Diaquabis(4-methylbenzoato-κO)bis(nicotinamide-κN 1)manganese(II)

In the mononuclear title complex, [Mn(C8H7O2)2(C6H6N2O)2(H2O)2], the MnII ion is located on a crystallographic inversion center. The asymmetric unit contains one 4-methylbenzoate anion, one nicotinamide (NA) ligand and one coordinated water molecule. The four O atoms in the equatorial plane around the MnII ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two pyridine N atoms of the NA ligands in the axial positions. The dihedral angle between the carboxylate group and the attached benzene ring is 9.01 (7)°, while the pyridine and benzene rings are oriented at a dihedral angle of 42.44 (5)°. In the crystal structure, intermolecular O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds, and O—H⋯π and C—H⋯π interactions link the molecules into a two-dimensional network parallel to (001).

In the mononuclear title complex, [Mn(C 8 H 7 O 2 ) 2 (C 6 H 6 N 2 O) 2 -(H 2 O) 2 ], the Mn II ion is located on a crystallographic inversion center. The asymmetric unit contains one 4-methylbenzoate anion, one nicotinamide (NA) ligand and one coordinated water molecule. The four O atoms in the equatorial plane around the Mn II ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two pyridine N atoms of the NA ligands in the axial positions. The dihedral angle between the carboxylate group and the attached benzene ring is 9.01 (7) , while the pyridine and benzene rings are oriented at a dihedral angle of 42.44 (5) . In the crystal structure, intermolecular O-HÁ Á ÁO, N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, and O-HÁ Á Á and C-HÁ Á Á interactions link the molecules into a two-dimensional network parallel to (001).

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, intermolecular O-H···O, N-H···O and C-H···O hydrogen bonds (Table 2) link the molecules into a two-dimensional network parallel to the (001). Weak O-H···π and C-H···π interactions involving the pyridine and benzene rings are also observed (Table 2).

Experimental
The title compound was prepared by the reaction of MnSO 4 .H 2 O (0.84 g, 5 mmol) in H 2 O (10 ml) and NA (1.22 g, 10 mmol) in H 2 O (10 ml) with sodium 4-methylbenzoate (1.58 g, 10 mmol) in H 2 O (150 ml). The mixture was filtered and set aside to crystallize at ambient temperature for one month, giving colourless single crystals.

Refinement
H atoms of the NH 2 group (H21 and H22) and water molecules (H41 and H42) were located in a difference Fourier map and refined isotropically; the water H atoms were refined with O-H and H···H distance restraints. The remaining H atoms supplementary materials sup-2 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. 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 operator:(') -x, -y, -z.