Density functional theory investigation of the alkyl-alkyl Negishi cross-coupling reaction catalyzed by N-heterocyclic carbene (NHC)-Pd complexes.
A novel mechanism is proposed for the Pd-1,3-(2,6-diisopropylphenyl)imidazolyl-2-ylidene (1) catalyzed Negishi reaction. DFT computations supported by atoms-in-molecules (AIM) analyses of non-truncated models show that a "steric wall" created by the N-substituent on the ligand guides reactants to and from the Pd center. Notably, transmetalation and not oxidative addition is found to be rate-limiting. Additionally, a key Pd-Zn interaction (approximately = 2.4 A, rho(b) approximately = 0.0600 au) is identified in the mechanism. This interaction persists beyond reductive elimination and, in combination with the ligand, facilitates reductive elimination by creating a highly sterically crowded environment in the coordination sphere of the Pd center.
Chass
Gregory A
GA
School of Chemistry, University of Wales, Bangor, LL57 2UW, UK. gchass@giocomms.org
O'Brien
Christopher J
CJ
Hadei
Niloufar
N
Kantchev
Eric Assen B
EA
Mu
Wei-Hua
WH
Fang
De-Cai
DC
Hopkinson
Alan C
AC
Csizmadia
Imre G
IG
Organ
Michael G
MG