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

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, α = 106.188 (3), β = 94.927, γ = 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 2θ range 9–63°. All remaining non-H atoms were located from successive difference-Fourier maps. The final agreement factors were R wp = 0.055, Rp = 0.042 and RF = 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.