We report a far-infrared vibrational study of (Ph4P)(2)IC60 which reveals a
room temperature Jahn-Teller distortion of the C-60 monoanion to either a
D-5d or D-3d reduced-symmetry point group. Temperature dependences of the i
ntramolecular C60 and counterion vibrations indicate a weak phase transitio
n of the bulk material occurring between 125 and 150 K.