德国卡尔斯鲁厄理工学院Dehnen, Stefanie团队报道了，钴基反三明治型配合物中平面π-芳香族Bi5环的分离。相关研究成果于2025年1月20日发表于国际顶尖学术期刊《自然—化学》。

作为工业过程中的合成子，催化或传感金属配合物的配体，以及作为生物活性分子，单环π-芳香族化合物在几乎所有自然科学领域都无处不在。平面有机环因其通过一组不可定位的（4n+2）π电子克服电子缺乏的特殊方式而脱颖而出。相比之下，全金属芳香单环仍然很少见，因为金属原子更喜欢与多键原子形成簇。这限制了相应化合物在化学合成或创新材料中的知识和潜力。

该文中，研究人员报告了Bi5的成功生成，Bi₅^-是（C₅H₅）^-最重的类似物。它作为配体在 [{IMesCo}₂(µ,η⁵:η⁵-Bi₅)]（1）是通过（TlBi₃）^2-与[（IMes）₂CoCl]（其中IMes是双（1,3-（2,4,6-三甲基苯基））咪唑-2-亚基）在邻二氟苯中反应实现的。经μ-SQUID测量和密度泛函理论验证，化合物1为混合价态Co⁰/Co^I，并以逆三明治型方式嵌入平面Bi₅^-循环。捕获Bi₅^-代表了全金属芳香分子化学的一个里程碑，并定义了芳香化合物的新时代。

附：英文原文

Title: Isolation of a planar π-aromatic Bi5 ring in a cobalt-based inverse-sandwich-type complex

Author: Rienmller, Julia, Peerless, Benjamin, Paul, Sagar, Bruder, Florian, Wernsdorfer, Wolfgang, Weigend, Florian, Dehnen, Stefanie

Issue&Volume: 2025-01-20

Abstract: Monocyclic π-aromatic compounds are ubiquitous throughout almost all fields of natural sciences—as synthons in industrial processes, as ligands of metal complexes for catalysis or sensing and as bioactive molecules. Planar organocycles stand out through their specific way of overcoming electron deficiency by a non-localizable set of (4n+2)π electrons. By contrast, all-metal aromatic monocycles are still rare, as metal atoms prefer to form clusters with multiply bonded atoms instead. This limits the knowledge and potential of corresponding compounds in chemical syntheses or for innovative materials. Here we report the successful generation of Bi5, the heaviest analogue of (C5H5). Its use as a ligand in [{IMesCo}2(μ,η5:η5-Bi5)] (1) was realized by reacting (TlBi3)2 with [(IMes)2CoCl] (where IMes is bis(1,3-(2,4,6-trimethylphenyl))imidazol-2-ylidene) in ortho-difluorobenzene. Compound 1 is mixed-valence Co0/CoI as verified by μ-SQUID measurements and density functional theory, and embeds the planar Bi5 cycle in an inverse-sandwich-type manner. Capturing Bi5 represents a landmark in the chemistry of all-metal aromatic molecules and defines a new era for aromatic compounds.

DOI: 10.1038/s41557-024-01713-8

Source: https://www.nature.com/articles/s41557-024-01713-8