Syntheses and crystal structures of catena -poly[[diiodidozinc(II)]-μ-2,3-dimethylpyrazine-κ 2 N 1 : N 4 ] and aqua(2,3-dimethylpyrazine-κ N )diiodidozinc(II)–2,3-dimethylpyrazine–water (2/1/1)

The reaction of zinc iodide with 2,3-dimethylpyrazine (C 6 H 8 N 2 ) in ethanol leads to the formation of [ZnI 2 (C 6 H 8 N 2 )] n ( 1 ), that according to powder X-ray diffraction was obtained as a pure phase. When the same reaction was performed in a mixture of ethanol and water as solvent, a few crystals of [ZnI 2 (C 6 H 8 N 2 )(H 2 O)]·0.5C 6 H 8 N 2 ·0.5H 2 O ( 2 ) were serendipitiously obtained in a mixture with compound 1 as the major phase. The asymmetric unit of 1 consists of one zinc cation, two crystallographically independent iodide anions and one 2,3-dimethylpyrazine ligand all of them located in general positions. In the extended structure, the Zn cations are tetrahedrally coordinated by two iodide anions and two symmetry-related 2,3-dimethylpyrazine ligands and are linked by bridging 2,3-dimethylpyrazine ligands into helical chains that proceed along the c -axis direction in the uncommon space group P 3 2 . Within these chains, intrachain C—H...I hydrogen bonding is observed. The asymmetric unit of 2 consists of two crystallographically independent [ZnI 2 (C 6 H 8 N 2 )(H 2 O)] complexes as well as one water molecule and one none-coordinating 2,3-dimethylpyrazine ligand. In the complexes, the Zn cations are tetrahedrally coordinated by two iodide anions, one 2,3-dimethylpyrazine ligand and one water molecule. These complexes are packed in such a way that cavities are formed, which are filled by water and 2,3-dimethylpyrazine solvate molecules that are hydrogen bonded to each other.