Some observations on triazene 1-oxide complexes of bivalent nickel, palladium and copper

Several triazene 1-oxide chelates of nickel(II), palladium(II) and copper(II) are described. These complexes show crystal field bands at unusually low energies. The nickel(II) complexes are uniformly diamagnetic in the solid state. However, in the solution (benzene, chloroform) phase a slight paramagnetism develops in all nickel(II) complexes except those having a non-coordinating substituent in the ortho position of the benzene ring. The pmr spectra of the partially paramagnetic complexes show small contact shifts. These shifts can be qualitatively interpreted on the basis of the existence of unpaired spin density in a π-orbital. The palladium(II) complexes having a substituent in the ortho position of the benzene ring exist in isomeric forms. In one case the isomeric forms have abeen separated by chromatography on a column of alumina. The copper(II) complexes have normal magnetic moments