Insights into the Catalytic Activity of Pd(NHC)(cin)Cl (NHC=IPr, IPrCl, IPrBr) Complexes in the Suzuki–Miyaura Reaction

Abstract The influence of C 4,5 ‐halogenation on palladium N‐heterocyclic carbene complexes and their activity in the Suzuki–Miyaura reaction were investigated. Two Pd(NHC)(cin)Cl complexes bearing IPr Cl and IPr Br ligands (IPr=1,3‐bis(2,6‐diisopropyl‐phenyl)imidazol‐2‐ylidene; cin=cinnamyl) were synthesized. After determining the electronic and steric properties of these ligands, their properties were compared to those of Pd(IPr) (cin)Cl. The three palladium complexes were studied by using DFT calculations to delineate their behavior in the activation step leading to the putative 12‐electron active catalyst. Experimentally, their catalytic activity in the Suzuki–Miyaura reaction involving a wide range of coupling partners (30 entries) at low catalyst loading was studied.