The Resonance-Ramsn and Infrared spectra of series of cluster compounds, [{CO)4M}xM'S4]^2^-[x=1 or 2; M=Mo(0) or W(0); M'=Mo(VI) or W(VI)] have been investigated. Besides the characteristic frequencies of ^νco, ^νM(VI)-s(b), ^νc-o, ^νM(VI)-s(t), ^νM(0)-c, and ^δM(0)-c-o were assigned. The assignment of ^νM(0)-s(b) and ^νM(0)-M(VI) were emphatically discussed. The relationship between Δν[^νM(VI)-s(b) ─^ν ,(0)-s(b)] and M(0)→M(VI) charge transfer were demonstrated by their IR spectra. The results from the studies on the Resonance-Raman spectra indicate that there evidently are couplings between the S(b)→ Mo(0) charge transfer and M(0)→Mo(VI) charge transfer in [(CO)4MS2WS2]^2^- and [(CO)4MoS2MoS2Mo(CO)4]^2^-, between S(b)→W(VI) and M(0)→W(VI) charge transfer and between S(t)→W(VI) and M(0)→W(VI) charge transfer in [(CO)4MS2WS2]^2^-. T his implies that the extensive electron delocalization exists in these cluster compounds with mixed-valence metal atoms and the electron delocalization in the dinuclear clusters is stronger than that in the trinuclear clusters.

Key words: INFRARED SPECTROPHOTOMETRY, MOLYBDENUM COMPLEX, CARBONYL COMPOUNDS, SULFIDE, TETRAETHYLAMMONIUM COMPOUNDS, TUNGSTEN COMPLEX, RAMAN SPECTROMETRY