Abstract: The adducts between heteropoly tungstic and molybdic acids and their salts and N, N-dimethyl formamide (DMF) were synthesized and characterized by IR, Raman, UV-VS, ¹Hand ¹³C NMRspectrometry, TG-DTAthermal analysis and X-ray diffraction analysis. The IRand NMRspectra showed that the coordinating atom of DMFwas oxygen of C = Obond, and the shift of C = Ovibration frequency might be considered as the criterion of M-Obond strength. The organic ligands do not coordinate with heteropoly anions, but with protons in heteropoly acids by hydrogen-bond, or metal cations in heteropoly tungstates and molybdates by coordination bond. The X-ray diffraction analysis showed that the DMFadduct of CaPWis monoclinic, and its space group is C⁵_2k-P2₁/n, with unit cell parameters; a = 12. 927(7) Å, 6=33.850(9) Å, c=17. 903(13) Å, B=106.78(4), V=7500. 37 ų.The figure of merit is F=M9(0. 016, 38).

Key words: Heteropoly tungstic and molybdic acid, Heteropoly tungstate and molybdate, N, N- Dimethyl formamide, Adduction