The compounds (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)NCMe]X (X = I, PF6), configurationally labile at the metal center, were used in the MeCN/ligand exchange reactions with cyclohexyl isocyanide (CyNC) and tert-butyl isocyanide (tBuNC). Kinetic measurements showed that the MeCN/CyNC exchange in diastereomerically pure (SFe,RC)-[CpFe(Prophos)NCMe]X proceeded via the slow SN1-type dissociation of the Fe–NCMe bond, already observed in the MeCN/phosphite exchange reactions. The product (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)CNCy]X (X = I, PF6) was formed in diastereomer ratios between 40:60 and 60:40. However, specific for the MeCN/CyNC exchange in (SFe,RC)-[CpFe(Prophos)NCMe]PF6, in some of the samples a fast initial reaction interfered, initiated by traces of oxygen, which oxidized the cation in (SFe,RC)-[CpFe(Prophos)NCMe]PF6 to (SFe,RC)-[CpFe(Prophos)NCMe]2+. This dipositive cation started an electrocatalytic chain reaction, producing (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)CNCy]PF6 with a high stereoselectivity of 2:98 in ...