catena-Poly[[bis(4-methylbenzoato-κ2 O:O′)lead(II)]-μ-nicotinamide-κ2 N 1:O]

In the title compound, [Pb(C8H7O2)2(C6H6N2O)]n, the PbII ion is coordinated by two 4-methylbenzoate (PMB) and one nicotinamide (NA) ligands while symmetry-related NA ligands bridge adjacent PbII ions, forming polymeric chains along the c axis. The carboxylate groups in the two PMB ions are twisted away from the attached benzene ring by 22.9 (2) and 4.6 (2)°. The two benzene rings of the PMB ions are oriented at a dihedral angle of 83.7 (1)°. In a polymeric chain, the NA ligands are linked to PMB ions through intramolecular N—H⋯O hydrogen bonds. In the crystal structure, adjacent polymeric chains interact via N—H⋯O and C—H⋯O hydrogen bonds, forming a two-dimensional network parallel to the bc plane.

In the title compound, [Pb(C 8 H 7 O 2 ) 2 (C 6 H 6 N 2 O)] n , the Pb II ion is coordinated by two 4-methylbenzoate (PMB) and one nicotinamide (NA) ligands while symmetry-related NA ligands bridge adjacent Pb II ions, forming polymeric chains along the c axis. The carboxylate groups in the two PMB ions are twisted away from the attached benzene ring by 22.9 (2) and 4.6 (2) . The two benzene rings of the PMB ions are oriented at a dihedral angle of 83.7 (1) . In a polymeric chain, the NA ligands are linked to PMB ions through intramolecular N-HÁ Á ÁO hydrogen bonds. In the crystal structure, adjacent polymeric chains interact via N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, forming a two-dimensional network parallel to the bc plane.

Comment
As a part of our ongoing investigation on transition metal complexes of nicotinamide (NA), one form of niacin (Krishnamachari, 1974), and/or the nicotinic acid derivative N,N-diethylnicotinamide (DENA), an important respiratory stimulant (Bigoli et al., 1972), the title compound was synthesized and its crystal structure is reported herein.
In the crystal structure of the title compound, each Pb II ion is coordinated by two 4-methylbenzoate (PMB) and one nicotinamide (NA) ligands ( Fig. 1), while symmetry related NA ligands bridge the Pb II ions forming polymeric chains along the c axis ( Fig. 2). The two PMB ions act as bidentate ligands, while the NA is monodentate ligand (Fig. 1) (Hökelek et al., 2009d) have also been reported. In (II), the two benzoate ions are coordinated to the Cd atom as bidentate ligands. In the other structures one of the benzoate ligands acts as a bidentate ligand, while the other is monodentate ligand.
In the crystal structure, N-H···O and C-H···O hydrogen bonds (Table 2) link adjacent chains into a two-dimensional network parallel to the bc plane (Fig.2).

Experimental
The title compound was prepared by the reaction of Pb(NO 3 ) 2 (1.656 g, 5 mmol) in H 2 O (50 ml) and nicotinamide (1.220 g, 10 mmol) in H 2 O (10 ml) with sodium 4-methylbenzoate (1.580 g, 10 mmol) in H 2 O (160 ml). The mixture was filtered and set aside to crystallize at ambient temperature for four weeks, giving colourless single crystals.
supplementary materials sup-2 Refinement Atoms H2A and H2B of the NH 2 group were located in a difference Fourier map and refined isotropically. The remaining H atoms were positioned geometrically with C-H = 0.93 and 0.96 Å for aromatic and methyl H atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = xU eq (C), where x = 1.5 for methyl H and x = 1.2 for aromatic H atoms. One low angle reflection (100) was partially obscured by the beam stop and was omitted from the refinement. The highest peak and deepest hole are located 0.86 and 0.68 Å, respectively, from Pb1.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.