Tran Ba L, Neisen Benjamin D, Speelman Amy L, Gunasekara Thilina, Wiedner Eric S, Bullock R Morris
Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
Angew Chem Int Ed Engl. 2020 May 25;59(22):8645-8653. doi: 10.1002/anie.201916406. Epub 2020 Mar 20.
We report mechanistic studies on the insertion reactions of [(NHC)Cu(μ-H)] complexes with carbonyl substrates by UV-vis and H NMR spectroscopic kinetic studies, H/D isotopic labelling, and X-ray crystallography. The results of these comprehensive studies show that the insertion of Cu-H with an aldehyde, ketone, activated ester/amide, and unactivated amide consist of two different rate limiting steps: the formation of Cu-H monomer from Cu-H dimer for more electrophilic substrates, and hydride transfer from a transient Cu-H monomer for less electrophilic substrates. We also report spectroscopic and crystallographic characterization of rare Cu-hemiacetalate and Cu-hemiaminalate moieties from the insertion of an ester or amide into the Cu-H bond.
我们通过紫外可见光谱和核磁共振光谱动力学研究、氢/氘同位素标记以及X射线晶体学，报告了关于[(NHC)Cu(μ-H)]配合物与羰基底物插入反应的机理研究。这些综合研究结果表明，铜-氢键与醛、酮、活化酯/酰胺和未活化酰胺的插入反应由两个不同的速率限制步骤组成：对于亲电性更强的底物，从铜-氢键二聚体形成铜-氢键单体；对于亲电性较弱的底物，从瞬态铜-氢键单体进行氢化物转移。我们还报告了酯或酰胺插入铜-氢键形成的罕见铜半缩醛和铜半缩胺部分的光谱和晶体学表征。
