Abstract
Four new bromidozinc(II) coordination compounds with pyrimidine as a ligand were prepared, either in solution or by thermal decomposition reactions, and the thermal reactivity and thermodynamic stability of these compounds were investigated. These results are compared with those for the corresponding ZnI~2~(pyrimidine) compounds. The ligand‐rich 1:2 compound dibromidobis(pyrimidine‐N)zinc(II) (I) crystallizes in the monoclinic space group __P__2~1~/n. In this structure the zinc atoms are coordinated by two bromido ligands and two pyrimidine ligands within distorted tetrahedra. On heating, compound I is transformed into the ligand‐deficient 2:3 intermediate bis(dibromido)bis(pyrimidine‐N)(μ~2~‐pyrimidine‐N,N′)dizinc(II) (II), which crystallizes in the monoclinic space group __C__2/c. The crystal structure consists of two ZnBr~2~(pyrimidine) subunits, which are connected by an additional pyrimidine ligand through μ‐N,N′ coordination. Thermal decomposition of compound II leads to the formation of the ligand‐deficient 1:1 compound dibromido(μ~2~‐pyrimidine‐N,N′)zinc(II) (III), which crystallizes in the orthorhombic space group Pmma. In compound III, the zinc atoms are coordinated by four bromine atoms and two pyrimidine ligands within distorted octahedra. The ZnBr~2~ units are connected through common edges into chains, which are linked by the pyrimidine ligands into layers. On heating, compound III is transformed into the ligand‐deficient 2:1 compound (ZnBr~2~)~2~(pyrimidine) (IV), which decomposes to give ZnBr~2~. Solvent‐mediated conversion experiments in solution show that not all of the compounds can be prepared by treating ZnBr~2~ and pyrimidine in the molar ratio given by the formula of the final product. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)