Magnetic properties of some low-spin iron(III) compounds

Abstract

The magnetic susceptibility of K₃[Fe(CN)₆], [Fe(phen)₃][ClO₄]₃,3H₂O, [Fe(phen)₃][PF₆]₃,[Fe(bipy)₃][ClO₄]₃, 3H₂O, and [Fe(bipy)₃][PF₆]₃ have been measured between 4 and 300 K. The e.s.r. g-values of the compounds, other than the first, were measured at ca. 85 K. The results are interpreted in terms of a three-parameter model for the splitting of the ²T_2g, ground term of the t_2g⁵ configuration. The spin–orbit coupling constant is ca. 270 cm^–1 in each compound. The t_2g, orbital angular-momentum reduction factor is 0.75 in K₃[Fe(CN)₆] and ca. 0.89 in the other compounds. The splitting of the t_2g orbital set by an axial ligand-field component is small for K₃[Fe(CN)₆](130cm^–1) and may not reflect details of the ligand positions. The splitting is larger in the other compounds (ca. 850 cm^–1) and appears to be an intrinsic property of the ion, not much affected by the nature of the anion or by the presence of solvent molecules.