N-Heterocyclic carbene ligands bearing a naphthoquinone appendage: Synthesis and coordination chemistry

Many biochemical transformations for small molecule functionalisation depend on the temporal delivery of multiple protons and electrons. For this purpose, Nature elegantly combines transition metals with redox-active cofactors. In a biomimetic spirit, we report on the synthesis and coordination chemistry of an N-heterocyclic carbene ligand bearing a naphthoquinone moiety NHC 1. Both the silver and palladium complexes [Ag(μ-Cl)(NHC 1)]22 and [Pd(η3-allyl)(NHC 1)Cl] 5 were characterized by X-ray crystallography. Cyclic voltammetry of the metal complexes suggest that redox events occur both on the naphthoquinone and on the metal for the iridium and ruthenium complexes.

Herein we report on the straighforward synthesis and coordination chemistry of an unsaturated N-heterocyclic carbene ligand bearing a naphthoquinone appendage. The electrochemical behaviour of the coinage metal complexes was scrutinized by cyclic voltammetry, revealing the potential of the NHC 1 moiety to act as a redox active ligand.Figure optionsDownload as PowerPoint slide