om7b00218_si_001.xyz (616.84 kB)
Transfer Hydrocyanation by Nickel(0)/Lewis Acid Cooperative Catalysis, Mechanism Investigation, and Computational Prediction of Shuttle Catalysts
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posted on 2017-07-20, 18:13 authored by Shao-Fei Ni, Ti-Long Yang, Li DangA 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.