σ Aromaticity Dominates in the Unsaturated Three-Membered Ring of Cyclopropametallapentalenes from Groups 7-9: A DFT Study
σ Aromaticity Dominates in the Unsaturated Three-Membered Ring of Cyclopropametallapentalenes from Groups 7-9: A DFT Study
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DOI：
10.1002/chem.201502390
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发表时间：
2015-12-14
影响因子：
4.3
通讯作者：
Zhu, Jun
中科院分区：
文献类型：
--
作者：
Hao, Yulei;Wu, Jingjing;Zhu, Jun
芳香性是一个古老而又奇妙的课题，长期以来一直引起了化学家们的极大兴趣。一般来说，芳香性是由不饱和化合物闭环中的pi电子离域描述的，而饱和环中的sigma电子离域导致sigma芳香性。有趣的是，我们最近的研究表明，在环丙戊烯的不饱和三元环（3MR）中，sigma芳香性可以占主导地位。提出了一个有趣的问题：在不饱和3MR中占主导地位的西格玛芳香性是否可以扩展到其他环丙烯烯烯？如果是这样，金属中心、配体和取代基如何影响sigma芳香性？在这里，我们报告了对这些问题的深入的理论研究。核无关的化学位移计算和电流诱导密度图的各向异性揭示了这些不饱和3MRs的主要芳香性。此外，我们的计算表明，3MRs上的取代基对sigma芳香性有显著的影响，而配体的影响特别小。
Aromaticity, an old but still fantastic topic, has long attracted considerable interest of chemists. Generally, pi aromaticity is described by pi-electron delocalization in closed circuits of unsaturated compounds whereas sigma-electron delocalization in saturated rings leads to sigma aromaticity. Interestingly, our recent study shows that sigma aromaticity can be dominating in an unsaturated three-membered ring (3MR) of cyclopropaosmapentalene. An interesting question is raised: Can the sigma aromaticity, which is dominant in the unsaturated 3MR, be extended to other cyclopropametallapen-talenes? If so, how could the metal centers, ligands, and substituents affect the sigma aromaticity? Here, we report a thorough theoretical study on these issues. The nucleus-independent chemical shift calculations and the anisotropy of the current-induced density plots reveal the dominant s aromaticity in these unsaturated 3MRs. In addition, our calculations show that substituents on the 3MRs have significant effects on the sigma aromaticity, whereas the ligand effect is particularly small.