Isotypic Mn(II) and Fe(II) binuclear complexes of the ligand 5,6-bis­(pyridin-2-yl)-pyrazine-2,3-di­carb­oxy­lic acid

The title isotypic complexes, bis­[μ-5,6-bis­(pyridin-2-yl)pyrazine-2,3-di­carboxylato]-κ(4) N (1),O (2),N (6):O (3);κ(4) O (3):N (1),O (2),N (6)-bis­[di­aqua­manganese(II)] tetra­hydrate, [Mn(2)(C(16)H(8)N(4)O(4))(2)(H(2)O)(4)]·4H(2)O, (I), and bis­[μ-5,6-bis­(pyridin-2-yl)pyrazine-2,3-di­carboxyl­ato]-κ(4) N (1),O (2),N (6):O (3);κ(4) O (3):N (1),O (2),N (6)-bis­[di­aqua­iron(II)] tetrahydrate, [Fe(2)(C(16)H(8)N(4)O(4))(2)(H(2)O)(4)]·4H(2)O, (II), are, respectively, the mangan­ese(II) and iron(II) complexes of the ligand 5,6-bis­(pyridin-2-yl)-pyrazine-2,3-di­carb­oxy­lic acid. The complete mol­ecule of each complex is generated by inversion symmetry. Each metal ion is coordinated by a pyrazine N atom, a pyridine N atom, two carboxyl­ate O atoms, one of which is bridging, and two water O atoms. The metal atoms have MN(2)O(4) coordination geometries and the complexes have a cage-like structure. In the crystals of both compounds, the complexes are linked by O—H⋯O and O—H⋯N hydrogen bonds involving the coordinating water mol­ecules, forming chains along [100]. These chains are linked by O—H⋯O hydrogen bonds involving the non-coordinating water mol­ecules, forming layers parallel to (011). The layers are linked by pairs of C—H⋯O hydrogen bonds and offset π–π inter­actions, so forming a hydrogen-bonded three-dimensional framework.