Consecutive C–F bond activation and C–F bond formation of heteroaromatics at rhodium: the peculiar role of FSi(OEt)3 † †Electronic supplementary information (ESI) available: Experimental procedures, additional spectra and computational details. See DOI: 10.1039/c5sc00877h Click here for additional data file.

The synthetic work was carried out with a Schlenk line under an atmosphere of argon or in an argonfilled glove-box with oxygen levels below 10 ppm. All solvents were dried and purified by conventional methods and distilled under argon before use. [D6]benzene, [D8]toluene and [D8]THF were purified by distillation from Na/K under argon. [Rh{Si(OEt)3}(PEt3)3] (1), [Rh(H)(PEt3)3] (6), [Rh(CH3)(PEt3)3] (9), FSiEt3 and FSi(OEt)3 were prepared according to the literature. 1 Alternatively, the latter was formed in situ. Compound 1 was freshly prepared before usage. In all experiments with 9 as starting compound, 9 was employed as a solution with a concentration of 0.106 mmol·mL -1 . 2,3,5,6-Tetrafluoropyridine, 2,3,4,6-tetrafluorobenzene, 2,3,5,6-tetrafluorobenzene, 2,3,5trifluoropyridine and 2,3,6-trifluoropyridine were supplied from ABCR. TASF was obtained from Sigma-Aldrich.