Abstract: The infrared spectra of three series of thirty-one kinds heteropoly compounds (2:18,1:11 and bis series) related to the Keggin structure e.g. NP₂W₁₈(N=(CH₃)₄N⁺,(C₂H₅),N⁺, (C₄H₉)₄N⁺), MP₂W₁₈ (M=Li⁺, Na⁺, Ag⁺, Cu²⁺); K_nZW₁₁ (Z=P, B, Ge, Si),MSiW₁₁(M=Mn,Zn,Cu,Co,Ni) and M(PW₁₁)₂(M=Ce,Pr,Nd,Sm,Eu,Gd,Tb,Ho,Yb),M (PMo₁₁)₂(M=La, Ce, Pr, Sm, Gd, Tb) have been compared. The vibrational regularity of oxygen-containing bonds in all heteropoly compounds has been deduced. The effects of countercations on the oxygen bonds of the heteropolyanion were discussed. The verical relationship of compounds related to the fifteen kinds were analysed. The results proved that 1:11 series of heteropoly compounds are octahadral weak-field ligands.

Key words: heteropoly compound, infrared spectrum