Paramagnetic Resonance Spectra of Chromium III and Manganese IV Hexafluoride Ions: CrF63— and MnF62

The paramagnetic resonance spectra of the ions CrF63— and MnF62— dilute solution in diamagnetic solids show fluorine hyperfine structure with both isotropic and anisotropic components. The anisotropic coupling constants are of the same order of magnitude as in the case of FeF63—, but have the opposite sign indicating important contributions of π-bonding electrons. Accordingly, the previously estimated degree of σ bonding in FeF63— is certainly too small, and estimates of the fluorine atomic orbital coefficients for the compound are made on the basis of the data presented here. The isotropic effects are to be understood in terms of configurational interactions. The isotropic coupling constants for the two ions have opposite signs and we are at present able to offer no rationalizations of this difference.