The reactivity of six Mn^IV–oxo complexes in C–H bond oxidation has been examined using a combination of kinetic experiments and computational methods. Variable-temperature studies of the oxidation of 9,10-dihydroanthracene (DHA) and ethylbenzene by these Mn^IV–oxo complexes yielded activation parameters suitable for evaluating electronic structure computations. Complementary kinetic experiments of the oxidation of deuterated DHA provided evidence for hydrogen-atom tunneling in C–H bond oxidation for all Mn^IV–oxo complexes. These results are in accordance with the Bell model, where tunneling occurs near the top of the transition-state barrier. Density functional theory (DFT) and DLPNO–CCSD(T₁) computations were performed for three of the six Mn^IV–oxo complexes to probe a previously predicted multistate reactivity model. The DFT computations predicted a thermal crossing from the ⁴B₁ ground state to a ⁴E state along the C–H bond oxidation reaction coordinate. DLPNO–CCSD(T₁) calculations further confirm that the ⁴E transition state offers a lower energy barrier, reinforcing the multistate reactivity model for these complexes. We discuss how this multistate model can be reconciled with recent computations that revealed that the kinetics of C–H bond oxidation by this set of Mn^IV–oxo complexes can be well-predicted on the basis of the thermodynamic driving force for these reactions.

中文翻译：

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MnIV-Oxo 配合物的 C-H 键氧化：氢原子隧道效应和多态反应性

结合动力学实验和计算方法，研究了六种 Mn ^IV-氧配合物在 C-H 键氧化中的反应性。对这些 Mn ^IV-氧配合物氧化 9,10-二氢蒽 (DHA) 和乙苯的变温研究产生了适合评估电子结构计算的活化参数。氘代 DHA 氧化的补充动力学实验为所有 Mn ^IV -氧配合物的 C-H 键氧化中的氢原子隧道效应提供了证据。这些结果与贝尔模型一致，其中隧道效应发生在过渡态势垒顶部附近。对六个 Mn ^IV -oxo 配合物中的三个进行了密度泛函理论 (DFT) 和 DLPNO-CCSD(T ₁ ) 计算，以探测先前预测的多态反应性模型。 DFT 计算预测沿着 C-H 键氧化反应坐标从⁴ B ₁基态到⁴ E 态的热交叉。 DLPNO-CCSD(T ₁ )计算进一步证实⁴ E过渡态提供了较低的能垒，增强了这些配合物的多态反应性模型。我们讨论了如何使这种多态模型与最近的计算相一致，这些计算表明可以根据这些反应的热力学驱动力很好地预测这组 Mn ^{IV -氧配合物的 C-H 键氧化动力学。}