Ridley, F;
Ghosh, S;
Hogarth, G;
Hollingsworth, N;
Holt, KB;
Unwin, DG;
(2013)
Fluorinated models of the iron-only hydrogenase: An electrochemical study of the influence of an electron-withdrawing bridge on the proton reduction overpotential and catalyst stability.
Journal of Electroanalytical Chemistry
, 703
14 - 22.
10.1016/j.jelechem.2013.05.018.
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Abstract
Here we report the synthesis, electrochemistry and electrocatalytic activity of Fe2(CO)6(μ-SC6F5)2 (1) where the highly fluorinated bridge is electron-withdrawing, resulting in decreased electron-density at the iron–iron bond. Additionally we discuss the related substituted complexes Fe2(CO)5(PPh3)(μ-SC6F5)2 (2) and Fe2(CO)4(μ-Ph2PCH2PPh2)(μ-SC6F5)2 (3). As none of the complexes could be protonated in their neutral form it was found that proton reduction catalysis in the presence of strong acid (HBF4) took place at the potential of the first reduction of complex 1 and 3, following an EC mechanism. Complex 2 was unstable in the presence of strong acid. For 1 the potential at which proton reduction took place represented a relatively mild reduction potential (−1.15 V vs. Fc/Fc+ in acetonitrile) that was comparable to examples of similar complexes in the literature. Complex 1 generated a small concentration of a highly catalytic species after electrochemical reduction, which we attribute to cleavage of the Fe–Fe bond and formation of a mono-nuclear iron species or to Fe–S bond breakage generating a vacant coordination site. The contributions to the catalytic currents were simulated using DigiSim, where it was found that the rate limiting step for 3 was the elimination of H2. It was also found that the highly catalytic species generated after reduction of 1 was more basic than 1− and also that protonation of this species was faster.
| Type: | Article |
|---|---|
| Title: | Fluorinated models of the iron-only hydrogenase: An electrochemical study of the influence of an electron-withdrawing bridge on the proton reduction overpotential and catalyst stability |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.jelechem.2013.05.018 |
| Publisher version: | http://dx.doi.org/10.1016/j.jelechem.2013.05.018 |
| Language: | English |
| Additional information: | This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. |
| Keywords: | Electrocatalysis, Di-iron complexes, Proton reduction, Hydrogenases, Phosphines, Fluorinated thiolate |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1400118 |
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