Paramagnetic anisotropies and zero-field splitting of some high-spin iron(III) complexes

The principal and mean magnetic moments of Fe acac3(acac = acetylacetonate) and K3Fe(oxalate)3,3H2O are reported over the temperature range 80–300°K. This appears to be the first time that anisotropy of the 6A1g ground-state of the iron(III) ion has been detected by crystal magnetic susceptibility measurements. The anisotropy is interpreted in terms of the zero-field splitting of the ground state arising from a low-symmetry ligand-field and spin–orbit coupling; values of the zero-field splitting are reported and discussed with reference to the molecular structures of the two complexes.