This work examines how N-donor bridged spacer ligands affect N-heterocyclic carbene (NHC) palladium complexes catalytic activities for Suzuki coupling reaction. Different degrees of structural flexibility binuclear NHC palladium complexes were synthesized. The more flexible nitrogen-based alkyl chain ligand shows similar performance with cycloamine counterparts in the Suzuki coupling reaction. Suzuki coupling examples were used in air and ambient temperature to reach moderate to completion yields in short time. Density functional theory calculations showed that the chelate effect, associated with a single Pd complex mechanism, plays a fundamental role in the pre-catalysis stage, supporting a reasonable of the kinetic activity observed experimentally.
- binuclear NHC–palladium complexes
- density functional theory (DFT)
- Suzuki–Miyaura reaction