The hydrated potassium hemimagnesium dihydrogen pyrophosphate KMg0.5H2P2O7 H2O was synthesized. It crystallizes in the triclinic system, space group (n. 2), Z=2, with the following unit-cell parameters: a=6.8565(2) A°, b=7.3621(3) A°, c=7.6202(3) A°, alfa =81.044(2)°, beta=72.248(2)°, gamma=83.314(3)°, V=360.90(2) A°3. The structure was obtained by single-crystal X-ray diffractometry, and a full-matrix least-squares refinement based on F2 gave a final R index OF =0.0368 (wR=0.0975), utilizing 1446 observed reflections with I>2sigma(I). The crystal packing consists in a three-dimensional network made by layers parallel to ab plane of PO4 double tetrahedra and MgO6 octahedra, linked by hydrogen bonds, while K atoms form complex coordination within cavities between tetrahedra and octahedra. The dihydro-pyrophosphate anion (H2P2O7)2- shows bent eclipsed conformation and the Mg2+ ion lies on inversion center. No coincidences observed between most of infrared and Raman spectral bands confirmed the centrosymmetric structure of the title compound; the vibrational spectra point to a bent POP bridge angle.
Synthesis, X-ray crystal structure and vibrational spectroscopy of the acidic pyrophosphate KMg0.5H2P2O7 H2O
F Capitelli;G Mattei;
2003
Abstract
The hydrated potassium hemimagnesium dihydrogen pyrophosphate KMg0.5H2P2O7 H2O was synthesized. It crystallizes in the triclinic system, space group (n. 2), Z=2, with the following unit-cell parameters: a=6.8565(2) A°, b=7.3621(3) A°, c=7.6202(3) A°, alfa =81.044(2)°, beta=72.248(2)°, gamma=83.314(3)°, V=360.90(2) A°3. The structure was obtained by single-crystal X-ray diffractometry, and a full-matrix least-squares refinement based on F2 gave a final R index OF =0.0368 (wR=0.0975), utilizing 1446 observed reflections with I>2sigma(I). The crystal packing consists in a three-dimensional network made by layers parallel to ab plane of PO4 double tetrahedra and MgO6 octahedra, linked by hydrogen bonds, while K atoms form complex coordination within cavities between tetrahedra and octahedra. The dihydro-pyrophosphate anion (H2P2O7)2- shows bent eclipsed conformation and the Mg2+ ion lies on inversion center. No coincidences observed between most of infrared and Raman spectral bands confirmed the centrosymmetric structure of the title compound; the vibrational spectra point to a bent POP bridge angle.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
