Swiss Science Concentrates

Alkyne hydrofunctionalization typically proceeds through syninsertion into metal-hydride bonds; anti-insertion pathways are rare and not well understood.In this paper, the authors investigate the anti-insertion of alkynes into a gold(III)-hydride complex stabilized by a (P^N^C) ligand.They demonstrate that a range of terminal and internal alkynes, both activated and unactivated ones, undergo anti-Markovnikov addition to yield Z-vinyl gold species.A combination of mechanistic investigations -including radical trapping, deuterium-labeling, kinetic analysis, and DFT calculations -rules out previously assumed reaction pathways and indicates a non-radical, bimolecular insertion mechanism.Additionally, water significantly accelerates the reaction rate, likely by stabilizing a T-shaped gold(I) intermediate.This represents the first clear experimental evidence for anti-insertion into a gold(III)-hydride complex and opens new possibilities for using gold catalysis to build structural complexity.