The compounds pip(+)CF(3)O(-), pip(+)CF(3)CF(2)O-pip(+)(CF3)(2)CFO-, and (CH3)(4)N+OCFCF2O- (pip(+) = 1,1,3,3,5,5- hexamethylpiperidinium) are obtained from pip(+)F(-) or (CH3)(4)N+F- and COF2, CF3COF, (CF3)(2)CO, and (COF)(2). The structures of pip(+)CF(3)CF(2)O(-), pip(+)(CF3)(2)CFO-, and (CH3)(4)N+OCFCF2O- have been investigated by single-crystal X-ray crystallography. Crystal data are as follows: for pip(+)CF(3)CF(2)O(-), monoclinic P2(1)/c, n = 1300.7(1) pm, b = 828.0(1) pm, c = 1513.3(2) pm, beta = 110.13(1)degrees, Z = 4; for pip(+)(CF3)(2)CFO-, monoclinic P2(1)/c, a 1182.2(1) pm, b = 1032.9(2) pm, c = 1459.1(1) pm, beta = 107.45(1)degrees, Z = 4; for (CH3)(4)N+OOCCC2O-, tetragonal P42(1)/c, a = 1115.9(1) pm, c = 1377.1(1) pm, Z = 8. All anion structures are indicative of a negative hyperconjugation effect. The structure of FCOCF2O- is clearly nonsymmetric and resembles a close to planar cis oxygen configuration with one additional fluorine bound to one carbon atom. This fluorine atom is positioned slightly toward the second carbon atom, which corresponds to a movement from the asymmetric to the symmetric fluorine-bridged structure. Interionic forces seem to be responsible for this peculiar structure. These findings are compared with structures predicted by nb initio calculations.