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Free keywords:
monothiophosphate; oxothiophosphates; solid state NMR (Na, P); X-ray powder diffractometry
Abstract:
Sodium monothiophosphate(V) Na3PO3S is dimorphic. The metastable high
temperature modification beta-Na3PO3S crystallizes hexagonal with a =
8.996(4) and c = 5.216(2) Angstrom. According to P-31 solid state NMR
experiments, alpha-Na3PO3S exhibits at 20 degreesC a
non-axial-symmetric environment for the phosphorus nuclei in contrast
to the results of the refined crystal structure. This discrepancy is
discussed assuming ordered and disordered structural models. However,
at 490 degreesC the chemical shift tensor of the phosphorus nuclei in
alpha-Na3PO3S is axial-symmetric. So, the distortion of the phosphorus
environment is abolished by the thermal motion of the atoms. The number
of crystallographically distinguishable positions for phosphorus and
for sodium in Na3PO2S2 and Na3POS3 can be confirmed in good agreement
with their crystal structures using solid state NMR spectroscopy.
