N-Heterocyclic Olefin-Ligated Palladium(II) Complexes as Pre-Catalysts for Buchwald–Hartwig Aminations

New N-heterocyclic olefins (NHOs) are described with functionalization on the ligand heterocyclic backbone and terminal alkylidene positions. Various Pd^II–NHO complexes have been formed and their use as pre-catalysts in Buchwald–Hartwig aminations was explored. The most active system for catalytic C?N bond formation between hindered arylamine and arylhalide substrates was accessed by combining a backbone methylated NHO with Pd(cinnamyl)Cl]₂ in the presence of NaOtBu as a base. In these active systems evidence suggests that catalysis is mediated by colloidal palladium metal, highlighting a different coordination ability of NHOs in comparison with commonly used N-heterocyclic carbene co-ligands.