Synthesis, Characterization and Electrochemical Reductive Properties of Complexes [Fe2(CO)4(κ2‐PPh2NR2)(µ‐dithiolato)] Related to the H‐Cluster of [FeFe]‐H2ases

Abstract

A series of dithiolato carbonyl diiron complexes with cyclic azadiphosphine, related to the active site of [FeFe]‐hydrogenases, has been prepared. Several combinations of diphosphines and dithiolato bridges have been examined in order to obtain information on the influence of electronic and steric effects of the group linked to the nitrogen atom of the phosphine (phenyl or benzyl) and the bridge‐head of the dithiolate (CH2, CEt2, CBn2). Products were spectroscopically and structurally characterized. Protonation experiments show that depending on the nature of the amine in the diphosphine, protonation processes are different. With NBn group, the process is arrested at N‐protonated species, while with NPh, the proton is transferred to the diiron site giving bridging‐hydrido species. The effect of the bridge‐head group of the dithiolate is very slight on the electronic properties of the compounds. Depending on the steric crowding of the bridge, different isomers related to the dibasal or basal‐apical position of the diphosphine, are observed in solution or in solid state. Electrochemical study was performed to examine the activity of these compounds in the presence of acid.