Résumé
Thermal decarbonylation of the acyl compounds [Mn(CO)(5)(CORF)] (R-F=CF3, CHF2, CH2CF3, CF2CH3) yielded the corresponding alkyl derivatives [Mn(CO)(5)(R-F)], some of which have not been previously reported. The compounds were fully characterized by analytical and spectroscopic methods and by several single-crystal X-ray diffraction studies. The solution-phase IR characterization in the CO stretching region, with the assistance of DFT calculations, has allowed the assignment of several weak bands to vibrations of the [Mn((CO)-C-12)(4)(eq-(CO)-C-13)(R-F)] and [Mn((CO)-C-12)(4)(ax-(CO)-C-13)(R-F)] isotopomers and a ranking of the R-F donor power in the order CF3<CHF2<CH2CF3 approximate to CF2CH3. The homolytic Mn-R-F bond cleavage in [Mn(CO)(5)(R-F)] at various temperatures under saturation conditions with trapping of the generated R-F radicals by excess tris(trimethylsilyl)silane yielded activation parameters Delta H-not equal and Delta S-not equal that are believed to represent close estimates of the homolytic bond dissociation thermodynamic parameters. These values are in close agreement with those calculated in a recent DFT study (J. Organomet. Chem. 2018, 864, 12-18). The ability of these complexes to undergo homolytic Mn-R-F bond cleavage was further demonstrated by the observation that [Mn(CO)(5)(CF3)] (the compound with the strongest Mn-R-F bond) initiated the radical polymerization of vinylidene fluoride (CH2=CF2) to produce poly(vinylidene fluoride) in good yields by either thermal (100 degrees C) or photochemical (UV or visible light) activation.