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

In the crystal structure of the polymeric title compound, {[Pb(C9H9O2)2(C6H6N2O)]·H2O}n, the six-coordinate PbII ion is chelated by two 4-ethylbenzoate (PEB) anions and is bridged by two nicotinamide (NA) ligands, forming a polymeric chain running along the b axis. The carboxylate groups of the PEB ions are twisted away from the attached benzene rings by 4.0 (6) and 13.3 (5)°. The two benzene rings of the PEB ions bonded to the same metal ion are oriented at a dihedral angle of 87.4 (3)°. In the polymeric chain, the NA ligand is linked to one of the carboxylate groups via N—H⋯O hydrogen bonding. In the crystal, adjacent polymeric chains interact via N—H⋯O and weak C—H⋯O hydrogen bonds; and the lattice water molecule links with the polymeric chains via N—H⋯O and O—H⋯O hydrogen bonding. π–π stacking between the benzene and the pyridine rings [centroid–centroid distance = 3.805 (5) Å] and weak C—H⋯π interactions are also observed in the crystal structure.

In the crystal structure of the polymeric title compound, {[Pb(C 9 H 9 O 2 ) 2 (C 6 H 6 N 2 O)]ÁH 2 O} n , the six-coordinate Pb II ion is chelated by two 4-ethylbenzoate (PEB) anions and is bridged by two nicotinamide (NA) ligands, forming a polymeric chain running along the b axis. The carboxylate groups of the PEB ions are twisted away from the attached benzene rings by 4.0 (6) and 13.3 (5) . The two benzene rings of the PEB ions bonded to the same metal ion are oriented at a dihedral angle of 87.4 (3) . In the polymeric chain, the NA ligand is linked to one of the carboxylate groups via N-HÁ Á ÁO hydrogen bonding. In the crystal, adjacent polymeric chains interact via N-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds; and the lattice water molecule links with the polymeric chains via N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonding.stacking between the benzene and the pyridine rings [centroid-centroid distance = 3.805 (5) Å ] and weak C-HÁ Á Á interactions are also observed in the crystal structure.

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-ethylbenzoate (PEB) and one nicotinamide (NA) ligands ( Fig. 1), while symmetry related NA ligands bridge the Pb II ions forming polymeric chains along the b axis (Fig. 2). The two PEB ions act as bidentate ligands, while the NA is monodentate ligand (Fig. 1) [Pb(C 8 H 7 O 2 ) 2 (C 6 H 6 N 2 O)] n , (VII) (Hökelek et al., 2010), have also been reported. In (II) and (VII), the two benzoate ions are coordinated to the Cd and Pb atoms, respectively, as bidentate ligands. In the other structures one of the benzoate ligands acts as a bidentate ligand, while the other is monodentate ligand.
The title compound was prepared by the reaction of Pb(NO 3 ) 2 (1.656 g, 5 mmol) in H 2 O (100 ml) and nicotinamide (1.220 g, 10 mmol) in H 2 O (50 ml) with sodium 4-ethylbenzoate (1.720 g, 10 mmol) in H 2 O (100 ml). The mixture was filtered and set aside to crystallize at ambient temperature for three weeks, giving colorless single crystals.

Refinement
Atoms H2A and H2B (for NH 2 ) and H61 and H62 (for H 2 O) were located in a difference Fourier map and refined isotropically. The C-bound H-atoms were positioned geometrically with C-H = 0.93, 0.97 and 0.96 Å, for aromatic, methylene and methyl H-atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = k × U eq (C), where k = 1.5 for methyl H-atoms and k = 1.2 for all other H-atoms. The highest peak and deepest hole are located 0.94 and 0.90 Å, respectively, from Pb1. Fig. 1. The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Primed atoms are generated by the symmetry operators: (') x, 2 -y, z, ('') x, 1 -y, z. Dashed lines indicate the N-H···O hydrogen-bondings. catena-Poly [[[bis(4-ethylbenzoato-κ

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.