Electrochemical Reduction Mechanism of [(η5‑C5H5)Fe(dppf)(CO)]+ (dppf = 1,1′-Bis(diphenylphosphino)ferrocene)

The complex [CpFe­(dppf)­(CO)]­[B­(ArF)4] [1]­[B­(ArF)4] (Cp = cyclopentadienyl, dppf = 1,1′-bis­(diphenylphosphino)­ferrocene, and [B­(ArF)4]− = tetrakis­[3,5-bis­(trifluoromethyl)­phenyl]­borate) was made by removal of one carbonyl ligand from the dicarbonyl complex [CpFe­(CO)2(κ1-dppf)]I and exchange of the I– for [B­(ArF)4]− that allowed for electrochemical investigations. The cyclic voltammogram of [1]+ showed a reversible anodic process due to oxidation of the ferrocenediyl moiety of the dppf ligand. A quasi-reversible cathodic process was also observed, and this reduction occurred at the CpFe moiety, as determined by variable-temperature (+22 and −30 °C) IR spectroelectrochemistry (SEC) and further supported by DFT calculations. This reduction event resulted in the formation of the two possible dimers [Cp2Fe2(μ-CO)2(μ-dppf)] and [Cp2Fe2(CO)2(μ-dppf)] along with deligation of one dppf ligand.