An Organocopper(III) Fluoride Triggering C-CF 3 Bond Formation.

Copper(III) fluorides are catalytically competent, yet elusive, intermediates in cross-coupling. The synthesis of [PPh 4 ][Cu III (CF 3 ) 3 F] (2), the first stable (isolable) Cu III -F, was accomplished via chloride addition to [Cu III (CF 3 ) 3 (py)] (1) yielding [PPh 4 ][Cu III (CF 3 ) 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-CF 3 bonds from silyl-capped alkynes. In-depth mechanistic studies combining probes, theoretical calculations, trapping of intermediate 4 a ([PPh 4 ][Cu III (CF 3 ) 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≡CCF 3 ), which are industrially relevant synthons in drug discovery, pharma and agrochemistry.