Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Hydrogenase biomimetics with redox-active ligands: Synthesis, structure and electrocatalytic studies on Fe2(CO)4(K2-dppn)(µ-edt) (edt = ethanedithiolate; dppn = 1,8-bis(diphenylphosphino)naphthalene)

Graeme Hogarth
* ,
Shishir Ghosh
* ORCID logo ,
Nathan Hollingsworth
,
Michael Richmond
ORCID logo ,
Shariff Kabir
,
Shahed Rana
Version 1 : Received: 28 August 2018 / Approved: 28 August 2018 / Online: 28 August 2018 (15:50:13 CEST)

A peer-reviewed article of this Preprint also exists.

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)4(κ2-dppn)(µ-edt)] (edt = Ethanedithiolate; dppn = 1,8-bis(Diphenylphosphino)Naphthalene). Inorganics 2018, 6, 122. 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)4(κ2-dppn)(µ-edt)] (edt = Ethanedithiolate; dppn = 1,8-bis(Diphenylphosphino)Naphthalene). Inorganics 2018, 6, 122.

Abstract

Addition of the bulky redox-active diphosphine 1,8-bis(diphenylphosphino)naphthalene (dppn) to [Fe2(CO)6(-edt)] (1) (edt = 1,2-ethanedithiolate) affords [Fe2(CO)4(2-dppn)(-edt)] (3) as the major product, together with small amounts of a P-C bond cleavage product [Fe2(CO)5{1-PPh2(1-C10H7)}(-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 HOMO is metal-centred (Fe-Fe -bonding), the 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 to afford two isomeric hydride complexes 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 negative potential.

Keywords

Hydrogenase biomimetics; dithiolate; proton-reduction; dppn; redox-active

Subject

Chemistry and Materials Science, Inorganic and Nuclear Chemistry

Copyright: 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.

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