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Title: Nonheme Oxoiron(IV) Complexed of Tris(2-pyridylmethyl)amine with cis-Monoanionic Ligands

Abstract

Treatment of [Fe{sup IV}(O)(TPA)(NCMe)](CF{sub 3}SO{sub 3}){sub 2} [TPA, N,N,N-tris(2-pyridylmethyl)amine] with 3 equiv of NR{sub 4}X (X = CF{sub 3}CO{sub 2}, Cl, or Br) in MeCN at -40 C affords a series of metastable [Fe{sup IV}(O)(TPA)(X)]{sup +} complexes. Some characteristic features of the S = 1 oxoiron(IV) unit are quite insensitive to the ligand substitution in the equatorial plane, namely, the Fe-O distances (1.65-1.66 Angstroms), the energy ({approx}7114.5 eV) and intensity [25(2) units] of the 1s-to-3d transition in the X-ray absorption spectra, and the M{umlt o}ssbauer isomer shifts (0.01-0.06 mm{center_dot}s{sup -1}) and quadrupole splittings (0.92-0.95 mm{center_dot}s{sup -1}). The coordination of the anionic X ligand, however, is evidenced by red shifts of the characteristic near-IR ligand-field bands (720-800 nm) and spectroscopic observation of the bound anion by 19F NMR for X = CF{sub 3}CO{sub 2} and by EXAFS analysis for X = Cl (r{sub Fe-Cl} = 2.29 Angstroms) and Br (r{sub Fe-Br} = 2.43 Angstroms). Density functional theory calculations yield M{umlt o}ssbauer parameters and bond lengths in good agreement with the experimental data and produce excited-state energies that follow the trend observed in the ligand-field bands. Despite mitigating the high effective charge of the iron(IV) center, the substitution of the MeCN ligandmore » with monoanionic ligands X{sup -} decreases the thermal stability of [Fe{sup IV}(O)(TPA)]{sup 2+} complexes. These anion-substituted complexes model the cis-X-Fe{sup IV}=O units proposed in the mechanisms of oxygen-activating nonheme iron enzymes.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914098
Report Number(s):
BNL-78666-2007-JA
Journal ID: ISSN 0020-1669; INOCAJ; TRN: US0801543
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Inorg. Chem.
Additional Journal Information:
Journal Volume: 45; Journal Issue: 16; Journal ID: ISSN 0020-1669
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ABSORPTION SPECTRA; ANIONS; BOND LENGTHS; EFFECTIVE CHARGE; ENZYMES; FUNCTIONALS; IRON; ISOMER SHIFT; QUADRUPOLES; STABILITY; LIGANDS; NSLS; national synchrotron light source

Citation Formats

Rohde, J, Stubna, A, Bominaar, E, Munck, E, Nam, W, and Que, Jr., L. Nonheme Oxoiron(IV) Complexed of Tris(2-pyridylmethyl)amine with cis-Monoanionic Ligands. United States: N. p., 2006. Web. doi:10.1021/ic060740u.
Rohde, J, Stubna, A, Bominaar, E, Munck, E, Nam, W, & Que, Jr., L. Nonheme Oxoiron(IV) Complexed of Tris(2-pyridylmethyl)amine with cis-Monoanionic Ligands. United States. https://doi.org/10.1021/ic060740u
Rohde, J, Stubna, A, Bominaar, E, Munck, E, Nam, W, and Que, Jr., L. Sun . "Nonheme Oxoiron(IV) Complexed of Tris(2-pyridylmethyl)amine with cis-Monoanionic Ligands". United States. https://doi.org/10.1021/ic060740u.
@article{osti_914098,
title = {Nonheme Oxoiron(IV) Complexed of Tris(2-pyridylmethyl)amine with cis-Monoanionic Ligands},
author = {Rohde, J and Stubna, A and Bominaar, E and Munck, E and Nam, W and Que, Jr., L.},
abstractNote = {Treatment of [Fe{sup IV}(O)(TPA)(NCMe)](CF{sub 3}SO{sub 3}){sub 2} [TPA, N,N,N-tris(2-pyridylmethyl)amine] with 3 equiv of NR{sub 4}X (X = CF{sub 3}CO{sub 2}, Cl, or Br) in MeCN at -40 C affords a series of metastable [Fe{sup IV}(O)(TPA)(X)]{sup +} complexes. Some characteristic features of the S = 1 oxoiron(IV) unit are quite insensitive to the ligand substitution in the equatorial plane, namely, the Fe-O distances (1.65-1.66 Angstroms), the energy ({approx}7114.5 eV) and intensity [25(2) units] of the 1s-to-3d transition in the X-ray absorption spectra, and the M{umlt o}ssbauer isomer shifts (0.01-0.06 mm{center_dot}s{sup -1}) and quadrupole splittings (0.92-0.95 mm{center_dot}s{sup -1}). The coordination of the anionic X ligand, however, is evidenced by red shifts of the characteristic near-IR ligand-field bands (720-800 nm) and spectroscopic observation of the bound anion by 19F NMR for X = CF{sub 3}CO{sub 2} and by EXAFS analysis for X = Cl (r{sub Fe-Cl} = 2.29 Angstroms) and Br (r{sub Fe-Br} = 2.43 Angstroms). Density functional theory calculations yield M{umlt o}ssbauer parameters and bond lengths in good agreement with the experimental data and produce excited-state energies that follow the trend observed in the ligand-field bands. Despite mitigating the high effective charge of the iron(IV) center, the substitution of the MeCN ligand with monoanionic ligands X{sup -} decreases the thermal stability of [Fe{sup IV}(O)(TPA)]{sup 2+} complexes. These anion-substituted complexes model the cis-X-Fe{sup IV}=O units proposed in the mechanisms of oxygen-activating nonheme iron enzymes.},
doi = {10.1021/ic060740u},
url = {https://www.osti.gov/biblio/914098}, journal = {Inorg. Chem.},
issn = {0020-1669},
number = 16,
volume = 45,
place = {United States},
year = {2006},
month = {1}
}