Selective activation of carbon-fluorine bonds in organic molecules is a challenge in organometallic chemistry since C-F bonds are among the strongest sigma bonds. Cleavage of C-F bonds using a metal complex is not always chemoselective, since competitive C-H and C-C activation typically results from lower C-H and C-C bond strengths and formation of kinetically stable M-H and M-C products. We report a �-diketiminato cobalt(I) complex, LtBuCo [LtBu= 2,2,6,6-tetramethyl-3,5-bis(2,6- diisopropylphenylimido)hept-4-yl] that selectively activates the carbon-fluorine bond in fluorobenzene and other aryl fluorides. We observe the cleavage of only the carbon-fluorine bond. UV/visible kinetic studies were performed to understand the mechanism of this C-F bond activation, and elementary second order rate constants were determined for a variety of fluoroarenes. Kinetic data point to a mechanism featuring oxidative addition of fluorobenzene to the cobalt(I) complex followed by disproportionation to give the cobalt(II) fluoride and aryl complexes [LtBuCo(�-F)]2 and LtBuCoPh  in the expected stoichiometry.

Kinetic studies of C-F activation by a masked two-coordinate cobalt(I) complex

243rd National Meeting (2012)

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