Raman and infrared spectroscopic studies of the low- and high-temperature forms of octahalo cyclic phosphazene tetramers, P4N4Cl8 and P4N4F8

Based on a study of the Raman and infrared spectra, normal vibrations of the low-temperature skew-tub (S 4) and high-temperature C i or C2h (skew-chair) forms of P4N4Cl8 have been assigned. A temperature variation study of the Raman spectra has shown the coexistence of both the forms of P4N4Cl8 in the phase transition region. Preliminary assignments of the Raman and infrared spectra of the low- and high-temperature forms of P4N4F8 are presented. One of the low-frequency Raman modes softens through the phase transition of P4N4F8 at 199 K.