Chemistry and reactivity of sulfur-bonded sulfenato-cobalt(III) complexes

Lydon, J. D.; Deutsch, Edward

doi:10.1021/ic00138a052

Cited by 27 publications

(22 citation statements)

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“…This stretching frequency would be extremely high for an Fe(V)═O (ν Fe═O = 798–828 cm −1 ) 96, 127 and is somewhat above the usual range (ν S═O = 970–900 cm −1 ) 24, 35, 46, 128–130 for a metal-sulfenate complex Sulfenate ν S═O stretches have, however, previously been shown to shift out of the usual range if the RS═O is η 2 -coordinated to a metal ion. 49, 131 For example, sulfenate/sufinate-ligated [Co III (η 2 -SO)(SO 2 )N 3 (Pr,Pr)] + (Scheme 2) has a sulfenate ν S═O stretch at 1066 cm −1 .…”

Section: Resultsmentioning

confidence: 90%

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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Section: Resultsmentioning

confidence: 90%

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

et al. 2016

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“…The spectrum of NHase Fe3Co oxidized by 500 mM potassium hexacyanoferrate was very similar to that of the Co-type NHase from P. putida NRRL-18668, which contained a low-spin non-corrin Co 3 at the active center [14]. It has been reported that the absorption in the 300^350 nm region of the Co-type NHase from P. putida NRRL-18668 has an SCCo 3 charge transfer, because synthetic low-spin Co 3 -thiolate complexes show ligand-to-metal charge transfer bands at about 280 nm [37,38]. Since the Feand Co-type ligand environments are thought to be similar [4,7,8,14], it was suggested that the Co atom in NHase Fe3Co was also changed to a low-spin Co 3 state by oxidation.…”

Section: Uv-vis Absorption Spectra Of Nhase Fe3comentioning

confidence: 99%

Cobalt‐substituted Fe‐type nitrile hydratase of Rhodococcus sp. N‐771

et al. 2000

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“…Cysteinate sulfurs could also potentially provide an alternate site for reactivity to occur with dioxygen, peroxides, or even hydroxides (vide infra). [69][70][71] This review will primarily focus on synthetic functional and structural models for the cysteinate-ligated non-heme iron enzymes NHase and SOR. For additional review articles focusing on the more biological aspects of these enzymes, see refs…”

Section: Introduction To Non-heme Iron Enzymesmentioning

confidence: 99%