect data for the asynchronous reactivity of a terminal Co-oxo complex with C–H bonds and find evidence of substantial quantum tunneling which is inconsistent with semi-classical models even when including tunneling corrections. This indicates substantial nonadiabatic tunneling in the CPET reactivity of this Co-oxo complex and further motivates the need for a quantum mechanical justification for the in-fluence of ΔG°PT and ΔG°ET on reactivity. To reconcile this dichotomy, we include ΔG°PT and ΔG°ET in nonadiabatic models of CPET by having them influence the anharmonicity and depth of the proton potential energy surfaces, which we approximate as Morse potentials. With this model we independently reproduce the dominant trend with ΔG°PT + ΔG°ET as well as the subtle effect of ΔG°PT − ΔG°ET (or η) in a nonadiabatic framework. The primary route through which these off-diagonal energies influence rates is through vibronic coupling. Our results reconcile predictions from semiclassical transition state theory with models that treat proton transfer quantum mechanically in CPET reactivity and suggest that similar treatments may be possible for other nonadiabatic processes.

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Statistical analysis of C–H activation by oxo complexes supports diverse thermodynamic control over reactivity

Abstract: Transition metal oxo species are key intermediates for the activation of strong C‒H bonds. As such, there has been interest in understanding which structural or electronic parameters of metal oxo...

Cited by 43 publications

References 106 publications

New Strategies for Direct Methane-to-Methanol Conversion from Active Learning Exploration of 16 Million Catalysts

New Strategies for Direct Methane-to-Methanol Conversion from Active Learning Exploration of 16 Million Catalysts

H-atom Abstraction Reactivity through the Lens of Asynchronicity and Frustration with their Counter-Acting Effects on Barriers

Reconciling Imbalanced Transition State Effects with Nonadiabatic CPET Reactions

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