Synthesis, characterization, and electrochemistry of diiron ethane-1,2-dithiolate complexes with monosubstituted ethyldiphenylphosphine or dicyclohexylphenylphosphine

Abstract

In this contribution, two diiron ethane-1,2-dithiolate complexes with one ethyldiphenylphosphine or dicyclohexylphenylphosphine ligand have been synthesized and characterized as mimics for the active site of [FeFe]-hydrogenases. Treatment of complex [Fe₂(CO)₆(μ-SCH₂CH₂S)] (1) with ethyldiphenylphosphine or dicyclohexylphenylphosphine and Me₃NO · 2 H₂O as decarbonylating agent gave complexes [Fe₂(CO)₅(Ph₂PCH₂CH₃)(μ-SCH₂CH₂S)] (2) and [Fe₂(CO)₅{PhP(C₆H₁₁)₂}(μ-SCH₂CH₂S)] (3) in 93% and 86% yields, respectively. Complexes 2 and 3 were characterized by elemental analysis, IR, and NMR spectroscopy. X-ray crystallographic studies confirmed the molecular structures of complexes 2 and 3, indicating that they contain a butterfly diiron ethane-1,2-dithiolate cluster with five terminal carbonyl ligands and an apically-coordinated phosphine ligand. Additionally, the electrochemical properties of these complexes were investigated by cyclic voltammetry, suggesting that they can be regarded as electrocatalysts for the reduction of protons to H₂ in the presence of HOAc. A possible mechanism for the proton reduction was proposed.

Graphical Abstract

Keywords:

• [FeFe]-hydrogenase
• diiron ethane-1,2-dithiolate
• carbonyl substitution
• crystal structure
• electrochemistry

Additional information

Funding

The authors gratefully acknowledge the support of the National Natural Science Foundation of China (Grant no. 21576230), the National Natural Science Foundation of China-Shanxi Coal-based Low Carbon Joint Fund (Grant no. U1810110), Key R & D program of Shanxi Province (Grant no. 201903D121105), and Key Subject Building Project of Yuncheng University (Grant no. XK-2019065).