Mild Redox Complementation Enables H<sub>2</sub> Activation by [FeFe]-Hydrogenase Models

Camara, James M.; Rauchfuss, Thomas B.

doi:10.1021/ja201731q

Cited by 103 publications

(92 citation statements)

References 29 publications

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“…Using D 2 , we obtained exclusively the corresponding deuterated products [ 1 D] + and [DP( o -tolyl) 3 ] + , as established by 2 H NMR spectroscopy. The reaction of [ 1 ] 2+ and H 2 in the presence of P( o -tolyl) 3 proceeds about four times faster than the previously reported reaction of [ 2 ] + with H 2 in the presence of Cp* 2 Fe + and P( o -tolyl) 3 under identical conditions 18 .…”

Section: Resultsmentioning

confidence: 60%

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Combining acid–base, redox and substrate binding functionalities to give a complete model for the [FeFe]-hydrogenase

2011

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Some enzymes function by coupling substrate turnover with electron transfer from a redox cofactor such as ferredoxin. In the [FeFe]-hydrogenases, nature’s fastest catalysts for the production and oxidation of H2, the one-electron redox by a ferredoxin complements the one-electron redox by the diiron active site. In this Article, we replicate the function of the ferredoxins with the redox-active ligand Cp*Fe(C5Me4CH2PEt2) (FcP*). FcP* oxidizes at mild potentials, in contrast to most ferrocene-based ligands, which suggests that it might be a useful mimic of ferredoxin cofactors. The specific model is Fe2[(SCH2)2NBn](CO)3(FcP*)(dppv) (1), which contains the three functional components of the active site: a reactive diiron centre, an amine as a proton relay and, for the first time, a one-electron redox module. By virtue of the synthetic redox cofactor, [1]2+ exhibits unique reactivity towards hydrogen and CO. In the presence of excess oxidant and base, H2 oxidation by [1]2+ is catalytic.

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Section: Resultsmentioning

confidence: 60%

“…Recently, we reported that the addition of mild oxidant to solutions of H ox models allows for facile oxidation of H 2 (ref. 18). This finding suggests that functional models of the H ox state require the presence of both an azadithiolate cofactor as well as a suitably tuned redox cofactor.…”

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confidence: 99%

Combining acid–base, redox and substrate binding functionalities to give a complete model for the [FeFe]-hydrogenase

2011

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“…291 In fact, [ 21 ] + effects H 2 heterolysis in the presence of the mild oxidant [FeCp* 2 ] + (Fc* + ) as well as the (optional) weak base P( o -tolyl) 3 . The reaction proceeds over the course of hours under only 2 atm H 2 at 0 °C to quantitatively afford [ 21 ( μ -H)] + and [HP( o -tolyl) 3 ] + ( k obs = 2.2 × 10 −5 s −1 at 0°C).…”

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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“…While the oxidation state of nickel in the compound NiÀthioP can be formally assigned as Ni I , the nature of the thiosemicarbazone ligand increases the possibility of a direct interaction between the amide hydrogen and the nickel center. 40,41 NiÀthioP is a representative example that could be used to elucidate how a stable photosynthetic system developed using organic dyes. This indicates that direct metalÀH interaction is able to assist the proton reduction process in the compound NiÀthioP.…”

Section: Introductionmentioning

confidence: 99%

Light-driven hydrogen evolution with a nickel thiosemicarbazone redox catalyst featuring Ni⋯H interactions under basic conditions

Liu

et al. 2015

New J. Chem.

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The photocatalytic hydrogen evolution inspired by the highly evolved, finely tuned molecular photosynthetic systems in nature represents an important process in sustainable solar energy conversion for the near future. By incorporating a phosphine donor within a thiosemicarbazone moiety, a new proton reduction catalyst NiÀthioP, featuring NiÁ Á ÁH interactions was synthesized and structurally characterized. Single crystal structure analysis revealed that the C-S, C-N and N-N bond lengths were all within the normal range of the single and double bonds, suggesting the extensive electron delocalization over the ligand skeleton. The presence of NiÁ Á ÁH interactions relative to the amide group coupled with the easy proton migration pathway involving thioamide/thiolate exchange suggested that the thiosemicarbazone complexes could serve as promising candidates for proton reduction. Luminescence titrations exhibited that NiÀthioP served as efficient luminescent quenchers for the photosensitizer Fl, providing the possibilities for the excited state of Fl to activate these catalysts for proton reduction. The direct generation of hydrogen was achieved by carrying out the photolysis of a solution containing fluorescein as the photosensitizer, and triethylamine as the sacrificial and the redox catalysts. NiÀthioP exhibited high activity with a turnover number (TON) of 8000 moles of H 2 per mole of the catalyst after 24 hours and an initial TOF larger than 500 moles of H 2 per catalyst per hour. To further investigate the potential mechanism for proton reduction, calculations were also performed using density functional theory.

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Mild Redox Complementation Enables H₂ Activation by [FeFe]-Hydrogenase Models

Cited by 103 publications

References 29 publications

Combining acid–base, redox and substrate binding functionalities to give a complete model for the [FeFe]-hydrogenase

Combining acid–base, redox and substrate binding functionalities to give a complete model for the [FeFe]-hydrogenase

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

Light-driven hydrogen evolution with a nickel thiosemicarbazone redox catalyst featuring Ni⋯H interactions under basic conditions

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Mild Redox Complementation Enables H2 Activation by [FeFe]-Hydrogenase Models

Cited by 103 publications

References 29 publications

Combining acid–base, redox and substrate binding functionalities to give a complete model for the [FeFe]-hydrogenase

Combining acid–base, redox and substrate binding functionalities to give a complete model for the [FeFe]-hydrogenase

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

Light-driven hydrogen evolution with a nickel thiosemicarbazone redox catalyst featuring Ni⋯H interactions under basic conditions

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Mild Redox Complementation Enables H₂ Activation by [FeFe]-Hydrogenase Models