Preparation of organocobalt complexes through C[sbnd]F/C[sbnd]H bond activation of polyfluoroaryl imines

Abstract

In this paper, we reported the CF and CH bond activation of polyfluoroimine ligands induced by CoMe(PMe3)4. The reaction of pentafluorophenylmethylidene-2,6-diisopropylaniline 1 with CoMe(PMe3)4 afforded an ortho-chelated cobalt(I) complex [Co(PMe3)3(C6F4-ortho-CH=N-C6H3(iso-Pr)2(ortho, ortho))] (5) via CF bond activation and subsequent elimination of methyl fluoride. Under similar reaction conditions, the reactions of polyfluoroaryl imines 2–4 with CoMe(PMe3)4 afforded the penta-coordinate cobalt(I) complexes 6–8 via CH bond activation and subsequent elimination of methane [Co(PMe3)3(C6H2F2(meta, meta)-ortho-(CH=N-C6H4Clpara)] (6), [Co(PMe3)3(C6H2F2(meta, para)-ortho-(CH=N-C6H4Clpara)] (7), and [Co(PMe3)3(C6HF3(meta, meta, para)-ortho-(CH=N-C6H4Clpara)] (8). Complexes 5–8 were characterized through IR, 1H NMR, 31P NMR, 19F NMR and elemental analyses. The crystal and molecular structures of complexes 5, 6 and 8 were determined by X-ray single crystal diffraction. The reactions of 8 with MeI and EtBr afforded organic fluorides 9–10. A proposed formation mechanism of 9–10 with the oxidative addition of RX at the cobalt(I) center of 8 and reductive elimination via C,C-coupling was discussed.