Elucidating cation effects in homogeneously catalyzed formic acid dehydrogenation
Nitish Govindarajan1, Evert Jan Meijer
1Van't Hoff Institute for Molecular Sciences, Amsterdam Center for Multiscale Modeling, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands. e.j.meijer@uva.nl.
Faraday Discussions
|September 24, 2019
Summary
Cations like Li+ and K+ hinder the hydride transfer step in ruthenium-catalyzed formic acid dehydrogenation. This stabilization of the formate intermediate raises reaction barriers, impacting catalyst efficiency.
Area of Science:
- Catalysis
- Computational Chemistry
- Physical Chemistry
Background:
- Formic acid dehydrogenation is a key reaction for hydrogen storage.
- Ruthenium PNP pincer complexes (RuPNP) are efficient catalysts for this process.
- The influence of solvent and cations on reaction mechanisms requires further investigation.
Purpose of the Study:
- To investigate the effect of cations (Li+, K+) on formic acid dehydrogenation catalyzed by a RuPNP complex.
- To elucidate the role of methanol solvent in the reaction mechanism.
- To understand cation-induced alterations in the catalytic cycle.
Main Methods:
- Density functional theory (DFT) based molecular dynamics simulations.
- Explicit inclusion of methanol solvent molecules.
- Analysis of reaction pathways and energy barriers for key steps.
Main Results:
- The reorientation step of the formate moiety proceeds with a low energy barrier in methanol, especially with Li+ present.
- The hydride transfer step is significantly hindered by the presence of both Li+ and K+ cations.
- Cations strongly stabilize the negatively charged formate intermediate, increasing the barrier for hydride transfer.
Conclusions:
- Cations play a crucial role in modulating the kinetics of formic acid dehydrogenation.
- The stabilization of intermediates by cations can impede catalytic activity.
- This study provides fundamental insights into cation effects in RuPNP-catalyzed reactions.
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