A <i>cis</i>‐Divacant Octahedral and Mononuclear Iron(IV) Imide

Searles, Keith; Fortier, Skye; Khusniyarov, Marat M.; Carroll, Patrick J.; Sutter, Jörg; Meyer, Karsten; Mindiola, Daniel J.; Caulton, Kenneth G.

doi:10.1002/ange.201407156

Cited by 31 publications

(23 citation statements)

References 43 publications

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“…15 This view is supported by the observation that natural as well as engineered enzymes can catalyze nitrene transfers. [16][17][18][19] Numerous iron-imido and ironimidyl complexes have been isolated over the past decade [20][21][22][23][24][25][26][27][28][29][30] but few studies of their catalytic activity have been reported. More recently, however, a few systems were considered more in depth and their nitrene transfer ability assessed in sulfimidation reaction 28,29,31 or H • abstraction.…”

Section: Introductionmentioning

confidence: 99%

Fe-Catalyzed Aziridination Is Governed by the Electron Affinity of the Active Imido-Iron Species

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Fe-Catalyzed Aziridination Is Governed by the Electron Affinity of the Active Imido-Iron Species

et al. 2020

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“…To the best of our knowledge, only two bona fide iron(IV) imido complexes have been previously characterized by Mössbauer spectroscopy (Table 2). 7,36 Although these complexes have different geometries and spin states from 3, their isomer shifts are similar to those of 3,…”

Section: X-ray Crystallographymentioning

confidence: 97%

“…We note that another trigonal fourcoordinate Fe(IV) imido complex ([{PhB(P tBu )2(pz′)}Fe IV (NAd)] + ;) exhibits an S = 1 ground state, so that the discussion here is generally applicable to these as well. There is a diamagnetic four-coordinate Fe(IV) imido complex, 36 but its geometry is quite different, namely cis-divacant octahedral so that its ideal symmetry is only Cs, thus with no orbital degeneracies. 144 As shown in the Supporting Information, however, the slight increase in θ angle (i.e., the angle between the B-Fe-N, approximate C3 axis, and the ligand carbene C atoms; see Scheme S1) between the imido complex 3 and the previously analyzed 33…”

Section: Ligand-field Theory (Lft)mentioning

confidence: 99%

Spectroscopic and Computational Studies of Spin States of Iron(IV) Nitrido and Imido Complexes

et al. 2017

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High-oxidation-state metal complexes with multiply bonded ligands are of great interest for both their reactivity as well as their fundamental bonding properties. This paper reports a combined spectroscopic and theoretical investigation into the effect of the apical multiply bonded ligand on the spin-state preferences of threefold symmetric iron(IV) complexes with tris(carbene) donor ligands. Specifically, singlet (S = 0) nitrido [{PhB(Im)}FeN], R = Bu (1), Mes (mesityl, 2) and the related triplet (S = 1) imido complexes, [{PhB(Im)}Fe(NR')], R = Mes, R' = 1-adamantyl (3), Bu (4), were investigated by electronic absorption and Mössbauer effect spectroscopies. For comparison, two other Fe(IV) nitrido complexes, [(TIMEN)FeN] (TIMEN = tris[2-(3-aryl-imidazol-2-ylidene)ethyl]amine; Ar = Xyl (xylyl), Mes), were investigated by Fe Mössbauer spectroscopy, including applied-field measurements. The paramagnetic imido complexes 3 and 4 were also studied by magnetic susceptibility measurements (for 3) and paramagnetic resonance spectroscopy: high-frequency and -field electron paramagnetic resonance (for 3 and 4) and frequency-domain Fourier-transform (FD-FT) terahertz electron paramagnetic resonance (for 3), which reveal their zero-field splitting parameters. Experimentally correlated theoretical studies comprising ligand-field theory and quantum chemical theory, the latter including both density functional theory and ab initio methods, reveal the key role played by the Fe 3d (a) orbital in these systems: the nature of its interaction with the nitrido or imido ligand dictates the spin-state preference of the complex. The ability to tune the spin state through the energy and nature of a single orbital has general relevance to the factors controlling spin states in complexes with applicability as single molecule devices.

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“…Pincer-supported Fe(II) complex 1 displays approximately CDO geometry and participates in two-electron oxidative chemistry upon treatment with adamantyl azide to afford the corresponding Fe(IV) imide complex. 17 The observation of CDO coordination in complex 1 was ascribed to minimization of steric interactions that would be encountered in a potential square planar complex. Similarly, transchelating bis-alkoxide complex 2 features an Fe(II) center that displays approximately CDO coordination.…”

Section: Introductionmentioning

confidence: 99%

Cis-Divacant Octahedral Fe(II) in a Dimensionally Reduced Family of 2-(Pyridin-2-yl)pyrrolide Complexes

Hyun

Reid

Vali

et al. 2021

Preprint

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Four-coordinate transition metal complexes can adopt a diverse array of coordination geometries, with square planar and tetra- hedral coordination being the most prevalent. Previously, we reported the synthesis of a trinuclear Fe(II) complex, Fe3TPM2, supported by a three-fold symmetric 2-pyridylpyrrolide ligand (i.e., tris(5-(pyridin-2-yl)-1H-pyrrol-2-yl)methane), that featured a rare cis-divacant octahedral (CDO) geometry at each Fe(II) center. Here, a series of truncated 2-pyridylpyrrolide ligands is described that support mono- and binuclear Fe(II) complexes that also exhibit CDO geometries. Metallation of tetradentate ligand bis(5-(pyridin-2-yl)-1H-pyrrol-2-yl)methane (H2BPM) in THF results in a binuclear complex Fe2(BPM)2(THF)2 in which both Fe(II) ions are octahedrally coordinated. The coordinated THF solvent ligands are labile: THF dissociation leads to Fe2(BPM)2, which features five-coordinate Fe(II) ions. The Fe–Fe distance in these binuclear complexes can be elongated by ligand methylation. Metalation of bis(5-(6-methylpyridin-2-yl)-1H-pyrrol-2-yl)methane (H2BPMMe) in THF leads to the formation of four-coordinate, CDO Fe(II) centers in Fe(BPMMe)2. Further ligand truncation affords bidentate ligands 2- (1H-pyrrol-2-yl)pyridine (PyrPyrrH) and 2-methyl-6-(1H-pyrrol-2-yl)pyridine (PyrMePyrrH). Metalation of these ligands in THF affords six-coordinate complexes Fe(PyrPyrr)2(THF)2 and Fe(PyrMePyrr)2(THF)2. Dissociation of labile solvent ligands provides access to four- coordinate Fe(II) complexes. Ligand disproportionation at Fe(PyrPyrr)2 results in the formation of Fe(PyrPyrr)3 and Fe(0). Ligand methyl- ation suppresses this disproportionation and enables isolation of Fe(PyrMePyrr)2, which is rigorously CDO. Complete ligand truncation, by separating the 2-pyridylpyrrolide ligands into the constituent monodentate pyridyl and pyrrolide donors, affords Fe(Pyr)2(Pyrr)2 in which the Fe(II) is tetrahedrally coordinated. Computational analysis indicates that the potential energy surface that dictates the coordination geometry in this family of four-coordinate complexes is fairly flat in the vicinity of CDO coordination. These synthetic studies provide the structural basis to explore the implications of CDO geometry on Fe-catalyzed reactions.

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A cis‐Divacant Octahedral and Mononuclear Iron(IV) Imide

Cited by 31 publications

References 43 publications

Fe-Catalyzed Aziridination Is Governed by the Electron Affinity of the Active Imido-Iron Species

Fe-Catalyzed Aziridination Is Governed by the Electron Affinity of the Active Imido-Iron Species

Spectroscopic and Computational Studies of Spin States of Iron(IV) Nitrido and Imido Complexes

Cis-Divacant Octahedral Fe(II) in a Dimensionally Reduced Family of 2-(Pyridin-2-yl)pyrrolide Complexes

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