Transfer Hydrocyanation by Nickel(0)/Lewis Acid Cooperative Catalysis, Mechanism Investigation, and Computational Prediction of Shuttle Catalysts

2017-07-20T18:13:30Z (GMT) by Shao-Fei Ni Ti-Long Yang Li Dang
A theoretical investigation on transfer hydrocyanation of simple olefins catalyzed by shuttle catalysts is presented in this work, which uncovers the reaction mechanism together with the important role of the Lewis acid. The calculated results show that Ni(0)/LA (Lewis acid)-catalyzed transfer hydrocyanation consists of five key steps: oxidative addition of the nitrile, β-H elimination, ligand exchange, alkene insertion, and reductive elimination. The computational results reveal that the effect of the Lewis acid is mainly reflected in the interaction with the N atom of the nitrile group, which weakens the C­(sp3)–C­(sp) σ bond, thus lowering the barrier of the oxidative addition step, which is the rate-determining step of the catalyzed reaction. These results are consistent with the experimental observations. Furthermore, our calculation results with several newly designed ligands show that the introduction of an electron-donating group to the phosphine ligand promotes transfer hydrocyanation, while an electron-withdrawing group blocks this reaction. The present work will provide great support for the understanding of transfer hydrocyanation and give a valuable guide for the further design of transition-metal/Lewis acid cooperative shuttle catalysts.