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Computational Insight into Nickel‐Catalyzed Carbon–Carbon versus Carbon–Boron Coupling Reactions of Primary, Secondary, and Tertiary Alkyl Bromides
Author(s) -
Cheung Man Sing,
Sheong Fu Kit,
Marder Todd B.,
Lin Zhenyang
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201500110
Subject(s) - alkyl , nickel , carbon fibers , catalysis , boron , primary (astronomy) , reinforced carbon–carbon , coupling (piping) , chemistry , coupling reaction , organic chemistry , materials science , metallurgy , physics , astronomy , composite number , composite material
The nickel‐catalyzed alkyl–alkyl cross‐coupling (CC bond formation) and borylation (CB bond formation) of unactivated alkyl halides reported in the literature show completely opposite reactivity orders in the reactions of primary, secondary, and tertiary alkyl bromides. The proposed Ni I /Ni III catalytic cycles for these two types of bond‐formation reactions were studied computationally by means of DFT calculations at the B3LYP level. These calculations indicate that the rate‐determining step for alkyl–alkyl cross‐coupling is the reductive elimination step, whereas for borylation the rate is determined mainly by the atom‐transfer step. In borylation reactions, the boryl ligand involved has an empty p orbital, which strongly facilitates the reductive elimination step. The inability of unactivated tertiary alkyl halides to undergo alkyl–alkyl cross‐coupling is mainly due to the moderately high reductive elimination barrier.