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)

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.

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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 ◽

10.3390/inorganics6040122 ◽

2018 ◽

Vol 6 (4) ◽

pp. 122 ◽

Cited By ~ 5

Author(s):

Shishir Ghosh ◽

Shahed Rana ◽

Nathan Hollingsworth ◽

Michael Richmond ◽

Shariff Kabir ◽

...

Keyword(s):

Molecular Orbital ◽

Bond Cleavage ◽

Major Product ◽

Proton Reduction ◽

Catalytic Current ◽

Redox Active ◽

Highest Occupied Molecular Orbital ◽

Lowest Unoccupied Molecular Orbital ◽

Active Nature ◽

Strong Acids

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)4(κ2-dppn)(µ-edt)] (3) as the major product, together with small amounts of a P–C bond cleavage product [Fe2(CO)5{κ1-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.

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