Iron-Mediated Amination of Hydrocarbons in the Gas Phase

Brönstrup, Mark; Kretzschmar, Ilona; Schröder, Detlef; Schwarz, Helmut

doi:10.1002/(sici)1522-2675(19981216)81:12<2348::aid-hlca2348>3.0.co;2-p

Cited by 31 publications

(5 citation statements)

References 22 publications

(40 reference statements)

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“…FeNH ϩ , for example, can activate methane to afford Fe ϩ and methylamine (63), but the reaction is much less efficient than for FeO ϩ . Bare metal-nitrido cations MN ϩ , which could potentially activate methane, could so far not be generated experimentally in yields sufficient for subsequent reactivity studies.…”

Section: Ligated Metal Cationsmentioning

confidence: 99%

Gas-phase activation of methane by ligated transition-metal cations

Schröder

Schwarz²

2008

Proc. Natl. Acad. Sci. U.S.A.

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232

135

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Motivated by the search for ways of a more efficient usage of the large, unexploited resources of methane, recent progress in the gas-phase activation of methane by ligated transition-metal ions is discussed. Mass spectrometric experiments demonstrate that the ligands can crucially influence both reactivity and selectivity of transition-metal cations in bond-activation processes, and the most reactive species derive from combinations of transition metals with the electronegative elements fluorine, oxygen, and chlorine. Furthermore, the collected knowledge about intramolecular kinetic isotope effects associated with the activation of C-H(D) bonds of methane can be used to distinguish the nature of the bond activation as a mere hydrogen-abstraction, a metal-assisted mechanism or more complex reactions such as formation of insertion intermediates or -bond metathesis.bond activation ͉ kinetic isotope effects ͉ mass spectrometry

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Section: Ligated Metal Cationsmentioning

confidence: 99%

Gas-phase activation of methane by ligated transition-metal cations

Schröder

Schwarz²

2008

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

232

135

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“…Traditional wisdom had viewed such complexes as highly reactive, nonisolable intermediates, and this knowledge had been largely restricted to theoretical and mass spectrometry studies on the bare iron imide [FeNH] + . 11 Recent studies showed that, by the use of appropriate ancillary ligands, iron terminal imido species can be effectively stabilized and are amenable to isolation. Since Lee's report on the first isolable iron terminal imido complex, [Fe 4 (μ 3 -NBu t ) 4 (NBu t )-Cl 3 ], in 2000, 12 more than 50 structurally well characterized iron terminal imido complexes have been reported.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Iron terminal imido species are often implicated as key intermediates in iron-catalyzed nitrogen-group-transfer reactions: e.g., alkene aziridation, sulfur imidation, and C–H bond amination. − A range of iron-mediated nitrogen fixation reactions have also proposed with iron imido species as intermediates en route to the final products, NH 3 and N(SiMe 3 ) 3 . − The importance of these chemical transformations has attracted great interest in the formation, structural and spectroscopic features, and reactivity of iron imido species. Traditional wisdom had viewed such complexes as highly reactive, nonisolable intermediates, and this knowledge had been largely restricted to theoretical and mass spectrometry studies on the bare iron imide [FeNH] + . Recent studies showed that, by the use of appropriate ancillary ligands, iron terminal imido species can be effectively stabilized and are amenable to isolation.…”

Section: Introductionmentioning

confidence: 99%

“…So far, the known iron imido complexes span a series of oxidation states ranging from iron(V) to iron(II). ,− Among them, mid- to high-valent iron species, iron(V), , iron(IV), ,,,,, and iron(III) imidos ,,,,, and iminyls , have been subjected to intensive studies, and diversified reactivity, for example nitrene transfer to CO, , isocyanides, and phosphine, , alkene aziridation, hydrogen atom abstraction (HAA), ,,,,, and C–H bond amination, ,,, has been observed. In general, the nitrogen groups in high-valent iron imidos are found to be electrophilic in character. , In contrast, few explorations on iron(II) imido species have been published.…”

Section: Introductionmentioning

confidence: 99%

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A Two-Coordinate Iron(II) Imido Complex with NHC Ligation: Synthesis, Characterization, and Its Diversified Reactivity of Nitrene Transfer and C–H Bond Activation

et al. 2019

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Iron terminal imido species are typically implicated as reaction intermediates in iron-catalyzed transformations. While a large body of work has been devoted to mid- and high-valent iron imidos, to date the chemistry of iron(II) imidos has remained largely unexplored due to the difficulty in accessing them. Herein, we present a study on the two-coordinate iron(II) imido complex [(IPr)Fe(NArTrip)] (3; IPr = 1,3-bis(2′,6′-diisopropylphenyl)imidazol-2-ylidene; ArTrip = 2,6-bis(2′,4′,6′-triisopropylphenyl)phenyl) prepared from the reaction of an iron(0) complex with the bulky azide ArTripN3. Spectroscopic investigations in combination with DFT calculations established a high-spin S = 2 ground spin state for 3, consistent with its long Fe–N multiple bond of 1.715(2) Å revealed by X-ray diffraction analysis. Complex 3 exhibits unusual activity of nitrene transfer and C–H bond activation in comparison to the reported iron imido complexes. Specifically, the reactions of 3 with CH2=CHArCF3, an electron-deficient alkene, and CO, a strong π acid, readily afford nitrene transfer products, ArCF3CH=CHNHArTrip and ArTripNCO, respectively, yet no similar reaction occurs when 3 is treated with electron-rich alkenes and PMe3. Moreover, 3 is inert toward the weak C(sp3)–H bonds in 1,4-cyclohexadiene, THF, and toluene, whereas it can cleave the stronger C(sp)–H bond in p-trifluoromethylphenylacetylene to form an iron(II) amido alkynyl complex. Interestingly, intramolecular C(sp3)–H bond functionalization was observed by adding (p-Tol)2CN2 to 3. The unique reactivity of 3 is attributed to its low-coordinate nature and the high negative charge population on the imido N atom, which render its iron–imido unit nucleophilic in nature.

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“…The presence of several electronic states within a few kilocalories per mole of each other is consistent with the proposal of two-state reactivity for the iron-mediated amination of hydrocarbons by the FeNH + ion in the gas phase. 74…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Reactivity of Pyridine Dipyrrolide Iron(II) Complexes with Organic Azides: C–H Amination and Iron Tetrazene Formation

et al. 2019

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Reaction of ( Mes PDP Ph )Fe(thf) (H 2 Mes PDP Ph = 2,6-bis(5-(2,4,6-trimethylphenyl)-3-phenyl-1H-pyrrol-2-yl)pyridine) with organic azides has been studied. The identity of the azide substituent had a profound impact on the transformation type and nature of the observed products. Reaction with aromatic p-tolyl azide, N 3 Tol, resulted in exclusive formation of the corresponding iron tetrazene complex ( Mes PDP Ph )Fe(N 4 Tol 2 ). In contrast, the use of bulky 1adamantyl azide led to clean intramolecular C−H amination of one of the benzylic C−H bonds of a mesityl substituent on the pyridine dipyrrolide, PDP, supporting ligand. The smaller aliphatic substituent in benzyl azide allowed for the isolation of two different compounds from distinct reaction pathways. One product is the result of double C−H amination of the PDP ligand via nitrene transfer, while the second one contains a dibenzyltetrazene and a benzaldimine ligand. All isolated complexes were characterized using a combination of X-ray crystallography, solid state magnetic susceptibility measurements, 1 H NMR and 57 Fe Mossbauer spectroscopy, and density functional theory (DFT), and their electronic structures were elucidated. Potential electronic structures for putative iron(IV) imido or iron(III) imidyl radical complexes were explored via DFT calculations.

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Iron-Mediated Amination of Hydrocarbons in the Gas Phase

Cited by 31 publications

References 22 publications

Gas-phase activation of methane by ligated transition-metal cations

Gas-phase activation of methane by ligated transition-metal cations

A Two-Coordinate Iron(II) Imido Complex with NHC Ligation: Synthesis, Characterization, and Its Diversified Reactivity of Nitrene Transfer and C–H Bond Activation

Reactivity of Pyridine Dipyrrolide Iron(II) Complexes with Organic Azides: C–H Amination and Iron Tetrazene Formation

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