NMR Reveals That a Highly Reactive Nonheme FeIV=O Complex Retains Its Six-Coordinate Geometry and S=1 State in Solution

Saikat Banerjee; Waqas Rasheed; Ruixi Fan; Apparao Draksharapu; Williamson N. Oloo; Yisong Guo; Larry Que

doi:10.1002/chem.201902048

NMR Reveals That a Highly Reactive Nonheme Fe^IV=O Complex Retains Its Six-Coordinate Geometry and S=1 State in Solution

Saikat Banerjee, Waqas Rasheed, Ruixi Fan, Apparao Draksharapu, Williamson N. Oloo, Yisong Guo, Larry Que

Chemistry (Twin Cities)

Research output: Contribution to journal › Article › peer-review

8 Scopus citations

Abstract

The [Fe^IV(O)(Me₃NTB)]²⁺ (Me₃NTB=tris[(1-methyl-benzimidazol-2-yl)methyl]amine) complex 1 has been shown by Mössbauer spectroscopy to have an S=1 ground state at 4 K, but is proposed to become an S=2 trigonal-bipyramidal species at higher temperatures based on a DFT model to rationalize its very high C−H bond-cleavage reactivity. In this work, ¹H NMR spectroscopy was used to determine that 1 does not have C₃-symmetry in solution and is not an S=2 species. Our results show that 1 is unique among nonheme Fe^IV=O complexes in retaining its S=1 spin state and high reactivity at 193 K, providing evidence that S=1 Fe^IV=O complexes can be as reactive as their S=2 counterparts. This result emphasizes the need to identify factors besides the ground spin state of the Fe^IV=O center to rationalize nonheme oxoiron(IV) reactivity.

Original language	English (US)
Pages (from-to)	9608-9613
Number of pages	6
Journal	Chemistry - A European Journal
Volume	25
Issue number	41
DOIs	https://doi.org/10.1002/chem.201902048
State	Published - Jul 22 2019

Bibliographical note

Funding Information:
We gratefully acknowledge the support of the U.S. National Science Foundation (grants CHE-1665391 to L.Q. and CHE-1654060 to Y.G.). The Bruker Avance III HD nanobay 400 MHz spectrometer used in this study was purchased from funds provided by the Office of the Vice President of Research, the College of Science and Engineering, and the Department of Chemistry at the University of Minnesota. We thank Dr. Letitia Yao for her advice on our NMR experiments and Prof. John Lipscomb and Shuangning Xu for their valuable input into the interpretation of our kinetic data.

Publisher Copyright:
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Keywords

DFT calculations
NMR spectroscopy
nonheme iron
oxoiron(IV) complexes
two-state reactivity

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title = "NMR Reveals That a Highly Reactive Nonheme FeIV=O Complex Retains Its Six-Coordinate Geometry and S=1 State in Solution",

abstract = "The [FeIV(O)(Me3NTB)]2+ (Me3NTB=tris[(1-methyl-benzimidazol-2-yl)methyl]amine) complex 1 has been shown by M{\"o}ssbauer spectroscopy to have an S=1 ground state at 4 K, but is proposed to become an S=2 trigonal-bipyramidal species at higher temperatures based on a DFT model to rationalize its very high C−H bond-cleavage reactivity. In this work, 1H NMR spectroscopy was used to determine that 1 does not have C3-symmetry in solution and is not an S=2 species. Our results show that 1 is unique among nonheme FeIV=O complexes in retaining its S=1 spin state and high reactivity at 193 K, providing evidence that S=1 FeIV=O complexes can be as reactive as their S=2 counterparts. This result emphasizes the need to identify factors besides the ground spin state of the FeIV=O center to rationalize nonheme oxoiron(IV) reactivity.",

keywords = "DFT calculations, NMR spectroscopy, nonheme iron, oxoiron(IV) complexes, two-state reactivity",

author = "Saikat Banerjee and Waqas Rasheed and Ruixi Fan and Apparao Draksharapu and Oloo, {Williamson N.} and Yisong Guo and Larry Que",

note = "Funding Information: We gratefully acknowledge the support of the U.S. National Science Foundation (grants CHE-1665391 to L.Q. and CHE-1654060 to Y.G.). The Bruker Avance III HD nanobay 400 MHz spectrometer used in this study was purchased from funds provided by the Office of the Vice President of Research, the College of Science and Engineering, and the Department of Chemistry at the University of Minnesota. We thank Dr. Letitia Yao for her advice on our NMR experiments and Prof. John Lipscomb and Shuangning Xu for their valuable input into the interpretation of our kinetic data. Publisher Copyright: {\textcopyright} 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim",

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T1 - NMR Reveals That a Highly Reactive Nonheme FeIV=O Complex Retains Its Six-Coordinate Geometry and S=1 State in Solution

AU - Banerjee, Saikat

AU - Rasheed, Waqas

AU - Fan, Ruixi

AU - Draksharapu, Apparao

AU - Oloo, Williamson N.

AU - Guo, Yisong

AU - Que, Larry

N1 - Funding Information: We gratefully acknowledge the support of the U.S. National Science Foundation (grants CHE-1665391 to L.Q. and CHE-1654060 to Y.G.). The Bruker Avance III HD nanobay 400 MHz spectrometer used in this study was purchased from funds provided by the Office of the Vice President of Research, the College of Science and Engineering, and the Department of Chemistry at the University of Minnesota. We thank Dr. Letitia Yao for her advice on our NMR experiments and Prof. John Lipscomb and Shuangning Xu for their valuable input into the interpretation of our kinetic data. Publisher Copyright: © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

PY - 2019/7/22

Y1 - 2019/7/22

N2 - The [FeIV(O)(Me3NTB)]2+ (Me3NTB=tris[(1-methyl-benzimidazol-2-yl)methyl]amine) complex 1 has been shown by Mössbauer spectroscopy to have an S=1 ground state at 4 K, but is proposed to become an S=2 trigonal-bipyramidal species at higher temperatures based on a DFT model to rationalize its very high C−H bond-cleavage reactivity. In this work, 1H NMR spectroscopy was used to determine that 1 does not have C3-symmetry in solution and is not an S=2 species. Our results show that 1 is unique among nonheme FeIV=O complexes in retaining its S=1 spin state and high reactivity at 193 K, providing evidence that S=1 FeIV=O complexes can be as reactive as their S=2 counterparts. This result emphasizes the need to identify factors besides the ground spin state of the FeIV=O center to rationalize nonheme oxoiron(IV) reactivity.

AB - The [FeIV(O)(Me3NTB)]2+ (Me3NTB=tris[(1-methyl-benzimidazol-2-yl)methyl]amine) complex 1 has been shown by Mössbauer spectroscopy to have an S=1 ground state at 4 K, but is proposed to become an S=2 trigonal-bipyramidal species at higher temperatures based on a DFT model to rationalize its very high C−H bond-cleavage reactivity. In this work, 1H NMR spectroscopy was used to determine that 1 does not have C3-symmetry in solution and is not an S=2 species. Our results show that 1 is unique among nonheme FeIV=O complexes in retaining its S=1 spin state and high reactivity at 193 K, providing evidence that S=1 FeIV=O complexes can be as reactive as their S=2 counterparts. This result emphasizes the need to identify factors besides the ground spin state of the FeIV=O center to rationalize nonheme oxoiron(IV) reactivity.

KW - DFT calculations

KW - NMR spectroscopy

KW - nonheme iron

KW - oxoiron(IV) complexes

KW - two-state reactivity

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