Quinone-Annulated N-Heterocyclic Carbene−Transition-Metal Complexes: Observation of π-Backbonding Using FT-IR Spectroscopy and Cyclic Voltammetry
journal contributionposted on 27.12.2006 by Matthew D. Sanderson, Justin W. Kamplain, Christopher W. Bielawski
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A new N-heterocyclic carbene architecture comprising a 1,4-naphthoquinone annulated to 1,3-dimesitylimidazolylidene (NpQ−NHC) was synthesized in two high yielding steps from commercially available starting materials. The free NpQ−NHC was characterized (solution and solid-state) and was used to synthesize various Rh and Ag complexes that ranged in π-electron density. Enabled by the quinone moiety, the π-systems of these complexes were analyzed using infrared spectroscopy and cyclic voltammetry. In contrast to previous reports, π-backbonding was found to be non-negligible and was directly influenced by the metal's electronic character.