catena-Poly[[lead(II)-bis(μ2-quinolin-8-olato)-κ3 N,O:O;κ3 O:N,O] N,N-dimethylformamide hemisolvate]

The asymmetric unit of the title compound, {[Pb(C9H6NO)2]·0.5C3H7NO}n, comprises Pb(quinolate)2 and half a dimethylformamide molecule (which is disordered about a centre of inversion). The quinolate ligands N,O-chelate to a PbII ion and simultaneously bridge a neighbouring PbII ion to form a polymeric chain along [100] comprising Pb-linked Pb2O2 distorted rhombi. These chains pack to form a square grid, with the channels thus defined occupied by the disordered solvent molecules.

The asymmetric unit of the title compound, {[Pb(C 9 H 6 NO) 2 ]Á0.5C 3 H 7 NO} n , comprises Pb(quinolate) 2 and half a dimethylformamide molecule (which is disordered about a centre of inversion). The quinolate ligands N,Ochelate to a Pb II ion and simultaneously bridge a neighbouring Pb II ion to form a polymeric chain along [100] comprising Pblinked Pb 2 O 2 distorted rhombi. These chains pack to form a square grid, with the channels thus defined occupied by the disordered solvent molecules.

Related literature
For a recent Pb II mixed quinolate carboxylate structure, see: Ghaemi et al. (2012). For the structure of the solvent-free Pb II quinolate, see: Zhu et al. (2005).
The asymmetric unit of (I) comprises Pb(quinolate) 2 and half a solvent DMF molecule (this is disordered over a centre It is noted that the O3 and O3' atoms (each with a 0.25 site occupancy factor) of disordered DMF molecule approach the Pb II at distances 2.903 (12) and 2.977 (12) Å, respectively. These are not trans to the axial N atom forming angles of approximately 140°. If one of the DMF-O atoms is included as part of the coordination sphere, the coordination geometry would be described as ψ-dodecahedral.
In the crystal packing, the polymeric chains pack into a square grid which defines channels in which reside the disordered solvent molecules, Fig. 3. The aforementioned weak Pb···O(DMF) interactions serve to connect the polymeric chains into a layer in the ab plane.

Experimental
The title complex was obtained by the following method. 8-Hydroxyquinoline (0.036 g, 0.25 mmol) was added to an aqueous solution (5 ml) of Pb(NO 3 ) 2 (0.082 g, 0.25 mmol). The mixture was stirred for 15 min. Then to this solution, a DMF solution (5 ml) of maleic acid (0.029 g, 0.25 mmol) which with triethylamine neutralized was added slowly at room temperature. This mixture was filtered. After keeping the filtrate in air, crystals were formed at the bottom of the vessel on slow evaporation of the solvents at room temperature. M.p. 590 K. Yield: 65%.

Refinement
Carbon-bound H atoms were placed in calculated positions [C-H 0.95-0.98 Å, U iso (H) 1.2-1.5U eq (C)] and were included in the refinement in the riding model approximation.
The DMF molecule is disordered over two sites over a centre of inversion. The C-O distances were restrained to 1.25 (1) Å, the C carbonyl -N distances to 1.35 (1) Å and the C methyl -N distances to 1.45 (1) Å. Each component was restrained supplementary materials sup-2 to lie on a plane; the anisotropic displacement parameters of the primed atoms were set to those of the unprimed ones, and they were tightly restrained to be nearly isotropic.
The final difference Fourier map had a peak of 1.23 Å -3 at 1.10 Å from the Pb atom. Fig. 1. The asymmetric unit of (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level.  Crystal data [Pb(C 9