Acetylenic SF5 Substituents

The doublet for the four equatorial fluorines appears at +83.8 ppm, while the pentet for the single axial fluorine appears at 77.6 ppm. The two-bond coupling constant is 161 Hz. 

TABLE 7.3. MF Chemical Shifts of the Equatorial and Axial Fluorines of Aryl-SFs Compounds9 

There is nothing special in the fluorine spectrum of the 4-fluoro compound. The signal for the fluorine at the 4-position appears as the typical heptet that one obtains when the smaller coupling of the triplet of triplets is about half that of the larger coupling. 

The spectrum for the 2-fluoro compound gives evidence of through-space coupling (4/ff = 20 Hz) between the 2-fluoro substituent and the equatorial fluorines of the SF5 group. 

The chemical shifts for the two fluorine signals of various substituted SF5-benzenes are given in Table 7.3. 

---