Azadithiolates cofactor of the iron-only hydrogenase and its PR3-monosubstituted derivatives: Synthesis, structure, electrochemistry and protonation

The core structure (μ-SCH2)2NH[Fe2(CO)6] (5) of Fe-only hydrogenases active site model has been synthesized by the condensation of iron carbonyl sulfides, formaldehyde and silyl protected amine. Its monosubstituted complexes (μ-SCH2)2NH[Fe2(CO)5PR3] (R = Ph (6), Me (7)) were accordingly prepared. The coordination configurations of 5 and 6 were characterized by X-ray crystallography. Protonation of complex 7 to form the N-protonated product occurs in an acetonitrile solution upon addition of triflic acid. The redox properties of these model complexes were studied by cyclic voltammetry.