Zhang Yuwei, Zhang Caiyun, Mo Yirong, Cao Zexing
State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian, Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemistry Engineering, Xiamen University, 422 Siming Rd., Xiamen, 361005, China.
Department of Nanoscience, Joint School of Nanoscience and Nanoengineering, University of North Carolina at Greensboro, 2907 East Gate City Blvd, Greensboro, NC, 27401, USA.
Chemistry. 2021 Jan 18;27(4):1402-1409. doi: 10.1002/chem.202004298. Epub 2020 Dec 15.
Designing and synthesizing a stable compound with a planar tetracoordinate silicon (ptSi) center is a challenging goal for chemists. Here, a series of potential aromatic ptSi compounds composed of four conjugated rings shared by a centrally embedded Si atom are theoretically designed and computationally verified. Both Born-Oppenheimer molecular dynamics (BOMD) simulations and potential energy surface scannings verify the high stability and likely existence of these compounds, particularly Si-16-5555 (SiN C H ) with 16 π electrons, under standard ambient temperature and pressure. Notably, the Hückel aromaticity rule, which works well for single rings, is inconsistent with the high stability of Si-16-5555 where the 16 p electrons are spread over four five-membered rings fused together. Bonding analyses show that the strong electron donation from the peripheral 12-membered conjugated ring with 16 π electrons to the vacant central atomic orbital Si 3p leads to the stabilization for both the ptSi coordination and planar aromaticity. The partial occupation of Si 3p results in the peculiar carbenoid-type behaviors for the amphoteric center. By modulating the electron density on the ring with substituent groups, we can regulate the nucleophilic and electrophilic properties of the central Si.
设计并合成一种具有平面四配位硅（ptSi）中心的稳定化合物，对化学家来说是一个具有挑战性的目标。在此，理论上设计并通过计算验证了一系列由中心嵌入的硅原子共享四个共轭环组成的潜在芳香族ptSi化合物。玻恩-奥本海默分子动力学（BOMD）模拟和势能面扫描均验证了这些化合物在标准环境温度和压力下具有高稳定性且可能存在，特别是具有16个π电子的Si-16-5555（SiN C H ）。值得注意的是，适用于单环的休克尔芳香性规则与Si-16-5555的高稳定性不一致，在Si-16-5555中，16个p电子分布在四个稠合在一起的五元环上。键合分析表明，具有16个π电子的外围12元共轭环向空的中心原子轨道Si 3p的强电子给予作用，导致了ptSi配位和平面芳香性的稳定。Si 3p的部分占据导致两性中心具有特殊的类卡宾型行为。通过用取代基调节环上的电子密度，我们可以调控中心硅的亲核和亲电性质。
