Stabilization of 3:1 Site-Differentiated Cubane-Type Clusters in the [Fe4S4]1+ Core Oxidation State by Tertiary Phosphine Ligation: Synthesis, Core Structural Diversity, and S = 1/2 Ground States

Deng, Liang; Majumdar, Amit; Lo, Wayne; Holm, R. H.

doi:10.1021/ic101702b

Cited by 31 publications

(33 citation statements)

References 28 publications

(52 reference statements)

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“…The added length of IMes as compared to I i Pr Me forces the bond lengths in [Fe4S4] + clusters has been previously observed and attributed to a shallow potential energy surface for core deformations. 21 This compressibility is exemplified by the structure of 2,…”

Section: Resultsmentioning

confidence: 99%

Controlling Substrate Binding to Fe₄S₄ Clusters through Remote Steric Effects

Brown

Suess

2019

Inorg. Chem.

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The extraordinary reactivity exhibited by many Fe-S enzymes is due in large part to the influence of the protein scaffold on substrate binding and activation. In principle, the coordination chemistry of synthetic Fe-S clusters could similarly be controlled through remote steric effects. Toward this end, we report the synthesis of 3:1 site-differentiated [Fe4S4] clusters ligated by Nheterocyclic carbene (NHC) ligands with variable steric profiles: IMes (1,3-dimesitylimidazol-2ylidene) and I i Pr Me (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene). Treatment of (IMes)3Fe4S4Cl with NaBAr F 4 in ethereal solvents (Et2O and THF) leads to the formation of an ether adduct, [(IMes)3Fe4S4(solv)][BAr F 4]; solvent can be displaced by addition of t BuNC to form the unusual mono-isocyanide adduct [(IMes)3Fe4S4(CN t Bu)][BAr F 4]. Carrying out the same reactions with the less sterically encumbered cluster (I i Pr Me)3Fe4S4Cl results in more typical reactivity: undesired ligand redistribution to form the homoleptic cluster [(I i Pr Me)4Fe4S4][BAr F 4] and generation of the tri-isocyanide adduct [(I i Pr Me)3Fe4S4(CN t Bu)3][BAr F 4]. The increased steric profile of the IMes ligands disfavors ligand redistribution and defines a binding pocket at the apical Fe, thereby enabling the generation of a coordinatively unsaturated and substitutionally labile Fe site. This method of controlling the coordination chemistry at the apical Fe site by modifying the sterics of ligands bound to adjacent Fe sites complements existing strategies for generating sitedifferentiated Fe-S clusters and provides new opportunities to direct reactivity at cuboidal metalloclusters.

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Section: Resultsmentioning

confidence: 99%

Controlling Substrate Binding to Fe₄S₄ Clusters through Remote Steric Effects

Brown

Suess

2019

Inorg. Chem.

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“…The generation of one unique iron site in a ½Fe 4 S 4 3þ cubane cluster by reduction of 1 is intriguing, and this reaction offers a new synthetic route to 3∶1-site differentiated ½Fe 4 S 4 clusters without invoking the use of tridentate thiolate auxiliaries (19,27,28 (29). Cluster 2 was structurally identified by X-ray crystallographic analysis.…”

Section: Resultsmentioning

confidence: 99%

Synthetic analogues of [Fe ₄ S ₄ (Cys) ₃ (His)] in hydrogenases and [Fe ₄ S ₄ (Cys) ₄ ] in HiPIP derived from all-ferric [Fe ₄ S ₄ {N(SiMe ₃ ) ₂ }
Ohki
¹
,
Tanifuji
²
,
Yamada
³

et al. 2011
Proc. Natl. Acad. Sci. U.S.A.
43
1
29
0
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The all-ferric ½Fe 4 S 4 4þ cluster ½Fe 4 S 4 fNðSiMe 3 Þ 2 g 4 1 and its oneelectron reduced form ½1 − serve as convenient precursors for the synthesis of 3∶1-site differentiated ½Fe 4 S 4 clusters and highpotential iron-sulfur protein (HiPIP) model clusters. The reaction of 1 with four equivalents (equiv) of the bulky thiol HSDmp (Dmp¼ 2,6-ðmesitylÞ 2 C 6 H 3 , mesityl ¼2,4,6-Me 3 C 6 H 2 ) followed by treatment with tetrahydrofuran (THF) resulted in the isolation of ½Fe 4 S 4 ðSDmpÞ 3 ðTHFÞ 3 2. Cluster 2 contains an octahedral iron atom with three THF ligands, and its FeðSÞ 3 ðOÞ 3 coordination environment is relevant to that in the active site of substrate-bound aconitase. An analogous reaction of ½1 − with four equiv of HSDmp gave ½Fe 4 S 4 ðSDmpÞ 4 − 3, which models the oxidized form of HiPIP. The THF ligands in 2 can be replaced by tetramethyl-imidazole (Me 4 Im) to give ½Fe 4 S 4 ðSDmpÞ 3 ðMe 4 ImÞ 4 modeling the ½Fe 4 S 4 ðCysÞ 3 ðHisÞ cluster in hydrogenases, and its one-electron reduced form ½4 − was synthesized from the reaction of 3 with Me 4 Im. The reversible redox couple between 3 and ½3 − was observed at E 1∕2 ¼−820 mV vs. Ag∕Ag þ , and the corresponding reversible couple for 4 and ½4 − is positively shifted by þ440 mV. The cyclic voltammogram of 3 also exhibited a reversible oxidation couple, which indicates generation of the all-ferric ½Fe 4 S 4 4þ cluster, ½Fe 4 S 4 ðSDmpÞ 4 .Fe4S4 cluster | thiolates C uboidal ½Fe 4 S 4 clusters are ubiquitous metal-centers in proteins, expediting electron transfer and enzymatic reactions. These ½Fe 4 S 4 cores are usually bound to four cysteinyl thiolates (Cys) as found in the high-potential iron-sulfur proteins (HiPIP) and widely distributed ferredoxins (Fd). Some ½Fe 4 S 4 clusters carrying an N-or O-donor ligand and three Cys ligands are also known, for example the ½Fe 4 S 4 ðCysÞ 3 ðHisÞ cluster (His ¼ histidinyl imidazole) in [NiFe] and [FeFe] hydrogenases ( Fig. 1) (1-6), and the ½Fe 4 S 4 ðCysÞ 3 ðO-donorÞ cluster in aconitase (7-9) and protochlorophyllide reductase (10). All of these ½Fe 4 S 4 clusters are present in three oxidation states, ½Fe 4 S 4 3þ (HiPIP ox ), ½Fe 4 S 4 2þ (HiPIP red ∕Fd ox ), and ½Fe 4 S 4 þ (Fd red ), while the ½Fe 4 S 4 0 state has been suggested for the cluster in the Fe-protein of nitrogenase (11,12). To date, no ½Fe 4 S 4 4þ cluster has been found in proteins.

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“…53,68 Other than [Fe 4 S 4 (LS 3 )(SR)] 3− , these are the only site-differentiated clusters isolated in the [Fe 4 S 4 ] 1+ state, stabilized in these cases by phosphine ligation.…”

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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Stabilization of 3:1 Site-Differentiated Cubane-Type Clusters in the [Fe₄S₄]¹⁺ Core Oxidation State by Tertiary Phosphine Ligation: Synthesis, Core Structural Diversity, and S = 1/2 Ground States

Cited by 31 publications

References 28 publications

Controlling Substrate Binding to Fe₄S₄ Clusters through Remote Steric Effects

Controlling Substrate Binding to Fe₄S₄ Clusters through Remote Steric Effects

Synthetic analogues of [Fe ₄ S ₄ (Cys) ₃ (His)] in hydrogenases and [Fe ₄ S ₄ (Cys) ₄ ] in HiPIP derived from all-ferric [Fe ₄ S ₄ {N(SiMe ₃ ) ₂ }
Ohki
¹
,
Tanifuji
²
,
Yamada
³

et al. 2011
Proc. Natl. Acad. Sci. U.S.A.
43
1
29
0
View full text Add to dashboard Cite

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

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Stabilization of 3:1 Site-Differentiated Cubane-Type Clusters in the [Fe4S4]1+ Core Oxidation State by Tertiary Phosphine Ligation: Synthesis, Core Structural Diversity, and S = 1/2 Ground States

Cited by 31 publications

References 28 publications

Controlling Substrate Binding to Fe4S4 Clusters through Remote Steric Effects

Controlling Substrate Binding to Fe4S4 Clusters through Remote Steric Effects

Synthetic analogues of [Fe 4 S 4 (Cys) 3 (His)] in hydrogenases and [Fe 4 S 4 (Cys) 4 ] in HiPIP derived from all-ferric [Fe 4 S 4 {N(SiMe 3 ) 2 } Ohki1, Tanifuji2, Yamada3 et al. 2011Proc. Natl. Acad. Sci. U.S.A.431290View full textAdd to dashboardCite

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

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Stabilization of 3:1 Site-Differentiated Cubane-Type Clusters in the [Fe₄S₄]¹⁺ Core Oxidation State by Tertiary Phosphine Ligation: Synthesis, Core Structural Diversity, and S = 1/2 Ground States

Controlling Substrate Binding to Fe₄S₄ Clusters through Remote Steric Effects

Controlling Substrate Binding to Fe₄S₄ Clusters through Remote Steric Effects

Synthetic analogues of [Fe ₄ S ₄ (Cys) ₃ (His)] in hydrogenases and [Fe ₄ S ₄ (Cys) ₄ ] in HiPIP derived from all-ferric [Fe ₄ S ₄ {N(SiMe ₃ ) ₂ }
Ohki
¹
,
Tanifuji
²
,
Yamada
³

et al. 2011
Proc. Natl. Acad. Sci. U.S.A.
43
1
29
0
View full text Add to dashboard Cite