The stereochemistry of the nickel(II), cobalt(II), copper(II) and palladium(II) complexes of the tetradentate Schiff base derived from salicylaldehyde and isobutylenediamine

The ligand N,N′-bis(salicylidene)-1,1-(dimethyl)ethylenediamine (Sal₂-i-bn) and its complexes with divalent nickel, cobalt, copper and palladium have been synthesized for the first time. The magnetic properties of the complexes have been investigated between 310 and 80°K. The nickel and palladium complexes are diamagnetic. The cobalt complex is low-spin with a magnetic moment of 2·40 → 2·22 B.M. and the copper complex has a temperature independent magnetic moment of 1·81 B.M. Electron paramagnetic resonance spectra of the powders have been measured at room and at liquid air temperatures while the solution spectra of the complexes were studied at room temperature only. The magnetic moment of the copper complex agrees with that calculated from the paramagnetic resonance g₀ ≅ 2·09 at liquid air temperature.The molecular weights were determined by mass spectrometry and by osmometry. Both methods provide evidence for the monomeric nature of the complexes. The i.r., u.v. and visible spectra are very similar to those of other related complexes. The complexes in the solid state and in solution and presumably in the vapor state are square-planar.