Abstract
The influence of C4,5‐halogenation on palladium N‐heterocyclic carbene complexes and their activity in the Suzuki–Miyaura reaction were investigated. Two [Pd(NHC)(cin)Cl] complexes bearing IPrCl and IPrBr 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.
With or without a halogen: The catalytic activities of [Pd(NHC)(cin)Cl] (NHC=IPr, IPrCl, IPrBr; cin=cinnamyl) complexes are compared in the Suzuki–Miyaura cross‐coupling reaction. The activation pathway involving these complexes is studied by DFT calculations, and their activities are extensively tested by using an operationally simple protocol.