Figure 4.

Solid-state boron-11 NMR spectroscopy of 2. Experimental spectra of a powdered sample undergoing MAS are shown in (a) ¹¹B at 9.40 T and (c) ¹¹B at 21.1 T. Best-fit spectra were simulated using WSolids (traces (b) and (d)) using the parameters given in Table 1. Experimental spectra of stationary powdered samples are shown in (e) ¹¹B at 9.40 T and (g) ¹¹B at 21.1 T. Best-fit spectra were simulated using WSolids (traces (f) and (h)) using the parameters given in Table 1. The small peaks in spectra (a−d) seen at ∼1 and 19 ppm are due to boric acid, and its spectral parameters may be found in Table 1.