X-ray crystal structures of three differently solvated forms of potassium pentaphenyl[60]fullerene, K(C60Ph5)(thf)(3), [K(thf)(6)][C60Ph5], and [K(18-crown-6)(dmf)][C60Ph5], indicate that the potassium cation and the fullerene cyclopentadienide become separated easily by cation solvation, and suggest that a solvent-separated ion pair is responsible for the formation of bilayer vesicles upon dissolution of KC60Ph5 in water.