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

Abstract

The base-free benzoborirene 1,2-BR-1,2-C₆H₄ (<b>7</b>) and its three-dimensional inorganic analogue 1,2-BR-1,2-C₂B₁₀H₁₀ (<b>13</b>) have been successfully synthesized by Cp₂ZrBr₂ and LiCl elimination, respectively. The Cl analogue of the key intermediate for the formation of benzoborirene <b>7</b> has been isolated and structurally characterized, thus suggesting the reaction pathway via benzyne Zr complex formation, B-Br/C_benzyne-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 ^MeI<i>i</i>Pr (<b>8</b>), thus allowing for the synthetic approach to the first carborane-substituted iminoborane <b>14</b>.