Metal–ligand bonding parameters and magnetic properties of some previously reported tetragonal nickel(II) complexes

Abstract

The variation of the magnetic moments of the complexes [Ni(py)₄X₂](py = pyridine), [Ni(Hpz)₄X₂](Hpz = pyrazole), [Ni(mim)₄X]X (mim = 2-methylimidazole, X = Cl or Br), and [Ni(en)₂(NO₂)₂](en = 1,2-diaminoethane) over the temperature range 300–4.3 K is reported. The magnetic behaviour, which is strongly influenced by the zero-field splitting of the ground state of each complex, has been interpreted in conjunction with the previously reported d—d transition energies in terms of angular overlap and metal–ligand σ- and π-bonding parameters. Though some anomalies are observed, notably the low values of the halide interactions in the pyrazole complexes and the zero-field splittings of the bromo complexes, the parameters which best reproduce the experimental data generally compare favourably with those derived in other studies on similar systems, and with the expectations of simple theory.