Syntheses and crystal structures of di­chlorido­bis(2,3-di­methyl­pyrazine-κN)zinc(II) and catena-poly[[di­chlorido­zinc(II)]-μ-2,3-di­methyl­pyrazine-κ2N1:N4]

Abstract

The syntheses and crystal structures of two new ZnCl₂–2,3-di­methyl­pyrazine (C₆H₈N₂) coordination compounds with the composition ZnCl₂(C₆H₈N₂)₂ (1) and ZnCl₂((C₆H₈N₂) (2) are reported. Compound 1 consists of discrete complexes, whereas in compound 2 the Zn cations are linked by the 2,3-di­methyl­pyrazine ligands into helical [001] chains.

The reactions of zinc(II)chloride with 2,3-di­methyl­pyrazine (C₆H₈N₂) in different ratios in aceto­nitrile lead to the formation of [ZnCl₂(C₆H₈N₂)₂] (1) and [ZnCl₂(C₆H₈N₂)]_n (2). The asymmetric unit of 1 consists of one Zn cation located on a twofold rotation axis, one chloride anion and one 2,3-di­methyl­pyrazine ligand that occupy general positions. In compound 2 the asymmetric unit is built up of one zinc cation, two chloride anions and one 2,3-di­methyl­pyrazine ligand that are located in general positions in the uncommon trigonal space group P3₂. In compound 1, the Zn cations are tetra­hedrally coordinated by two chloride anions and two 2,3-di­methyl­pyrazine ligands forming discrete complexes. These complexes are arranged in columns that proceed along the c-axis direction. The Zn cations in 2 are also tetra­hedrally coordinated by two chloride anions and two 2,3-di­methyl­pyrazine ligands but linked via the bridging 2,3-di­methyl­pyrazine ligands into helical infinite chains that propagate along the c-axis direction. Powder X-ray diffraction measurements indicate that both compounds were obtained as pure crystalline phases.