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

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 Angstrom, alpha = 106.188 (3), beta = 94.927, gamma = 96.977 degrees, V = 851.04(8) Angstrom(3), space group <P(1)over bar> and Z = 4. Initial positional parameters for Pb atoms were obtained from direct methods using 556 structure factors in the 28 range 9-63 degrees. All remaining non-II 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. P-31 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 P-31 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.