Organic/inorganic composite materials: Synthesis and properties of one-dimensional polymeric haloplumbate(II) systems

In this paper we report the synthesis and the thermal, spectroscopic and electrical characterization of 1-D polymeric haloplumbates(II) of formula (A) [PbX3] (A=piperidinium (pdH), morpholinium (mpH) cation; X=Br, I for pdH and Cl, Br for mpH). For the morpholinium compounds we report also the structural analysis. The (mpH) [PbX3] (X=Cl, Br) complexes are isomorphous and crystallize in space group P212121. The unit cell dimensions are a=15.249(3), b=8.001(2), c=7.625(2) Å, V=930.3(4) Å3, Z=4 for (mpH) [PbCl3] and a=15.760(3), b=8.254(2), c=7.866(6) Å, V=1023.2(4) Å3, Z=4 for (mpH) [PbBr3]. The final R value is 0.0428 (Rw=0.0442) for (mpH) [PbCl3] and 0.0434 (Rw=0.0453) for (mpH) [PbBr3]. The structure consists of morpholinium cations and infinite polymeric anions [PbX3-]n; each lead atom is surrounded by six halogen atoms forming a strongly distorted octahedron; adjacent octahedra share faces to form 1-D endless chains in which two consecutive lead atoms are bridged by three halogen atoms. The distortion in the (PbX6) octahedra of (mpH) [PbX3] enables the metal ion to be involved in a semicoordinative bond with the oxygen atom of the morpholinium cation, which makes the lead(II) coordination 6 + 1. All the structures are tridimensionally built up by a network of intermolecular N-H⋯X bonds.