Benzoate-functionalized diiron propanedithiolate complexes with mono- and di-phosphine ligands as catalysts for reduction of protons

Abstract

Reaction of the diiron propanedithiolate complex [μ-(SCH₂)₂CHO₂CC₆H₅]Fe₂(CO)₆ (A) with triphenylphosphine (PPh₃) or cis-1,2-bis(diphenylphosphine)ethylene (cis-dppv) in the presence of one equivalent of Me₃NO·2H₂O yielded a mono-substituted complex [μ-(SCH₂)₂CHO₂CC₆H₅]Fe₂(CO)₅(PPh₃) (1) or an asymmetrically substituted complex [(μ-SCH₂)₂CHO₂CC₆H₅]Fe₂(CO)₄(κ²-dppv) (2), respectively. The structures of both complexes were characterized by spectroscopic methods and X-ray crystallography. In the solid state, the PPh₃ ligand in 1 occupies an apical position of the square pyramidal geometries of the Fe2, while the cis-dppv in 2 coordinates Fe2 in an apical-basal manner. The electrochemistry of both complexes was investigated. The electron-withdrawing benzoate functionality on the bridgehead carbon of the propanedithiolate bridge shifts the oxidation and reduction potentials of 1 or 2 slightly. Both complexes can catalyze the reduction of protons from CF₃COOH but with a higher efficiency for 2.

Keywords:

• [FeFe]-hydrogenase
• Diiron dithiolate complex
• Phosphine ligand
• Crystal structure
• Electrochemistry
• Catalysis of reduction of protons

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

¹ In a six-membered ring in chair conformation, axial hydrogen means that the C–H bond is perpendicular to the average plane of the six-membered ring, while equatorial hydrogen means that the C–H bond is approximately horizontal to the average plane of the six-membered ring.

Additional information

Funding

This work was supported by the Chinese National Natural Science Foundation [grant number 21072046]; the Chinese National Training Programs of Innovation and Entrepreneurship for Undergraduates [grant number 201210467022].