ESR Studies of Electron Irradiated K3IrIII(CN)6 in KCl Single Crystals. I. Ligand Hyperfine Structure in IrII(CN)5 Species

Electron irradiation of the diamagnetic [Ir(CN)₆]³⁻ ion in a KCl host lattice produces two paramagnetic species. ESR studies reveal that one of the species can be assigned to the pentacoordinated [Ir(CN)₅]³⁻, of approximate C_4ν symmetry, with 5d⁷ low spin configuration, arising from the trapping of an electron in a $d_z^2$ orbital followed by the loss of an axial cyanide. Ligand hyperfine structure with four equivalent and one nonequivalent nitrogens is observed and confirmed by isotopic substitution. The g values and the ligand hyperfine tensors are presented and discussed. Ligand f_s and f_p spins densities are calculated and discussed.