A new lead diphosphonate, Pb-2(O3PCH2C6H4CH2PO3) was hydrothermally synthesized from tetraethyl alpha,alpha'-p-xylenediphosphonate and Pb(NO3)(2). The structure was solved and refined using X-ray powder diffraction data. It crystallizes in the monoclinic space group P2(1)/c, with a = 467.84(2), b = 2007.98(9), c = 639.10(2) pm, beta = 101.020(3)degrees, V = 589.31(4) 10(6) pm, Z = 2 wR(p) = 0.034, R-p = 0.0277 R(F)2 = 0.061, R-F = 0.036. The structure is built from corner-linked [PbO4] polyhedra, containing a lone pair of electrons. These polyhedra are connected to layers by phosphonate groups, RPO32- and through the organic diphosphonic acid to a three-dimensional structure. Thermogravimetric as well as IR spectroscopic studies are also presented. (C) 2003 Elsevier Science (USA). All rights reserved.