Vapor phase vibrational spectra for Re2O7 and the infrared spectrum of gaseous HReO4. Molecular shapes of Mn2O7, Tc2O7, and Re2O7

The Raman and infrared spectra of gas phase Re2O7 are reported. The experimental vibrational spectra of molecular Tc2O7 and Re2O7 are compared with calculated spectra. The results of these studies agree with a nonlinear M-O-M bridge for Tc2O7 and Re2O7. For infrared intensity calculations, the point charge approximation is used, while for the Raman calculations a combination of bond and atom polarizabilities is adopted. Pure Re2O7 was prepared from rhenium wire, but attempts to prepare it from rhenium powder and oxygen always led to infrared spectra showing serious contamination from a species containing an -OH linkage. Detailed experiments identified this molecule as HReO4, a unique transition metal analogue of the perhalic acids, and a partial infrared spectrum of this molecule is reported.