Cl Nuclei Research Articles

Complex hyperfine structures in microwave spectra of covalent iridium compounds

Magnetic resonance spectra are described for two compounds containing covalently bound [IrCl 6 ] 2- complexes and one containing [IrBr 6 ] 2- , and the results are analyzed using the π-bonding theory developed by Stevens. The spectra show hyperfine structure lines arising from interaction of the magnetic electrons both with the Ir nucleus ( I = 3/2) and w ith the Cl ( I = 3/2) or Br ( I = 3/2) nuclei, and different examples are discussed where the numbers of resolved lines are 4, 8, 13, 16 and 22. It is shown how these structures, the ( g -values and the difference between the spectra in [IrCl 6 ] 2- and [IrBr 6 ] 2- are all consistent with the hypothesis that the magnetic electrons move partly in d -orbits round the central Ir nucleus and partly in p π-orbits round the outer halogen nuclei of the complex.

Paramagnetic resonance in palladium and platinum group compounds

The paramagnetic resonance method has been applied to investigate the magnetic properties of complexes containing elements of the 4 d and 5 d groups. It is shown that the resonance results, and such information as is available from susceptibility measurements, can be accounted for to a good approximation by assuming that there are either covalent σ -bonds or very strong electrostatic bonds in the complex (Van Vleck 1935). In the case of d 5 complexes, however, accurate measurements of the spectroscopic splitting factors show small discrepancies with this theory. Furthermore, an anomalous hyperfine structure is observed for the complex [IrCl 6 ] 2- , which displays lines arising not only from the Ir nucleus, but also from the surrounding Cl nuclei. These effects are ascribed to the presence of weak π -bonds, in addition to σ -bonds, in the complex (Stevens 1953). In magnetically concentrated salts of the 5 d group, it is found that there is strong exchange interaction between paramagnetic neighbours.