Imine-assisted C–F bond activation by electron-rich iron complexes supported by trimethylphosphine

Abstract

C–F bond activation of ortho-fluorinated benzalimines 2,6-F₂C₆R1R2R3–CHN–R (1–3) using the electron-rich complex Fe(PMe₃)₄ is reported. With the assistance of the imine group as the anchoring group, bis-chelated iron(II) complexes (C₆FR1R2R3–CHN–R)₂Fe(PMe₃)₂ (4–6) were formed. The reaction of 2,6-difluorobenzylidenenaphthalen-1-amine 2,6-F₂C₆H₃–CHN–C₁₀H₇ (9) with Fe(PMe₃)₄ affords [CNC]-pincer iron(II) complex (C₆H₃F–CHN–C₁₀H₆)Fe(PMe₃)₃ (10) through both C–F and C–H bond activation and π-(CN) coordinate iron(0) complex (C₆H₃F–CHN–C₁₀H₇)₂Fe(PMe₃)₂ (11) with C,C-coupling, while a similar reaction with perfluorobenzylidenenaphthalen-1-amine C₆F₅–CHN–C₁₀H₇ (14) gave rise to only [CNC]-pincer iron(II) complex (C₆F₄–CHN–C₁₀H₆)Fe(PMe₃)₃ (15). The proposed formation mechanisms of these complexes are discussed. The structures of complexes 5, 6, 10 and 11 were confirmed by X-ray single crystal diffraction.