The Bridged Binding Mode as a New, Versatile Template for the Selective Activation of Carbon−Fluorine Bonds in Fluoroolefins: Activation of Trifluoroethylene

We report the selective activation of carbon−fluorine bonds in trifluoroethylene using the diiridium complex [Ir2(CH3)(CO)2(dppm)2][OTf] (1). Coordination of trifluoroethylene in a bridging position between the two metals in 1 results in facile fluoride ion loss in three different ways. Attack by strong fluorophiles such as Me3SiOTf and HOTf results in F− removal from one of the geminal fluorines to give the cis-difluorovinyl-bridged product [Ir2(CH3)(OTf)(CO)2(μ-κ1:η2-C(F)CFH)(dppm)2][OTf]. A second activation can also be accomplished by addition of excess Me3SiOTf to give the fluorovinylidene-bridged product [Ir2(CH3)(OTf)(CO)2(μ-C2FH)(dppm)2][OTf]2. Interestingly, activation of the trifluoroethylene-bridged precursor by water also occurs, yielding [Ir2(CH3)(CO)2(κ1-C(H)CF2)(μ-OH)(dppm)2][OTf], in which the lone vicinal fluorine is removed, leaving a geminal arrangement of fluorines in the product. A [1,2]-fluoride shift can also be induced in the trifluoroethylene-bridged precursor upon the addition of CO to give the 2,2,2-trifluoroethylidene-bridged product [Ir2(CH3)(CO)3(μ-C(H)CF3)(dppm)2][CF3SO3]. Addition of hydrogen to the cis-difluorovinyl-bridged product results in the quantitative elimination of cis-difluoroethylene, while its reaction with CO yields a mixture of cis-difluoropropene and 2,3-difluoropropene by reductive elimination of the methyl and difluorovinyl groups with an accompanying isomerization in the case of the second product. Finally, protonation of the 2,2,2-trifluoroethylidene-bridged product liberates 1,1,1-trifluoroethane, in which one hydrogen (H+) is from the acid while the other hydrogen (H−) is derived from activation of the methyl group.