Synthesis of Iminoboryl -Carboranes by Lewis Base Promoted Aminoborirane-to-Iminoborane Isomerization.

The iminoboryl -carboranes (MeSi)-Cb-B≡N-R (Cb = BCH, , R = SiMe; , R = Bu) have been successfully synthesized by tetrahydrofuran (THF)-promoted isomerization from the corresponding -carborane-fused aminoboriranes Cb{BN(SiMe)R} (). The synthetic protocol of the previously reported borirane was optimized. The borirane Cb{BN(SiMe)Bu} () and the iminoboranes and were fully characterized by NMR, IR, and single-crystal X-ray diffraction analyses. The borirane isomerizes more readily than . The kinetics study revealed a bimolecular mechanism between borirane and THF, which is in good agreement with the computationally proposed reaction pathway. The title compounds are thermally robust, but compound dimerized in the presence of a catalytic amount of BuNC to give the cyclodimer . Quick equilibrium between and the isonitrile adduct was observed in solution.