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How Accurate is DFT for Iridium-Mediated Chemistry?

机译：DFT对铱介化学的精确度如何？

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Iridium chemistry is versatile and widespread, with superior performance for reaction types such as enantioselective hydrogenation and C-H activation. In order to gain insight into the mechanistic details of such systems, density functional theory (DFT) studies are often employed. But how accurate is DFT for modeling iridium-mediated transformations in solution? We have evaluated how well DFT reproduces the energies and reactivities of 11 iridium-mediated transformations, which were carefully chosen to correspond to elementary steps typically encountered in iridium-catalyzed chemistry (bond formation, isomerization, ligand substitution, and ligand association). Five DFT functionals, B3LYP, PBE, PBE0, M06L, and M11L, were evaluated as-is or in combination with an empirical dispersion correction (D2, D3, or D3BJ), leading to 13 combinations. Different solvent models (IEFPCM and SMD) were evaluated, alongside various correction terms such as big basis set effects, counterpoise corrections, frequency scaling, and different entropy modifications. PBE-D type functionals are clearly superior, with PBE-D2,IEFPCM providing average absolute errors for uncorrected Gibbs free energies of 0.9 kcal/mol for the nine reactions with a constant number of moles (1.2 kcal/mol for all 11 reactions). This provides a straightforward and accurate computational protocol for computing free energies of iridium-mediated transformations in solution. However, because the good results may originate from favorable error cancellations of larger and oppositely signed enthalpy and entropy errors, this protocol is recommended for free energies only.
机译：铱化学用途广泛，应用广泛，对反应类型（如对映选择性氢化和C-H活化）具有卓越的性能。为了深入了解此类系统的机械细节，经常采用密度泛函理论（DFT）研究。但是DFT对溶液中铱介导的转化建模的准确性如何？我们已经评估了DFT很好地再现了11个铱介导的转化的能量和反应性，精心选择了它们以对应于铱催化化学中通常遇到的基本步骤（键形成，异构化，配体取代和配体缔合）。按原样或结合经验色散校正（D2，D3或D3BJ）对五个DFT功能B3LYP，PBE，PBE0，M06L和M11L进行了评估，得出13种组合。评估了不同的溶剂模型（IEFPCM和SMD），以及各种校正项，例如大的基集效应，平衡力校正，频率缩放和不同的熵修饰。 PBE-D型功能明显优越，PBE-D2，IEFPCM在恒定摩尔数下（对所有11个反应而言均为1.2 kcal / mol）对9个反应的未校正Gibbs自由能提供0.9 kcal / mol的平均绝对误差。这提供了一种简单而准确的计算协议，用于计算溶液中铱介导的转化的自由能。但是，由于良好的结果可能源于较大且符号相反的焓和熵误差的有利误差消除，因此建议仅对自由能使用此协议。

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