Preparation and crystal structure of the trans(O-5) isomer of magnesium(ethylenediamine-N,N,N '-triacetato-N '-3-propionato)cuprate(II) octahydrate, Mg[Cu(ed3ap)]center dot 8H(2)O. Stereochemistry of octahedral Cu(II)-EDTA-type complexes in relation to the structure of the ligand

The hexadentate complex trans(O-5)-Mg[Cu(ed3ap)]. 8H(2)O (1) (ed3ap = ethyl enediamine-N,N,N'- triacetate-N'-3-propionate (4-) ion) has been prepared a nd its structure established by X-ray crystallography. The complex crystall izes in space group Pna2(1) of the orthorhombic crystal system. The structu re converged to R = 0.076 for 2213 observed reflections. The Cu(II) ion is surrounded by two nitrogen and four oxygen atoms of the ligand, making an e longated rhombic octahedron (tetragonality, T = 0.859). The conformations o f the chelate rings of the complex anion were found to be an envelope (or t wist) for the five-membered rings and a distorted skew-boat (half-chair) fo r the G2 beta -alaninate ring. The extremely large total deviation observed for the R2 ring (-11 degrees) is not common for axially coordinated glycin ates in M-edta-type complexes. A comparison of the structures of octahedral Cu(II)-edta-type complexes shows an expected variation in their stereochem istry, depending on the structure of the ligand and the geometry of the com plex. Data for the electronic absorption and reflectance spectra are also r eported.