Metal-metal and metal-ligand vibrational interaction in compounds of the Fe3EE '(CO)(9) (E, E ' = S, Se, Te) series and the low-frequency vibrational spectra of Co2FeS(CO)(9) and Os3S2(CO)(9)

The infrared and Raman spectra of the title compounds in the ca. 400-150 cm-1 region are reported. For the first time, detailed assignments are given for all of the features in this region for the first series of compounds. An attempt is made to extend to all of the modes the plastic cluster model of vibrational analysis, which is normally applied only to ν(M-M) vibrations. While mixing occurs between ν(Fe-Fe) and ν(Fe-E), species containing Te posed particular problems; the reasons for this are discussed and give new insights into the plastic cluster model itself.