Ligand-Enabled Oxidative Fluorination of Gold(I) and Light-Induced Aryl–F Coupling at Gold(III)
David Vesseur, Shuo Li, Sonia Mallet‐Ladeira, Karinne Miqueu, Didier Bourissou
Abstract
MeDalphos Au(I) complexes featuring aryl, alkynyl, and alkyl groups readily react with electrophilic fluorinating reagents such as N -fluorobenzenesulfonimide and Selectfluor. The ensuing [(MeDalphos)Au(R)F] + complexes have been isolated and characterized by multinuclear NMR spectroscopy as well as X-ray diffraction. They adopt a square-planar contra-thermodynamic structure, with F trans to N. DFT/IBO calculations show that the N lone pair of MeDalphos assists and directs the transfer of F + to gold. The [(MeDalphos)Au(Ar)F] + (Ar = Mes, 2,6-F 2 Ph) complexes smoothly engage in C–C cross-coupling with PhCCSiMe 3 and Me 3 SiCN, providing direct evidence for the oxidative fluorination/transmetalation/reductive elimination sequence proposed for F + -promoted gold-catalyzed transformations. Moreover, direct reductive elimination to forge a C–F bond at Au(III) was explored and substantiated. Thermal means proved unsuccessful, leading mostly to decomposition, but irradiation with UV–visible light enabled efficient promotion of aryl–F coupling (up to 90% yield). The light-induced reductive elimination proceeds under mild conditions; it works even with the electron-deprived 2,6-difluorophenyl group, and it is not limited to the contra-thermodynamic form of the aryl Au(III) fluoride complexes.