The magnetic susceptibility of some tetrahedral tetrahalogenoferrate(II) complexes

Abstract

The variation of the magnetic susceptibility with temperature and field strength for the 3d⁶[FeX₄]^2– anions, where X = Cl, Br, or I, when associated with a number of large cations, has been studied. The cations used were [Me₄N]⁺, [Et₄N]⁺, [Prⁿ₄N]⁺, [Ph₃MeAs]⁺, and [Ph₄P]⁺. Difficulty is experienced in certain cases in obtaining pure compounds but it is found that in those derivatives for which the state of purity has been clearly established abnormally high magnetic moments are observed, even after allowance for temperature-independent paramagnetism and mixing due to spin–orbit coupling. It is suggested that these high moments can be explained if some contribution from the 3d⁵ 4s configuration is assumed.