Au-iClick mirrors the mechanism of copper catalyzed azide-alkyne cycloaddition (CuAAC)

This report outlines the investigation of the iClick mechanism between gold(i)-azides and gold(i)-acetylides to yield digold triazolates. Isolation of digold triazolate complexes offer compelling support for the role of two copper(i) ions in CuAAC. In addition, a kinetic investigation reveals the reaction is first order in both Au(i)-N3 and Au(i)-C[triple bond, length as m-dash]C-R, thus second order overall. A Hammett plot with a ρ = 1.02(5) signifies electron-withdrawing groups accelerate the cycloaddition by facilitating the coordination of the second gold ion in a π-complex. Rate inhibition by the addition of free triphenylphosphine to the reaction indicates that ligand dissociation is a prerequisite for the reaction. The mechanistic conclusions mirror those proposed for the CuAAC reaction.