Hochauflösende 31P-Festkörper-NMR bei 109,3 MHz an den Pentanatrium-catena-triphosphaten Na5P3O10-I,Na5P3O10-II und Na5P3O10 · 6 H2O

High-resolution Solid-state ³¹P NMR at 109.3 MHz of Penta-sodium Catena-triphosphates, Na₅P₃O₁₀-I, Na₅P₃O₁₀-II, and Na₅P₃O₁₀ · 6 H₂O Using high-resolution solid-state ³¹P n.m.r. exact values of the isotropic chemical shift, the chemical shift anisotropy, and the asymmetry parameter of the PO₄ units (end and middle groups) of the three penta-sodium catena-triphosphates Na₅P₃O₁₀-I, Na₅P₃O₁₀-II, and Na₅P₃O₁₀ · 6 H₂O have been determined. Although the geometries of the P₃O₁₀^5? anions of the three polycrystalline phases are not very different, the afore-mentioned NMR parameters show significant differences for each PO₄ tetrahedron. Starting from a semi-quantitative theory of the ³¹P chemical shift of phosphates the differences between the isotropic chemical shifts of the end and middle groups are rationalized in terms of differences of the electronegativities of the terminal and bridging oxygens. This interpretation differs from that given by Andrew et al. 3].