Investigation of organic condensed phoshates

Preparation, crystal structure and infra‐red absorption spectra are reported for a new organic salt of the cyclohexaphosphate, [C 6 H 5 (CH 2 ) 3 NH 3 ] 6 P 6 O 18 · 2 H 2 O. The new compound crystallizes in the triclinic system (P $\bar 1$ space group) with Z = 2 and the following unit cell dimensions: a = 10.528(3), b = 19.183(2), c = 9.839(3) Å, α = 74.92(5), β = 117.48(6) and γ = 99.90(5)°. The structure was solved by using 6709 independent reflections down to R value of 0.039. The ring anion exhibits $\bar 1$ 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 P 6 O 18 –6 ring. The H‐bond interactions induce local distortions of the ring leading to the existence of three different types of phosphate tetrahedra. Solid‐state 31 P 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 PO 4 groups. They are characterized by different chemical shift tensor parameters, which are in agreement with the local geometrical features of the tetrahedra. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)