Stabilizing Borinium Cations [X–B–X] + through Conjugation and Hyperconjugation Effects
Stabilizing Borinium Cations [X–B–X] + through Conjugation and Hyperconjugation Effects
复制标题
通过共轭和超共轭效应稳定硼阳离子 [X–B–X]
DOI：
10.1021/acs.inorgchem.8b02316
复制
发表时间：
2018
影响因子：
4.6
通讯作者：
Wu, Judy I-Chia
中科院分区：
文献类型：
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作者：
Zhang, Yan;Xie, Yaoming;Schaefer, Henry F.;Wu, Judy I-Chia
硼，一种双配位的硼阳离子，是一种强刘易斯酸，由于配位配体的数量较少和对亲核反应的敏感性，被认为难以制备。最近，Shoji及其同事合成并表征了具有高热稳定性的二均三甲苯基硼阳离子（Mes 2B+）。这些发现表明，尽管硼阳离子非常需要电子，但可以用某些取代的官能团来稳定。本文用NBO和BLW方法研究了一系列不同取代基的硼离子[X-B-X]+。计算结果表明，π共轭和超共轭效应都能有效地稳定取代硼阳离子[X-B-X]+。取代基如X = C = CH 2通过高度离域的π键稳定硼中心，包括形式上的“空”硼px和pyorbitals。我们建议硼离子[X-B-X]+（X = cyc-N（CH）2，特别是X = C CH 2）作为新型硼离子的可能合成目标。
Borinium, a two-coordinated boron cation, is a strong Lewis acid that was thought difficult to prepare due to a lower number of coordinating ligands and susceptibility toward nucleophilic reactions. Recently a dimesityl borinium cation (Mes2B+) with high thermal stability has been synthesized and characterized by Shoji and co-workers. These findings suggest that, despite being extremely electron-demanding, borinium cations might be stabilized with certain substituted function groups. In the present study, we have studied a series of the borinium cations [X–B–X]+with different substituted groups using the NBO and the BLW methods. Our computations revealed that both π-conjugation and hyperconjugation effects can effectively stabilize substituted borinium cations [X–B–X]+. Substituents such as X = C═CH2stabilize the borinium center through highly delocalized π-bonding, involving the formally “empty” boron pxand pyorbitals. We suggest the borinium cations [X–B–X]+with X = cyc-N(CH)2and especially X = C═CH2as possible synthetic targets of novel borinium cations.