Figure 3.

Partial ¹⁹F NMR spectra of [n-Bu₄N]⁺F⁻ in DMSO-d₆ at room temperature, showing the downfield shift of F⁻ resonance upon the gradual addition of L. (a) Free [n-Bu₄N]⁺F⁻ (δ_F = −105.2 ppm), (b) [n-Bu₄N]⁺F⁻ + 0.25 equiv. of L (δ_F = −102.5 ppm), (c) [n-Bu₄N]⁺F⁻ + 0.50 equiv. of L (δ_F = −96.4 ppm), and (d) [n-Bu₄N]⁺F⁻ + 1.0 equiv. of L (δ_F = −90.1 ppm).