π-Bis(benzene)chromium(0)-catalyzed oligomerization of perfluoropropylene

In the presence of zerovalent π-bis(benzene)chromium(0) (I), perfluoropropylene (II) was found to undergo oligomerization under very mild conditions to dimers (b.p. 46°, M⁺, 300) and trimers (b.p. 100–102°C, M⁺ - 19, 431) in the ratio of 2.5–3.0 to 1. One mol of metal complex could catalyze the conversion of 50 mol of perfluoropropylene. On the basis of ¹⁹F NMR, the structures of the dimers are III and IV in a ratio of ca. 80/20 and the trimers V and VI; VII and VIII also seemed to be present. V/VI/(VII + VIII) is 80/10/4. In benzene solution, perfluoropropylene was shown not to be catalytically oligomerized by fluoride ion (KF, CrF₂ or (CH₃)₄NF) (nor by monovalent π-dibenzenchromium(I). A possible mechanism of the reaction was proposed.