Modulating Iron Spin States with Radical Ligands: A Density Functional Theoretical Study

Herein, we introduce an electrochemically assisted generation of nitryl radicals from ferric nitrate under mild reaction conditions using a simple setup with inexpensive graphite and stainless-steel electrodes. The mechanism of the reaction is supported by detailed spectroscopic and experimental studies. Powered by electricity and driven by electrons, the synthetic diversity of this reaction has been demonstrated through the development of highly efficient nitration protocols of various unsaturated hydrocarbons. In addition to a broad application area, these protocols are easy to scale for decagram quantities, and exhibit exceptional substrate generality and functional-group compatibility.

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“…Chemie to radical ligand transfer event from iron. [33] Indeed, only traces or no product formation were detected (page S27).…”

Section: Methodsmentioning

confidence: 99%

Electron‐Driven Nitration of Unsaturated Hydrocarbons

et al. 2023

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“…Um eine mögliche Oxidation des Nitroalkylradikals zum entsprechenden Carbokation auszuschließen, untersuchten wir eine nitrative Difunktionalisierung von 1 mit verschiedenen Nukleophilen (AcO À , F À , N 3 À ), die weniger anfällig für einen radikalischen Ligandentransfer vom Eisen sind. [33] In der Tat wurden nur Spuren oder keine Produktbildung festgestellt (Seite S27). Andererseits führten Halonitrierungsreaktionen von 1 in Gegenwart von Radikalfängern wie CBr 4 und CCl 4 zur Bildung der Produkte 2 und 17 mit 11 % bzw.…”

Section: Ergebnisse Und Diskussionunclassified

Eine durch Elektronen angetriebene Nitrierung von Kohlenwasserstoffen

et al. 2023

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Hiermit stellen wir einen elektrochemisch unterstützten Prototypen für die Erzeugung von Nitrylradikalen aus Eisen(III)‐nitrat unter milden Reaktionsbedingungen vor, wobei eine einfache Vorrichtung mit kostengünstigen Graphit‐ und Edelstahlelektroden verwendet wurde. Die einzigartige Reaktionsweise wurde durch detaillierte spektroskopische und experimentelle Studien mechanistisch bewiesen. Die synthetische Vielseitigkeit dieses Konzepts wurde durch die Entwicklung hocheffizienter Nitrierungsprotokolle für verschiedene ungesättigte Kohlenwasserstoffe demonstriert, die durch Elektrizität betrieben und durch Elektronen angetrieben werden. Diese Protokolle haben nicht nur einen breiten Anwendungsbereich, sondern lassen sich auch leicht auf Dekagramme skalieren und weisen eine außergewöhnliche Substratvielfalt und Kompatibilität mit funktionellen Gruppen auf.

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“…The respective roles of the metal ions and redox-innocent ligands are well-understood in these systems . However, studies on spin-state changes of mononuclear iron(III), − iron(II), cobalt(III), , and cobalt(II) in coordination complexes with redox-active NILs, to the best of our knowledge, have been carried out only on a handful of systems. Consequently, the roles and influence of the metal ion and ligand(s) to changes in the total spin state ( S t ) of the overall complex are far less understood.…”

Section: Introductionmentioning

confidence: 99%

Iron(III) Complexes of a Hexadentate Thioether-Appended 2-Aminophenol Ligand: Redox-Driven Spin State Switchover

et al. 2022

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A green complex [Fe(L3)] (1), supported by the deprotonated form of a hexadentate noninnocent redox-active thioether-appended 2-aminophenolate ligand (H4L3 = N,N′-bis(2-hydroxy-3,5-di-tert-butylphenyl)-2,2′-diamino(diphenyldithio)ethane), has been synthesized and structurally characterized at 100(2) K and 298(2) K. In CH2Cl2, 1 displays two oxidative and a reductive one-electron redox processes at E 1/2 values of −0.52 and 0.20 V, and −0.85 V versus the Fc+/Fc redox couple, respectively. The one-electron oxidized 1 + and one-electron reduced 1 – forms, isolated as a blackish-blue solid 1(PF6)·CH2Cl2 (2) and a gray solid [Co(η 5–C5H5)2]1·DMF (3), have been structurally characterized at 100(2) K. Structural parameters at 100 K of the ligand backbone and metrical oxidation state values unambiguously establish the electronic states as [FeIII{(LAP O,N )2–}{(LISQ O,N )•–}{(L S,S )0}] (1) (two tridentate halves are electronically asymmetric–ligand mixed-valency), [FeIII{(LISQ O,N )•–}{(LISQ O,N )•–}{(L S,S )0}]+ (1 +), and [FeIII{(LAP O,N )2–}{(LAP O,N )2–}{(L S,S )0}]− (1 −) [dianionic 2-amidophenolate(2−) (LAP O,N )2– and monoanionic 2-iminobenzosemiquinonate(1−) π-radical (S rad = 1/2) (LISQ)•– redox level]. Mössbauer spectral data of 1 at 295, 200, and 80 K reveal that it has a major low-spin (ls)-Fe(III) and a minor ls-Fe(II) component (redox isomers), and at 7 K, the major component exists exclusively. Thus, in 1, the occurrence of a thermally driven valence-tautomeric (VT) equilibrium (asymmetric) [FeIII{(LAP O,N )2–}{(LISQ O,N )•–}{(L S,S )0}] ⇌ (symmetric) [FeII{(LISQ O,N )•–}{(LISQ O,N )•–}{(L S,S )0}] (80–295 K) is implicated. Mössbauer spectral parameters unequivocally establish that 1 + is a ls-Fe(III) complex. In contrast, the monoanion 1 – contains a high-spin (hs)-Fe(III) center (S Fe = 5/2), as is deduced from its Mössbauer and EPR spectra. Complexes 1–3 possess total spin ground states S t = 0, 1/2, and 5/2, respectively, based on 1H NMR and EPR spectra, the variable-temperature (2–300 K) magnetic behavior of 2, and the μ eff value of 3 at 300 K. Broken-symmetry density functional theory (DFT) calculations at the B3LYP-level of theory reveal that the unpaired electron in 1 +/2 is due to the (LISQ)•– redox level [ls-Fe(III) (S Fe = 1/2) is strongly antiferromagnetically coupled to one of the (LISQ)•– radicals (S rad = 1/2)], and 1 –/3 is a hs-Fe(III) complex, supported by (L3)4– with two-halves in the (LAP)2– redox level. Complex 1 can have either a symmetric or asymmetric electronic state. As per DFT calculation, the former state is stabilized by −3.9 kcal/mol over the latter (DFT usually stabilizes electronically symmetric structure). Time-dependent (TD)-DFT calculations shed light on the origin of observed UV–vis–NIR spectral absorptions for 1–3 and corroborate the results of spectroelectrochemical experiments (300–1100 nm) on 1 (CH2Cl2; 298 K). Variable-temperature (218–298 K; CH2Cl2) absorption spectral (400–1000 nm) studies on 1 justify the presence of VT equilib...

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Modulating Iron Spin States with Radical Ligands: A Density Functional Theoretical Study

Cited by 5 publications

References 96 publications

Electron‐Driven Nitration of Unsaturated Hydrocarbons

Electron‐Driven Nitration of Unsaturated Hydrocarbons

Eine durch Elektronen angetriebene Nitrierung von Kohlenwasserstoffen

Iron(III) Complexes of a Hexadentate Thioether-Appended 2-Aminophenol Ligand: Redox-Driven Spin State Switchover

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