Pentamethylcyclopentadienyl rhodium(III) trifluorovinyl phosphine complexes and attempted intramolecular dehydrofluorinative coupling of pentamethylcyclopentadienyl and trifluorovinyl phosphine ligands

The trifluorovinyl phosphine complexes [Cp*RhCl2{PR3−x(CFCF2)x}] (1x = 1, a R = Ph, b Pri, c Et; 2x = 2, R = Ph) have been prepared by treatment of [Cp*RhCl(μ-Cl)]2 with the relevant phosphine. The salt [Cp*RhCl(CNBut){PPh2(CFCF2)}]BF4, 3, was prepared by addition of ButNC to 1a in the presence of NaBF4. The salt [Cp*RhCl{κP,κS-(CF2CF)PPh(C6H4SMe-2)}]BF4 was prepared as a mixture of cis (5a) and trans (5b) isomers by treatment of [Cp*RhCl(μ-Cl)]2 with the phosphine-thioether (CF2CF)PPh(C6H4SMe-2), 4, in the presence of NaBF4. The structures of 1a–c and 5a have been determined by single-crystal X-ray diffraction. Intramolecular dehydrofluorinative carbon–carbon coupling between pentamethylcyclopentadienyl and trifluorovinylphosphine ligands of 1a, 3 and 5 has been attempted. No reaction was observed on treatment of the neutral complex [Cp*RhCl2{PPh2(CFCF2)}], 1a, with proton sponge, however, 5a underwent dehydrofluorinative coupling to yield [{η5,κP,κS-(C5Me4CH2CFCF)PPh(C6H4SMe-2)}RhCl]BF4, 6. Other reactions, in particular addition of HF across the vinyl bonds of 5, occurred leading to a mixture of products. The cation of 3 underwent similar reactions.

Graphical abstractTreatment of cationic rhodium piano stool complexes with trifluorovinylphosphines with proton sponge yields complexes of tethered ligands.Figure optionsDownload full-size imageDownload as PowerPoint slide