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Synthesis, Molecular Structures and Electrochemical Investigations of [FeFe]-Hydrogenase Biomimics [Fe2(CO)6-n(EPh3)n(µ-edt)] (E = P, As, Sb; n = 1, 2)

Research output: Contribution to journalArticle

Shishir Ghosh, Ahibur Rahaman, Georgia Orton, Gregory Gregori, Martin Bernat, Ummey Kulsume, Nathan Hollingsworth, Katherine B. Holt, Shariff E. Kabir, Graeme Hogarth

Original languageEnglish
Pages (from-to)4506-4515
Number of pages10
JournalEUROPEAN JOURNAL OF INORGANIC CHEMISTRY
Volume2019
Issue number42
Early online date10 Oct 2019
DOIs
E-pub ahead of print10 Oct 2019
Published14 Nov 2019

King's Authors

Abstract

A series of ethane-dithiolate (edt = S(CH2)2S) complexes [Fe2(CO)5(EPh3)(µ-edt)] and [Fe2(CO)4(EPh3)2(µ-edt)] (E = P, As, Sb), biomimics of the core of [FeFe]-hydrogenases, have been prepared and structurally characterised. The introduced ligand(s) occupies apical sites lying trans to the iron-iron bond. NMR studies reveal that while in the mono-substituted complexes the Fe(CO)3 moiety undergoes facile trigonal rotation, the Fe(CO)2(PPh3) centres do not rotate on the NMR timescale. The reductive chemistry has been examined by cyclic voltammetry both in the presence and absence of CO and the observed behavior is found to be dependent upon the nature of the substituents. With L = CO or SbPh3 potential inversion is seen leading to a two-electron reduction, while for others (L = PPh3, AsPh3) a quasi-reversible one-electron reduction is observed. Protonation studies reveal that [Fe2(CO)5(PPh3)(µ-edt)] is only partially protonated by excess HBF4·Et2O, thus ruling complexes [Fe2(CO)5(EPh3)(µ-edt)(µ-H)]+ out as a catalytic intermediates, but [Fe2(CO)4(PPh3)2(µ-edt)] reacts readily with HBF4·Et2O to produce [Fe2(CO)4(PPh3)2(µ-edt)(µ-H)]+. While all new complexes are catalysts for the reduction of protons in MeCN, their poor stability and relatively high reduction potentials does not make them attractive in this respect.

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