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Hydrogenase Biomimetics with Redox-Active Ligands: Synthesis, Structure, and Electrocatalytic Studies on [Fe2(CO)42-dppn)(µ-edt)] (edt = Ethanedithiolate; dppn = 1,8-bis(Diphenylphosphino)Naphthalene)

1
Department of Chemistry, King’s College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
2
Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh
3
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
4
Department of Chemistry, University of North Texas, 1155 Union Circle, Box 305070, Denton, TX 76203, USA
*
Authors to whom correspondence should be addressed.
Inorganics 2018, 6(4), 122; https://doi.org/10.3390/inorganics6040122
Received: 28 August 2018 / Revised: 5 November 2018 / Accepted: 9 November 2018 / Published: 20 November 2018
(This article belongs to the Special Issue Binuclear Complexes)
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Abstract

Addition of the bulky redox-active diphosphine 1,8-bis(diphenylphosphino)naphthalene (dppn) to [Fe2(CO)6(µ-edt)] (1) (edt = 1,2-ethanedithiolate) affords [Fe2(CO)42-dppn)(µ-edt)] (3) as the major product, together with small amounts of a P–C bond cleavage product [Fe2(CO)51-PPh2(1-C10H7)}(µ-edt)] (2). The redox properties of 3 have been examined by cyclic voltammetry and it has been tested as a proton-reduction catalyst. It undergoes a reversible reduction at E1/2 = −2.18 V and exhibits two overlapping reversible oxidations at E1/2 = −0.08 V and E1/2 = 0.04 V. DFT calculations show that while the Highest Occupied Molecular Orbital (HOMO) is metal-centred (Fe–Fe σ-bonding), the Lowest Unoccupied Molecular Orbital (LUMO) is primarily ligand-based, but also contains an antibonding Fe–Fe contribution, highlighting the redox-active nature of the diphosphine. It is readily protonated upon addition of strong acids and catalyzes the electrochemical reduction of protons at Ep = −2.00 V in the presence of CF3CO2H. The catalytic current indicates that it is one of the most efficient diiron electrocatalysts for the reduction of protons, albeit operating at quite a negative potential. View Full-Text
Keywords: hydrogenase biomimetics; dithiolate; proton-reduction; dppn; redox-active hydrogenase biomimetics; dithiolate; proton-reduction; dppn; redox-active
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Ghosh, S.; Rana, S.; Hollingsworth, N.; Richmond, M.G.; Kabir, S.E.; Hogarth, G. Hydrogenase Biomimetics with Redox-Active Ligands: Synthesis, Structure, and Electrocatalytic Studies on [Fe2(CO)42-dppn)(µ-edt)] (edt = Ethanedithiolate; dppn = 1,8-bis(Diphenylphosphino)Naphthalene). Inorganics 2018, 6, 122.

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