The crystal structure of a strontium(II) complex with pyrazine-2,6-dicarboxylate and water ligands

Crystals of catena-tetraqua{[hexaquabis(mu-pyrazine-2,6-dicarboxylato-O,O')distrontium(II)][tetraquabis-(mu-pyrazine-2,6-dicarboxylato-O,O')distrontium(II)]}trihydrate are triclinic, space group P (1) over bar. Two types of symmetry independent dimeric structural units, each composed of two Sr(II) ions, two ligand molecules and water molecules, are bridged by a pair of water molecules which simultaneously are coordinated to the metal ions in the adjacent dimers. In both types of the dimers the Sr(II) ions are bridged by two carboxylate oxygen atoms, each bidentate, donated by a different ligand. The metal ion is also coordinated by one hetero ring nitrogen atom, one carboxylate oxygen atom and five water molecules in one dimer and two water molecules in the other. Two of the water molecules attached to each Sr(II) ion are bridging the dimers into an infinite molecular ribbon. The coordination numbers of the Sr(II) ions in the first and second type dimers are nine and eight, respectively. Solvation water molecules, the coordinated water molecules and the carboxylate oxygen atoms take part in an extended system of hydrogen bonds.