Accelerating the insertion reactions of (NHC)Cu-H via remote ligand functionalization.

Autor: Speelman AL; Institute for Integrated Catalysis, Pacific Northwest National Laboratory Richland WA 99352 USA morris.bullock@pnnl.gov ba.tran@pnnl.gov., Tran BL; Institute for Integrated Catalysis, Pacific Northwest National Laboratory Richland WA 99352 USA morris.bullock@pnnl.gov ba.tran@pnnl.gov., Erickson JD; Institute for Integrated Catalysis, Pacific Northwest National Laboratory Richland WA 99352 USA morris.bullock@pnnl.gov ba.tran@pnnl.gov., Vasiliu M; Department of Chemistry and Biochemistry, University of Alabama Tuscaloosa AL 35487 USA., Dixon DA; Department of Chemistry and Biochemistry, University of Alabama Tuscaloosa AL 35487 USA., Bullock RM; Institute for Integrated Catalysis, Pacific Northwest National Laboratory Richland WA 99352 USA morris.bullock@pnnl.gov ba.tran@pnnl.gov.
Jazyk: angličtina
Zdroj: Chemical science [Chem Sci] 2021 Jul 29; Vol. 12 (34), pp. 11495-11505. Date of Electronic Publication: 2021 Jul 29 (Print Publication: 2021).
DOI: 10.1039/d1sc01911b
Abstrakt: Most ligand designs for reactions catalyzed by (NHC)Cu-H (NHC = N-heterocyclic carbene ligand) have focused on introducing steric bulk near the Cu center. Here, we evaluate the effect of remote ligand modification in a series of [(NHC)CuH] 2 in which the para substituent (R) on the N -aryl groups of the NHC is Me, Et, t Bu, OMe or Cl. Although the R group is distant (6 bonds away) from the reactive Cu center, the complexes have different spectroscopic signatures. Kinetics studies of the insertion of ketone, aldimine, alkyne, and unactivated α-olefin substrates reveal that Cu-H complexes with bulky or electron-rich R groups undergo faster substrate insertion. The predominant cause of this phenomenon is destabilization of the [(NHC)CuH] 2 dimer relative to the (NHC)Cu-H monomer, resulting in faster formation of Cu-H monomer. These findings indicate that remote functionalization of NHCs is a compelling strategy for accelerating the rate of substrate insertion with Cu-H species.
Competing Interests: There are no conflicts to declare.
(This journal is © The Royal Society of Chemistry.)
Databáze: MEDLINE
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