Preparation, structures and electrochemical property of diiron dithiolate complexes with hydrophilic N-donor ligands

Diiron dithiolate complexes [Fe2(μ-pdt)(CO)5L] (2: L = 2-NH2Py; 3: L = 3-NH2Py; 4: L = 4-NH2Py; 5: L = Im; 6: L = 4-MeIm; 7: L = 2,4-Me2Im) were prepared as biomimetic models for the active site of [FeFe] hydrogenase, by CO substitution of [Fe2(μ-pdt)(CO)6] (1) with monoaminopyridines and imidazole ligands. All the complexes were characterized by MS, IR, 1H NMR spectra and elemental analysis. Their molecular structures were further confirmed by single crystal X-ray analysis. An intramolecular N−H⋯S hydrogen bond was observed in the molecular structure of 2 while intermolecular N−H⋯S hydrogen bonds were found in the crystal structures of 3, 4, 6 and 7. The ligands in 2−7 are loosely coordinated to the diiron centers and can be totally or partially replaced by solvent molecules. The electrochemistry of 2–7 was studied and the electrocatalytic property of 2 was investigated for proton reduction in the presence of acetic acid in THF or mixed THF/H2O solvents with varying volume ratios.