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.