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In this Special Issue on N-Heterocyclic Carbenes and Their Complexes in Catalysis, we report the first example of Suzuki–Miyaura cross-coupling of amides catalyzed by well-defined, air- and moisture-stable nickel/NHC (NHC = N-heterocyclic carbene) complexes. The selective amide bond N–C(O) activation is achieved by half-sandwich, cyclopentadienyl [CpNi(NHC)Cl] complexes. The following order of reactivity of NHC ligands has been found: IPr > IMes > IPaul ≈ IPr*. Both the neutral and the cationic complexes are efficient catalysts for the Suzuki–Miyaura cross-coupling of amides. Kinetic studies demonstrate that the reactions are complete in < 1 h at 80 °C. Complete selectivity for the cleavage of exocyclic N-acyl bond has been observed under the experimental conditions. Given the utility of nickel catalysis in activating unreactive bonds, we believe that well-defined and bench-stable [CpNi(NHC)Cl] complexes will find broad application in amide bond and related cross-couplings of bench-stable acyl-electrophiles.
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This content will become publicly available on July 1, 2026
Cis versus Trans C-F Activation of Hexafluorobenzene with N-heterocyclic Carbene Ni(0) Complexes
Fluorine is an essential component in many highly effective pharmaceutical drugs, however the selective fluorination of organic molecules poses a challenge. A common route to installing fluorine involves C-F bond cleavage, which is often accomplished using second- or third-row transition metals. Base metal catalysts such as nickel may provide a facile, sustainable, and cheaper alternative for C-F activation. Monodentate N-heterocyclic carbene (NHC) nickel complexes have been reported to undergo C-F activation, however bis-bidentate NHC (RNHC2R1; R, R1 = alkyl or aryl) analogs remain underexplored. This work reports a series of RNHC2R1 nickel(0) complexes with various R1 linkers to determine the effect of the linker on the C-F activation of hexafluorobenzene. Comparisons include a reference nickel(0) complex with two monodentate NHC ligands, and results show that low-valent nickel NHC complexes readily break the C-F bond in C6F6 via oxidative addition. Crystallographic and NMR characterization demonstrate that ligand design and denticity affect the cis versus trans orientation of the final product, with the possibility for additional ligand C-H activation.
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- Award ID(s):
- 2350537
- PAR ID:
- 10623926
- Publisher / Repository:
- ChemRxiv
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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