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

Abstract

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.