Crystallographic and computational investigation of nitrate salts of nickel(II) ethylenediamine complexes

Two nitrate salts of Ni(II) and ethylenediamine (en), trans-diaquabis(ethylenediamine)nickel(II) nitrate (1) and A-delta delta delta-tris(ethylenediamine)nickel(II) nitrate (2), were investigated crystallographically and the nature of the intermolecular interactions in 2 were explored using the quantum theory of atoms in molecules (QTAIM) of Bader from a X3LYP/6-31 + G(d) single point calculation on a portion of the crystal structure. In 1 the two chelate rings, related by inversion, are in the lambda and delta conformations, respectively. The metal complex cations are hydrogen bonded to the axial H2O ligands and the amino protons and pack in ribbons along the crystallographic a axis. In 2, which is the enantiometric form of the known Delta-lambda lambda lambda-tris(ethylenediamine)nickel(II) nitrate, each nitrate is in a distorted tetrahedral site defined by [Ni(en)(3)](2+) cations. QTAIM analysis indicates that NO3- forms O center dot center dot center dot center dot HN hydrogen bonds to amino groups of en, as well as a O center dot center dot center dot center dot HC hydrogen bond to one of the methylene groups of the ligand. In addition, neighbouring [Ni(en)(3)](2+) ions are connected by a weak H-H bond between en methylene groups. (C) 2010 Elsevier B.V. All rights reserved.