Acta Crystallographica Section B

Structural Science

Volume 52, Part 6 (December 1996)

research papers

Acta Cryst. (1996). B52, 982-988 [ doi:10.1107/S0108768196006829 ]

Ab initio powder structure determination and thermal behavior of a new lead(II) phenylphosphonate, Pb(O₃PC₆H₅)

A. Cabeza, M. A. G. Aranda, M. Martinez-Lara, S. Bruque and J. Sanz

Abstract: The crystal structure of Pb(O₃PC₆H₅) has been solved from X-ray powder diffraction data. Crystal data: triclinic, a = 13.6907 (5), b = 9.3327 (4), c = 7.0432 Å, [alpha] = 106.188 (3), = 94.927, = 96.977°, V = 851.04 (8) Å³, space group P ${\bar 1}$ and Z = 4. Initial positional parameters for Pb atoms were obtained from direct methods using 556 structure factors in the 2 range 9-63°. All remaining non-H atoms were located from successive difference-Fourier maps. The final agreement factors were R_wp = 0.055, R_p = 0.042 and R_F = 0.017. There are 22 atoms in the asymmetric part of the unit cell and 66 positional parameters have been refined with the help of soft constraints. The lead coordination environment is irregular due to a marked inert pair effect. The three-dimensional structure of this organic inorganic compound is layered with inorganic layers built up from CPO₃ tetrahedra and PbO₆ units. ³¹P MAS and CP-MAS (cross-polarization magic angle spinning) NMR studies have been carried out to confirm the triclinic symmetry with two independent structural units. In optimum conditions two ³¹P resonance signals are observed, indicating that there are two crystallographically independent P atoms with closely similar environments. The thermal behavior of this material has been studied and the thermal decomposition products identified.