Cobalt Fluorocarbenes: Cycloaddition Reactions with Tetrafluoroethylene and Reactivity of the Perfluorometallacyclic Products

Cobalt fluorocarbene complexes CpCo(=CFRF)(PPh2Me) (Cp = eta(5)-C5H5, R-F = F or CF3) react with tetrafluoroethylene to give the metallacyclobutanes CpCo(kappa(2)-(CFRCF2CF2)-C-F-)(PPh2Me) in the first examples of cycloaddition reactions between perfluoroalkenes and metal perfluorocarbenes. The metallacyclic products undergo a variety of reactions upon activation of the C-F bonds, including Bronsted acid-catalyzed C-F/Co-C scrambling. Implications for metal-catalyzed metathesis and polymerization of perfluoroalkenes are discussed.