Investigation of organic condensed phoshates -: Synthesis and structural characterization by 31P MAS NMR and X-ray diffraction of the 3-phenylpropylamonium cyclohexaphosphate dihydrate

Preparation, crystal structure and infra-red absorption spectra are reported for a new organic salt of the cyclohexaphosphate, [C6H5 (CH2) NH3](6)P6O18 center dot 2H(2)O. The new compound crystallizes in the triclinic system (P (1) over bar space group) with Z = 2 and the following unit cell dimensions: a = 10.528(3), b = 19.183(2), c = 9.839(3) angstrom, alpha = 74.92(5), beta = 117.48(6) and gamma = 99.90(5)degrees. The structure was solved by using 6709 independent reflections down to R value of 0.039. The P6O186- ring anion exhibits I internal symmetry. Its main geometrical features are those commonly observed in the atomic arrangements of cyclohexaphosphates. The three dimensional cohesion of this atomic arrangement is maintained through H-bonds between organic cations, water molecules and the external oxygen atoms of the P6O18 ring. The H-bond interactions induce local distortions of the P6O186- ring leading to the existence of three different Is types of phosphate tetrahedra. Solid-state P-31 magic-angle-spinning nuclear magnetic resonance (MAS NMR), performed at 162 MHz shows three isotropic resonances at -19.8, -22.6 and -24.5 ppm, confirming the non-equivalence of the three PO4 groups. They are characterized by different chemical shift tensor parameters, which are in agreement with the local geometrical features of the tetrahedra. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.