State Key Laboratory of Chemical Resource Engineering, Institute of Computational Chemistry, College of Chemistry, Beijing University of Chemical Technology, Beijing, 100029, China.
Dalton Trans. 2021 Oct 26;50(41):14738-14744. doi: 10.1039/d1dt02410h.
The density functional theory (DFT) method was employed to investigate the reaction mechanism of the hydrogen activation and asymmetric transfer hydrogenation (ATH) of acetophenone catalyzed by a well-defined phosphine-free Mn(I)-NNS complex. The calculation results indicate that the Mn-NNS complex has potential high catalytic hydrogenation activity. Meanwhile, the hydrogen transfer step of this reaction is proposed to be a concerted but asynchronous process, and the hydride transfer precedes proton transfer. This work also pointed out that the stereoselectivity of ATH catalyzed by the Mn(I)-NNS complex mainly originates from the noncovalent interaction between the substrate and the catalyst. Additionally, the catalytic activities of Mn-NNS complexes with different X ligands (X = CO, Cl, H, OMe, NCMe, CCMe, and CHCHMe) were compared, and the calculated total reaction energy barriers were all viable, which indicates that these Mn-NNS complexes show higher CO bond hydrogenation activity under mild conditions. This theoretical study predicts that the reactions catalyzed by complexes with H and NCMe ligands exhibit high stereoselectivity with enantiomeric excess (ee) values of 97% and 93%, respectively.
采用密度泛函理论（DFT）方法研究了由结构明确的无膦锰（I）-NNS 配合物催化的苯乙酮的氢活化和不对称转移氢化（ATH）反应机理。计算结果表明，Mn-NNS 配合物具有潜在的高催化加氢活性。同时，该反应的氢转移步骤被提出为协同但异步过程，氢化物转移先于质子转移。这项工作还指出，Mn（I）-NNS 配合物催化的 ATH 的立体选择性主要源于底物与催化剂之间的非共价相互作用。此外，还比较了具有不同 X 配体（X = CO、Cl、H、OMe、NCMe、CCMe 和 CHCHMe）的 Mn-NNS 配合物的催化活性，计算出的总反应能垒都是可行的，这表明这些 Mn-NNS 配合物在温和条件下具有更高的 C-O 键加氢活性。这项理论研究预测，具有 H 和 NCMe 配体的配合物催化的反应具有高立体选择性，对映过量（ee）值分别为 97%和 93%。
