Mechanistic Study on Catalytic Disproportionation of Hydrazine by a Protic Pincer-Type Iron Complex through Proton-Coupled Electron Transfer

Hiromasa Tanaka, Seiji Hitaoka, Kazuki Umehara, Kazunari Yoshizawa, Shigeki Kuwata

Research output: Contribution to journalArticlepeer-review

Abstract

Density functional theory calculations have been performed for the proposal of a plausible reaction pathway for disproportionation of hydrazine catalyzed by an iron complex bearing a multiproton-responsive pincer-type bis(pyrazole) ligand. The pyrazole arms in this ligand are capable of serving as both Brønsted acid and base. At the first stage of the catalytic cycle, a hydrazine molecule bound to the iron center is converted into two molecules of ammonia by two successive protonation steps from the pyrazole NH groups. The deprotonated pyrazolate arms later abstract two protons from another hydrazine molecule to afford an iron–diazene complex, which is a possible intermediate leading to formation of dinitrogen and ammonia. This bidirectional proton transfer (pyrazole arm ↔ hydrazine) is coupled with electron shuttling along a different pathway (iron center ↔ hydrazine). Overall energy profiles of the proposed mechanism calculated in different spin states elucidate the importance of the spin-state flexibility of this iron complex.

Original languageEnglish
Pages (from-to)1472-1482
Number of pages11
JournalEuropean Journal of Inorganic Chemistry
Volume2020
Issue number15-16
DOIs
Publication statusPublished - Apr 30 2020

All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

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