The synthesis and characterization of original NHC ligands based on an imidazo[1,5‐a]pyridin‐3‐ylidene (IPy) scaffold functionalized with a flanking barbituric heterocycle is described as well as their use as tunable ligands for efficient gold‐catalyzed C−N, C−O, and C−C bond formations. High activity, regio‐, chemo‐, and stereoselectivities are obtained for hydroelementation and domino processes, underlining the excellent performance (TONs and TOFs) of these IPy‐based ligands in gold catalysis. The gold‐catalyzed domino reactions of 1,6‐enynes give rise to functionalized heterocycles in excellent isolated yields under mild conditions. The efficiency of the NHC gold 5Me complex is remarkable and mostly arises from a combination of steric protection and stabilization of the cationic AuI active species by ligand 1Me.

A series of NHC pre-ligands featuring a pendant phosphonium moiety attached to N' position through a propyl linker was readily obtained upon quaternization of N-mesityl- and N-methyl-imidazole, or N-mesityl-imidazoline using (3-bromo-propyl)-triphenylphosphonium bromide. Reactions of the resulting dicationic salts with [PdCl(allyl)] in the presence of KCO afforded the anticipated NHC-ligated Pd(ii) metal complexes in high yields. Further treatment of the latter complexes with tBuOK induced a deprotonation of the carbon atom adjacent to the phosphonium moiety and the formation of the corresponding C,C-chelating NHC-phosphonium ylide Pd(ii) complexes. Investigation of an alternative synthetic route involving a silver transmetallation reaction incidentally allowed isolation and full characterization of an unusual dimeric tetranuclear NHC Ag(i) complex of general formula [(NHC∼P)(AgBr)].