Synthesis and X-ray structural study of magnesium (1,3-propanediaminetetraacetato)cuprate(II) octahydrate, Mg[Cu(1,3-pdta)] center dot 8H(2)O. Stereochemistry of hexadentate copper(II)-edta-type complexes in relation to the structure of the ligand

The hexadentate complex Mg[Cu(1,3-pdta)]. 8H(2)O (1) (where 1,3-pdta repres ents the 1,3-propanediaminetetraacetate ion) has been prepared and isolated and its structure established by X-ray crystallography. The structure conv erged to R = 0.030 for 1537 observed reflections. The Cu(II) ion is surroun ded by two nitrogen atoms and four oxygen atoms of the ligand, making a tet ragonally elongated octahedron (T=0.868). The Mg cation is bonded octahedra lly to six water molecules. Both complex ions utilize a two-fold symmetry a xis that is present in the crystal. The conformations of the chelate rings were found to be envelope for the glycinates and skew-boat for the six-memb ered diamine (T) ring. Comparison of the structures of the hexadentate copp er(II)-edta-type complexes shows an expected variation in their stereochemi stry, depending on the structure of the ligand. Infrared (carboxylate regio n) and electronic absorption spectra are also given. (C) 2000 Elsevier Scie nce Ltd All rights reserved.