Synthesis of Complexes with Abnormal "Protic" N-Heterocyclic Carbenes

Neutral 4‐iodo‐N‐ethylimidazole 3 oxidatively adds to [Pt(PPh3)4] to give, in the presence of different tetraalkylammonium salts, complexes trans‐[4], trans‐[5], and trans‐[6] containing an anionic C4‐bound heterocycle with an unsubstituted ring‐nitrogen atom. Complex trans‐[4] reacts with the proton source NH4I under protonation of the ring‐nitrogen atom to produce complex trans‐[7]I which bears an NH,NR‐substituted aNHC ligand. The reaction of trans‐[4] with CH3I yields the complex trans‐[8]I which has a classical aNHC ligand with two alkylated ring‐nitrogen atoms. The oxidative addition of neutral 4‐iodo‐N‐ethylimidazole to [Pt(PPh3)4] yields the complex trans‐[1] bearing an anionic C4‐bound heterocycle. Complex trans‐[1] can be N3‐protonated and N3‐methylated giving complexes with protic and conventional aNHC ligands, respectively. (aNHC=abnormal N‐heterocyclic carbene; NHC=N‐heterocyclic carbene).