A Pentacoordinated Di-N-carboxamido-dithiolato-O-sulfinato-iron(III) Complex Related to the Metal Site of Nitrile Hydratase

Heinrich, Laurent; Li, Yun; Vaissermann, Jacqueline; Chottard, Geneviève; Chottard, Jean‐Claude

doi:10.1002/(sici)1521-3773(19991203)38:23<3526::aid-anie3526>3.0.co;2-z

Cited by 58 publications

(76 citation statements)

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“…The observed bond distances in 6 correlate well with other iron(II)-sulfinate species showing comparable Fe–O and Fe–S distances to those reported in the literature (Fe–O = 1.9–2.0 Å, Fe–S = 3.1 – 3.3 Å, Table 3). 42 FTIR showed peaks at 1001 and 1152 cm −1 for 6 that compare favorably with those obtained for complexes 3 and 4 (Figure S8, Supporting Information). Furthermore, the Mössbauer parameters for 6 correlate well with those obtained for 3 (ΔE Q = 3.92 mm/s, δ = 1.13 mm/s, see Table 2, and Figure S9 Supporting Information).…”

Section: Resultssupporting

confidence: 68%

“…The Fe–O–S bond angle was ~130°. These parameters are consistent with other iron(II)-sulfinate moieties that have been described in the literature 41,42. Parameters for 4 were calculated for a modification of the DFT structure published for 2 in which an O-bound sulfinate was introduced, such that the Fe•••S distance was increased to 3.3 Å and an O atom bound to the sulfur was placed at a distance of 2.0 Å from the Fe center.…”

Section: Methodssupporting

confidence: 66%

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Sulfur versus Iron Oxidation in an Iron−Thiolate Model Complex

et al. 2010

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In the absence of base, the reaction of [FeII(TMCS)]PF6 (1, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) with peracid in methanol at −20 °C did not yield the oxoiron(IV) complex (2, [FeIV(O)(TMCS)]PF6), as previously observed in the presence of strong base (KOtBu). Instead, the addition of one equivalent of peracid resulted in 50% consumption of 1. The addition of a second equivalent of peracid resulted in the complete consumption of 1, and the formation of a new species 3 as monitored by UV-Vis, ESI-MS and Mössbauer spectroscopies. ESI-MS showed 3 to be formulated as [FeII(TMCS) + 2O]+), while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe–O = 1.95 Å, Fe–S = 3.26 Å). The addition of a third equivalent of peracid resulted in the formation of yet another compound, 4, which showed electronic absorption properties typical of an oxoiron(IV) species. Mössbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe=O = 1.64 Å) and resonance Raman (νFe=O = 834 cm−1) showed that indeed an oxoiron(IV) unit had been generated in 4. Furthermore, both infra-red and Raman spectroscopy gave indications that 4 contains a metal-bound sulfinate moiety (νs(SO2) = ~ 1000 cm −1, νas(SO2) = ~ 1150 cm −1). Investigations into the reactivity of 1 and 2 towards H+ and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which 2 could form even in the absence of base, but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of 2 to 3.

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Section: Resultssupporting

confidence: 68%

Section: Methodssupporting

confidence: 66%

Sulfur versus Iron Oxidation in an Iron−Thiolate Model Complex

et al. 2010

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“…26, 46, 47, 49 There are significantly more examples of doubly oxygenated, structurally rearranged, oxygen-bound metal-sulfinate (RSO 2 − ) complexes. 16–20 …”

Section: Resultsmentioning

confidence: 99%

“…15–20 For example, cysteinate-ligated TpFe II S cys reacts with O 2 to afford cys SO 2 − (the product of CDO 5 ); however, no intermediates were observed. 21 Iron complexes containing a non-tethered, monodentate RS ligand trans to the O 2 binding site have been shown to react with O 2 to afford an Fe IV ═O + RSSR, 3, 22 in contrast to cis -thiolate-ligated complexes, which have been shown to react with O 2 to afford doubly (RSO 2 -Fe) or triply (RSO 3 -Fe) oxygenated derivatives.…”

Section: Introductionmentioning

confidence: 99%

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Metal-Assisted Oxo Atom Addition to an Fe(III) Thiolate

et al. 2016

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Cysteinate oxygenation is intimately tied to the function of both cysteine dioxygenases (CDOs) and nitrile hydratases (NHases), and yet the mechanisms by which sulfurs are oxidized by these enzymes are unknown, in part because intermediates have yet to be observed. Herein, we report a five-coordinate bis-thiolate ligated Fe(III) complex, [FeIII(S2Me2N3-(Pr,Pr))]+ (2), that reacts with oxo atom donors (PhIO, IBX-ester, and H2O2) to afford a rare example of a singly oxygenated sulfenate, [FeIII(η2-SMe2O)(SMe2)N3(Pr,Pr)]+ (5), resembling both a proposed intermediate in the CDO catalytic cycle and the essential NHase Fe-S(O)Cys114 proposed to be intimately involved in nitrile hydrolysis. Comparison of the reactivity of 2 with that of a more electron-rich, crystallographically characterized derivative, [FeIIIS2Me2NMeN2amide(Pr,Pr)]− (8), shows that oxo atom donor reactivity correlates with the metal ion’s ability to bind exogenous ligands. Density functional theory calculations suggest that the mechanism of S-oxygenation does not proceed via direct attack at the thiolate sulfurs; the average spin-density on the thiolate sulfurs is approximately the same for 2 and 8, and Mulliken charges on the sulfurs of 8 are roughly twice those of 2, implying that 8 should be more susceptible to sulfur oxidation. Carboxamide-ligated 8 is shown to be unreactive towards oxo atom donors, in contrast to imine-ligated 2. Azide (N3−) is shown to inhibit sulfur oxidation with 2, and a green intermediate is observed, which then slowly converts to sulfenate-ligated 5. This suggests that the mechanism of sulfur oxidation involves initial coordination of the oxo atom donor to the metal ion. Whether the green intermediate is an oxo atom donor adduct, Fe-O═I-Ph, or an Fe(V)═O remains to be determined.

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Iron Enzymes and Models

Marlin

Mascharak

2002

Encyclopedia of Catalysis

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In recent years, iron complexes of designed ligands have been synthesized as mimics of the active sites of the various non‐heme iron enzymes. The reactions of these model complexes have been studied to establish the mechanisms of the enzymatic reactions as well as the identities of the intermediates involved in the biocatalytic processes. The ultimate goal in these endeavors is to isolate functional mimics that could be employed in biomimetic catalysis under mild conditions. This review provides key references to the burgeoning literature on the results of research performed by various groups in the area of oxygen activation, oxygenation of organic substrates, amide hydrolysis, and other useful chemical transformations. Examples of good structural and functional models have been included along with brief descriptions of the enzymes. The role of the coordination spheres of the iron centers and the nature of the key iron‐peroxo and/or hypervalent iron‐oxo intermediates have been discussed. Results of the attempted catalysis by the functional model complexes have also been discussed to highlight the challenge involved in bio‐inspired catalysis as well as the success of the modeling work completed so far.

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A Pentacoordinated Di-N-carboxamido-dithiolato-O-sulfinato-iron(III) Complex Related to the Metal Site of Nitrile Hydratase

Cited by 58 publications

References 5 publications

Sulfur versus Iron Oxidation in an Iron−Thiolate Model Complex

Sulfur versus Iron Oxidation in an Iron−Thiolate Model Complex

Metal-Assisted Oxo Atom Addition to an Fe(III) Thiolate

Iron Enzymes and Models

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