Catalytic C(sp³)-F Bond Activation at Low-Valent Germanium and Tin Redox Platforms

The activation and functionalization of the trifluoromethyl group remain formidable challenges in main group catalysis, primarily due to the inert nature of the C-F bond. Herein, we report an effective strategy for the activation and transformation of C(sp³)-F bonds in trifluoromethyl alkenes through E(II)/E(IV) (E = Ge, Sn) redox cycling. Organogermanium(II) and tin(II) species can cleave C(sp³)-F bonds, accompanied by an intriguing rearrangement, to afford well-defined adducts, which have been characterized by nuclear magnetic resonance spectroscopy and single-crystal X-ray diffraction. Mechanistic studies indicate that the reactions proceed via an S_N2'-type pathway involving intramolecular fluorine abstraction, driven by the nucleophilicity of Ge(II) and Sn(II) centers. Treatment of the resulting adducts with phenylsilane leads to stoichiometric hydrodefluorination via ligand metathesis and reductive elimination, yielding α-fluorinated methylalkenes and regenerating the divalent tin species. Under catalytic conditions, notably, trifluoromethyl alkenes are selectively converted to either mono- or gem-difluoroalkenes. Further mechanistic investigations reveal that the catalytic cycle follows an intermolecular fluoride abstraction pathway in the oxidative addition step, thereby steering the reaction toward divergent product outcomes. This work establishes a tunable main group redox platform for C(sp³)-F bond activation and opens new avenues for utilizing main group redox systems in the functionalization of inert chemical bonds.