In the reaction of TAS-fluoride, (Me2N)(3)S+Me3SiF2-; with carbonyl sulfur difluoride imides RC(O)NSF2 (R=F, CF3), C-N bond cleavage is observed, and TAS(+)RC(O)F-2(-) and NSF are the final products. From TASF and RC(O)NS(CF3)F, the salts TAS(+)RC(O)NS(CF3)F-2(-) (R = F (14), CF3 (15)), with psi -pentacoordinate sulfur centers in the anions, are formed. An X-ray structure investigation of 14 shows that the fluorine atoms occupy axial positions and CF3, NC(O)F, and the sulfur lone pair occupy equatorial positions of the trigonal bipyramid. The -C(O)F group lies in the equatorial plane with the CO bond synperiplanar to the SN bond. According to B3LYP calculations, this structure corresponds to a global minimum and the expected axial orientation cif the -C(O)F group represents a transition state. Calculations for the unstable FC(O)NSF3- anion show a different geometry. The -C(O)F group deviates 40 degrees from axial orientation, and the equatorially bonded fluorine is; in contrast to the -CF3 group in 14, syn positioned.