Pendant bases as proton transfer relays in diiron dithiolate complexes inspired by [Fe–Fe] hydrogenase active site

Three dinuclear iron complexes containing pendant nitrogen bases in phosphine ligands with general formular (μ-pdt) [Fe2(CO)5L] (where pdt is SCH2CH2CH2S, L = PPh2NH(CH2)2N(CH3)2 (5), PPh2NH(2-NH2C6H4) (6), PPh2[2-N(CH3)2CH2C6H4] (7)), were prepared as the models of the [Fe–Fe] hydrogenase active site. The molecular structures of 5–7 were characterized by X-ray crystallography. The secondary amine in 6 has weak intramolecular hydrogen bonding with both the terminal nitrogen and sulfur atom, which may suggest a proton transfer pathway from amine in phosphine ligand to the sulfur atom of active site. Protonation of complexes 5 and 6 only occurred at the terminal nitrogen atom. Electrochemical properties of the complexes were studied in the presence of triflic acid by cyclic voltammetry.

Graphical abstractThree dinuclear iron complexes containing pendant nitrogen bases in phosphine ligands with general formula (μ-pdt) [Fe2(CO)5L] (where pdt is SCH2CH2CH2S, L = PPh2NHC2H4N(CH3)2 (5), PPh2NH(2-NH2C6H4) (6), PPh2[2-CH2N(CH3)2C6H4] (7)), were prepared as the models of the [Fe–Fe] hydrogenase active site. Electrochemical properties of the complexes were studied in the presence of triflic acid by cyclic voltammetry.Figure optionsDownload full-size imageDownload as PowerPoint slide