Sinha Vivek, Govindarajan Nitish, de Bruin Bas, Meijer Evert Jan
Homogenous, Supramolecular and Bio-Inspired Catalysis, Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
Amsterdam Center for Multiscale Modeling and Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
ACS Catal. 2018 Aug 3;8(8):6908-6913. doi: 10.1021/acscatal.8b01177. Epub 2018 Jun 12.
Insights into the mechanism of the catalytic cycle for methanol dehydrogenation catalyzed by a highly active PNP pincer ruthenium complex in methanol solvent are presented, using DFT-based molecular dynamics with an explicit description of the solvent, as well as static DFT calculations using microsolvation models. In contrast to previous results, we find the amido moiety of the catalyst to be permanently protonated under catalytic conditions. Solvent molecules actively participate in crucial reaction steps and significantly affect the reaction barriers when compared to pure gas-phase models, which is a direct result of the enhanced solvent stabilization of methoxide anion intermediates. Further, the calculations reveal that this system does not operate via the commonly assumed Noyori-type outer-sphere metal-ligand cooperative pathway. Our results show the importance of incorporating a molecular description of the solvent to gain a deeper and accurate understanding of the reaction pathways, and stress on the need to involve explicit solvent molecules to model complex catalytic processes in a realistic manner.
本文利用基于密度泛函理论（DFT）的分子动力学方法对溶剂进行了明确描述，并结合使用微溶剂化模型的静态DFT计算，揭示了在甲醇溶剂中由高活性PNP钳形钌配合物催化甲醇脱氢的催化循环机制。与之前的结果相反，我们发现催化剂的酰胺部分在催化条件下会永久质子化。与纯气相模型相比，溶剂分子积极参与关键反应步骤并显著影响反应势垒，这是甲氧基阴离子中间体溶剂稳定性增强的直接结果。此外，计算结果表明该体系并非通过通常假设的Noyori型外球金属-配体协同途径运行。我们的结果表明，纳入溶剂的分子描述对于深入准确理解反应途径非常重要，并强调了需要引入明确的溶剂分子以实际模拟复杂催化过程。
