Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate

Ruixi Fan, Joan Serrano-Plana, Williamson N. Oloo, Apparao Draksharapu, Estefanía Delgado-Pinar, Anna Company, Vlad Martin-Diaconescu, Margarida Borrell, Julio Lloret-Fillol, Enrique García-España, Yisong Guo, Emile L. Bominaar, Lawrence Que, Miquel Costas, Eckard Münck

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

The reaction of [(PyNMe3)FeII(CF3SO3)2], 1, with excess peracetic acid at -40 °C generates a highly reactive intermediate, 2b(PAA), that has the fastest rate to date for oxidizing cyclohexane by a nonheme iron species. It exhibits an intense 490 nm chromophore associated with an S = 1/2 EPR signal having g-values at 2.07, 2.01, and 1.94. This species was shown to be in a fast equilibrium with a second S = 1/2 species, 2a(PAA), assigned to a low-spin acylperoxoiron(III) center. Unfortunately, contaminants accompanying the 2(PAA) samples prevented determination of the iron oxidation state by Mössbauer spectroscopy. Use of MeO-PyNMe3 (an electron-enriched version of PyNMe3) and cyclohexyl peroxycarboxylic acid as oxidant affords intermediate 3b(CPCA) with a Mössbauer isomer shift δ = -0.08 mm/s that indicates an iron(V) oxidation state. Analysis of the Mössbauer and EPR spectra, combined with DFT studies, demonstrates that the electronic ground state of 3b(CPCA) is best described as a quantum mechanical mixture of [(MeO-PyNMe3)FeV(O)(OC(O)R)]2+ (∼75%) with some FeIV(O)(OC(O)R) and FeIII(OOC(O)R) character. DFT studies of 3b(CPCA) reveal that the unbound oxygen of the carboxylate ligand, O2, is only 2.04 Å away from the oxo group, O1, corresponding to a Wiberg bond order for the O1-O2 bond of 0.35. This unusual geometry facilitates reversible O1-O2 bond formation and cleavage and accounts for the high reactivity of the intermediate when compared to the rates of hydrogen atom transfer and oxygen atom transfer reactions of FeIII(OC(O)R) ferric acyl peroxides and FeIV(O) complexes. The interaction of O2 with O1 leads to a significant downshift of the Fe-O1 Raman frequency (815 cm-1) relative to the 903 cm-1 value predicted for the hypothetical [(MeO-PyNMe3)FeV(O)(NCMe)]3+ complex.

Original languageEnglish (US)
Pages (from-to)3916-3928
Number of pages13
JournalJournal of the American Chemical Society
Volume140
Issue number11
DOIs
StatePublished - Mar 21 2018

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Discrete Fourier transforms
Iron
Paramagnetic resonance
Peracetic Acid
Oxygen
Atoms
Oxidation
Acids
Peroxides
Chromophores
Cyclohexane
Oxidants
Isomers
Ground state
Hydrogen
Spectrum Analysis
Ligands
Spectroscopy
Electrons
Impurities

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

Cite this

Fan, R., Serrano-Plana, J., Oloo, W. N., Draksharapu, A., Delgado-Pinar, E., Company, A., ... Münck, E. (2018). Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate. Journal of the American Chemical Society, 140(11), 3916-3928. https://doi.org/10.1021/jacs.7b11400

Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate. / Fan, Ruixi; Serrano-Plana, Joan; Oloo, Williamson N.; Draksharapu, Apparao; Delgado-Pinar, Estefanía; Company, Anna; Martin-Diaconescu, Vlad; Borrell, Margarida; Lloret-Fillol, Julio; García-España, Enrique; Guo, Yisong; Bominaar, Emile L.; Que, Lawrence; Costas, Miquel; Münck, Eckard.

In: Journal of the American Chemical Society, Vol. 140, No. 11, 21.03.2018, p. 3916-3928.

Research output: Contribution to journalArticle

Fan, R, Serrano-Plana, J, Oloo, WN, Draksharapu, A, Delgado-Pinar, E, Company, A, Martin-Diaconescu, V, Borrell, M, Lloret-Fillol, J, García-España, E, Guo, Y, Bominaar, EL, Que, L, Costas, M & Münck, E 2018, 'Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate', Journal of the American Chemical Society, vol. 140, no. 11, pp. 3916-3928. https://doi.org/10.1021/jacs.7b11400
Fan R, Serrano-Plana J, Oloo WN, Draksharapu A, Delgado-Pinar E, Company A et al. Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate. Journal of the American Chemical Society. 2018 Mar 21;140(11):3916-3928. https://doi.org/10.1021/jacs.7b11400
Fan, Ruixi ; Serrano-Plana, Joan ; Oloo, Williamson N. ; Draksharapu, Apparao ; Delgado-Pinar, Estefanía ; Company, Anna ; Martin-Diaconescu, Vlad ; Borrell, Margarida ; Lloret-Fillol, Julio ; García-España, Enrique ; Guo, Yisong ; Bominaar, Emile L. ; Que, Lawrence ; Costas, Miquel ; Münck, Eckard. / Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate. In: Journal of the American Chemical Society. 2018 ; Vol. 140, No. 11. pp. 3916-3928.
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abstract = "The reaction of [(PyNMe3)FeII(CF3SO3)2], 1, with excess peracetic acid at -40 °C generates a highly reactive intermediate, 2b(PAA), that has the fastest rate to date for oxidizing cyclohexane by a nonheme iron species. It exhibits an intense 490 nm chromophore associated with an S = 1/2 EPR signal having g-values at 2.07, 2.01, and 1.94. This species was shown to be in a fast equilibrium with a second S = 1/2 species, 2a(PAA), assigned to a low-spin acylperoxoiron(III) center. Unfortunately, contaminants accompanying the 2(PAA) samples prevented determination of the iron oxidation state by M{\"o}ssbauer spectroscopy. Use of MeO-PyNMe3 (an electron-enriched version of PyNMe3) and cyclohexyl peroxycarboxylic acid as oxidant affords intermediate 3b(CPCA) with a M{\"o}ssbauer isomer shift δ = -0.08 mm/s that indicates an iron(V) oxidation state. Analysis of the M{\"o}ssbauer and EPR spectra, combined with DFT studies, demonstrates that the electronic ground state of 3b(CPCA) is best described as a quantum mechanical mixture of [(MeO-PyNMe3)FeV(O)(OC(O)R)]2+ (∼75{\%}) with some FeIV(O)(•OC(O)R) and FeIII(OOC(O)R) character. DFT studies of 3b(CPCA) reveal that the unbound oxygen of the carboxylate ligand, O2, is only 2.04 {\AA} away from the oxo group, O1, corresponding to a Wiberg bond order for the O1-O2 bond of 0.35. This unusual geometry facilitates reversible O1-O2 bond formation and cleavage and accounts for the high reactivity of the intermediate when compared to the rates of hydrogen atom transfer and oxygen atom transfer reactions of FeIII(OC(O)R) ferric acyl peroxides and FeIV(O) complexes. The interaction of O2 with O1 leads to a significant downshift of the Fe-O1 Raman frequency (815 cm-1) relative to the 903 cm-1 value predicted for the hypothetical [(MeO-PyNMe3)FeV(O)(NCMe)]3+ complex.",
author = "Ruixi Fan and Joan Serrano-Plana and Oloo, {Williamson N.} and Apparao Draksharapu and Estefan{\'i}a Delgado-Pinar and Anna Company and Vlad Martin-Diaconescu and Margarida Borrell and Julio Lloret-Fillol and Enrique Garc{\'i}a-Espa{\~n}a and Yisong Guo and Bominaar, {Emile L.} and Lawrence Que and Miquel Costas and Eckard M{\"u}nck",
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T1 - Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate

AU - Fan, Ruixi

AU - Serrano-Plana, Joan

AU - Oloo, Williamson N.

AU - Draksharapu, Apparao

AU - Delgado-Pinar, Estefanía

AU - Company, Anna

AU - Martin-Diaconescu, Vlad

AU - Borrell, Margarida

AU - Lloret-Fillol, Julio

AU - García-España, Enrique

AU - Guo, Yisong

AU - Bominaar, Emile L.

AU - Que, Lawrence

AU - Costas, Miquel

AU - Münck, Eckard

PY - 2018/3/21

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N2 - The reaction of [(PyNMe3)FeII(CF3SO3)2], 1, with excess peracetic acid at -40 °C generates a highly reactive intermediate, 2b(PAA), that has the fastest rate to date for oxidizing cyclohexane by a nonheme iron species. It exhibits an intense 490 nm chromophore associated with an S = 1/2 EPR signal having g-values at 2.07, 2.01, and 1.94. This species was shown to be in a fast equilibrium with a second S = 1/2 species, 2a(PAA), assigned to a low-spin acylperoxoiron(III) center. Unfortunately, contaminants accompanying the 2(PAA) samples prevented determination of the iron oxidation state by Mössbauer spectroscopy. Use of MeO-PyNMe3 (an electron-enriched version of PyNMe3) and cyclohexyl peroxycarboxylic acid as oxidant affords intermediate 3b(CPCA) with a Mössbauer isomer shift δ = -0.08 mm/s that indicates an iron(V) oxidation state. Analysis of the Mössbauer and EPR spectra, combined with DFT studies, demonstrates that the electronic ground state of 3b(CPCA) is best described as a quantum mechanical mixture of [(MeO-PyNMe3)FeV(O)(OC(O)R)]2+ (∼75%) with some FeIV(O)(•OC(O)R) and FeIII(OOC(O)R) character. DFT studies of 3b(CPCA) reveal that the unbound oxygen of the carboxylate ligand, O2, is only 2.04 Å away from the oxo group, O1, corresponding to a Wiberg bond order for the O1-O2 bond of 0.35. This unusual geometry facilitates reversible O1-O2 bond formation and cleavage and accounts for the high reactivity of the intermediate when compared to the rates of hydrogen atom transfer and oxygen atom transfer reactions of FeIII(OC(O)R) ferric acyl peroxides and FeIV(O) complexes. The interaction of O2 with O1 leads to a significant downshift of the Fe-O1 Raman frequency (815 cm-1) relative to the 903 cm-1 value predicted for the hypothetical [(MeO-PyNMe3)FeV(O)(NCMe)]3+ complex.

AB - The reaction of [(PyNMe3)FeII(CF3SO3)2], 1, with excess peracetic acid at -40 °C generates a highly reactive intermediate, 2b(PAA), that has the fastest rate to date for oxidizing cyclohexane by a nonheme iron species. It exhibits an intense 490 nm chromophore associated with an S = 1/2 EPR signal having g-values at 2.07, 2.01, and 1.94. This species was shown to be in a fast equilibrium with a second S = 1/2 species, 2a(PAA), assigned to a low-spin acylperoxoiron(III) center. Unfortunately, contaminants accompanying the 2(PAA) samples prevented determination of the iron oxidation state by Mössbauer spectroscopy. Use of MeO-PyNMe3 (an electron-enriched version of PyNMe3) and cyclohexyl peroxycarboxylic acid as oxidant affords intermediate 3b(CPCA) with a Mössbauer isomer shift δ = -0.08 mm/s that indicates an iron(V) oxidation state. Analysis of the Mössbauer and EPR spectra, combined with DFT studies, demonstrates that the electronic ground state of 3b(CPCA) is best described as a quantum mechanical mixture of [(MeO-PyNMe3)FeV(O)(OC(O)R)]2+ (∼75%) with some FeIV(O)(•OC(O)R) and FeIII(OOC(O)R) character. DFT studies of 3b(CPCA) reveal that the unbound oxygen of the carboxylate ligand, O2, is only 2.04 Å away from the oxo group, O1, corresponding to a Wiberg bond order for the O1-O2 bond of 0.35. This unusual geometry facilitates reversible O1-O2 bond formation and cleavage and accounts for the high reactivity of the intermediate when compared to the rates of hydrogen atom transfer and oxygen atom transfer reactions of FeIII(OC(O)R) ferric acyl peroxides and FeIV(O) complexes. The interaction of O2 with O1 leads to a significant downshift of the Fe-O1 Raman frequency (815 cm-1) relative to the 903 cm-1 value predicted for the hypothetical [(MeO-PyNMe3)FeV(O)(NCMe)]3+ complex.

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