Abstract:
In 1932 Van Vleck (Van Vleck, J. H., The Theory of Electric and Magnetic Susceptibilities.) drew attention to the fact that complexes of the platinum and palladium series seemed, from the meagre data then available, to conform neither to the theory of free ions (with both spin and orbit contributing) so successful for compounds of the rare earths, nor to the Bose-Stoner "spin only" theory, which satisfactorarily described the behaviour of many compounds of elements of the iron series. The magnetic properties of the rare earths with the incomplete 4f shell responsible for paramagnetism buried deep within the atom, would not be expected to bear close resemblance to the magnetic properties of the elements of the iron, palladium and platinum series where the incomplete sub shell (3d, 4d, or 5d), responsible for paramagnetism, lies outer most. The fact that the platinum metals do not conform to the "spin only" theory is no longer considered anomalous since the theory is not universally successful in the iron transition series.
Pauling (Pauling, L., J.A.C.S., 1931, 53, 1367.) developed a theory to account for the lowering of the moment in terms of the effect of covalent bond formation on the number of unpaired electron spins. He predicted magnetic moments of the iron, platinum and palladium series (Table 1) and for confirmation examined the iron, cobalt, nickel series where reasonably good agreement was obtained. In 1943 D. P. Mellor (J.R.S. (N.S.W.), 1943, 77, 145.) carried out work on complexes of RuIII, RuIV, OsIII, OsIV, IrII, IrIV, RhII, which should be paramagnetic according to Pauling’s predictions. It was decided to extend the work on rhodium and iridium compounds.
