Chemical Non-Innocence in Mn Porphyrin-Catalyzed Nitrene Transfer
6 affiliations
- 1Department of Chemistry
- 2Texas A&M University
- 3Department of Biological and Physical Sciences
- 4Roosevelt University
- 5National High Magnetic Field Laboratory
- 6Florida State University
Abstract
Manganese porphyrins have been widely employed as catalysts for nitrogen-group transfer (NGT) and oxygen-atom transfer (OAT) reactions with olefins and C–H bonds. These transformations are typically proposed to proceed via high-valent manganese nitrenoid and oxo intermediates, respectively. While porphyrin redox non-innocence — in which electron transfer from the ligand to the metal delocalizes high-valent states across the metal and the ancillary ligand — is well established. The potential role of porphyrin chemical non-innocence — in which an atom or group inserts into the M–pyrrolide bond — is much less appreciated. Here, we demonstrate that treatment of Mn(tpp)Cl with iminoiodinanes (PhI═NR, R = Ts (tosyl) and Ns (nosyl)) affords the corresponding tucked-in Mn porphyrins in which the iminoiodinane-derived nitrene fragment has inserted into one of the Mn–N bonds. Nitrene insertion into the Mn–N bond was characterized by NMR, UV-vis, and high-frequency and -field EPR (HFEPR) spectroscopies, as well as single-crystal X-ray diffraction. Nitrene insertion into the Mn–N bond is reversible under both thermal and photochemical conditions; untucking in the presence of styrene affords the corresponding aziridine, demonstrating that the tucked-in porphyrin can function as a latent nitrene equivalent. In situ UV-vis spectroscopy and kinetics experiments of Mn(tpp)Cl-catalyzed styrene aziridination demonstrate that, despite the chemical viability of nitrene insertion / de-insertion reactions, the formation of tuck-in porphyrins is slow relative to olefin aziridination. These results demonstrate that reversible formation of nitrene tuck-in porphyrins is chemically accessible and represents a latent source of electrophilic nitrene equivalents and that in the context of Mncatalyzed aziridination, these elementary steps are slow relative to catalysis.
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BibTeX
@misc{sinha2026chemical,
title = {{Chemical Non-Innocence in Mn Porphyrin-Catalyzed Nitrene Transfer}},
author = {Arka Sinha and Ryan X. Gruen and Matthew T. Figgins and Joseph Reibenspies and Joshua Telser and J. Krzystek and David C. Powers},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010103/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010103/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Chemical Non-Innocence in Mn Porphyrin-Catalyzed Nitrene Transfer
AU - Arka Sinha
AU - Ryan X. Gruen
AU - Matthew T. Figgins
AU - Joseph Reibenspies
AU - Joshua Telser
AU - J. Krzystek
AU - David C. Powers
PY - 2026
DA - 2026/10/08
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010103/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010103/v1
AB - Manganese porphyrins have been widely employed as catalysts for nitrogen-group transfer (NGT) and oxygen-atom transfer (OAT) reactions with olefins and C–H bonds. These transformations are typically proposed to proceed via high-valent manganese nitrenoid and oxo intermediates, respectively. While porphyrin redox non-innocence — in which electron transfer from the ligand to the metal delocalizes high-valent states across the metal and the ancillary ligand — is well established. The potential role of porphyrin chemical non-innocence — in which an atom or group inserts into the M–pyrrolide bond — is much less appreciated. Here, we demonstrate that treatment of Mn(tpp)Cl with iminoiodinanes (PhI═NR, R = Ts (tosyl) and Ns (nosyl)) affords the corresponding tucked-in Mn porphyrins in which the iminoiodinane-derived nitrene fragment has inserted into one of the Mn–N bonds. Nitrene insertion into the Mn–N bond was characterized by NMR, UV-vis, and high-frequency and -field EPR (HFEPR) spectroscopies, as well as single-crystal X-ray diffraction. Nitrene insertion into the Mn–N bond is reversible under both thermal and photochemical conditions; untucking in the presence of styrene affords the corresponding aziridine, demonstrating that the tucked-in porphyrin can function as a latent nitrene equivalent. In situ UV-vis spectroscopy and kinetics experiments of Mn(tpp)Cl-catalyzed styrene aziridination demonstrate that, despite the chemical viability of nitrene insertion / de-insertion reactions, the formation of tuck-in porphyrins is slow relative to olefin aziridination. These results demonstrate that reversible formation of nitrene tuck-in porphyrins is chemically accessible and represents a latent source of electrophilic nitrene equivalents and that in the context of Mncatalyzed aziridination, these elementary steps are slow relative to catalysis.
ER -