Titanium‐Catalyzed Defluorination of Poly(Vinyl Fluoride) and Poly(Vinylidene Fluoride) Under Friedel–Crafts Conditions

The defluorination of poly(vinyl fluoride) (PVF) and poly(vinylidene fluoride) (PVDF) fluoropolymers catalyzed by titanium species in the presence of triethylsilane (Et 3 SiH) and aromatic solvents is reported. Commercially available Ti complexes (e.g., [Cp 2 TiCl 2 ] ( Ti3 ) or [CpTiCl 3 ] ( Ti5 ); Cp = η 5 ‐C 5 H 5 ) activated by the silylium reagent [(Et 3 Si) 2 H](B(C 6 F 5 ) 4 ) ( Si + ) defluorinate PVF and PVDF with turnover frequencies (TOF) of up to 3.7 h −1 , affording copolymers with low residual fluorine content (down to 0.8%). The obtained polymers were characterized by multiple techniques including solid‐state nuclear magnetic resonance (NMR) and Fourier‐transform Infrared (FTIR) spectroscopies, combustion ion chromatography (CIC), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). Density functional theory (DFT) calculations conducted in bromobenzene on 2‐fluoropropane as a model indicate that the turnover‐limiting step is the concerted fluoride abstraction (by Ti)/hydride transfer (by Et 3 SiH).