Initial synthesis and structure of an all-ferrous analogue of the fully reduced [Fe
 4
 S
 4
 ]
 0
 cluster of the nitrogenase iron protein

Scott, Thomas Allan; Berlinguette, Curtis P.; Holm, R. H.; Zhou, Hong‐Cai

doi:10.1073/pnas.0504258102

Cited by 75 publications

(50 citation statements)

References 28 publications

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“…The latter feature is of potential interest because aqueous buffer solutions of Ti III (citrate)-reduced Av Fe protein are red and display a band at 520 nm which has been suggested as a signature of a [Fe 4 S 4 ] 0 cluster in protein 6. Further credence to this possibility is offered by the 518 nm band observed for 8 in acetonitrile/THF in the presence of excess reductant 24. Given the transparency of the carbene ligand (Figure 7) and a minor dependence on terminal ligand, this transition appears to be confined to the cluster core.…”

Section: Resultsmentioning

confidence: 97%

“…[Fe 4 S 4 (Pr i 2 NHCMe 2 ) 4 ] has a cubane-type structure in which the all-ferrous state has been previously isolated only as the highly unstable [Fe 4 S 4 (CN) 4 ]4–24 and as [Fe 4 S 4 (S Cys ) 4 ] in the Av Fe protein of nitrogenase 5–11. Structural parameters and the 57 Fe isomer shift are fully consistent with the all-ferrous formulation.…”

Section: Discussionmentioning

confidence: 99%

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Stabilization of Fully Reduced Iron−Sulfur Clusters by Carbene Ligation: The [Fe_nS_n]⁰ Oxidation Levels (n = 4, 8)

2008

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The all-ferrous [Fe4S4]0 state has been demonstrated in the fully reduced Fe protein of the Azotobacter vinelandii nitrogenase complex. We seek synthetic analogues of this state more tractable than the recently prepared but highly unstable cluster [Fe4S4(CN)4]4− (Scott, Berlinguette, Holm, and Zhou, Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 9741). The N-heterocyclic carbene 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (Pri2NHCMe2) has been found to stabilize the fully reduced clusters [Fe8S8(Pri2NHCMe2)6] (4) and [Fe4S4(Pri2NHCMe2)4] (5), which are prepared by cluster assembly or phosphine substitution of FenSn (n = 8, 16) clusters. Cluster 4 is also obtained by reaction of the carbene with all-ferrous [Fe7S6(PEt3)5Cl2] (3) and cluster 5 by carbene cleavage of 4. Detailed structures of 3 (monocapped prismatic), 4, and 5 are described; the latter two are the first iron–sulfur clusters with Fe–Cσ bonds. Cluster 4 possesses the [Fe8(μ3-S)6(μ4-S)2] edge-bridged double cubane structure and 5 the cubane-type [Fe4(μ3-S)4] stereochemistry. The all-ferrous formulations of the clusters are confirmed by X-ray structure parameters and 57Fe isomer shifts. Both clusters are stable under conventional aprotic anaerobic conditions, enabling further study of reactivity. The collective properties of 5 indicate that it is a meaningful synthetic analogue of the core of the fully reduced protein-bound cluster.

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Section: Resultsmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Stabilization of Fully Reduced Iron−Sulfur Clusters by Carbene Ligation: The [Fe_nS_n]⁰ Oxidation Levels (n = 4, 8)

2008

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“…32 This cluster is further reduced with the powerful reductant benzophenone ketyl radical anion to the all-ferrous cluster 10 which was authenticated by an X-ray structure determination and Mossbauer spectroscopy. 33 It is the first [Fe 4 S 4 ] 0 site analogue isolated in substance. However, this cluster is extraordinarily sensitive to oxidation and is an impractical object of investigation, particularly in solution.…”

Section: Fe4s4 Clustersmentioning

confidence: 99%

Developments in the Biomimetic Chemistry of Cubane-Type and Higher Nuclearity Iron–Sulfur Clusters

Lo²,

2014

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“…The first such species was isolated from the substitution reaction of [Fe 4 S 4 (PPr i 3 ) 4 ] 1+ with cyanide in the presence of the strong reductant [Ph 2 CO] • - (76). However, [Fe 4 S 4 (CN) 4 ] 4- , while in the desired oxidation state, was intensely unstable to oxidation and difficult to manipulate.…”

Section: Iron-sulfur Proteinsmentioning

confidence: 99%

Biomimetic Chemistry of Iron, Nickel, Molybdenum, and Tungsten in Sulfur-Ligated Protein Sites

Groysman

Holm

2009

Biochemistry

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Biomimetic inorganic chemistry has as its primary goal the synthesis of molecules that approach or achieve the structures, oxidation states, and electronic and reactivity features of native metalcontaining sites of variant nuclearity. Comparison of properties of accurate analogues and these sites ideally provides insight into the influence of protein structure and environment on intrinsic properties as represented by the analogue. For polynuclear sites in particular, the goal provides a formidable challenge for, with the exception of iron-sulfur clusters, all such site structures have never been achieved and few even closely approximated by chemical synthesis. This account describes the current status of the synthetic analogue approach as applied to the mononuclear sites in certain molybdoenzymes and the polynuclear sites in hydrogenases, nitrogenase, and carbon monoxide dehydrogenases. Synthetic AnaloguesA strategy of demonstrated value in the study of protein-bound metal sites is the synthetic analogue or biomimetic approach defined by the protocol of Figure 1 (1). As developed and implemented in this laboratory, this approach has as its objective the preparation and detailed characterization of relatively small molecules that simulate or achieve the coordination sphere, composition, stereochemistry, and oxidation states of the native metal mononuclear or polynuclear site. A structural analogue allows deduction of site characteristics common to the site and itself by property comparisons. A functional analogue supports substrate transformations to products as do enzymes, although not necessarily at the same rate or with the same stereochemistry. A functional analogue is not inevitably a structural analogue, but a high-fidelity structural analogue should be a functional analogue provided a protein environment is not obligatory to reactivity. The approach is iterative in order to improve as necessary the accuracy of a site analogue. Here we describe the current status of selected biomimetic chemistry of four metals (Fe, Ni, Mo, W) in relation to proteins that are the objects of widespread contemporary interest: molybdenum and tungsten oxotransferases and hydroxylases, iron and nickel-iron hydrogenases, iron-sulfur proteins, molybdenum-copper and nickel-iron-sulfur carbon monoxide dehydrogenases, and nitrogenase. The sites in these proteins exhibit a range of metal nuclearities and have the common features of variable oxidation states and sulfur-rich coordination environments. Space limitations do not allow detailed accounts of enzyme reactions and mechanisms, protein structure, and inclusion of all meritorious results in site modeling. The emphasis is on the native sites themselves and recent

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Initial synthesis and structure of an all-ferrous analogue of the fully reduced [Fe ₄ S ₄ ] ⁰ cluster of the nitrogenase iron protein

Cited by 75 publications

References 28 publications

Stabilization of Fully Reduced Iron−Sulfur Clusters by Carbene Ligation: The [Fe_nS_n]⁰ Oxidation Levels (n = 4, 8)

Stabilization of Fully Reduced Iron−Sulfur Clusters by Carbene Ligation: The [Fe_nS_n]⁰ Oxidation Levels (n = 4, 8)

Developments in the Biomimetic Chemistry of Cubane-Type and Higher Nuclearity Iron–Sulfur Clusters

Biomimetic Chemistry of Iron, Nickel, Molybdenum, and Tungsten in Sulfur-Ligated Protein Sites

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Initial synthesis and structure of an all-ferrous analogue of the fully reduced [Fe 4 S 4 ] 0 cluster of the nitrogenase iron protein

Cited by 75 publications

References 28 publications

Stabilization of Fully Reduced Iron−Sulfur Clusters by Carbene Ligation: The [FenSn]0 Oxidation Levels (n = 4, 8)

Stabilization of Fully Reduced Iron−Sulfur Clusters by Carbene Ligation: The [FenSn]0 Oxidation Levels (n = 4, 8)

Developments in the Biomimetic Chemistry of Cubane-Type and Higher Nuclearity Iron–Sulfur Clusters

Biomimetic Chemistry of Iron, Nickel, Molybdenum, and Tungsten in Sulfur-Ligated Protein Sites

Contact Info

Product

Resources

About

Initial synthesis and structure of an all-ferrous analogue of the fully reduced [Fe ₄ S ₄ ] ⁰ cluster of the nitrogenase iron protein

Stabilization of Fully Reduced Iron−Sulfur Clusters by Carbene Ligation: The [Fe_nS_n]⁰ Oxidation Levels (n = 4, 8)

Stabilization of Fully Reduced Iron−Sulfur Clusters by Carbene Ligation: The [Fe_nS_n]⁰ Oxidation Levels (n = 4, 8)