Synthesis, vibrational study, crystal structure and density functional calculations of [Ni(dien)(2)](2+) complexes. Configurational and conformational study of [M(dien)(2)](n+) complexes

Two new complexes containing the complex cation [Ni(dien)(2)](2+) (dien = d iethylenetriamine) have been synthesised [Ni(dien)(2)]CA . 2H(2)O (CA = chl oranilate) (1) and [Ni(dien)(2)][Ni(CN)(4)]. 2H(2)O (2). The structures of compounds have been determined by single crystal X-ray diffraction methods. In the cationic unit of compound 1, the ligand geometry around nickel(II) is nearly octahedral. Two chelating tridentate diethylenetriamine molecules with terminal amino groups in cis and secondary amino groups in trans posi tion define the s-fac geometry. The conformations of the two independent ch elate rings are enantiomeric with each other. The nickel atom of [Ni(dien)( 2)](2+) unit in compound 2 also shows a distorted octahedral environment, b ut the two tridentate dien molecules are coordinated meridionally. Crystall ographic observations of fused five-membered ring of bis(dien) complexes, r etrieved from Cambridge Structural Database, have been mapped and classifie d using principal component analysis. Several density functional calculatio ns of the geometry of the s-fac and mer isomers of the complex cation [Ni(d ien)(2)](2+) have been carried out, and the results have been compared to t he crystallographic data. (C) 1999 Elsevier Science S.A. All rights reserve d.