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

The base-free benzoborirene 1,2-BR-1,2-CH () and its three-dimensional inorganic analogue 1,2-BR-1,2-CBH () have been successfully synthesized by CpZrBr and LiCl elimination, respectively. The Cl analogue of the key intermediate for the formation of benzoborirene has been isolated and structurally characterized, thus suggesting the reaction pathway via benzyne Zr complex formation, B-Br/C-Zr σ-bond metathesis, and a CpZrBr 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 IPr (), thus allowing for the synthetic approach to the first carborane-substituted iminoborane .