X-ray structure analysis of diaquobis (2-pyrazinecarboxylato) manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes

The crystal structures of diaquobis (2-pyrazinecarboxylato) manganese(II) and isostructural diaquobis(2-pyrazinecarboxylato) cobalt(II), nickel(II), copper(II) and zinc(II) have been determined using single crystal X-ray intensity data. The former complex is orthorhombic (space group Fdd2), with unit cell dimensions a = 15.418(1), b = 23.537(3) Angstrom, c = 6.940(4) Angstrom, the latter compounds are monoclinic (space group P2(1)/c) with unit cell dimensions a = 5.241(1) Angstrom, b = 11.108(1) Angstrom, c = 10.286(2) Angstrom, beta = 99.54(1) deg for the cobalt complex. All structures show monomeric molecules consisting of a metal ion chelated by two oxygen atoms belonging to two monodentate carboxylic groups and two heteronitrogen atoms of two pyrazinic acid molecules and two water molecules. In the case of manganese dipyrazinate dihydrate the coordination polyhedron around the manganese ion is a distorted octahedron with the water molecules cis, while in the remaining compounds the octahedra are fairly regular with two water molecules above and below the plane defined by the metal ion and two pyrazinic acid molecules. The observed T-O and T-N (T-transition metal ion) distances are typical for complexes of the respective metals.