Pérez Patricia, Yepes Diana, Jaque Pablo, Chamorro Eduardo, Domingo Luis R, Rojas Rene S, Toro-Labbé Alejandro
Universidad Andres Bello, Facultad de Ciencias Exactas, Departamento de Ciencias Químicas, Laboratorio de Química Teórica, Av. República 275, 8370146 Santiago, Chile.
Phys Chem Chem Phys. 2015 Apr 28;17(16):10715-25. doi: 10.1039/c5cp00306g.
A computational and conceptual density functional theory (DFT) study on the mechanism of molecular hydrogen activation by a set of three frustrated Lewis pairs (FLPs) was performed at the ωB97X-D/6-311G(d,p) level of theory. A reduced model and other two prototypes derived from experimental data, based on the donor nitrogen and acceptor boron atoms, were used. Analysis based on the energy results, geometries and the global electron density transfer at the TSs made it possible to obtain some interesting conclusions: (i) despite the well-known very low reactivity of molecular hydrogen, the catalytic effectiveness of the three FLPs produces reactions with almost unappreciable activation energies; (ii) the reactions, being exothermic, follow a one-step mechanism via polarised TSs; (iii) there are neither substituent effects on the kinetics nor on the thermodynamics of these reactions; (iv) the activation of molecular hydrogen seems to be attained when the N-B distance in the FLP derivatives is around 2.74 Å; and (v) the proposed FLP model is consistent with the behaviour of the experimental prototypes. Finally, the ability of the three FLPs as efficient catalysts was evaluated studying the hydrogenation of acetylene to yield ethylene.
在ωB97X-D/6-311G(d,p)理论水平上，对一组三个受阻路易斯酸碱对（FLP）活化分子氢的机理进行了计算和概念性密度泛函理论（DFT）研究。基于供体氮原子和受体硼原子，使用了一个简化模型以及从实验数据推导得到的其他两个原型。基于能量结果、几何结构以及过渡态处的全局电子密度转移进行分析，从而得出了一些有趣的结论：（i）尽管众所周知分子氢的反应活性非常低，但这三个FLP的催化效果使得反应的活化能几乎可以忽略不计；（ii）这些反应是放热反应，通过极化的过渡态遵循一步反应机理；（iii）这些反应的动力学和热力学均不存在取代基效应；（iv）当FLP衍生物中的N-B距离约为2.74 Å时，似乎可以实现分子氢的活化；（v）所提出的FLP模型与实验原型的行为一致。最后，通过研究乙炔加氢生成乙烯，评估了这三个FLP作为高效催化剂的能力。
