Characterization of the FeH Bond in a Three‐Coordinate Terminal Hydride Complex of Iron(I)

Chiang, Karen P.; Scarborough, Christopher C.; Horitani, Masaki; Lees, Nicholas S.; Ding, Keying; Dugan, Thomas R.; Brennessel, William W.; Bill, Eckhard; Hoffman, Brian M.; Holland, Patrick L.

doi:10.1002/anie.201109204

Cited by 52 publications

(63 citation statements)

References 34 publications

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“…6,86 Analogous ENDOR experiments on isolable Fe-H compounds with terminal hydrides showed an axial tensor, while bridging hydrides gave a rhombic tensor. 6,175,176 This combination of experiments validated the idea that that the signals from the FeMoco-hydride (“E 4 ”) are most consistent with bridging hydrides in E 4 H 4 . 6 However, the active form might have transient terminal hydrides, as is currently believed for hydrogenase enzymes based on synthetic modeling studies.…”

Section: Fe-h Complexes With Sulfur and N2 Ligandssupporting

confidence: 62%

Insight into the Iron–Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands

2016

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Nitrogenase enzymes are used by microorganisms for converting atmospheric N2 to ammonia, which provides an essential source of N atoms for higher organisms. The active site of the molybdenum-dependent nitrogenase is the unique carbide-containing iron-sulfur cluster called the iron-molybdenum cofactor (FeMoco). On the FeMoco, N2 binding is suggested to occur at one or more iron atoms, but the structures of the catalytic intermediates are not clear. In order to establish the feasibility of different potential mechanistic steps during biological N2 reduction, chemists have prepared iron complexes that mimic various structural aspects of the iron sites in FeMoco. This reductionist approach gives mechanistic insight, and also uncovers fundamental principles that could be used more broadly for small molecule activation. Here, we review recent results and highlight directions for future research. In one direction, synthetic iron complexes have now been shown to bind N2, break the N-N triple bond, and produce ammonia catalytically. Carbon and sulfur based donors have been incorporated into the ligand spheres of Fe-N2 complexes to show how these atoms may influence the structure and reactivity of the FeMoco. Hydrides have been incorporated into synthetic systems, which can bind N2, reduce some nitrogenase substrates, and/or reductively eliminate H2 to generate reduced iron centers. Though some carbide-containing iron clusters are known, none yet have sulfide bridges or high-spin iron atoms like the FeMoco.

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Section: Fe-h Complexes With Sulfur and N2 Ligandssupporting

confidence: 62%

Insight into the Iron–Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands

2016

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“…Each value is consistent with high-spin ( S = 3/2) iron(I) ions, as found in other three-coordinate iron(I) diketiminate complexes. 32, 41, 42 The paramagnetically shifted 1 H NMR spectra of D under argon in C 6 D 6 , C 6 D 12 , Et 2 O, and THF- d 8 (Figure S2) give peak integrations consistent with local C 2v symmetry around each iron atom. This indicates that the core of D is fluxional, though the high solubility suggests that the potassium ions remain surrounded by bound arenes.…”

Section: Resultsmentioning

confidence: 89%

“…We note that the related iron(I) hydride complex, K 2 [LFeH] 2 , can similarly be broken up into monomers with potassium chelating agents. 41 In the hydride system, breaking up the dimer gave upfield shifts in the same resonance of the supporting ligand, with the amount of shift increasing from 18-crown-6 to cryptand-2.2.2.…”

Section: Resultsmentioning

confidence: 99%

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Multimetallic cooperativity in activation of dinitrogen at iron–potassium sites

et al. 2014

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The reaction of soluble iron-oxygen-potassium assemblies with N2 gives insight into the mechanisms of multimetallic N2 coordination. We report a series of very electron-rich three-coordinate, β-diketiminate-supported iron(I) phenoxide complexes, which are metastable but have been characterized under Ar by both crystallography and solution methods. Both monomeric and dimeric Fe-OPh-K compounds have been characterized, and their iron environments are very similar in the solid and solution states. In the dimer, potassium ions hold together the phenoxide oxygens and aryl rings of the two halves, to give a flexible diiron core. The reactions of the monomeric and dimeric iron(I) compounds with N2 are surprisingly different: the mononuclear iron(I) complexes give no reaction with N2, but the dimeric Fe2K2 complex reacts rapidly to give a diiron-N2 product. Computational studies show that the key to the rapid N2 reaction of the dimer is the preorganization of the two iron atoms. Thus, cooperation between Fe (which weakens the N-N bond) and K (which orients the Fe atoms) can be used to create a low-energy pathway for N2 reactions.

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“…He has reported in Angewandte Chemie on the characterization of FeÀH bonds. [2] Max Bergmann Medal for Claudio Toniolo Claudio Toniolo (Università degli Studi di Padova) has been awarded the 2013 Max Gold Medal by the Max-Bergmann-Kreis for his work on the "characterization of protein secondary structure by using synthetic model peptides". Toniolo was awarded He has reported in ChemPhysChem on a peptidebased approach to solar energy conversion.…”

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confidence: 99%

Ryoji Noyori Prize: B. M. Trost / F. A. Cotton Medal: B. M. Hoffman / Max Bergmann Medal: C. Toniolo / Royal Australian Chemical Institute Awards: M. Kelso, C. Jones, S. Perrier, M. J. Crossley, and D. W. Lupton / 2013–2014 International Solvay Chair of Chemistry; Prelog Medal and Lectureship: E. W. Meijer / Linus Pauling Medal: C. A. Mirkin

2014

Angew Chem Int Ed

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Characterization of the FeH Bond in a Three‐Coordinate Terminal Hydride Complex of Iron(I)

Cited by 52 publications

References 34 publications

Insight into the Iron–Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands

Insight into the Iron–Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands

Multimetallic cooperativity in activation of dinitrogen at iron–potassium sites

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