Octahedral ditertiary arsine complexes of quadrivalent iron

Abstract

The octahedral iron(IV) complexes [Fe(diars)₂X₂][BF₄]₂(X = Cl, Br; diars =o-phenylenebisdimethylarsine) have been prepared by treating the solid tervalent compounds [Fe(diars)₂X₂][FeX₄] with nitric acid (15N) followed by concentrated tetrafluoroboric acid. The electrical conductivity of these compounds in nitromethane solution is consistent with their formulation as bi-univalent electrolytes. The magnetic susceptibility of the complexes has been measured over the range 80–300°K. Magnetic moments calculated therefrom indicate two unpaired electrons, consistent with a spin-paired d_ε⁴ octahedral configuration having a large tetragonal distortion. A study of the long-wavelength infrared spectra of the [Fe(diars)₂X₂]^a(a= 0, +1, and +2) ions agree with the oxidation states assigned; the spectra indicate that in all cases the two halogen atoms are in trans-positions. The visible and ultraviolet spectra have been determined but are difficult to interpret owing to charge-transfer bands which are superimposed on those arising from d–d transitions.