Synthesis, Structure and Reactivity of a Mononuclear N,N,O-Bound Fe(II) α-Keto-Acid Complex

Emily C. Monkcom; Laura Gómez; Martin Lutz; Shengfa Ye; Eckhard Bill; Miquel Costas; Robertus J.M. Klein Gebbink

doi:10.1002/chem.202302710

Synthesis, Structure and Reactivity of a Mononuclear N,N,O-Bound Fe(II) α-Keto-Acid Complex

Emily C. Monkcom, Laura Gómez, Martin Lutz, Shengfa Ye, Eckhard Bill, Miquel Costas, Robertus J.M. Klein Gebbink^*

^*Corresponding author for this work

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

Abstract

A bulky, tridentate phenolate ligand (Im^Ph2NNO^tBu) was used to synthesise the first example of a mononuclear, facial, N,N,O-bound iron(II) benzoylformate complex, [Fe(Im^Ph2NNO^tBu)(BF)] (2). The X-ray crystal structure of 2 reveals that the iron centre is pentacoordinate (τ=0.5), with a vacant site located cis to the bidentate BF ligand. The Mössbauer parameters of 2 are consistent with high-spin iron(II), and are very close to those reported for α-ketoglutarate-bound non-heme iron enzyme active sites. According to NMR and UV-vis spectroscopies, the structural integrity of 2 is retained in both coordinating and non-coordinating solvents. Cyclic voltammetry studies show that the iron centre has a very low oxidation potential and is more prone to electrochemical oxidation than the redox-active phenolate ligand. Complex 2 reacts with NO to form a S=³/₂ {FeNO}⁷ adduct in which NO binds directly to the iron centre, according to EPR, UV-vis, IR spectroscopies and DFT analysis. Upon O₂ exposure, 2 undergoes oxidative decarboxylation to form a diiron(III) benzoate complex, [Fe₂(Im^Ph2NNO^tBu)₂(μ₂-OBz)(μ₂-OH)₂]⁺ (3). A small amount of hydroxylated ligand was also observed by ESI-MS, hinting at the formation of a high-valent iron(IV)-oxo intermediate. Initial reactivity studies show that 2 is capable of oxygen atom transfer reactivity with O₂, converting methyl(p-tolyl)sulfide to sulfoxide.

Original language	English
Article number	e202302710
Number of pages	13
Journal	Chemistry - A European Journal
Volume	30
Issue number	11
Early online date	26 Oct 2023
DOIs	https://doi.org/10.1002/chem.202302710
Publication status	Published - 21 Feb 2024

Bibliographical note

Publisher Copyright:
© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

Funding

Financial support was provided by the European Union through the Marie Sklodowska‐Curie NoNoMeCat ITN network (675020‐MSCA‐ITN‐2015‐ETN) and Utrecht University (UU). The X‐ray diffractometer was funded by the Dutch organisation for scientific research (NWO). This work was also sponsored by NWO Exacte en Natuurwetenschappen (Physical Sciences) for the use of supercomputer facilities. We are grateful to Dr. Marc‐Etienne Moret and Dr. Danny Broere (UU) for their input during scientific discussions. We thank Dr. Johann Jastrzebski (UU) for assistance with the NMR measurements. We also thank Bernd Mienert and Andreas Göbels (MPI) for their technical assistance with the Mössbauer and SQUID measurements. We thank Prof. Dr. Miquel Costas for the kind hospitality during a secondment undertaken by E.C.M. at the University of Girona (UdG). Dr. Brenda Nataly Sánchez‐Eguía is gratefully acknowledged for her help and the fruitful discussions in and outside the lab at UdG. Finally, we thank Serhii Tretiakov (UU) for assistance with DFT calculations.

Funders	Funder number
NWO Exacte en Natuurwetenschappen
Universitat de Girona
European Commission	675020‐MSCA‐ITN‐2015‐ETN
Universiteit Utrecht
Nederlandse Organisatie voor Wetenschappelijk Onderzoek

Keywords

2-His-1-Carboxylate facial triad
bioinspired
enzyme models
N,N,O ligand
non-heme iron

Access to Document

10.1002/chem.202302710Licence: CC BY-NC

Chemistry A European J - 2023 - Monkcom - Synthesis Structure and Reactivity of a Mononuclear N N O‐Bound Fe II Final published version, 5.23 MBLicence: CC BY-NC

Cite this

@article{bdbc1c0e270142bab67eddc5bc52261e,

title = "Synthesis, Structure and Reactivity of a Mononuclear N,N,O-Bound Fe(II) α-Keto-Acid Complex",

abstract = "A bulky, tridentate phenolate ligand (ImPh2NNOtBu) was used to synthesise the first example of a mononuclear, facial, N,N,O-bound iron(II) benzoylformate complex, [Fe(ImPh2NNOtBu)(BF)] (2). The X-ray crystal structure of 2 reveals that the iron centre is pentacoordinate (τ=0.5), with a vacant site located cis to the bidentate BF ligand. The M{\"o}ssbauer parameters of 2 are consistent with high-spin iron(II), and are very close to those reported for α-ketoglutarate-bound non-heme iron enzyme active sites. According to NMR and UV-vis spectroscopies, the structural integrity of 2 is retained in both coordinating and non-coordinating solvents. Cyclic voltammetry studies show that the iron centre has a very low oxidation potential and is more prone to electrochemical oxidation than the redox-active phenolate ligand. Complex 2 reacts with NO to form a S=3/2 {FeNO}7 adduct in which NO binds directly to the iron centre, according to EPR, UV-vis, IR spectroscopies and DFT analysis. Upon O2 exposure, 2 undergoes oxidative decarboxylation to form a diiron(III) benzoate complex, [Fe2(ImPh2NNOtBu)2(μ2-OBz)(μ2-OH)2]+ (3). A small amount of hydroxylated ligand was also observed by ESI-MS, hinting at the formation of a high-valent iron(IV)-oxo intermediate. Initial reactivity studies show that 2 is capable of oxygen atom transfer reactivity with O2, converting methyl(p-tolyl)sulfide to sulfoxide.",

keywords = "2-His-1-Carboxylate facial triad, bioinspired, enzyme models, N,N,O ligand, non-heme iron",

author = "Monkcom, {Emily C.} and Laura G{\'o}mez and Martin Lutz and Shengfa Ye and Eckhard Bill and Miquel Costas and {Klein Gebbink}, {Robertus J.M.}",

note = "Publisher Copyright: {\textcopyright} 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.",

year = "2024",

month = feb,

day = "21",

doi = "10.1002/chem.202302710",

language = "English",

volume = "30",

journal = "Chemistry - A European Journal",

issn = "0947-6539",

publisher = "Wiley-VCH Verlag",

number = "11",

}

TY - JOUR

T1 - Synthesis, Structure and Reactivity of a Mononuclear N,N,O-Bound Fe(II) α-Keto-Acid Complex

AU - Monkcom, Emily C.

AU - Gómez, Laura

AU - Lutz, Martin

AU - Ye, Shengfa

AU - Bill, Eckhard

AU - Costas, Miquel

AU - Klein Gebbink, Robertus J.M.

PY - 2024/2/21

Y1 - 2024/2/21

N2 - A bulky, tridentate phenolate ligand (ImPh2NNOtBu) was used to synthesise the first example of a mononuclear, facial, N,N,O-bound iron(II) benzoylformate complex, [Fe(ImPh2NNOtBu)(BF)] (2). The X-ray crystal structure of 2 reveals that the iron centre is pentacoordinate (τ=0.5), with a vacant site located cis to the bidentate BF ligand. The Mössbauer parameters of 2 are consistent with high-spin iron(II), and are very close to those reported for α-ketoglutarate-bound non-heme iron enzyme active sites. According to NMR and UV-vis spectroscopies, the structural integrity of 2 is retained in both coordinating and non-coordinating solvents. Cyclic voltammetry studies show that the iron centre has a very low oxidation potential and is more prone to electrochemical oxidation than the redox-active phenolate ligand. Complex 2 reacts with NO to form a S=3/2 {FeNO}7 adduct in which NO binds directly to the iron centre, according to EPR, UV-vis, IR spectroscopies and DFT analysis. Upon O2 exposure, 2 undergoes oxidative decarboxylation to form a diiron(III) benzoate complex, [Fe2(ImPh2NNOtBu)2(μ2-OBz)(μ2-OH)2]+ (3). A small amount of hydroxylated ligand was also observed by ESI-MS, hinting at the formation of a high-valent iron(IV)-oxo intermediate. Initial reactivity studies show that 2 is capable of oxygen atom transfer reactivity with O2, converting methyl(p-tolyl)sulfide to sulfoxide.

AB - A bulky, tridentate phenolate ligand (ImPh2NNOtBu) was used to synthesise the first example of a mononuclear, facial, N,N,O-bound iron(II) benzoylformate complex, [Fe(ImPh2NNOtBu)(BF)] (2). The X-ray crystal structure of 2 reveals that the iron centre is pentacoordinate (τ=0.5), with a vacant site located cis to the bidentate BF ligand. The Mössbauer parameters of 2 are consistent with high-spin iron(II), and are very close to those reported for α-ketoglutarate-bound non-heme iron enzyme active sites. According to NMR and UV-vis spectroscopies, the structural integrity of 2 is retained in both coordinating and non-coordinating solvents. Cyclic voltammetry studies show that the iron centre has a very low oxidation potential and is more prone to electrochemical oxidation than the redox-active phenolate ligand. Complex 2 reacts with NO to form a S=3/2 {FeNO}7 adduct in which NO binds directly to the iron centre, according to EPR, UV-vis, IR spectroscopies and DFT analysis. Upon O2 exposure, 2 undergoes oxidative decarboxylation to form a diiron(III) benzoate complex, [Fe2(ImPh2NNOtBu)2(μ2-OBz)(μ2-OH)2]+ (3). A small amount of hydroxylated ligand was also observed by ESI-MS, hinting at the formation of a high-valent iron(IV)-oxo intermediate. Initial reactivity studies show that 2 is capable of oxygen atom transfer reactivity with O2, converting methyl(p-tolyl)sulfide to sulfoxide.

KW - 2-His-1-Carboxylate facial triad

KW - bioinspired

KW - enzyme models

KW - N,N,O ligand

KW - non-heme iron

UR - http://www.scopus.com/inward/record.url?scp=85181919593&partnerID=8YFLogxK

U2 - 10.1002/chem.202302710

DO - 10.1002/chem.202302710

M3 - Article

AN - SCOPUS:85181919593

SN - 0947-6539

VL - 30

JO - Chemistry - A European Journal

JF - Chemistry - A European Journal

IS - 11

M1 - e202302710

ER -

Synthesis, Structure and Reactivity of a Mononuclear N,N,O-Bound Fe(II) α-Keto-Acid Complex

Abstract

Bibliographical note

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this