Exchange interactions in copper(II)-nickel(II) and nickel(II)-nickel(II) pairs in tetra(.mu.-benzoato-O,O')bis(quinoline)dimetal(II) complexes

Tetra(pbenzoat0-O,O')bis(quinoline)dinickel(II) was prepared and found to be isomorphous to the copper(I1) and cobalt(I1) complexes previously described. The structure is similar to that of the copper acetate dimer, and the magnetic susceptibility data show an antiferromagnetic coupling, J = -250 cm-l. By doping the copper(I1) derivative with low concentrations of nickel(II), nickel(I1)-copper(I1) pairs are obtained, which yield ESR spectra at 4.2 K. They can be interpreted by using an effective spin Hamiltonian with S = yielding g, = 4.51, g2 = 3.44, g, = 2.24. A ferromagnetic coupling between the two metal ions is suggested. The implications on the nature of the exchange interactions in the copper acetate type dimers are discussed