The preparation and properties of nickel in the oxidation state (III)

Abstract

Several new series of nickel(III) compounds containing diamine ligands have been prepared and investigated by physical techniques. The nickel(III) ion is six coordinate in the diamine complexes. Various salts have been prepared and their magnetic properties have been studied over a wide range of temperatures. The magnetic moments of the diamine complexes are in the range of 1.8 - 2.2 B.M. at room temperature and indicate the presence of one unpaired electron and low spin nickel(HI). Some compounds show magnetic interactions and possibly have bridge or polymeric structures. The reflectance spectra of the ethylenediamine, of the propylenediamine and of the alkyl and dialkyl substituted ethylenediamine complexes provide evidence for tetragonally distorted octahedral nickel(IIl) complexes. The charge transfer bands shift to longer wavelengths, as the bonding becomes more covalent. The bonding becomes more covalent as the number of alkyl groups in the ligand molecule increases. E.s.r. spectra have also been measured for some compounds. The g-values splitting factors have been calculated, this gives information about the orbital degeneracy in the metal complexes. Low and high spin behaviour, cross-over situations and Jahn-Teller distortion in octahedral species have also been discussed. The infra-red spectra have been used to distinguish between coordinated and ionic species, and as a means for the differentiation of cis and trans isomers in the bis diamine complexes.