Effect of anchoring group and valent of cobalt center on the competitive cleavage of C–F or C–H bond activation

Treatment of CoMe(PMe3)4 with 2,6-difluorobenzophenone imine and 2,6-difluorobenzophenone resulted in C–H bond activation complex, [Co(2-C6H4)-(Cdouble bond; length as m-dashNH)-(2′,6″-F2C6H3)(PMe3)3] (2), and C–F bond activation complex [Co(Me)(F)(2-(6-FC6H3)-(Cdouble bond; length as m-dashO)-C6H5)(PMe3)2] (3) respectively. Using Co(PMe3)4 instead of CoMe(PMe3)4 the C–F activation Co(І) complex [Co(2-(6-FC6H3)-(Cdouble bond; length as m-dashNH)-C6H5)(PMe3)3] (1), was obtained by the reaction of Co(PMe3)4 with 2,6-difluorobenzophenone imine. In the case of mono-fluorinated aromatic ketone, the reaction of CoMe(PMe3)4 with 2,4′-difluorobenzophenone afforded only C–H bond activation complex, [Co(2-(4-FC6H3)-(Cdouble bond; length as m-dashO)-(2′-FC6H4)(PMe3)3] (4) in comparison with the C–F activation in the di-fluorinated aromatic ketone 2,6-difluorobenzophenone system. The crystal structures of complexes 1, 3 and 4 were determined by X-ray diffraction. The proposed mechanisms were discussed.