Diaquabis(pyrazine-2-carboxylato-κ2 N 1,O)manganese(II) dihydrate

In the title compound, [Mn(C5H3N2O2)2(H2O)2]·2H2O, the MnII atom, lying on an inversion centre, has a distorted octahedral environment and the molecules are linked by O—H⋯O and N—H⋯O hydrogen bonds to form a three-dimensional supramolecular structure.

In the title compound, [Mn(C 5 H 3 N 2 O 2 ) 2 (H 2 O) 2 ]Á2H 2 O, the Mn II atom, lying on an inversion centre, has a distorted octahedral environment and the molecules are linked by O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds to form a threedimensional supramolecular structure.
Ptasiewicz-Bak et al. reported an orthorhombic manganese(II) dipyrazinate dihydrate complex (space group Fdd2), in which the coordination polyhedron around the Mn II atom is a distorted octahedron with cis positioned water molecules. The title complex is another monomeric complex of Mn II with the 2-pyrazinecarboxylic acid ligand, which is isostructrual to the cobalt(II) complex (Ptasiewicz-Bak et al., 1995).
The Mn II atom sits on an inversion center and the coordination geometry for the Mn II atom (Fig. 1) is distorted octahedral (Table 1). Each Mn II atom is axially coordinated by water molecules and consists of an equatorial plane of two oxygen donors and two nitrogen donors from two chelating 2-pyrazinecarboxylato group. As a consequence of the reaction the carboxylic  Table 2 for the geometric parameters describing these interactions.

Experimental
A mixture of manganese(II) chloride tetrahydrate, (0.4 mmol, 79.2 mg), pyrazine-2,3-dicarboxylic acid (0.8 mmol, 134.5 mg), and H 2 O (1.0 mol, 18.0 ml) in the molar ratio of 1: 2: 2500 was sealed in a 40 ml stainless steel reactor with Teflon liner and directly heated to 160 °C, kept at 160 °C for 72 h, and then directly cooled to the room temperature. Light-yellow block-shaped crystals of the title complex were collected by filtration and washed with ethanol (2×5 ml) for the structural analysis.

Refinement
All H atoms were initially located in difference Fourier maps and were treated isotropically in the riding-model approxim-  Fig. 1. The structure of the title compound and the atomic numbering scheme, with atom labels and 35% probability displacement ellipsoids for non-H atoms (small spheres for the H atoms).