Benzoborirene: A Starting Point to Metallaboraarenes and Diazaborole-fused Boroles

苯并硼烯是一种硼烯-苯炔配合物，其特征是2 π Hückel芳香硼烯环与6 π Hückel芳香苯环稠合，构成一个有趣的6 π-2 π双环高张力平台。可分离的苯并硼烯的液相合成是一个巨大的挑战，直到最近才得到解决。本实验室首次报道了通过η 2-苯炔锆茂配合物与氨基（二卤）硼烷之间的Zr-B交换反应成功合成。在本项目中，我们打算应用这种合成方法，通过改变苯炔中间体的取代基和硼上的环外取代基来合成各种苯并硼烯（子项目A）。苯并硼烯家族的富集是特别紧迫的，因为这对于评估取代基对芳香性、结构和反应性的空间和电子效应是必不可少的。另一方面，金属芳烃和二硼芳烃都是引人注目的化合物，由于许多迷人的方面，从根本上重要的概念（如Hückel/Möbius芳香性，反芳香性，刘易斯酸性），在丰富的反应化学，在催化和材料科学中的潜在应用。然而，金属硼杂芳烃化学仍然是一个空白领域。我们的初步研究结果表明，苯并硼在合成锆，B-9，10-蒽配合物中的应用，其中蒽的9-和10-位的CH单元分别被三配位硼和锆茂片段取代。在这个项目中，我们的目标是通过应用/修改B，Zr-9，10-蒽的合成策略来启动金属硼杂芳烃化学。将系统地研究键合情况、芳香性、物理性质和反应性，特别是与小分子活化有关的键合情况（子项目B）。此外，我们的初步研究表明，从苯并硼杂环戊二烯合成苯并硼杂环戊二烯二酰胺配合物。在本计画中，我们利用二胺配合物来合成迄今未知的含二氮硼杂环戊烯的硼杂环戊烯。将研究成环作用对反芳香性、刘易斯酸性、电化学和物理化学性质的影响（子项目C）。

Benzoborirene, a formal borylene-benzyne complex, features a 2π Hückel-aromatic borirene ring that is fused to a 6π Hückel-aromatic benzene ring, and thus constituting an intriguing 6π-2 π bicyclic and highly strained platform. The solution-phase synthesis of isolable benzoborirenes is of great challenge that has not been addressed until very recently. Our laboratory reported the first successful synthesis by the Zr-B exchange reaction between a η2-benzyne zirconocene complex and an amino(dihalo)borane. In this project, we intend to apply this synthetic approach to synthesize a variety of benzoborirenes by variation of the substituents of the benzyne intermediate and the exocyclic substituent on boron (subproject A). The enrichment of the benzoborirene family is particularly urgent, as this is essential for the assessment of the steric as well as the electronic effect of the substituents on the aromaticity, structure, and reactivity. On the other hand, metallaarenes and diboraarenes are both striking compounds owing to numerous fascinating aspects, which span from the fundamentally significant concepts (e.g. Hückel/Möbius aromaticity, antiaromaticity, Lewis acidity), over the rich reaction chemistry, to potential applications in catalysis and material science. However, metallaboraarene chemistry is still a gaping area. Our preliminary results demonstrated the application of benzoborirene in the synthesis of a Zr,B-9,10-anthracene complex, in which the CH units at the 9- and 10-position of anthracene are replaced with tricoordinate boron and a zirconocene fragment, respectively. In this project, we aim at initiating the metallaboraarene chemistry by applying/modifying the synthetic strategy for the B,Zr-9,10-anthracene. The bonding situations, aromaticity, physical properties, and reactivity, in particular that associated with small molecule activation, will be systematically studied (subproject B). Furthermore, our preliminary study demonstrated the synthesis of benzoborole diamide complexes from benzoborirene. In this project, we utilize the diamide complexes to synthesize the heretofore unknown diazaborole-fused boroles. The effect of annulation on antiaromaticity, Lewis acidity, electrochemistry, and photophysical properties will be investigated (subproject C).