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(But)­C2B10H10]­B­(NHC) (1) (Dipp = 2,6-diisopropylphenyl, NHC = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is an excellent precursor for the preparation of the unprecedented carborane-fused azaborolyl radical cation [{(Dipp)­NC­(But)­C2B10H10}­B­(NHC)]•+ ([2]•+) and dicarbollyl-fused azaborole 7,8-nido-C2B9H9-7,8-C­(But)­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]•+ is delocalized over the BNC unit, and the two fused five-membered rings in 3 form a sort of π-conjugated system.