Au(I) Fluorido Phosphine Complexes: Tools for the Hydrofluorination of Alkynes

The reactivity of the Au(I) fluorido complex [Au(F)(SPhos)] (SPhos = dicyclohexyl(2',6'-dimethoxy[1,1'-biphenyl]-2-yl)phosphine) (1) towards several alkynes was studied. The formation of fluorovinyl species by formal insertion of the alkyne in the metal-fluorine bond was observed. Addition of HCI to vinyl complexes resulted in protodeauration and elimination of the hydrofluorinated alkynes. Treatment of 1 with the terminal alkyne 1-hexyne resulted in clean formation of the alkynyl complex [Au(C=CC4H9)(SPhos)] (15), whereas with an excess alkyne hydrofluorination was also observed. Various Au(I) phosphine complexes including 1 were then compared in their ability to catalyze hydrofluorination reactions of 1-phenyl-propyne with Et3N center dot 3HF as HF source. Model reactions suggested a reaction mechanism, which imparts a pre-coordination of an alkyne to a cationic gold center followed by nucleophilic addition of a fluoride. Mechanistic investigations included reactivity studies at [Au(SPhos)][B(C6F5)(4))] (17), which was treated with 4-phenyl-3-butyn-2-one and TMAF (TMAF - tetramethylammonium fluoride). The reaction led to the formation of the complex [Au(CH3C(O)C=C(F)Ph)(SPhos)] (13), but not the fluorido complex 1. commonly 1.

Automated summary

The reactivity of an Au(I) fluorido complex with alkynes was studied, leading to the formation of fluorovinyl species and hydrofluorination of alkynes. The catalytic ability of various Au(I) phosphine complexes in hydrofluorination reactions was compared, suggesting a reaction mechanism involving pre-coordination and nucleophilic addition. Mechanistic investigations confirmed the formation of a complex through nucleophilic addition, rather than the fluorido complex.