Synthesis of 12-Substituted 1-Carba-closo-dodecaborate Anions and First Hyperpolarizability of the 12-C7H6+-CB11H11- Ylide

Salts of 12-alkyl and 12-phenyl derivatives of the CB11H12- anion are prepared in 50−60% yields from the 12-iodo-CB11H11- anion by Pd-catalyzed cross-coupling with Grignard reagents. The tropylium ylide 12-C7H6+-CB11H11- is made in 54% yield by reaction of C7H7+ with CB11H12-. Its ground-state dipole moment is 11.25 ± 0.1 D and its first hyperpolarizability is β = 236 × 10-30 esu at 1064 nm, as determined by hyper-Rayleigh scattering measurement. This value is ten times that of p-nitroaniline and is surprisingly large considering that the compound is colorless.