Wang Shi-Sheng, Ding Yi-Hong
Key Laboratory of Carbon Materials of Zhejiang Province, Wenzhou Key Lab of Advanced Energy Storage and Conversion, Zhejiang Province Key Lab of Leather Engineering, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, P. R. China.
Inorg Chem. 2024 Oct 7;63(40):18608-18614. doi: 10.1021/acs.inorgchem.4c02333. Epub 2024 Sep 17.
Substituents are widespread in chemistry, but it has remained quite difficult to reliably determine the thermodynamic and kinetic stabilities of substituted compounds, though they are key to helping establish a structural rule and synthetic viability, respectively. As an important class of valence isomers in the benzene family, benzvalene-like structures have been extensively studied in systems associated with electron-neutral (i.e., C, Si, Ge, Pb, and Sn) and electron-rich (e.g., P) skeletons. However, stable benzvalene-like examples associated with electron-deficient skeletons have been very limited, possibly due to the very complicated bonding patterns of electron-deficient elements. Here, we performed an extensive structural search at the density functional theory (DFT) and CBS-QB3 level for the well-known six-vertex dicarboranes (CBR), one of the central families of boranes and carboranes chemistry. We unexpectedly found that all of the previously reported benzvalene-like structures (CBR) as the long-chased "rule breaker" examples of the Wade-Mingos rule (W-M rule) are not the lowest-lying structures. Promisingly, for the first time, we succeeded in identifying several substituted as the genuine lowest-lying structures and thus true "rule breakers." Thus, "benzvalenes" present hitherto the fourth member of the lowest-lying structural patterns for the family of six-vertex dicarboranes. Moreover, the presently revealed good kinetic stability of (CBRR') over a wide range of substituents promoted us to recommend a novel kind of synthesizable carboranes beyond the Wade-Mingos rule, i.e., "benzvalene-like carboranes" with all of the classical skeletal atoms.
取代基在化学中广泛存在，但可靠地确定取代化合物的热力学和动力学稳定性一直相当困难，尽管它们分别是帮助建立结构规则和合成可行性的关键。作为苯系中一类重要的价异构体，类戊搭烯结构已在与电子中性（即C、Si、Ge、Pb和Sn）和富电子（如P）骨架相关的体系中得到广泛研究。然而，与缺与缺电子骨架相关的稳定类戊搭烯实例非常有限，这可能是由于缺电子元素的键合模式非常复杂。在此，我们在密度泛函理论（DFT）和CBS-QB3水平上对硼烷和碳硼烷化学的核心家族之一——著名的六顶点二碳硼烷（CBR）进行了广泛的结构搜索。我们意外地发现，所有先前报道的作为长期追寻的瓦德-明戈斯规则（W-M规则）“规则破坏者”实例的类戊搭烯结构（CBR）并非能量最低的结构。令人鼓舞的是，我们首次成功鉴定出几种取代的[结构]作为真正的能量最低结构，因此是真正的“规则破坏者”。因此，“戊搭烯”目前是六顶点二碳硼烷家族能量最低结构模式的第四个成员。此外，目前揭示的[结构]（CBRR'）在广泛的取代基范围内具有良好的动力学稳定性，促使我们推荐一种超越瓦德-明戈斯规则的新型可合成碳硼烷，即具有所有经典骨架原子的“类戊搭烯型碳硼烷”。
