An Organocopper(III) Fluoride Triggering C-CF₃ Bond Formation

Copper(III) fluorides are catalytically competent, yet elusive, intermediates in cross-coupling. The synthesis of [PPh₄ ][Cu^III (CF₃ )₃ F] (2), the first stable (isolable) Cu^III -F, was accomplished via chloride addition to [Cu^III (CF₃ )₃ (py)] (1) yielding [PPh₄ ][Cu^III (CF₃ )₃ Cl(py)] (1⋅Cl), followed by treatment with AgF. The Cu^III halides 1⋅Cl and 2 were fully characterized using nuclear magnetic resonance (NMR) spectroscopy, single crystal X-ray diffraction (Sc-XRD) and elemental analysis (EA). Complex 2 proved capable of forging C-CF₃ bonds from silyl-capped alkynes. In-depth mechanistic studies combining probes, theoretical calculations, trapping of intermediate 4_a ([PPh₄ ][Cu^III (CF₃ )₃ (C≡CPh)]) and radical tests unveil the key role of the Cu^III acetylides that undergo facile 2e^- reductive elimination furnishing the trifluoromethylated alkynes (RC≡CCF₃ ), which are industrially relevant synthons in drug discovery, pharma and agrochemistry.