Fluoride-mediated rearrangement of phenylfluorosilanes

Combining Ph3SiF and fluoride ion under conditions used for the Hiyama coupling causes rapid formation of the expected [Ph3SiF2]−; however, real-time electrospray mass spectrometric analysis reveals that phenyl-fluoride exchange occurs concomitantly, also producing substantial quantities of [PhnSiF5–n]− (n = 0–2). The exchange process is verified using 19F NMR spectroscopy. This observation may have implications for Hiyama reaction protocols, which use transmetallation from triaryldifluorosilicates as a key step in cross-coupling.