According to the previous single-crystal (\mathrm{X})-ray structure determination the cyclotetraphosphate (\mathrm{NaLi}\left[\mathrm{NH}{3}-\left(\mathrm{CH}{2}\right){2}-\mathrm{NH}{3}\right] \mathrm{P}{4} \mathrm{O}{12}). (3 \mathrm{H}{2} \mathrm{O}) belongs to the (\operatorname{Pcca}\left(D{2 h}^{8}\right.) ) space group (M. Bdiri and A. Jonini, J. Solid State Chem. 83, 350 (1989)); there are four anions per unit cell at a (C_{2}) symmetry site. A vibrational spectroscopy is expected to give real information about the geometry of the (\mathrm{P}{4} \mathrm{O}{12}) group since its symmetry determines the number of normal vibration modes and their IR and Raman activities. According to the IR spectrum and a theoretical group analysis, symmetry of the ring anion (\mathrm{P}{4} \mathrm{O}{12}^{4-}) is found to be idealized from (C_{2}) to (C_{2 v}) symmetry site. An assignment of observed bands at room temperature is proposed. Thermodynamic parameters of dehydration, (\Delta H) and (E_{\mathrm{a}}), are determined by differential scanning calorimetry (DSC). Experimental NMR absorption lineshapes, for ({ }^{1} \mathrm{H},{ }^{31} \mathrm{P}), and ({ }^{\prime} \mathrm{Li}) nuclei in the solid state, at temperatures between 170 and (300 \mathrm{~K}), have becn carefully examined. Analysis of ' (\mathrm{H}) data indicates the rigid character of (\mathrm{CH}{2}) groups and the reorientation motion of proton in (\mathrm{H}{2} \mathrm{O}) and (\mathrm{NH}_{3}). Analysis of static and MAS absorption lineshapes for the ({ }^{31} \mathrm{P}(I=1 / 2)) and ({ }^{7} \mathrm{Li}(I=3 / 2)) resonance in the title compound leads to two tetrahedral atomic sites for phosphorous and to one for lithium, in agreement with the (\mathrm{X})-ray crystallographic studies. The ({ }^{7} \mathrm{Li}) NMR spectrum obtained at low temperature suggests a static distribution so that only half of the Li general positions is occupied. D 1994 Academic Press. Inc.