Preparation and Metalation of N‑Heterocyclic\nCarbene Ligands with Sterically Tunable 2,6-dialkoxyphenyl Wingtip\nGroups

N-Heterocyclic carbenes (NHCs) featuring\n2,6-dialkoxyphenyl wingtip\ngroups are synthesized, and their coordination chemistry and properties\nare studied. Linear [(NHC)CuCl] complexes composed of ligands synthesized\nherein were characterized by X-ray crystallography and used to analyze\nthe ligand steric parameters. We demonstrate that the use of different\nalkyl halides in the preparation of these ligands results in NHCs\nthat are sterically tunable and potentially capable of hemilability.\nFurthermore, the electronic properties of these ligands are assessed\nby computational methods, which demonstrate these NHCs to be highly\nelectron donating in nature. Additional metalation of these ligands\nto sulfur, silver, and palladium is reported, and the resulting palladium\ncomplexes are tested in the Suzuki–Miyaura reaction of challenging\naryl chlorides to benchmark catalytic activity. A direct correlation\nbetween steric impacts and catalytic performance is observed.