Catalytically Active Iron(IV)oxo Species Based on a Bis(pyridinyl)phenanthrolinylmethane

Hüppe, Henrika M.; Keisers, Kristina; Fink, Fabian; Mürtz, Sonja D.; Hoffmann, Alexander; Iffland, Linda; Apfel, Ulf‐Peter; Herres‐Pawlis, Sonja

doi:10.1002/ijch.202000009

Cited by 4 publications

(1 citation statement)

References 48 publications

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“…In the spectrum of the latter, this is the main species (81%) with an isomer shift of 0.44 mm s –1 along with a quadrupole splitting of 0.43 mm s –1 and a set of two minor signals with isomer shifts of 1.28 and 1.05 mm s –1 and quadrupole splittings with 3.24 and 2.86 mm s –1 . The observed data for the main species and the species observed for the dissolved crystals are in accordance to values reported for low-spin iron(II) species with a {N 6 }-coordination indicating that the bis(acetonitrile) species is dominant in acetonitrile solution. ,− …”

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confidence: 85%

Triflate vs Acetonitrile: Understanding the Iron(II)-Based Coordination Chemistry of Tri(quinolin-8-yl)amine

et al. 2023

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In this study, a synthesis route of tri(quinolin-8yl)amine (L), a recent member of the tetradentate tris(2pyridylmethyl)amine (TPA) ligand family, is reported. With the neutral ligand L bound to an iron(II) center in κ 4 mode, two cisoriented coordination sites remain vacant. These can be occupied by coligands such as counterions and solvent molecules. How sensitive this equilibrium can be is most evident if both triflate anions and acetonitrile molecules are available. All three combinations�bis(triflato), bis(acetonitrile), and mixed coligand species�could be characterized by single-crystal X-ray diffraction (SCXRD), which is unique so far for this class of ligand. While at room temperature, the three compounds tend to crystallize concomitantly, the equilibrium can be shifted in favor of the bis(acetonitrile) species by lowering the crystallization temperature. Removed from their mother liquor, the latter is very sensitive to evaporation of the residual solvent, which was observed by powder X-ray diffraction (PXRD) and Mossbauer spectroscopy. The solution behavior of the triflate and acetonitrile species was studied in detail using time-and temperature-resolved UV/vis spectroscopy, Mossbauer spectroscopy of frozen solution, NMR spectroscopy, and magnetic susceptibility measurements. The results indicate a bis(acetonitrile) species in acetonitrile showing a temperature-dependent spin-switching behavior between highand low-spin. In dichloromethane, the results reveal a high-spin bis(triflato) species. In pursuit of understanding the coordination environment equilibria of the [Fe(L)] 2+ complex, a series of compounds with different coligands was prepared and analyzed with SCXRD. The crystal structures indicate that the spin state can be controlled by changing the coordination environment�all of the {N 6 }-coordinated complexes display geometries expected for low-spin species, while any other donor atom in the coligand position induces a shift to the high-spin state. This fundamental study sheds light on the coligand competition of triflate and acetonitrile, and the high number of crystal structures allows further insights into the influence of different coligands on the geometry and spin state of the complexes.

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Section: Resultssupporting

confidence: 85%

Triflate vs Acetonitrile: Understanding the Iron(II)-Based Coordination Chemistry of Tri(quinolin-8-yl)amine

et al. 2023

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Tuning the H‐Atom Transfer Reactivity of Iron(IV)‐Oxo Complexes as Probed by Infrared Photodissociation Spectroscopy

et al. 2021

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Reactivities of non‐heme iron(IV)‐oxo complexes are mostly controlled by the ligands. Complexes with tetradentate ligands such as [(TPA)FeO]2+ (TPA=tris(2‐pyridylmethyl)amine) belong to the most reactive ones. Here, we show a fine‐tuning of the reactivity of [(TPA)FeO]2+ by an additional ligand X (X=CH3CN, CF3SO3−, ArI, and ArIO; ArI=2‐(tBuSO2)C6H4I) attached in solution and reveal a thus far unknown role of the ArIO oxidant. The HAT reactivity of [(TPA)FeO(X)]+/2+ decreases in the order of X: ArIO > MeCN > ArI ≈ TfO−. Hence, ArIO is not just a mere oxidant of the iron(II) complex, but it can also increase the reactivity of the iron(IV)‐oxo complex as a labile ligand. The detected HAT reactivities of the [(TPA)FeO(X)]+/2+ complexes correlate with the Fe=O and FeO−H stretching vibrations of the reactants and the respective products as determined by infrared photodissociation spectroscopy. Hence, the most reactive [(TPA)FeO(ArIO)]2+ adduct in the series has the weakest Fe=O bond and forms the strongest FeO−H bond in the HAT reaction.

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Tuning the H‐Atom Transfer Reactivity of Iron(IV)‐Oxo Complexes as Probed by Infrared Photodissociation Spectroscopy

et al. 2021

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Reactivities of non-heme iron(IV)-oxo complexes are mostly controlled by the ligands.C omplexes with tetradentate ligands such as [(TPA)FeO] 2+ (TPA = tris(2-pyridylmethyl)amine) belong to the most reactive ones.Here,weshow af ine-tuning of the reactivity of [(TPA)FeO] 2+ by an additional ligand X(X= CH 3 CN,CF 3 SO 3 À ,ArI, and ArIO;ArI = 2-(t BuSO 2)C 6 H 4 I) attached in solution and reveal at hus far unknown role of the ArIO oxidant. The HATr eactivity of [(TPA)FeO(X)] +/2+ decreases in the order of X: ArIO > MeCN > ArI % TfO À .Hence,ArIO is not just amere oxidant of the iron(II) complex, but it can also increase the reactivity of the iron(IV)-oxo complex as alabile ligand. The detected HAT reactivities of the [(TPA)FeO(X)] +/2+ complexes correlate with the Fe = Oand FeO À Hstretching vibrations of the reactants and the respective products as determined by infrared photodissociation spectroscopy. Hence,t he most reactive [(TPA)FeO-(ArIO)] 2+ adduct in the series has the weakest Fe=Obond and forms the strongest FeOÀHb ond in the HATreaction. Scheme 1. Iron(IV)-oxo complexes formed by oxidation of [(TPA)Fe II-(TfO) 2 ]w ith ArIO (ArI = 2-(t BuSO 2)C 6 H 4 I).

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Catalytically Active Iron(IV)oxo Species Based on a Bis(pyridinyl)phenanthrolinylmethane

Cited by 4 publications

References 48 publications

Triflate vs Acetonitrile: Understanding the Iron(II)-Based Coordination Chemistry of Tri(quinolin-8-yl)amine

Triflate vs Acetonitrile: Understanding the Iron(II)-Based Coordination Chemistry of Tri(quinolin-8-yl)amine

Tuning the H‐Atom Transfer Reactivity of Iron(IV)‐Oxo Complexes as Probed by Infrared Photodissociation Spectroscopy

Tuning the H‐Atom Transfer Reactivity of Iron(IV)‐Oxo Complexes as Probed by Infrared Photodissociation Spectroscopy

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