Revisiting the photochemical synthesis of [FeFe]-hydrogenase mimics: reaction optimization, mechanistic study and electrochemical behaviour

The photoreaction of [(μ-S)(2)Fe(2)(CO)(6)] and alkenes or alkynes has been optimized to readily obtain functionalized [FeFe]-hydrogenase mimics. Irradiation under low CO pressure in THF produces the corresponding photo-adducts in good/acceptable (alkenes/alkynes) yields, with retention of the starting olefin stereochemistry. DFT-calculations provide plausible reaction pathways in both, singlet and triplet states. The DFT-calculation based in the singlet state is energetically more favorable. The electrochemical behavior of the synthesized compounds is also presented, including studies in acidic media. The electrochemical properties of the products vary in the presence of a double bond (cycloaddition of [(μ-S)(2)Fe(2)(CO)(6)] to alkynes), respect to a single bond (cycloaddition to alkenes).