Reversible Reductive Dimerization of Diiron μ-Vinyl Complex via C–C Coupling: Characterization and Reactivity of the Intermediate Radical Species

The diiron μ-vinyl complex [Fe2Cp2(CO)2(μ-CO){μ-η1:η2-CHCH(Ph)}][BF4], [1][BF4], reacted with CoCp2 affording selectively the C–C coupling product [Fe2Cp2(CO)2(μ-CO){μ-CHCH(Ph)}]2, 2. The cation [1]+ was regenerated from 2 in good yield by I2-induced oxidative cleavage. The cation [1]+ underwent two sequential monoelectron reductions, the first one being an electrochemically reversible process that generated the radical species [Fe2Cp2(CO)2(μ-CO){μ-CHCH(Ph)}], [1]•. The latter was characterized by EPR spectroelectrochemistry. The structures of [1]+, [1]•, and 2 were optimized for the gas phase by DFT calculations. The reaction of [1][BF4] with NEt3 in the presence of excess PhSSPh gave [Fe2Cp2(CO)2(μ-CO){μ-CHCH(Ph)(SPh)}], 3. The new compounds 2 and 3 were fully characterized by IR and NMR spectroscopy, elemental analysis, and X-ray diffraction studies.