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Realistic Modeling of Ruthenium-Catalyzed Transfer Hydrogenation
journal contribution
posted on 2007-03-21, 00:00 authored by Jan-Willem Handgraaf, Evert Jan MeijerWe report the first computational study of a fully atomistic model of the ruthenium-catalyzed
transfer hydrogenation of formaldehyde and the reverse reaction in an explicit methanol solution. Using ab
initio molecular dynamics techniques, we determined the thermodynamics, mechanism, and electronic
structure along the reaction path. To assess the effect of the solvent quantitatively, we make a direct
comparison with the gas-phase reaction. We find that the energy profile in solution bears little resemblance
to the profile in the gas phase and a distinct solvation barrier is found: the activation barriers in both
directions are lowered and the concerted hydride and proton transfer in the gas phase are converted into
a sequential mechanism in solution with the substrate appearing as methoxide-like intermediate. Our results
indicate that besides the metal−ligand bifunctional mechanism, as proposed by Noyori, also a concerted
solvent-mediated mechanism is feasible. Our study gives a new perspective of the active role a solvent
can have in transition-metal-catalyzed reactions.