Abstract
We studied the mechanism of the pyrrole synthesis catalyzed by a PN3P–Mn pincer ligand system and show that a bifunctional double hydrogen transfer mechanism is favored over the alternative β-hydride elimination. Both dehydrogenation and hydrogen-formation steps benefit from proton shuttles, with alcohol-mediated processes being consistently favored, leading to energy barriers that, in good agreement with the experimental results, are similar to those for the previously reported corresponding iridium-catalyzed process. We also show that the coordination of one potassium ion to the ligand lowers the energy barriers for the key steps. The overall rate-determining step is the regeneration of the catalyst with an energy barrier of 30.7 kcal/mol with potassium and 31.1 kcal/mol without potassium. Our results support the involvement and the importance of the aromatization/dearomatization paradigm in the reaction.
Original language | English (US) |
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Pages (from-to) | 18-24 |
Number of pages | 7 |
Journal | Organometallics |
Volume | 39 |
Issue number | 1 |
DOIs | |
State | Published - Dec 13 2019 |