Elucidating the Mechanism of Aryl Aminations Mediated by NHC-Supported Nickel Complexes: Evidence for a Nonradical Ni(0)/Ni(II) Pathway

Silvia G. Rull, Ignacio Funes-Ardoiz, Celia Maya, Feliu Maseras, Manuel R. Fructos, Tomás R. Belderrain, M. Carmen Nicasio

Research output: Contribution to journalArticleResearchpeer-review

25 Citations (Scopus)

Abstract

© 2018 American Chemical Society. Nickel catalysis is gaining in popularity in recent years, mostly within the area of cross-coupling. However, unlike Pd, the mechanisms of Ni-catalyzed C-C and C-heteroatom bond forming reactions have been much less studied, in particular when N-heterocyclic carbenes are used as ligands. Here, we present a thorough study of the mechanism of C-N cross-coupling reactions catalyzed by an NHC-Ni complex. Focusing on the coupling of 2-chloropyridines with indole catalyzed by [(IPrNi(styrene)2] (IPr = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), we have examined each of the elementary steps: i.e., oxidative addition, ligand substitution, and reductive elimination. All relevant catalytic intermediates have been isolated and structurally characterized by both spectroscopic and crystallographic methods. Kinetic studies have revealed that the reductive elimination is the rate-limiting step. Catalyst deactivation is related to the formation of unproductive dinuclear pyridyl-bridged NHC-NiII species, which can be prevented by increasing the size of the heteroaryl chloride. These investigations support a neutral Ni(0)/Ni(II) catalytic cycle. Calculations corroborate the experimental evidence and confirm the influence exerted by the ligands in each of the elementary steps.
Original languageEnglish
Pages (from-to)3733-3742
JournalACS Catalysis
Volume8
Issue number5
DOIs
Publication statusPublished - 4 May 2018

Keywords

  • C-N bond formation
  • NHC
  • amination
  • cross-coupling
  • indole
  • mechanism
  • nickel

Fingerprint Dive into the research topics of 'Elucidating the Mechanism of Aryl Aminations Mediated by NHC-Supported Nickel Complexes: Evidence for a Nonradical Ni(0)/Ni(II) Pathway'. Together they form a unique fingerprint.

Cite this