Computational mechanistic studies of ruthenium catalysed methanol dehydrogenation.

Felix J De Zwart,Bas De Bruin,Monica Trincado,Hansjörg Grützmacher,Vivek Sinha

doi:10.1039/d1dt04168a

Abstract

Homogeneous ruthenium catalysed methanol dehydrogenation could become a key reaction for hydrogen production in liquid fuel cells. In order to improve existing catalytic systems, mechanistic insight is paramount in directing future studies. Herein, we describe what computational mechanistic research has taught us so far about ruthenium catalysed dehydrogenation reactions. In general, two mechanistic pathways can be operative in these reactions: a metal-centered or a metal–ligand cooperative (Noyori–Morris type) minimum energy reaction pathway (MERP). Discerning between these mechanisms on the basis of computational studies has proven to be highly input dependent, and to circumvent pitfalls it is important to consider several factors, such as solvent effects, metal–ligand cooperativity, alternative geometries, and complex electronic structures of metal centres. This Frontiers article summarizes the reported computational research performed on ruthenium catalyzed dehydrogenation reactions performed in the past decade, and serves as a guide for future research.

Highlights

View Article OnlineTwo mechanistic pathways can be operative in these reactions: a metal-centered or a metal–ligand cooperative (Noyori–Morris type) minimum energy reaction pathway (MERP)
Felix J. de Zwart, a Vivek Sinha, *b Monica Trincado, c Hansjörg Grützmacher c and Bas de Bruin *a
Hydrogen produced from electrolysis of water using renewable energy sources such as wind and solar can be stored in stable liquid organic compounds such as methanol by direct reduction of carbon dioxide, which can be obtained from atmospheric carbon capture technology.[1]

Summary

View Article Online

Two mechanistic pathways can be operative in these reactions: a metal-centered or a metal–ligand cooperative (Noyori–Morris type) minimum energy reaction pathway (MERP) Discerning between these mechanisms on the basis of computational studies has proven to be highly input dependent, and to circumvent pitfalls it is important to consider several factors, such as solvent effects, metal–ligand cooperativity, alternative geometries, and complex electronic structures of metal centres. This Frontiers article summarizes the reported computational research performed on ruthenium catalyzed dehydrogenation reactions performed in the past decade, and serves as a guide for future research. Key findings from this line of research are: (a) The electronic structures of ruthenium complexes are intricate and can show significant multireference character depending on the substrate. (b) Metal–ligand cooperativity (MLC) is a promising design strategy for active, selective and additivefree catalysts. (c) The pKa of the ligand and hydricity of metal centre are key descriptors of catalytic activity, determine the mechanism and explain the dependence on external base. (d) Explicit solvent effects are important in mechanistic studies of these systems

What does aqueous methanol dehydrogenation entail?

Mechanism of methanol dehydrogenation

Solvent effects

Findings

Conclusions