Vibrational Spectra of MoF6 and TcF6

Infrared spectra of gaseous MoF6 and TcF6 from 6–43 μ, the Raman spectrum of MoF6 gas, and an incomplete Raman spectrum of liquid TcF6 are reported. These are interpreted in terms of the octahedral point group 0h. The fundamental frequencies for MoF6 are 741(ν1), 643(ν2), 741(ν3), 264(ν4), 306(ν5), and 190(ν6). For TcF6 they are 705(ν1), 551(ν2), 748(ν3), 265(ν4), 255(ν5) and ν6 has not been determined. Differences between the spectra of MoF6 and TcF6 are explained as a consequence of orbital degeneracy in the ground state of the latter, in analogy with similar differences in the 5d series.