Synthesis and crystallographic characterization of bis(tetramethylammonium) carbidohexadecacarbonylhexaferrate, a hexanuclear carbidocarbonyl derivative of iron

Churchill, Melvyn Rowen; Wormald, John; Knight, John A.; Mays, Martin J.

doi:10.1021/ja00741a058

Cited by 90 publications

(52 citation statements)

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“…15,36 We reproduced this RT structure with an R 1 value of 5.1%, solving in the space group Pnmb , a non-standard setting of Pnma , in order to facilitate comparison to LT . In the asymmetric unit of RT there are two independent iron anion clusters that are bisected by crystallographic mirror planes (thus one half of each is unique) and two independent tetramethylammonium cations with atoms in general positions.…”

Section: Resultsmentioning

confidence: 99%

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Identification of a Single Light Atom within a Multinuclear Metal Cluster Using Valence-to-Core X-ray Emission Spectroscopy

et al. 2011

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Iron valence-to-core Fe Kβ x-ray emission spectroscopy (V2C XES) is established as a means to identify light atoms (C. N, O) within complex multimetallic frameworks. The ability to distinguish light atoms, particularly in the presence of heavier atoms, is a well-known limitation of both crystallography and EXAFS. Using the sensitivity of V2C XES to the ionization potential of the bound ligand energetic shifts of ~10 eV in the ligand 2s ionization energies of bound C, N and O may be observed. As V2C XES is a high-energy X-ray method, it is readily applicable to samples in any physical form. This method thus has great potential for application to multimetallic inorganic frameworks involved in both small molecule storage and activation.

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Section: Resultsmentioning

confidence: 99%

“…15 The 13 C NMR spectrum of the compound was not reported in that paper, but we recorded it in order to verify the presence of a central carbide. 13 C{ 1 H} NMR (125.7 MHz, THF- d 8 ): δ 56 (CH 3 ), 229 (CO), 485 (C 4− ) ppm.…”

Section: Methodsmentioning

confidence: 99%

Identification of a Single Light Atom within a Multinuclear Metal Cluster Using Valence-to-Core X-ray Emission Spectroscopy

et al. 2011

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“…9a) was studied in the early 1970’s as a model of possible intermediates in the iron-catalyzed Fischer-Tropsch process. 129,130 In collaboration with DeBeer, we recently reported more extensive crystallographic characterization of 19 , as well as X-ray emission studies that elucidated the electronic structure of the iron-carbide core and demonstrated the delocalized orbitals that give rise to Fe-C bond-ing. 145 Oxidation of 19 leads to related Fe 5 and Fe 4 carbide/carbonyl clusters.…”

Section: Carbide Complexes and Fe-n2 Complexes With Carbon Ligandsmentioning

confidence: 99%

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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“…A host of iron-carbonyl clusters have been synthesized with a variety of bridging (≥ μ 3 ) single atom ligands, including μ 6 -C clusters, such as [(μ 6 -C)Fe 6 (CO) 16 ] 2− , with arrangements reminiscent of the FeMoco structure (Figure 1B, see SI for a comprehensive list). 5 While a related cluster has been reported displaying a μ 6 -N ligand, [( μ 6 -N)Fe 6 (CO) 15 ] 3− , with potential for structure function studies of the effect of the interstitial ligand, changes in the structure and number of CO ligands complicates interpretations. In the cases where completely isostructural clusters can be prepared with bridging elements of the second row of the periodic table, the large number (≥ 9) of diatomic ligands limits interpretations regarding the activation of a single small molecule substrate, which is most relevant to biological systems.…”

Section: Introductionmentioning

confidence: 99%

Tetranuclear Fe Clusters with a Varied Interstitial Ligand: Effects on the Structure, Redox Properties, and Nitric Oxide Activation

Reed

Agapie

2017

Inorg. Chem.

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A new series of tetranuclear iron clusters displaying an interstitial μ4-F ligand was prepared for comparison to μ4-O analogs. With a single NO coordinated as a reporter of small molecule activation, the μ4-F clusters were characterized in five redox states, from FeII3{FeNO}8 to FeIII3{FeNO}7, with N–O stretching frequencies ranging from 1680 cm−1 to 1855 cm−1, respectively. Despite accessing more reduced states with an F− bridge, a two electron reduction of the distal Fe centers is necessary for the μ4-F clusters to activate NO to the same degree as the μ4-O system; consequently, NO reactivity is observed at more positive potentials with μ4-O than μ4-F. Moreover, the μ4-O ligand better translates redox changes of remote metal centers to diatomic ligand activation. The implication for biological active sites is that the higher charge bridging ligand is more effective in tuning cluster properties, including the involvement of remote metal centers, for small molecule activation

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Synthesis and crystallographic characterization of bis(tetramethylammonium) carbidohexadecacarbonylhexaferrate, a hexanuclear carbidocarbonyl derivative of iron

Cited by 90 publications

References 0 publications

Identification of a Single Light Atom within a Multinuclear Metal Cluster Using Valence-to-Core X-ray Emission Spectroscopy

Identification of a Single Light Atom within a Multinuclear Metal Cluster Using Valence-to-Core X-ray Emission Spectroscopy

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

Tetranuclear Fe Clusters with a Varied Interstitial Ligand: Effects on the Structure, Redox Properties, and Nitric Oxide Activation

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