non-active aryl and vinylhalides with [CpFe(CO)2]− by means of a specially introduced mediator (a reversible redox couple () has been demonstrated. The efficiency of different mediators for several aryl and vinylhalides as well as the corresponding σ-aryl and σ-vinyl derivatives of (η5-cyclopentadienyl)irondicarbonyl has been examined. It was shown that by carefully selecting the mediator it becomes