Investigation of the zinc(II) acetylacetonate/benzotriazole reaction system in the presence of bridging N,N′-ligands: Pentanuclear, enneanuclear and polymeric complexes

The reaction of Zn(acac)2 with btaH (1,2,3-benzotriazole) in dmf yielded the pentanuclear complex [Zn5(bta)6(acac)4(dmf)]·dmf (1·dmf). In the presence of pyrazine, the pentanuclear [Zn5(bta)6(acac)4(dmf)]·3.7dmf (2·3.7dmf) and enneanuclear [Zn9(bta)12(acac)6]·6dmf (3·6dmf) complexes were formed, whereas in the presence of 4,4′-bpy the 1D coordination polymer [Zn(acac)2(4,4′-bpy)]n (4) was isolated. The molecular structures of 1·dmf and 2·3.7dmf reveal that the [Zn5] clusters consist of four ZnII ions which span the corners of a tetrahedron and the fifth resides at its centre. The molecular structure of 3·6dmf reveals that the [Zn9] clusters consist of two corner sharing tetrahedra and the structure can be described as the addition of two [Zn5] clusters of 1·dmf and/or 2·3.7dmf followed by the simultaneous abstraction of [Zn(acac)2] and dmf molecules; this alternative was accomplished by recrystallization of 1·dmf from dmf which yielded 3·6dmf. Each of the μ3-κN:κN′:κN′′ benzotriazolate ligands in 1·dmf, 2·3.7dmf and 3·6dmf spans an edge of the tetrahedron. The molecular structure of 4 reveals mononuclear [Zn(acac)2] units bridged via 4,4′-bpy molecules to 1D coordination polymer. Characteristic IR bands of the four complexes are discussed in terms of the coordination modes of the ligands and known structures.

The reaction of Zn(acac)2 with btaH in dmf yields [Zn5(bta)6(acac)4(dmf)]·dmf (1·dmf). In the presence of pyrazine, [Zn5(bta)6(acac)4(dmf)]·3.7dmf (2·3.7dmf) and [Zn9(bta)12(acac)6]·6dmf (3·6dmf) are obtained, and in the presence of 4,4′-bpy the 1D coordination polymer [Zn(acac)2(4,4′-bpy)]n (4) is isolated. 3·6dmf can be alternatively prepared from dissolution of 1·dmf in dmf.Figure optionsDownload as PowerPoint slide