Lee Vladimir Ya, Ito Yuki, Gapurenko Olga A, Minyaev Ruslan M, Gornitzka Heinz, Sekiguchi Akira
Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Institute of Physical and Organic Chemistry, Southern Federal University, Rostov on Don 344090, Russian Federation.
J Am Chem Soc. 2020 Sep 23;142(38):16455-16460. doi: 10.1021/jacs.0c08052. Epub 2020 Sep 10.
(Silatrigerma)cyclobutenylium ion salt was readily prepared by the reaction of cyclotrigermene with an equimolar amount of [EtSi(benzene)][B(CF)] in benzene. The homoaromatic nature of was firmly established by its crystallographic analysis, which revealed a highly folded SiGe four-membered ring (40.4°) and a remarkably short transannular Ge-Ge distance of 2.9346(3) Å. The homoaromaticity of was supported by DFT calculations, which confirmed an extensive transannular bonding orbital interaction. One-electron reduction of with potassium graphite resulted in the selective formation of (silatrigerma)cyclobutenyl free radical , which has an allylic-type structure as confirmed by its X-ray and EPR studies. Cation and free radical can be readily interconverted, thus constituting a fully reversible redox pair.
（硅杂环丁三烯）环丁烯鎓离子盐可通过环三锗烯与等摩尔量的[EtSi(苯)][B(CF)]在苯中反应轻松制备。通过晶体学分析确定了其同芳香性，该分析揭示了一个高度折叠的SiGe四元环（40.4°）以及显著短的跨环Ge-Ge距离2.9346(3) Å。密度泛函理论计算支持了其同芳香性，证实了广泛的跨环键合轨道相互作用。用钾石墨对其进行单电子还原导致选择性形成（硅杂环丁三烯）环丁烯基自由基，通过X射线和电子顺磁共振研究证实其具有烯丙基型结构。阳离子和自由基可以轻松相互转化，从而构成一个完全可逆的氧化还原对。
