A Redox-Switchable Gold(I) Complex for the Hydroamination of Acetylenes: A Convenient Way for Studying Ligand-Derived Electronic Effects

Abstract

A gold complex with a naphthalene-di-imide-functionalized N-heterocyclic carbene (NHC) ligand was prepared and characterized. The electrochemical studies reveal that the complex is able to undergo two successive reduction events, associated to the reduction of the NDI moiety of the NHC ligand. Once the redox-switchable properties of this Au(I) complex were proven, the complex was tested in the hydroamination of terminal alkynes. The activity of the neutral complex was moderate-to-high for this reaction, but the one-electron reduced species did not show any activity in the reaction. The activity of the catalyst could be toggled off and on several times by successively adding a reducing agent (cobaltocene) or an oxidant (acetylferrocenium tetrafluoroborate). The results indicate that the rate-determining step of the catalytic cycle is the nucleophilic attack of the amine on the Au-coordinated alkyne.