DFT investigation of C[sbnd]F bond activation by a low-coordinate cobalt(I) complex

Abstract

A low-coordinate cobalt(I) complex, LtBuCo [LtBu=bulky β-diketiminate ligand] was reported to be capable of cleaving the CF bond in fluoroarenes. To investigate the mechanism of CF bond activation, a simplified ligand model (LMeCo) with methyl substituents was first used as a guide before the full LtBuCo complex was calculated. DFT calculations indicate the free energy change of CF oxidative addition is −3.9kcalmol−1 to yield a Co(III) product. When the initial interaction of Co(I) complexes and the π-ring of PhF occurs, the free energy increases by 0.4kcalmol−1. As a result, the formation of π-adducts is deemed to be an important mechanistic step, but is very sensitive to the steric influence of the supporting ligand substituents. The calculations indicate oxidative addition as a viable pathway for the activation of strong CF bonds by Earth-abundant 3d metals.