Polymeric versus monomeric and tetrahedral versus octahedral coordination in zinc(ii) pyridine complexes

Abstract

The first one-dimensional chain polymers of the type [Zn(μ-Cl)₂py]_∞ (py⊕=⊕3,5-dichloropyridine and 3,5-dibromopyridine) were synthesized by reaction of the 3,5-dihalopyridines with ZnCl₂. In the resulting linear coordination polymer octahedral zinc(II) centres are linked in an edge-sharing fashion by halogen bridges in their pseudo-equatorial plane. In contrast to these findings the analogous reaction between ZnBr₂ and the 3,5-dihalopyridines results in the formation of mononuclear tetrahedral complexes. Both of the zinc dihalides react with 3,4,5-trichloropyridine with formation of isotypic molecular crystals which show relatively short halogen⋯halogen contacts; their projections along the [001] direction exhibit a remarkable similarity to those of the chain polymers. From ZnX₂ (X⊕=⊕Cl, Br) and 4,4′-bipyridyl (bpy) a zigzag chain coordination polymer of composition [ZnX₂(μ-bpy)]_∞ was obtained.