Liu Xiaoqing, Li Xue, Yao Xiaoqian, Zhao Weizhen, Liu Lei
School of Environment and Safety Engineering, North University of China, Taiyuan, 030051, China.
Beijing Key Laboratory of Ionic Liquids Clean Process, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100049, China.
Chemphyschem. 2021 May 17;22(10):968-974. doi: 10.1002/cphc.202100093. Epub 2021 Apr 16.
Nowadays, hydrogen activation by frustrated Lewis pairs (FLPs) and their applications are one of the emerging research topics in the field of catalysis. Previous studies have shown that the thermodynamics of this reaction is determined by electronic structures of FLPs and solvents. Herein, we investigated systems consisting of typical FLPs and ionic liquids (ILs), which are well known by their large number of types and excellent solvent effects. The density functional theory (DFT) calculations were performed to study the thermodynamics for H activation by both inter- and intra-molecular FLPs, as well as the individual components. The results show that the computed overall Gibbs free energies in ILs are more negative than that computed in toluene. Through the thermodynamics partitioning, we find that ILs favor the H-H cleavage elemental step over the elemental steps of proton attachment, hydride attachment and zwitterionic stabilization. Moreover, the results show that these effects are strongly dependent on the type of FLPs, where intra-molecular FLPs are more affected compared to the inter-molecular FLPs.
如今，受阻路易斯酸碱对（FLPs）活化氢及其应用是催化领域新兴的研究课题之一。先前的研究表明，该反应的热力学由FLPs的电子结构和溶剂决定。在此，我们研究了由典型的FLPs和离子液体（ILs）组成的体系，离子液体因其种类繁多和优异的溶剂效应而闻名。进行密度泛函理论（DFT）计算以研究分子间和分子内FLPs以及各组分活化氢的热力学。结果表明，在离子液体中计算得到的总吉布斯自由能比在甲苯中计算得到的更负。通过热力学分配，我们发现离子液体相比于质子附着、氢化物附着和两性离子稳定化的基本步骤，更有利于氢-氢键断裂的基本步骤。此外，结果表明这些效应强烈依赖于FLPs的类型，与分子间FLPs相比，分子内FLPs受到的影响更大。
