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Mechanistic Study on Catalytic Disproportionation of Hydrazine by a Protic Pincer‐Type Iron Complex through Proton‐Coupled Electron Transfer
Author(s) -
Tanaka Hiromasa,
Hitaoka Seiji,
Umehara Kazuki,
Yoshizawa Kazunari,
Kuwata Shigeki
Publication year - 2020
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201901135
Subject(s) - chemistry , disproportionation , pincer movement , pyrazole , deprotonation , protonation , hydrazine (antidepressant) , catalysis , ligand (biochemistry) , electron transfer , catalytic cycle , molecule , pincer ligand , photochemistry , imidazole , medicinal chemistry , stereochemistry , organic chemistry , ion , biochemistry , receptor , chromatography
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.