Synthesis and X-Ray Structural Study of Magnesium (1,3-Propanediaminetetraacetato)nickelate(II) Octahydrate, Mg[Ni(1,3-pdta)]•H2O. Structural Parameters and Strain Analysis of [M(1,3-pdta)]<i>n</i>− Complexes in Relation to Their Octahedral Distortion

Abstract

Abstract The hexadentate complex Mg[Ni(1,3-pdta)]•H2O (1,3-pdta = 1,3-propanediaminetetraacetate ion) was prepared and its structure established by X-ray crystallography. The complex salt crystallizes in the space group Pnna (# 52) of the orthorhombic crystal system with a = 13.251(2), b = 11.645(2), c = 13.818(3) Å and Z = 4. The Ni(II) ion is surrounded octahedrally by two nitrogen and four oxygen atoms of the ligand. The Mg cation is bonded octahedrally to six water molecules. Both complex ions utilize a two-fold symmetry axis that is present in the crystal. The conformations of the chelate rings were found to be envelope or twist for the glycinates and skew-boat for the six-membered diamine ring. A comparison of structures of hexadentate [M(1,3-pdta)]n− complexes shows an expected variation in their octahedral distortion depending on the central metal ion M. Some spectral characteristics of the complex studied have also been reported.