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Ligand Steric Effects of α‑Diimine Nickel(II) and Palladium(II) Complexes in the Suzuki–Miyaura Cross-Coupling Reaction
journal contribution
posted on 2020-09-10, 06:14 authored by Md Muktadir Talukder, John Michael O. Cue, Justin T. Miller, Prabhath L. Gamage, Amina Aslam, Gregory T. McCandless, Michael C. Biewer, Mihaela C. StefanNickel catalysts
represent a low cost and environmentally friendly
alternative to palladium-based catalytic systems for Suzuki–Miyaura
cross-coupling (SMC) reactions. However, nickel catalysts have suffered
from poor air, moisture, and thermal stabilities, especially at high
catalyst loading, requiring controlled reaction conditions. In this
report, we examine a family of mono- and dinuclear Ni(II) and Pd(II)
complexes with a diverse and versatile α-diimine ligand environment
for SMC reactions. To evaluate the ligand steric effects, including
the bite angle in the reaction outcomes, the structural variation
of the complexes was achieved by incorporating iminopyridine- and
acenaphthene-based ligands. Moreover, the impact of substrate bulkiness
was investigated by reacting various aryl bromides with phenylboronic
acid, 2-naphthylboronic acid, and 9-phenanthracenylboronic acid. Yields
were the best with the dinuclear complex, being nearly quantitative
(93–99%), followed by the mononuclear complexes, giving yields
of 78–98%. Consequently, α-diimine-based ligands have
the potential to deliver Ni-based systems as sustainable catalysts
in SMC.
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reaction conditionsα- diimine ligand environmentligand steric effectsSuzuki2- naphthylboronic acidphenylboronic acidnickel catalystscomplexreaction outcomesNi-based systemsaryl bromidesdinuclearsubstrate bulkinessacenaphthene-based ligandsα- diimine-based ligandsSMC reactionscatalyst loadingLigand Steric Effects9- phenanthracenylboronic acid
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