Lu Wei, Do Dinh Cao Huan, Kinjo Rei
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore.
Nat Commun. 2020 Jul 6;11(1):3370. doi: 10.1038/s41467-020-17166-9.
It is widely known that the skeletal structure of clusters reflects the number of skeletal bonding electron pairs involved, which is called the polyhedral skeletal electron pair theory (PSEPT) or Wade and Mingos rules. While recent computational studies propose that the increase of skeletal electrons of polyhedral clusters leads to the flat structure beyond the PSEPT, little experimental evidence has been demonstrated. Herein, we report the synthesis of a CBR carborane 2 featuring a flat ribbon-like structure. The CB core of 2 bearing 16 skeletal electrons in the singlet-ground state defies both the [4n + 2] Hückel's rule and Baird's rule. Nevertheless, the delocalization of those electrons simultaneously induces two independent π- and two independent σ-aromatic ring currents, rendering quadruple aromaticity.
众所周知，簇合物的骨架结构反映了所涉及的骨架成键电子对的数量，这被称为多面体骨架电子对理论（PSEPT）或韦德和明戈斯规则。虽然最近的计算研究表明，多面体簇合物的骨架电子增加会导致超出PSEPT的平面结构，但几乎没有实验证据得到证实。在此，我们报告了一种具有扁平带状结构的CBR碳硼烷2的合成。2的CB核心在单重基态下具有16个骨架电子，既不符合[4n + 2]休克尔规则，也不符合贝尔德规则。然而，这些电子的离域同时诱导了两个独立的π和两个独立的σ芳香环电流，呈现出四重芳香性。
