“…At −80 °C, the 11 B NMR spectrum showed two broad signals at δ =−4.8 and 77.6 ppm (half‐width h 1/2 =1700 and 6200 Hz, respectively), assigned to the central and terminal boron nuclei of 2 , respectively. The negative chemical shift of δ =−4.8 ppm is comparable to those of nucleophilic Lewis base stabilized borylenes (−32.2–0.8 ppm) ,,,,,,,. The chemical shift δ =77.6 ppm is comparable to those of low‐coordinate silaborene and azaborataallene, and the quite large half‐width is similar to that of dimesitylborinium cation ( h 1/2 =5000 Hz) .…”