One Electron Makes Differences: From Heme {FeNO}<sup>7</sup> to {FeNO}<sup>8</sup>

Hu, Bin; Li, Jianfeng

doi:10.1002/ange.201505166

Cited by 12 publications

(8 citation statements)

References 46 publications

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“…15,50 Noteworthy, all observed NO stretching frequencies of 2, 3, and 4 are 40−100 cm −1 higher than most reported Fe−NO complexes with the corresponding number of valence electrons in its unit. 5,30,51,52 The successful reduction of the {Fe−NO} 9 (4) to the nitrosoalkane complex 5 also was confirmed by IR vibrational spectroscopy. The intense NO stretching band νÑ O = 1550 cm −1 of 4 is shifted to 1358 cm −1 upon reduction to 5.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 74%

A Series of Iron Nitrosyl Complexes {Fe–NO}^6–9 and a Fleeting {Fe–NO}¹⁰ Intermediate en Route to a Metalacyclic Iron Nitrosoalkane

et al. 2019

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Iron–nitrosyls have fascinated chemists for a long time due to the noninnocent nature of the NO ligand that can exist in up to five different oxidation and spin states. Coordination to an open-shell iron center leads to complex electronic structures, which is the reason Enemark−Feltham introduced the {Fe–NO} n notation. In this work, we succeeded in characterizing a series of {Fe–NO}6–9 complexes, including a reactive {Fe–NO}10 intermediate. All complexes were synthesized with the tris-N-heterocyclic carbene ligand tris[2-(3-mesitylimidazol-2-ylidene)ethyl]amine (TIMENMes), which is known to support iron in high and low oxidation states. Reaction of NOBF4 with [(TIMENMes)Fe]2+ resulted in formation of the {Fe–NO}6 compound [(TIMENMes)Fe(NO)(CH3CN)](BF4)3 (1). Stepwise chemical reduction with Zn, Mg, and Na/Hg leads to the isostructural series of high-spin iron nitrosyl complexes {Fe–NO}7,8,9 (2–4). Reduction of {Fe–NO}9 with Cs electride finally yields the highly reduced {Fe–NO}10 intermediate, key to formation of [Cs(crypt-222)][(TIMENMes)Fe(NO)], (5) featuring a metalacyclic [Fe−(NO−NHC)3−] nitrosoalkane unit. All complexes were characterized by single-crystal XRD analyses, temperature and field-dependent SQUID magnetization methods, as well as 57Fe Mössbauer, IR, UV/vis, multinuclear NMR, and dual-mode EPR spectroscopy. Spectroscopy-based DFT analyses provide insight into the electronic structures of all compounds and allowed assignments of oxidation states to iron and NO ligands. An alternative synthesis to the {Fe–NO}8 complex was found via oxygenation of the nitride complex [(TIMENMes)Fe(N)](BF4). Surprisingly, the resulting {Fe–NO}8 species is electronically and structural similar to the [(TIMENMes)Fe(N)]+ precursor. Based on the structural and electronic similarities between this nitrosyl/nitride complex couple, we adopted the strategy, developed by Wieghardt et al., of extending the Enemark−Feltham nomenclature to nitrido complexes, rendering [(TIMENMes)Fe(N)]+ as a {Fe–N}8 species.

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Section: Journal Of the American Chemical Societymentioning

confidence: 74%

A Series of Iron Nitrosyl Complexes {Fe–NO}^6–9 and a Fleeting {Fe–NO}¹⁰ Intermediate en Route to a Metalacyclic Iron Nitrosoalkane

et al. 2019

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“…Importantly for this anion, the optimized metrical parameters, including the Fe−N(O) distance and the FeNO angle, are in near-perfect agreement with experiment (Figure 2). 21 Thus, the exact nature of the {FeNO} 8 state may well be somewhat sensitive to environmental influences such as subtituent effects and solvation.…”

Section: ■ Methodsmentioning

confidence: 99%

“…2,3,17−20 In a key recent development, a relatively stable {FeNO} 8 complex of an electron-deficient porphyrin has been isolated and crystallographically characterized. 21 By contrast, much less is known about the interactions of NO − and HNO with nonheme metalloporphyrins such as Mn(II) and Co(II) porphyrins. 22−24 The present exploratory DFT 25−29 study was motivated by a desire to shed light on these less-known interactions and potentially to identify new, reduced metalloporphyrin−NO species.…”

Section: ■ Introductionmentioning

confidence: 99%

Metalloporphyrin–Nitroxyl Interactions: The Low-Energy States of Reduced Manganese, Iron, and Cobalt Porphyrin Nitrosyls

Conradie

Ghosh

2016

J. Phys. Chem. B

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DFT calculations employing the OLYP and B3LYP functionals have been used to map out the low energy states of the metalloporphyrin-nitroxyl adducts "M(Por) + NO(-)" and "M(Por) + HNO", where M = Fe, Co, and Mn and Por(2-) is the dianion of unsubstituted porphyrin. For [Fe(Por)(NO)](-), the calculations yield two low-energy solutions, with MS = 0 and 1. The MS = 0 solution is thought to represent the experimentally observed diamagnetic ground states of {FeNO}(8) porphyrins, and both functionals yield FeNO geometrical parameters in excellent agreement with a recent crystal structure. For [Co(Por)(NO)](-), the lowest-energy solution for both OLYP and B3LYP is a true {CoNO}(9) state that appears to be best described as a high-spin Co(II) center with a dxy(2)dxz(1)dyz(1)dz2(2)dx2-y2(1) configuration antiferromagnetically coupled to a NO(-) diradical. Such an electronic configuration is expected to lead to diagnostic structural features, including long equatorial Co-N distances (∼2.1 Å), a strong displacement (∼0.4 Å) of the metal from the mean plane of the equatorial nitrogens, and a relatively short Co-N(O) distance (1.8 Å), which should all be experimentally observable. The dx2-y2(1) electronic configuration should also lead to characteristic EPR hyperfine parameters. The calculations also indicate a number of other low-energy states for [Co(Por)(NO)](-), including multiple {CoNO}(8) porphyrin anion radical states. For [Mn(Por)(NO)](-), both functionals indicate a rather complex electronic state landscape, including multiple {MnNO}(6) porphyrin anion radical states as well as a high-spin S = 3/2 {MnNO}(7) state. Both functionals clearly indicate a low-spin Fe(II) state for [Fe(Por)(HNO)]. On the other hand, two comparably low-energy states are predicted for both [Co(Por)(HNO)] and [Mn(Por)(HNO)]. For [Co(Por)(HNO)], the two states are a low-spin Co(II) state with a dxy(2)dxz(2)dyz(2)dz2(1) configuration and a low-spin Co(III)(HNO)(•-) state. For [Mn(Por)(HNO)], the two states may be described as low- (S = 1/2) and intermediate-spin (S = 3/2) Mn(II). The latter state has a relatively long Mn-N(O) distance of about 2.07 Å, which may be indicative of facile HNO dissociation.

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“…of hemenitroxyl compounds. [4,96] Of particular interest is the experimental evidence of the expected increased bending of the FeÀ NÀ O adducts, displaying angles of 122°and 127°r espectively, compared to their nitrosyl precursors at 148.5°and 143°.…”

Section: Ironmentioning

confidence: 99%

Structure and Reactivity of NO/NO⁺/NO⁻Pincer and Porphyrin Complexes

et al. 2021

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This review covers recent progress in the field of nitrosyl pincer and porphyrinate complexes, and how their reactivity depends on the redox state of the NO ligand. Synthetic methods, and the most significant structural information, spectroelectrochemical studies, and different reactivities of nitrosyl pincer complexes are presented. These include selective activation and functionalization of carbon-halogen bonds, catalysis for a variety of specific organic reactions, mediation of NO dispro-portionation and reversible coordination of solvents and weakly-coordinating anions. Regarding the porphyrinate complexes, the focus is on biorelevant nitroxyl (NO À /HNO) complexes, discussing pioneering studies along with preparation and common characterization methods. Their relative stability in different conditions is compared, and possible decomposition mechanisms are discussed in terms of their ability to act as biomimetic models for enzymatic systems.

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One Electron Makes Differences: From Heme {FeNO}⁷ to {FeNO}⁸

Cited by 12 publications

References 46 publications

A Series of Iron Nitrosyl Complexes {Fe–NO}^6–9 and a Fleeting {Fe–NO}¹⁰ Intermediate en Route to a Metalacyclic Iron Nitrosoalkane

A Series of Iron Nitrosyl Complexes {Fe–NO}^6–9 and a Fleeting {Fe–NO}¹⁰ Intermediate en Route to a Metalacyclic Iron Nitrosoalkane

Metalloporphyrin–Nitroxyl Interactions: The Low-Energy States of Reduced Manganese, Iron, and Cobalt Porphyrin Nitrosyls

Structure and Reactivity of NO/NO⁺/NO⁻Pincer and Porphyrin Complexes

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One Electron Makes Differences: From Heme {FeNO}7 to {FeNO}8

Cited by 12 publications

References 46 publications

A Series of Iron Nitrosyl Complexes {Fe–NO}6–9 and a Fleeting {Fe–NO}10 Intermediate en Route to a Metalacyclic Iron Nitrosoalkane

A Series of Iron Nitrosyl Complexes {Fe–NO}6–9 and a Fleeting {Fe–NO}10 Intermediate en Route to a Metalacyclic Iron Nitrosoalkane

Metalloporphyrin–Nitroxyl Interactions: The Low-Energy States of Reduced Manganese, Iron, and Cobalt Porphyrin Nitrosyls

Structure and Reactivity of NO/NO+/NO−Pincer and Porphyrin Complexes

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One Electron Makes Differences: From Heme {FeNO}⁷ to {FeNO}⁸

A Series of Iron Nitrosyl Complexes {Fe–NO}^6–9 and a Fleeting {Fe–NO}¹⁰ Intermediate en Route to a Metalacyclic Iron Nitrosoalkane

A Series of Iron Nitrosyl Complexes {Fe–NO}^6–9 and a Fleeting {Fe–NO}¹⁰ Intermediate en Route to a Metalacyclic Iron Nitrosoalkane

Structure and Reactivity of NO/NO⁺/NO⁻Pincer and Porphyrin Complexes