Synthesis of coordination compounds via dehalogenation of zinc bromoacetate in presence of some amines

The dehalogenation reactions of pure zinc bromoacetate and its mixtures with hexamethylenetetramine, 2,2′-bipyridine, 1,10-phenanthroline were studied in water solutions. Due to the decomposition of hexamethylenetetramine during reaction, the cadmium bromoacetate–hexamethylenetetramine system was also studied. The four new coordination compounds, catena-[bis(μ2-α-hydroxyacetato-κ3O1,O2:O1′)-zinc], catena[μ2-1-(8-carboxylateethyl)-1,3,5,7-tetra-aza-adamantan-1-ium-N,O′]-dibromo-cadmium, dibromo-(2,2′-bipyridine-N,N′)-zinc, dibromo-(1,10-phenanthroline-N,N′)-zinc were synthesised and characterised by elemental and thermal analysis, IR and UV–vis spectroscopy, and X-ray crystallography. All compounds are air stable and well soluble in water. The zinc hydroxyacetate creates two-dimensional 4-c uninodal net. The zinc atoms are four and six coordinated and the cadmium atom is five coordinated. The coordination polyhedra of central atoms can be described as octahedron and trapezoidal pyramid for Zn and Cd polymers, respectively, and as trigonal pyramid for ZnBr2 complexes. The bond valences considerations show that the chelating amines are bonded almost two times stronger to the central atoms than the chelating carboxylate groups. In the structures of polymeric compounds exist O–H⋯O, C–H⋯O, C–H⋯N and C–H⋯Br hydrogen bonds. The IR spectra show typical vibrations for chelating amine molecules. The thermal decomposition of studied compounds proceeds via multiple steps with gradual evolution of ligands.