Dai Chenshu, Zhu Jun
State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China.
Phys Chem Chem Phys. 2022 Jun 15;24(23):14651-14657. doi: 10.1039/d2cp01233b.
The activation of thermodynamically stable and kinetically inert dinitrogen (N) has been a great challenge due to the significant strength of the triple bond. Recently, in an experimental study on N activation by boron species, a highly reactive two-coordinated borylene broke through the limitations of traditional strategies of N activation by metal species. Still, studies on metal-free N activation remain underdeveloped. Here, we systematically investigate a frustrated Lewis pair (FLP) combining carbene and borenium (or borinium) cations to screen potential candidates for N activation density functional theory calculations. As a result, we found that two FLPs (closed form FLP, borenium and open form FLP, borinium) are able to activate N in a thermodynamically and kinetically favorable manner, with a low energy barrier of 9.6 and 7.3 kcal mol, respectively. Furthermore, aromaticity was found to play an important role in the stabilization of the products, supported by nucleus-independent chemical shift (NICS), anisotropy of the current-induced density (ACID) and electron density of delocalized bonds (EDDB) analysis. Our findings provide an alternative approach for metal-free N activation, highlighting the importance of FLP chemistry and aromaticity in N activation.
由于氮氮三键的键能很强，激活热力学稳定且动力学惰性的双氮（N₂）一直是一项巨大的挑战。最近，在一项关于硼物种激活氮的实验研究中，一种高反应活性的双配位硼烯突破了金属物种激活氮的传统策略的限制。尽管如此，无金属氮激活的研究仍不发达。在此，我们通过密度泛函理论计算系统地研究了一种结合卡宾和硼正离子（或硼鎓离子）的受阻路易斯酸碱对（FLP），以筛选氮激活的潜在候选物。结果，我们发现两种FLP（闭式FLP，硼正离子和开式FLP，硼鎓离子）能够以热力学和动力学上有利的方式激活氮，其低能垒分别为9.6和7.3 kcal/mol。此外，通过非核独立化学位移（NICS）、电流感应密度各向异性（ACID）和离域键电子密度（EDDB）分析发现，芳香性在产物的稳定性中起重要作用。我们的研究结果为无金属氮激活提供了一种替代方法，突出了FLP化学和芳香性在氮激活中的重要性。
