Thermal decarbonylation of the acyl compounds [Mn(CO)
5(COR
F)] (R
F=CF
3, CHF
2, CH
2CF
3, CF
2CH
3) 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(
12CO)
4(
eq-
13CO)(R
F)] and [Mn(
12CO)
4(
ax-
13CO)(R
F)] isotopomers and a ranking of the R
F donor power in the order CF
3<CHF
2<CH
2CF
3≈CF
2CH
3. 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 Δ
H≠ and Δ
S≠ 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(CF
3)] (the compound with the strongest Mn−R
F bond) initiated the radical polymerization of vinylidene fluoride (CH
2=CF
2) to produce poly(vinylidene fluoride) in good yields by either thermal (100 °C) or photochemical (UV or visible light) activation.
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