Mechanism of Carbon−Fluorine Bond Activation by (C₅Me₅)Rh(PMe₃)H₂

Abstract

The complex Cp*Rh(PMe3)H2 (Cp* = C5Me5) reacts with C6F6, C6F5H, C12F10, or C10F8 in pyridine or 1:1 pyridine/benzene to give the C−F cleavage products Cp*Rh(PMe3)(arylF)H in high yield. Kinetic studies reveal that the reaction has autocatalytic character, and fluoride ion is shown to be responsible for the catalysis. The anion [Cp*Rh(PMe3)H]- reacts rapidly with C12F10 or C10F8 to give the same C−F cleavage products as Cp*Rh(PMe3)H2. A mechanism initiated by deprotonation of Cp*Rh(PMe3)H2 followed by nucleophilic attack of the resulting anion on the polyfluoroaromatic with subsequent loss of fluoride is proposed. The fluoride ion continues the cycle by deprotonating Cp*Rh(PMe3)H2.

The Reaction of the [CpFe(CO)2]− Anion with Pentafluorochlorobenzene: Nucleophilic Aromatic Substitution by Halogen-Metal Exchange

“…It should be mentioned that the reactions of perfluoroarenes with nucleophiles belong with the classic examples of nucleophilic aromatic substitution, and could hardly be regarded as specific C ± F bond activation as was suggested in several recent publications. [13] The substitution of the fluorine para to chlorine on the aromatic ring with a carbon-centred nucleophile agrees well with the predictions derived from previous studies.…”

Activation of Aromatic, Aliphatic, and Olefinic Carbon–Fluorine Bonds Using Cp*2HfH2

“…On the basis of 19 F NMR spectroscopic data, the final ratio of 2:3: β,β-difluoro-α-methylstyrene was 0.8:1.0: 1.5. (8) The reaction involving difluoromethylenecyclohexane was carried out in the same manner, producing 2, 3, and fluoromethylenecyclohexane in a 12.8:1.0: 38.0 ratio (by 19 F NMR) after 93 h of reaction at 160°C [Equation (9)]. Initial formation of 2 was not observed until after 22 h had elapsed at 120°C.…”

“…There was nothing unusual about the solution or refinement of any of the structures, although the fluoride and hydride ligands in 2 were disordered (76/24 and 60/40). Compound 4 refined with a Flack parameter of 0.055 (8). Further experimental details of the X-ray diffraction studies are provided in Table 2.…”

“…[7] Similar considerations have been implicated in reactions involving Ni and Rh. [8][9] (1) Electrophilic C-F bond activation has been suggested to occur by fluoride transfer, especially when strong Lewis acids are employed. For example, fluoride transfer from an aromatic fluorocarbon to an open coordination site in [L 2 TiMe] + systems has recently been proposed by Ziegler and co-workers.…”

Synthese fluorierter Bausteine durch Übergangsmetall‐vermittelte Hydrodefluorierungsreaktionen

“…Ein alternativer Mechanismus, bei dem der Metallkomplex deprotoniert wird und anschließend in einer nukleophilen Substitution am Aren angreift, wurde ebenfalls diskutiert. [27] Schema 11. Eisen-katalysierte HDF von Hexafluorpropen (Ar = 2,6-(iPr 2 C 6 H 3 ).…”