Figure 2.

All ¹H NMR spectra [(a)–(d) 500 MHz; CD₂Cl₂], and ¹⁹F NMR spectra [(e)–(h) 470 MHz; CD₂Cl₂] were recorded at −60 °C, except spectrum (d) which was acquired at −30 °C. In each case, several spectra were acquired to check that the system had come to equilibrium. The shoulder at −78 ppm in (h) is a shimming artefact.