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Hydrogen-atom and oxygen-atom transfer reactivities of iron(

Munshi, Sandip ; Sinha, Arup LU ; Yiga, Solomon LU ; Banerjee, Sridhar ; Singh, Reena LU ; Hossain, Md Kamal ; Haukka, Matti ; Valiati, Andrei Felipe ; Huelsmann, Ricardo Dagnoni and Martendal, Edmar , et al. (2022) In Dalton Transactions 51(3). p.870-884
Abstract

A series of iron(ii) complexes with the general formula [FeII(L2-Qn)(L)]n+ (n = 1, L = F−, Cl−; n = 2, L = NCMe, H2O) have been isolated and characterized. The X-ray crystallographic data reveals that metal–ligand bond distances vary with varying ligand field strengths of the sixth ligand. While the complexes with fluoride, chloride and water as axial ligand are high spin, the acetonitrile-coordinated complex is in a mixed spin state. The steric bulk of the quinoline moieties forces the axial ligands to deviate from the Fe–Naxial axis. A higher deviation/tilt is noted for the high spin complexes, while the acetonitrile coordinated complex displays least deviation. This... (More)

A series of iron(ii) complexes with the general formula [FeII(L2-Qn)(L)]n+ (n = 1, L = F−, Cl−; n = 2, L = NCMe, H2O) have been isolated and characterized. The X-ray crystallographic data reveals that metal–ligand bond distances vary with varying ligand field strengths of the sixth ligand. While the complexes with fluoride, chloride and water as axial ligand are high spin, the acetonitrile-coordinated complex is in a mixed spin state. The steric bulk of the quinoline moieties forces the axial ligands to deviate from the Fe–Naxial axis. A higher deviation/tilt is noted for the high spin complexes, while the acetonitrile coordinated complex displays least deviation. This deviation from linearity is slightly less in the analogous low-spin iron(ii) complex [FeII(L1-Qn)(NCMe)]2+ of the related asymmetric ligand L1-Qn due to the presence of only one sterically demanding quinoline moiety. The two iron(ii)-acetonitrile complexes [FeII(L2-Qn)(NCMe)]2+ and [FeII(L1-Qn)(NCMe)]2+ generate the corresponding iron(iv)-oxo species with higher thermal stability of the species supported by the L1-Qn ligand. The crystallographic and spectroscopic data for [FeIV(O)(L1-Qn)](ClO4)2 bear resemblance to other crystallographically characterized S = 1 iron(iv)-oxo complexes. The hydrogen atom transfer (HAT) and oxygen atom transfer (OAT) reactivities of both the iron(iv)-oxo complexes were investigated, and a Box–Behnken multivariate optimization of the parameters for catalytic oxidation of cyclohexane by [FeII(L2-Qn)(NCMe)]2+ using hydrogen peroxide as the terminal oxidant is presented. An increase in the average Fe–N bond length in [FeII(L1-Qn)(NCMe)]2+ is also manifested in higher HAT and OAT rates relative to the other reported complexes of ligands based on the N4Py framework. The results reported here confirm that the steric influence of the ligand environment is of critical importance for the reactivity of iron(iv)-oxo complexes, but additional electronic factors must influence the reactivity of iron-oxo complexes of N4Py derivatives.

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publishing date
type
Contribution to journal
publication status
published
subject
in
Dalton Transactions
volume
51
issue
3
pages
15 pages
publisher
Royal Society of Chemistry
external identifiers
  • pmid:34994361
  • scopus:85123639323
ISSN
1477-9226
DOI
10.1039/d1dt03381f
language
English
LU publication?
yes
additional info
Publisher Copyright: This journal is © The Royal Society of Chemistry
id
95f02d1c-324d-4edb-8af9-23d952671eb8
date added to LUP
2022-02-16 13:01:27
date last changed
2024-04-18 06:34:22
@article{95f02d1c-324d-4edb-8af9-23d952671eb8,
  abstract     = {{<p>A series of iron(ii) complexes with the general formula [Fe<sup>II</sup>(L2-Qn)(L)]<sup>n+</sup> (n = 1, L = F<sup>−</sup>, Cl<sup>−</sup>; n = 2, L = NCMe, H<sub>2</sub>O) have been isolated and characterized. The X-ray crystallographic data reveals that metal–ligand bond distances vary with varying ligand field strengths of the sixth ligand. While the complexes with fluoride, chloride and water as axial ligand are high spin, the acetonitrile-coordinated complex is in a mixed spin state. The steric bulk of the quinoline moieties forces the axial ligands to deviate from the Fe–N<sub>axial</sub> axis. A higher deviation/tilt is noted for the high spin complexes, while the acetonitrile coordinated complex displays least deviation. This deviation from linearity is slightly less in the analogous low-spin iron(ii) complex [Fe<sup>II</sup>(L1-Qn)(NCMe)]<sup>2+</sup> of the related asymmetric ligand L1-Qn due to the presence of only one sterically demanding quinoline moiety. The two iron(ii)-acetonitrile complexes [Fe<sup>II</sup>(L2-Qn)(NCMe)]<sup>2+</sup> and [Fe<sup>II</sup>(L1-Qn)(NCMe)]<sup>2+</sup> generate the corresponding iron(iv)-oxo species with higher thermal stability of the species supported by the L1-Qn ligand. The crystallographic and spectroscopic data for [Fe<sup>IV</sup>(O)(L1-Qn)](ClO<sub>4</sub>)<sub>2</sub> bear resemblance to other crystallographically characterized S = 1 iron(iv)-oxo complexes. The hydrogen atom transfer (HAT) and oxygen atom transfer (OAT) reactivities of both the iron(iv)-oxo complexes were investigated, and a Box–Behnken multivariate optimization of the parameters for catalytic oxidation of cyclohexane by [Fe<sup>II</sup>(L2-Qn)(NCMe)]<sup>2+</sup> using hydrogen peroxide as the terminal oxidant is presented. An increase in the average Fe–N bond length in [Fe<sup>II</sup>(L1-Qn)(NCMe)]<sup>2+</sup> is also manifested in higher HAT and OAT rates relative to the other reported complexes of ligands based on the N4Py framework. The results reported here confirm that the steric influence of the ligand environment is of critical importance for the reactivity of iron(iv)-oxo complexes, but additional electronic factors must influence the reactivity of iron-oxo complexes of N4Py derivatives.</p>}},
  author       = {{Munshi, Sandip and Sinha, Arup and Yiga, Solomon and Banerjee, Sridhar and Singh, Reena and Hossain, Md Kamal and Haukka, Matti and Valiati, Andrei Felipe and Huelsmann, Ricardo Dagnoni and Martendal, Edmar and Peralta, Rosely and Xavier, Fernando and Wendt, Ola F. and Paine, Tapan K. and Nordlander, Ebbe}},
  issn         = {{1477-9226}},
  language     = {{eng}},
  month        = {{01}},
  number       = {{3}},
  pages        = {{870--884}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Dalton Transactions}},
  title        = {{Hydrogen-atom and oxygen-atom transfer reactivities of iron(}},
  url          = {{http://dx.doi.org/10.1039/d1dt03381f}},
  doi          = {{10.1039/d1dt03381f}},
  volume       = {{51}},
  year         = {{2022}},
}