Theoretical study on the mechanism of selective C−F bond activation of perfluorinated toluene promoted by Co(PMe3)4

While the selective C−F bond activation of perfluorinated toluene (CF3C6F5) by a trimethylphosphine-supported cobalt(0) complex Co(PMe3)4 has been achieved in our previous work (Organometallics, 2009, 28, 5771–5776), the proposed mechanism has not been demonstrated directly through quantum chemistry calculations. The present work provides a supplementary theoretical study on a detailed mechanism to better understand the synergistic effect of cobalt center and free PMe3 ligand on the selective C−F bond activation of CF3C6F5. The calculated results indicate two C−F bonds in CF3C6F5 are activated successively via a similar mechanism: the initial oxidative addition of C−F bond to cobalt(0) center, followed by F atom abstraction by a free PMe3 ligand. However, it is found that the F atom abstraction with a barrier of 34.92 kcal mol−1 is the bottle-neck step of the first C−F bond activation, while the oxidative addition of C−F bond is the rate-determining step of the second C−F bond activation with a barrier of 30.85 kcal mol−1. The theoretical results confirm the C−F activation mechanism proposed in our early work, i.e., the Co complex and free PMe3 ligands cooperatively promote the C−F bond activation.