DONALD E. IRISH and RODERICK V. THORPE. Can. J. Chem. 53, 1414Chem. 53, (1975. Raman spectra of aqueous solutions containing CdZ+ and NO2-clearly reveal the presence of solvated nitrite ion and of complexes. A band at 861 cm-I is characteristic of the latter. The free nitrite concentration was measured from the intensity of the 817 cm-I line and the average ligand number was evaluated for solutions with composition prescribed by the moleratio method. Four cumulative formation constants were deduced: Dl = 61.6; pz = 993; p3 = 2390; p4 = 1899. Evidence that nitrite chelates Cd2+ through the two oxygen atoms is presented. The diagnostic spectral evidence consists of a high intensity, high frequency deformation mode and low intensity N-0 stretching Raman bands with frequencies almost identical to those of the solvated nitrite ion. Data are also presented for solid Cd(N0,)2 and K,-2Cd(NOz), (X = 3, 4, 5). Chem. 53,1414Chem. 53, (1975. Les spectres Raman de solutions aqueuses contenant du Cd2+ et du NO,-montrent clairement la presence d'ions nitrites solvates de m&me que la presence de complexes. Une bande a 861 cm-' est caracteristique de ces derniers. On a mesure la concentration en nitrite libre a partir de I'intensite de la bande a 817 cm-I et on a &value le nombre moyen de ligands pour des solutions ayant une composition prescrite par la methode des rapports molaires. On a diduit quatre constantes de formation cumulative: p1 = 61.6; p, = 993; p3 = 2390; p4 = 1899. On prbente des rksultats indiquant que le nitrite se chelate au Cd2+ par I'intermtdiaire des deux atomes d'oxygkne. Cette conclusion, basee sur les spectres, est obtenue en se basant sur un mode de deformation de haute intensite et de haute frequence et sur des bandes dY6longa-tion N-0 en spectroscopie Raman qui sont de basse intensite et qui ont des frequences pratiquement identiques a celles des ions nitrites solvat6s. On presente aussi des donnees pour le Cd(NO,), et le K,-,Cd(N02), (x = 3, 4, 5) a 1'6tat solide.[Traduit par le journal] Raman spectra of aqueous solutions of alkali tended to a study of the species formed between metal nitrites only exhibit lines characteristic of Cd2+ and NO2-in water. In addition to a deterthe solvated nitrite ion; no lines characteristic of mination of the stability constants for four monothe nitrite ion bonded to a cation are observed nuclear complexes, structures of the species are despite the very high solubilities of these salts (1). proposed consistent with the parameters of the In contrast, divalent cations such as Ni2+, Mg2+, vibrational lines. Spectra of related solids are Ca2+. and Zn2+ form com~lexes with nitrite ion also re~orted. and ama an lines attributaile to both the bound Experimental and free forms of the anion are observed (2, 3). From measurement of the relative integrated in-p r~~a~~~~~~~r d