Biologically inspired 3Fe4S cluster as structural mimics of FeMoco M-cluster

A 3Fe4S cluster related to M-cluster of Mo-nitrogenase is reported. K(THF)₅]Fe₃(μ-bdt)₂(μ-PPh₂)(CO)₅] ( 1 ) is synthesized from photo-assisted structural rearrangement of K(THF)₂](μ,κ²-bdt)Fe₂(μ-PPh₂)(CO)₅] under visible light irradiation. The molecular structure of 1 consists of a Fe₃ core bearing one dithiolate bridge and the second dithiolate group capping onto the metallic plane. The structural motif of 1 is analogous to that of Mo-participated 3Fe4S unit in M-cluster of Mo-nitrogenase, with the similar Fe-Fe and Fe-S bond distances. Upon protonation in 193 K, a Fe-hydride species ( 1H ) is generated and characterized to possess the bridging hydride group (δ = ?12.57 ppm) by ¹H-NMR spectroscopy and DFT calculation. In CH₃CN solution, complex 1 exhibits a reversible reduction and oxidation process at $E_{1/2}^{\mathrm{red}}$ = ?1.94 V and $E_{1/2}^{\mathrm{ox}}$ = ?0.18 V, respectively, at 273 K. The reduction behavior of 1 in CH₂Cl₂ solution at 243 K displays a slight modification in the presence of trifluoroacetic acid, revealing a moderate anodic potential shift (~50 mV). The current amplitude of the reduction wave is linearly increased with the increasement of acid added, indicative of the catalytic event.