Computational investigation of functionalized carbenes on dinitrogen activation
Computational investigation of functionalized carbenes on dinitrogen activation
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DOI：
10.1002/jcc.27046
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发表时间：
2022-12
影响因子：
3
通讯作者：
J. Kirkland;Sophia K. Johnson;K. Vogiatzis
中科院分区：
文献类型：
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作者：
J. Kirkland;Sophia K. Johnson;K. Vogiatzis
氮氮三键的激活是将大气氮整体固定成工业和生物应用的可用形式的关键一步。目前的合成催化剂中加入了金属离子，以促进氮的活化和裂解。金属基催化剂的高价格和工业催化过程中催化剂回收的挑战使人们对无金属催化剂的兴趣与日俱增。迈向无金属催化的一步是使用受挫刘易斯对(FLP)。在这项研究中，我们研究了18个功能化的卡宾作为FLPs，以阐明空间和电子效应对氮素激活的影响。为了验证官能化对氮素活化的影响，我们进行了密度泛函理论(DFT)、多重参考、非过渡态和扩展过渡态-自然轨道化学价态(ETS-NOCV)计算。我们的结果表明，引入强吸电子效应的官能团和/或参与扩展的π/π*体系的官能团导致氮键的解离能降低，这进一步有助于更大的氮活化。我们推测，这些效应是由于卡宾碳原子的p轨道与邻近的氮原子的背键能力增强(增加了卡宾碳原子的Lewis碱度)和解离产物的稳定性所致。我们的结束语包括有机会扩展这项活化研究，以探索整个催化循环，有希望的官能化卡宾用于实验评估。
Activation of the dinitrogen triple bond is a crucial step in the overall fixation of atmospheric nitrogen into usable forms for industrial and biological applications. Current synthetic catalysts incorporate metal ions to facilitate the activation and cleavage of dinitrogen. The high price of metal‐based catalysts and the challenge of catalyst recovery during industrial catalytic processes has led to increasing interest in metal‐free catalysts. One step toward metal‐free catalysis is the use of frustrated Lewis pairs (FLPs). In this study, we have examined 18 functionalized carbenes as FLPs to elucidate the influence of steric and electronic effects on the activation of dinitrogen. To test the effects of functionalization on dinitrogen activation, we have performed density functional theory (DFT), multireference, non and extended transition state‐natural orbital for chemical valence (ETS‐NOCV) calculations. Our results suggest that functional groups which introduce strong electron‐withdrawing effects and/or engage in extended π/π* systems lead to the lowering of the dissociation energy of the dinitrogen bond, which further contributes to greater nitrogen activation. We conjecture that these effects are due to enhanced back‐bonding capability of the p orbital of the carbene carbon atoms to the adjacent nitrogen atoms (increasing Lewis basicity of the carbene carbon atom) and enhanced stability of dissociated products. Our concluding remarks include opportunities to extend this activation study to explore the entire catalytic cycle with promising functionalized carbenes for experimental evaluation.