Redox active iron nitrosyl units in proton reduction electrocatalysis

Hsieh, Chu‐Chin; Ding, Shengda; Erdem, Özlen F.; Crouthers, Danielle J.; Liu, Tianbiao; McCrory, Charles C. L.; Lubitz, Wolfgang; Popescu, Codrina V.; Reibenspies, Joseph H.; Hall, Michael B.; Darensbourg, Marcetta Y.

doi:10.1038/ncomms4684

Cited by 64 publications

(94 citation statements)

References 39 publications

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“…The [Fe-Fe] + complex, described here with NO ligands on both irons, is also an effective electrocatalyst for H 2 production with HBF 4• OEt 2 (32). Fig.…”

Section: Mechanism Of H 2 Production On the Fe-fe Model Complexmentioning

confidence: 93%

“…As shown in Fig. 2, multiple electron-buffering NO ligands have been introduced into the N 2 S 2 -based bimetallic models, in attempts to reproduce the electron-buffering function of the [Fe 4 S 4 ] subcluster of [FeFe]-hydrogenase (32)(33)(34)(35). The electronic flexibility introduced by NO raises the optimistic expectation that buffer ligands might convert first-row transition metals that are 1e − catalysts into 2e − catalysts (36,37).…”

Section: Synthetic Analogsmentioning

confidence: 99%

“…Generally, the E and C steps alternate to avoid the accumulation of like charges (31,40). The likelihood of each C step is evaluated in our computations by comparing the acidities of the protonated species vs. the proton provider HOEt 2 + (as the acid is HBF 4• OEt 2 or HOEt 2• BF 4 ) (32,38). A positive ΔpK a (ΔpK a = pK a (CatH) − pK a ([HOEt 2 ] + ) indicates a thermodynamically favorable C step.…”

Section: Synthetic Analogsmentioning

confidence: 99%

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Interplay of hemilability and redox activity in models of hydrogenase active sites

Ding

Ghosh

Darensbourg

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The hydrogen evolution reaction, as catalyzed by two electrocatalysts [M(NS)·Fe(NO)], [-Fe] (M = Fe(NO)) and [Ni-Fe] (M = Ni) was investigated by computational chemistry. As nominal models of hydrogenase active sites, these bimetallics feature two kinds of actor ligands: Hemilabile, MNS ligands and redox-active, nitrosyl ligands, whose interplay guides the H production mechanism. The requisite base and metal open site are masked in the resting state but revealed within the catalytic cycle by cleavage of the MS-Fe(NO) bond from the hemilabile metallodithiolate ligand. Introducing two electrons and two protons to [Ni-Fe] produces H from coupling a hydride temporarily stored on Fe(NO) (Lewis acid) and a proton accommodated on the exposed sulfur of the MNS thiolate (Lewis base). This Lewis acid-base pair is initiated and preserved by disrupting the dative donation through protonation on the thiolate or reduction on the thiolate-bound metal. Either manipulation modulates the electron density of the pair to prevent it from reestablishing the dative bond. The electron-buffering nitrosyl's role is subtler as a bifunctional electron reservoir. With more nitrosyls as in [-Fe], accumulated electronic space in the nitrosyls' π*-orbitals makes reductions easier, but redirects the protonation and reduction to sites that postpone the actuation of the hemilability. Additionally, two electrons donated from two nitrosyl-buffered irons, along with two external electrons, reduce two protons into two hydrides, from which reductive elimination generates H.

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“…The [Fe-Fe] + complex, described here with NO ligands on both irons, is also an effective electrocatalyst for H 2 production with HBF 4• OEt 2 (32). Fig.…”

Section: Mechanism Of H 2 Production On the Fe-fe Model Complexmentioning

confidence: 93%

Section: Synthetic Analogsmentioning

confidence: 99%

Section: Synthetic Analogsmentioning

confidence: 99%

See 1 more Smart Citation

Interplay of hemilability and redox activity in models of hydrogenase active sites

Ding

Ghosh

Darensbourg

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…While donors such as carbenes, 227–231 isonitriles, 232–235 and even nitrosyls 236,237 have been used, tertiary phosphines have proven the most useful. 23 …”

Section: [Fefe]-h2asesmentioning

confidence: 99%

Hydrogenase Enzymes and Their Synthetic Models: The Role of Metal Hydrides

et al. 2016

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Hydrogenase enzymes efficiently process H2 and protons at organometallic FeFe, NiFe, or Fe active sites. Synthetic modeling of the many H2ase states has provided insight into H2ase structure and mechanism, as well as afforded catalysts for the H2 energy vector. Particularly important are hydride-bearing states, with synthetic hydride analogues now known for each hydrogenase class. These hydrides are typically prepared by protonation of low-valent cores. Examples of FeFe and NiFe hydrides derived from H2 have also been prepared. Such chemistry is more developed than mimicry of the redox-inactive monoFe enzyme, although functional models of the latter are now emerging. Advances in physical and theoretical characterization of H2ase enzymes and synthetic models have proven key to the study of hydrides in particular, and will guide modeling efforts toward more robust and active species optimized for practical applications.

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“…Rauchfuss and co‐workers firstly prepared the parent azadithiolate Fe 2 [(μ‐SCH 2 ) 2 NH](CO) 6 by treatment of Fe 2 (μ‐SH) 2 (CO) 6 with a mixture of paraformaldehyde and (NH 4 ) 2 CO 3 . Afterwards, the azadithiolate complexes of the type Fe 2 [(μ‐SCH 2 ) 2 NR](CO) 6 can be prepared by the alkylation of Fe 2 (μ‐SLi) 2 (CO) 6 using (ClCH 2 ) 2 N R or the reaction of Fe 2 (μ‐SH) 2 (CO) 6 with formaldehyde in the presence of amines …”

Section: Introductionmentioning

confidence: 99%