Solution-Phase Synthesis of a Base-Free Benzoborirene and a Three-Dimensional Inorganic Analogue.

The base-free benzoborirene 1,2-BR-1,2-C6H4 (7) and its three-dimensional inorganic analogue 1,2-BR-1,2-C2B10H10 (13) have been successfully synthesized by Cp2ZrBr2 and LiCl elimination, respectively. The Cl analogue of the key intermediate for the formation of benzoborirene 7 has been isolated and structurally characterized, thus suggesting the reaction pathway via benzyne Zr complex formation, B-Br/Cbenzyne-Zr σ-bond metathesis, and a Cp2ZrBr2 elimination/ring-closing process. The rationality of the reaction pathway has been confirmed by DFT calculations. In addition, the title compounds shared the same reactivity pattern (i.e., 1,3-silyl migration) toward MeIiPr (8), thus allowing for the synthetic approach to the first carborane-substituted iminoborane 14.