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Di- and tetrairon(III) μ-oxido complexes of an N3S-donor ligand : Catalyst precursors for alkene oxidations

Das, Biswanath LU ; Al-Hunaiti, Afnan ; Sánchez-Eguía, Brenda N. ; Zeglio, Erica ; Demeshko, Serhiy ; Dechert, Sebastian ; Braunger, Steffen ; Haukka, Matti ; Repo, Timo and Castillo, Ivan , et al. (2019) In Frontiers in Chemistry 7(MAR).
Abstract


The new di- and tetranuclear Fe(III) μ-oxido complexes [Fe
4
(μ-O)
4
(PTEBIA)
4
](CF
3
SO
... (More)


The new di- and tetranuclear Fe(III) μ-oxido complexes [Fe
4
(μ-O)
4
(PTEBIA)
4
](CF
3
SO
3
)
4
(CH
3
CN)
2
] (1a), [Fe
2
(μ-O)Cl
2
(PTEBIA)
2
](CF
3
SO
3
)
2
(1b), and [Fe
2
(μ-O)(HCOO)
2
(PTEBIA)
2
](ClO
4
)
2
(MeOH) (2) were prepared from the sulfur-containing ligand (2-((2,4-dimethylphenyl)thio)-N,N-bis ((1-methyl-benzimidazol-2-yl)methyl)ethanamine (PTEBIA). The tetrairon complex 1a features four μ-oxido bridges, while in dinuclear 1b, the sulfur moiety of the ligand occupies one of the six coordination sites of each Fe(III) ion with a long Fe-S distance of 2.814(6) Å. In 2, two Fe(III) centers are bridged by one oxido and two formate units, the latter likely formed by methanol oxidation. Complexes 1a and 1b show broad sulfur-to-iron charge transfer bands around 400-430 nm at room temperature, consistent with mononuclear structures featuring Fe-S interactions. In contrast, acetonitrile solutions of 2 display a sulfur-to-iron charge transfer band only at low temperature (228 K) upon addition of H
2
O
2
/CH
3
COOH, with an absorption maximum at 410 nm. Homogeneous oxidative catalytic activity was observed for 1a and 1b using H
2
O
2
as oxidant, but with low product selectivity. High valent iron-oxo intermediates could not be detected by UV-vis spectroscopy or ESI mass spectrometry. Rather, evidence suggest preferential ligand oxidation, in line with the relatively low selectivity and catalytic activity observed in the reactions.

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organization
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publication status
published
subject
keywords
Fe-S interaction, Homogeneous catalysis, Iron-oxo complex, Oxidation, Thioether
in
Frontiers in Chemistry
volume
7
issue
MAR
article number
97
publisher
Frontiers Media S. A.
external identifiers
  • scopus:85064708910
DOI
10.3389/fchem.2019.00097
language
English
LU publication?
yes
id
6d68fe30-03b8-4c72-9883-84b2a4df777c
date added to LUP
2019-05-07 13:10:29
date last changed
2019-11-25 09:29:37
@article{6d68fe30-03b8-4c72-9883-84b2a4df777c,
  abstract     = {<p><br>
                                                         The new di- and tetranuclear Fe(III) μ-oxido complexes [Fe                             <br>
                            <sub>4</sub><br>
                                                         (μ-O)                             <br>
                            <sub>4</sub><br>
                                                         (PTEBIA)                             <br>
                            <sub>4</sub><br>
                                                         ](CF                             <br>
                            <sub>3</sub><br>
                                                         SO                             <br>
                            <sub>3</sub><br>
                                                         )                             <br>
                            <sub>4</sub><br>
                                                         (CH                             <br>
                            <sub>3</sub><br>
                                                         CN)                             <br>
                            <sub>2</sub><br>
                                                         ] (1a), [Fe                             <br>
                            <sub>2</sub><br>
                                                         (μ-O)Cl                             <br>
                            <sub>2</sub><br>
                                                         (PTEBIA)                             <br>
                            <sub>2</sub><br>
                                                         ](CF                             <br>
                            <sub>3</sub><br>
                                                         SO                             <br>
                            <sub>3</sub><br>
                                                         )                             <br>
                            <sub>2</sub><br>
                                                          (1b), and [Fe                             <br>
                            <sub>2</sub><br>
                                                         (μ-O)(HCOO)                             <br>
                            <sub>2</sub><br>
                                                         (PTEBIA)                             <br>
                            <sub>2</sub><br>
                                                         ](ClO                             <br>
                            <sub>4</sub><br>
                                                         )                             <br>
                            <sub>2</sub><br>
                                                          (MeOH) (2) were prepared from the sulfur-containing ligand (2-((2,4-dimethylphenyl)thio)-N,N-bis ((1-methyl-benzimidazol-2-yl)methyl)ethanamine (PTEBIA). The tetrairon complex 1a features four μ-oxido bridges, while in dinuclear 1b, the sulfur moiety of the ligand occupies one of the six coordination sites of each Fe(III) ion with a long Fe-S distance of 2.814(6) Å. In 2, two Fe(III) centers are bridged by one oxido and two formate units, the latter likely formed by methanol oxidation. Complexes 1a and 1b show broad sulfur-to-iron charge transfer bands around 400-430 nm at room temperature, consistent with mononuclear structures featuring Fe-S interactions. In contrast, acetonitrile solutions of 2 display a sulfur-to-iron charge transfer band only at low temperature (228 K) upon addition of H                             <br>
                            <sub>2</sub><br>
                                                         O                             <br>
                            <sub>2</sub><br>
                                                         /CH                             <br>
                            <sub>3</sub><br>
                                                         COOH, with an absorption maximum at 410 nm. Homogeneous oxidative catalytic activity was observed for 1a and 1b using H                             <br>
                            <sub>2</sub><br>
                                                         O                             <br>
                            <sub>2</sub><br>
                                                          as oxidant, but with low product selectivity. High valent iron-oxo intermediates could not be detected by UV-vis spectroscopy or ESI mass spectrometry. Rather, evidence suggest preferential ligand oxidation, in line with the relatively low selectivity and catalytic activity observed in the reactions.                         <br>
                        </p>},
  author       = {Das, Biswanath and Al-Hunaiti, Afnan and Sánchez-Eguía, Brenda N. and Zeglio, Erica and Demeshko, Serhiy and Dechert, Sebastian and Braunger, Steffen and Haukka, Matti and Repo, Timo and Castillo, Ivan and Nordlander, Ebbe},
  language     = {eng},
  month        = {03},
  number       = {MAR},
  publisher    = {Frontiers Media S. A.},
  series       = {Frontiers in Chemistry},
  title        = {Di- and tetrairon(III) μ-oxido complexes of an N3S-donor ligand : Catalyst precursors for alkene oxidations},
  url          = {http://dx.doi.org/10.3389/fchem.2019.00097},
  doi          = {10.3389/fchem.2019.00097},
  volume       = {7},
  year         = {2019},
}