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 )C 2 B 10 H 10 ]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(Bu t )C 2 B 10 H 10 }B(NHC)] •+ ([ 2 ] •+ ) and dicarbollyl-fused azaborole 7,8- nido -C 2 B 9 H 9 -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 ] •+ is delocalized over the BNC unit, and the two fused five-membered rings in 3 form a sort of π-conjugated system.