From Chelating to Bridging Ligands: N‑Sulfonyliminoimidazolium Ylides as Precursors to Anionic N‑Heterocyclic Carbene Ligands

The synthesis and investigation of a new family of anionic N-heterocyclic carbene (NHC) ligands, based on N-sulfonyliminoimidazolium ylides, is reported. Their corresponding silver complexes have been synthesized and present distinctive geometries compared to the previously reported ligands derived from the N-acyliminoimidazolium family. A comparison of the two ligand families was performed with palladium­(II) allyl complexes to investigate their binding mode preference. The N-sulfonyl derived ligands were found to strongly favor bridging binding instead of chelation. This strong preference was exploited to synthesize a novel copper­(I)–palladium­(II) heterotrimetallic complex.