Comparison of S and Se dichalcogenolato [FeFe]-hydrogenase models with central S and Se atoms in the bridgehead chain

Harb, Mohammad K.; Windhager, Jochen; Niksch, Tobias; Görls, Helmar; Sakamoto, Takahiro; Smith, Elliott R.; Glass, Richard S.; Lichtenberger, Dennis L.; Evans, Dennis H.; El‐khateeb, Mohammad; Weigand, Wolfgang

doi:10.1016/j.tet.2012.10.021

Cited by 48 publications

(43 citation statements)

References 65 publications

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“…. Orbital characters of 4DT , 4DS , and 5DS were calculated to be similar to those of PDS , and also similar to the previously studied PDT and PDT ‐like compounds .…”

Section: Resultssupporting

confidence: 77%

Effects of Alkane Linker Length and Chalcogen Character in [FeFe]‐Hydrogenase Inspired Compounds

Harb

Daraosheh

Görls

et al. 2014

Heteroatom Chemistry

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Models of [FeFe]‐hydrogenases containing diselenolato ligands with different bridge linker length have been prepared: Fe2(μ‐Se(CH2)4Se‐μ)(CO)6 (4DS), and Fe2(μ‐Se(CH2)5Se‐μ)(CO)6 (5DS) as well as dithiolato Fe2(μ‐S(CH2)4S‐μ)(CO)6 (4DT) and compared with Fe2(μ‐S(CH2)3S‐μ)(CO)6 (PDT) and Fe2(μ‐Se(CH2)3Se‐μ)(CO)6 (PDS). Compounds 4DT, PDS, 4DS, and 5DS were characterized by spectroscopic techniques including NMR, IR, mass spectrometry, ultraviolet photoelectron spectroscopy (UPS), elemental analysis, and X‐ray crystal structure analysis. Combinations of electrochemical measurements, UPS, and density functional theory calculations indicate that oxidations of these five compounds are not significantly affected by chalcogen character but instead are governed by linker length. Cations for all compounds are calculated to adopt a bridged CO “rotated” structure with a vacant site on one of the Fe centers. In 4DT, 4DS, and 5DS, the alkane linker forms an agostic interaction with the vacant site on the rotated Fe. The reduction potentials for these compounds shift positively on average 0.16 V for each carbon added to the alkane linker with shifts being as large as 0.23 V between PDT and 4DT, and as small as 0.09 V between 4DS and 5DS. Catalytic reduction of protons from acetic acid in CH2Cl2 occurs at −1.79 and −1.86 V for PDT and 4DT and −2.02, −2.09, and −2.04 V for PDS, 4DS, and 5DS, indicating that chalcogen character is the primary factor that affects catalytic potential. On average the S‐containing compounds catalyze proton reduction at potentials, which are 0.23 V less negative than the Se‐containing compounds in this study.

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“…. Orbital characters of 4DT , 4DS , and 5DS were calculated to be similar to those of PDS , and also similar to the previously studied PDT and PDT ‐like compounds .…”

Section: Resultssupporting

confidence: 77%

Effects of Alkane Linker Length and Chalcogen Character in [FeFe]‐Hydrogenase Inspired Compounds

Harb

Daraosheh

Görls

et al. 2014

Heteroatom Chemistry

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“…Because the I pa / I pc value (anodic to cathodic peak currents ratio) at 0.2 V s −1 of the complexes 2 – 4 a is less than 1, the E 1/2 can be considered as approximated values. [c] E ox,rot is the potential of a weak oxidation peak attributed to initial oxidation to the rotated structure as discussed previously for related compounds . [d] E ox1 is the potential of the primary oxidation peak.…”

Section: Resultsmentioning

confidence: 99%

[FeFe]‐Hydrogenase H‐Cluster Mimics with Unique Planar μ‐(SCH₂)₂ER₂ Linkers (E=Ge and Sn)

Abul‐Futouh

Almazahreh

Sakamoto

et al. 2016

Chemistry A European J

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Analogues of the [2Fe-2S] subcluster of hydrogenase enzymes in which the central group of the three-atom chain linker between the sulfur atoms is replaced by GeR and SnR groups are studied. The six-membered FeSCECS rings in these complexes (E=Ge or Sn) adopt an unusual conformation with nearly co-planar SCECS atoms perpendicular to the Fe-Fe core. Computational modelling traces this result to the steric interaction of the Me groups with the axial carbonyls of the Fe (CO) cluster and low torsional strain for GeMe and SnMe moieties owing to the long C-Ge and C-Sn bonds. Gas-phase photoelectron spectroscopy of these complexes shows a shift of ionization potentials to lower energies with substantial sulfur orbital character and, as supported by the computations, an increase in sulfur character in the predominantly metal-metal bonding HOMO. Cyclic voltammetry reveals that the complexes follow an ECE-type reduction mechanism (E=electron transfer and C=chemical process) in the absence of acid and catalysis of proton reduction in the presence of acid. Two cyclic tetranuclear complexes featuring the sulfur atoms of two Fe S (CO) cores bridged by CH SnR CH , R=Me, Ph, linkers were also obtained and characterized.

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“…The reduction peaks of complexes 1 and 2 are due to two‐electron reduction in a single step based on the study of the current function, ( I pc /c·ν 1/2 , I = peak current; c = concentration; ν = scan rate) of these complexes and compare it to that of complex 3 which is known to undergo an overall two‐electron reduction . Upon initiating the electrochemical scan in the positive direction of complexes 1 and 2 , an irreversible oxidation peak is observed for each complex ( E pa = 0.72 V for 1 and E pa = 0.71 V for 2 ), which could be assigned to the one‐electron oxidation process of Fe I Fe I → Fe I Fe II as previously reported for various diiron complexes …”

Section: Resultsmentioning

confidence: 96%

“…Generally, the higher the electron density of the iron cores, the more the negative reduction potential is observed. This fact contrasts with our results as such behavior can be explained in terms of reorganization and stabilization of the reduced species as previously reported . Furthermore, increasing the scan rates of complexes 1 and 2 up to 15 V/s enhances the reversibility of their reduction events as shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

[FeFe]‐hydrogenase H‐cluster mimics mediated by mixed (S, Se) and (S, Te) bridging moieties: Insight into molecular structures and electrochemical characteristics

Abul‐Futouh

El‐khateeb

Görls

et al. 2018

Heteroatom Chemistry

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Two synthetic models of the active site of [FeFe]‐hydrogenase containing mixed (S, Se) and (S, Te) bridges have been synthesized and characterized. These complexes [Fe2(CO)6{μ‐S(CH2)4E‐μ)}] (E = Se (1), Te (2)) are obtained in moderate yields from the reaction of Fe3(CO)12 with 1,2‐thiaselenane or 1,2‐thiatellurane. They have been characterized by spectroscopic techniques (IR, 1H‐, 13C{1H}‐, 77Se{1H}‐, 125Te{1H}‐NMR, and MS) and elemental analysis. The structures of [Fe2(CO)6{μ‐S(CH2)4Se‐μ)}] and [Fe2(CO)6{μ‐S(CH2)4Te‐μ)}] are determined by X‐ray structure determination and show the expected butterfly geometry. Moreover, the influence of the mixed chalcogen atoms on the redox properties and the catalytic behavior of 1 and 2 are studied using cyclic voltammetry.

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Comparison of S and Se dichalcogenolato [FeFe]-hydrogenase models with central S and Se atoms in the bridgehead chain

Cited by 48 publications

References 65 publications

Effects of Alkane Linker Length and Chalcogen Character in [FeFe]‐Hydrogenase Inspired Compounds

Effects of Alkane Linker Length and Chalcogen Character in [FeFe]‐Hydrogenase Inspired Compounds

[FeFe]‐Hydrogenase H‐Cluster Mimics with Unique Planar μ‐(SCH₂)₂ER₂ Linkers (E=Ge and Sn)

[FeFe]‐hydrogenase H‐cluster mimics mediated by mixed (S, Se) and (S, Te) bridging moieties: Insight into molecular structures and electrochemical characteristics

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Comparison of S and Se dichalcogenolato [FeFe]-hydrogenase models with central S and Se atoms in the bridgehead chain

Cited by 48 publications

References 65 publications

Effects of Alkane Linker Length and Chalcogen Character in [FeFe]‐Hydrogenase Inspired Compounds

Effects of Alkane Linker Length and Chalcogen Character in [FeFe]‐Hydrogenase Inspired Compounds

[FeFe]‐Hydrogenase H‐Cluster Mimics with Unique Planar μ‐(SCH2)2ER2 Linkers (E=Ge and Sn)

[FeFe]‐hydrogenase H‐cluster mimics mediated by mixed (S, Se) and (S, Te) bridging moieties: Insight into molecular structures and electrochemical characteristics

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[FeFe]‐Hydrogenase H‐Cluster Mimics with Unique Planar μ‐(SCH₂)₂ER₂ Linkers (E=Ge and Sn)