Formation of a Room Temperature Stable Fe<sup>V</sup>(O) Complex: Reactivity Toward Unactivated C–H Bonds

Ghosh, Munmun; Singh, Kundan K.; Panda, Chakadola; Weitz, Andrew C.; Hendrich, Michael P.; Collins, Terrence J.; Dhar, Basab Bijayi; Gupta, Sayam Sen

doi:10.1021/ja412537m

Cited by 153 publications

(230 citation statements)

References 33 publications

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“…107, 109, 111 In contrast to Fe(IV)═O compounds, 52, 98, 114–123 however, very few synthetic non-heme Fe(V)═O species have been observed. 93, 95, 96, 104, 113, 124 The most thoroughly characterized example, [Fe(V)(TAML)(O)] − , incorporates an electron-donating tetra-anionic carboxamide ligand ( vide inf ra ), TAML 4–93, 95, 104, 125, 126 .…”

Section: Resultsmentioning

confidence: 99%

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: 99%

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

et al. 2016

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“…Then, this stronger propensity for HAA implies the faster HAA rate according to the BEP principle. The BEP principle was invoked in many kinetic studies on NHFe species, demonstrating a correlation between a decreased C─H bond strength and an increased HAA reaction rate -see for example refs [176,177]. Thus, high basicity can explain why some NHFe complexes are competent for HAA despite their very low reduction potential (and vice versa).…”

Section: Reduction Potential / Basicity Correlated To H-atom Abstractmentioning

confidence: 99%

Mono- and binuclear non-heme iron chemistry from a theoretical perspective

et al. 2016

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In this minireview, we provide an account of the current state-of-the-art developments in the area of mono-and binuclear non-heme enzymes (NHFe and NHFe2) and the smaller NHFe(2) synthetic models, mostly from a theoretical and computational perspective. The sheer complexity, and at the same time the beauty, of the NHFe(2) world represent a challenge for both experimental as well as theoretical methods. We emphasize that the concerted progress on both theoretical and experimental side is a conditio sine qua non for future understanding, exploration and utilization of the NHFe(2) systems.After briefly discussing the current challenges and advances in the computational methodology, we review the recent spectroscopic and computational studies of NHFe(2) enzymatic and inorganic systems and highlight the correlations between various experimental data (spectroscopic, kinetic, thermodynamic, electrochemical) and computations. Throughout, we attempt to keep in mind the most fascinating and attractive phenomenon in the NHFe(2) chemistry which is the fact that despite the strong oxidative power of many reactive intermediates, the NHFe(2) enzymes perform catalysis with high selectivity. We conclude with our personal viewpoint and hope that further developments in quantum chemistry and especially in the field of multireference wave function methods are needed to have a solid theoretical basis for the NHFe(2) studies, mostly by providing benchmarking and calibration of the computationally efficient and easy-to-use DFT methods.

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“…The g -values are near to those of previously characterized iron(V)oxo complexes of TAML: g = (1.99, 1.97, 1.74) 4 and g = (1.98, 1.94, 1.73). 19 Spin quantitation indicated that the concentration of the iron(V)oxo complex generated in water or acetonitrile were both in quantitative agreement with the concentration of the initial iron(III) complex.…”

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confidence: 93%

NaClO-Generated Iron(IV)oxo and Iron(V)oxo TAMLs in Pure Water

et al. 2016

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The unique properties of entirely aliphatic TAML activator [FeIII{(Me2CNCOCMe2NCO)2CMe2}-OH2]− (3), namely the increased steric bulk of the ligand and the unmatched resistance to the acid-induced demetalation, enables the generation of high-valent iron derivatives in pure water at any pH. An iron(V)oxo species is readily produced with NaClO at pH values from 2 to 10.6 without any observable intermediate. This is the first reported example of iron(V)oxo formed in pure water. At pH 13, iron(V)oxo is not formed and NaClO oxidizes 3 to an iron(IV)oxo derivative.

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Formation of a Room Temperature Stable Fe^V(O) Complex: Reactivity Toward Unactivated C–H Bonds

Cited by 153 publications

References 33 publications

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

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

Mono- and binuclear non-heme iron chemistry from a theoretical perspective

NaClO-Generated Iron(IV)oxo and Iron(V)oxo TAMLs in Pure Water

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Formation of a Room Temperature Stable FeV(O) Complex: Reactivity Toward Unactivated C–H Bonds

Cited by 153 publications

References 33 publications

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

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

Mono- and binuclear non-heme iron chemistry from a theoretical perspective

NaClO-Generated Iron(IV)oxo and Iron(V)oxo TAMLs in Pure Water

Contact Info

Product

Resources

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Formation of a Room Temperature Stable Fe^V(O) Complex: Reactivity Toward Unactivated C–H Bonds