Synthesis and Structural Characterization of Carbene-Stabilized Carborane-Fused Azaborolyl Radical Cation and Dicarbollyl-Fused Azaborole

The carbene-stabilized electron-rich iminocarboranyl boron-(I) compound [(Dipp)NC(Bu-t)C2B10H10]B(NHC) (1) (Dipp = 2,6-diisopropylphenyl, NHC = 1,3-diisopropy1-4,5-dimethylimidazol-2-ylidene) is an excellent precursor for the preparation of the unprecedented carborane-fused azaborolyl radical cation [{(Dipp)NC(Bu-t)C2B10H10}B-(NHC)(center dot+) ([2](center dot+)) and dicarbollyl-fused azaborole 7,8-nido-C2B9H9-7,8-C(Bu-t)N(Dipp)B(NHC) (3) via controlled single-electron oxidation and two-electron oxidative deboration, respectively. Single-crystal X-ray analyses and DFT calculations indicate that the unpaired electron in [2](center dot+) is delocalized over the BNC unit, and the two fused five-membered rings in 3 form a sort of pi-conjugated system.