An Octahedral Coordination Complex of Iron(VI)

Berry, John F.; Bill, Eckhard; Bothe, Eberhard; DeBeer, Serena; Mienert, Bernd; Neese, Frank; Wieghardt, Karl

doi:10.1126/science.1128506

Cited by 303 publications

(314 citation statements)

References 42 publications

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“…[23] The differences between the IRPD spectra of 14 N-and 15 N-labelled 3 (Figure 3 b ) and this band has almost zero intensity (Figure 3 d). This is further confirmed when comparing the experimental (Figure 3 b) and theoretical (Figure 3 c) difference spectra, which show the same changes in band patterns between 14 N and 15 N labelling. Specifically, the bands with strong FeÀN stretching character in the theoretical spectra (Figure 3 d, blue trace) match the features at 855 and 867 cm À1 in the experimental spectra (Figure 3 a, blue trace).…”

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confidence: 76%

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Detection of Indistinct Fe−N Stretching Bands in Iron(V) Nitrides by Photodissociation Spectroscopy

Andris

Navrátil

Jašík

et al. 2018

Chemistry A European J

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We report for the first time infrared spectra of three non‐heme pseudo‐octahedral iron(V) nitride complexes with assigned Fe−N stretching vibrations. The intensities of the Fe−N bands in two of the complexes are extremely weak. Their detection was enabled by the high resolution and sensitivity of the experiments performed at 3 K for isolated complexes in the gas phase. Multireference CASPT2 calculations revealed that the Fe−N bond in the ground doublet state is influenced by two low‐lying excited doublet states. In particular, configuration interaction between the ground and the second excited state leads to avoided crossing of their potential energy surfaces along the Fe−N coordinate, which thus affects the ground‐state Fe−N stretching frequency and intensity. Therefore, DFT calculated Fe−N stretching frequency strongly depends on the amount of Hartree–Fock exchange potential. As a result, by tuning the amount of Hartree–Fock exchange potential in the B3LYP functional, it was possible to obtain theoretical spectra perfectly consistent with the experimental data. The theory shows that the intensity of the Fe−N stretching vibration can almost vanish due to strong coupling with other stretching modes of the ligands.

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confidence: 76%

“…[12] All other attempts to detect the FeÀN transitions have failed, presumably due to their low IR intensities. [13,14] Alternatively, 57 Fe nuclear resonance vibrational spectroscopy (NRVS) [15] can be used. ).…”

Section: Detection Of Indistinct Feàn Stretching Bands In Iron(v) Nitmentioning

confidence: 99%

Detection of Indistinct Fe−N Stretching Bands in Iron(V) Nitrides by Photodissociation Spectroscopy

Andris

Navrátil

Jašík

et al. 2018

Chemistry A European J

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“…The assignment is further supported by a short Fe-N distance of 1.57 Å (determined by EXAFS), a complementary computational analysis, and a linear relationship between the isomer shifts and oxidation states in a series of complexes with similar iron complex core structures and varying formal oxidation states, ranging from + II to + VI (ref. 84). This is the first Fe VI coordination complex ever reported, with the ferrate anion FeO 4 2 − being the only other known example of an Fe VI ion.…”

Section: Iron-nitrido Model Complexesmentioning

confidence: 82%

“…Furthermore, the (photochemically inactive) ferric azide of the corresponding methylated cyclam ligand can be oxidized to yield [(Me 3 cy-ac)Fe IV (N 3 )] 2 + , which, in turn, is photochemically active. Accordingly, photolysis at 650 nm in frozen matrix yields another, yellow product, [(Me 3 cy-ac)Fe VI (N)] 2 + with one major component (73%) at δ = − 0.29 mms − 1 and ∆E Q = 1.53 mms − 1 in the Mössbauer spectrum 84 . This unusually low, negative isomer shift is consistent with a hexavalent Fe VI ≡N species.…”

Section: Iron-nitrido Model Complexesmentioning

confidence: 99%

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

2012

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selective functionalization of unactivated c-H bonds and ammonia production are extremely important industrial processes. a range of metalloenyzmes achieve these challenging tasks in biology by activating dioxygen and dinitrogen using cheap and abundant transition metals, such as iron, copper and manganese. High-valent iron-oxo and -nitrido complexes act as active intermediates in many of these processes. the generation of well-described model compounds can provide vital insights into the mechanism of such enzymatic reactions. advances in the chemistry of model high-valent iron-oxo and -nitrido systems can be related to our understanding of the biological systems.H igh-valent oxoiron(IV) and formally oxoiron(V) species have been spectroscopically identified as active intermediates in the catalytic cycles of a number of enzymatic systems 1-10 . Haem and non-haem proteins use these reactive intermediates to couple the activation of dioxygen to the oxidation of their substrates. In most cases, an oxygen atom is inserted into an unactivated C-H bond of the substrate; for example, in hydroxylation reactions [1][2][3][4][5][6][7][8][9][10] . However, many other reactions, including halogenation, desaturation, cyclization, epoxidation and decarboxylation, are also known to involve oxoiron species 1,3 . Superoxidized iron complexes with (valence) isoelectronic imido and nitrido ligands, as well as 'surface nitrides' , have also been implicated as key intermediates in the nitrogen atom transfer reactions 11 , the biological synthesis of ammonia by the nitrogenase enzyme 12-16 and the industrial Haber-Bosch process 17 .The generation of well-described model compounds can provide vital insights into the mechanism of such enzymatic reactions. Consequently, considerable effort has been made by synthetic chemists to prepare viable models for the putative reaction intermediates in the catalytic cycles of O 2 and N 2 activating enzymes. In this review, we provide an overview of all high-valent oxoiron and nitridoiron species that have been either identified or proposed as reactive intermediates in biology. Subsequently, we summarize some of the recent advances in bioinorganic chemistry that have led to the identification and isolation of iron complexes in unusually high formal oxidation states, containing iron-oxygen or iron-nitrogen multiple bonds. The spectroscopic characterization and the reactivity studies of these model complexes provide vital insights into the mechanism that nature uses to induce the reductive cleavage of dioxygen or dinitrogen in carrying out a number of important biochemical oxidative transformations. Moreover, the comparative review of the electronic structures of the isoelectronic oxoiron and nitridoiron functionalities reveals that the Fe-N bonds are intrinsically more covalent than the Fe-O bonds.

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“…Hence, it constitutes an ideal low-molecular weight model system for heme biochemistry involving super-oxidized iron. [1][2][3][4] …”

Section: Introductionmentioning

confidence: 99%

Femtosecond UV-pump mid-IR probe spectroscopy of the ultrafast photodissociation of azide radicals from an azidoiron(III) complex

Vennekate

Schwarzer

Torres-Alacan

et al. 2013

EPJ Web of Conferences

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Abstract. The ultrafast photolysis of the cation complex [(cyclam-ac)FeN 3 ] + is studied by femtosecond spectroscopy with ultraviolet excitation and mid-infrared probing. Immediately after UV absorption, the excited complex undergoes internal conversion and azide dissociation within 2 ps. The subsequent vibrational relaxation in the electronic ground state and geminate recombination of the fragments take place on time scales of 13 and 20 ps, respectively.

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An Octahedral Coordination Complex of Iron(VI)

Cited by 303 publications

References 42 publications

Detection of Indistinct Fe−N Stretching Bands in Iron(V) Nitrides by Photodissociation Spectroscopy

Detection of Indistinct Fe−N Stretching Bands in Iron(V) Nitrides by Photodissociation Spectroscopy

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

Femtosecond UV-pump mid-IR probe spectroscopy of the ultrafast photodissociation of azide radicals from an azidoiron(III) complex

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