Octahedral geometry spectra

The hexafluorides [RuFg] and [OsFg] are known. The rather unstable RuFg can be obtained as a brown solid in high yield by the interaction of [RuFs] with F2 at 220 °C and 30 atm. The IR spectrum is consistent with an octahedral geometry. " The metal K-edge EXAFS data for RuFg have been obtained and a Ru F distance of 1.83 A was found. ... 

The absorption spectrum of low-spin NiFg- shows four absorption bands in the region below 25000 cm 1. Find the symmetry- and spin-allowed transtions in octahedral geometry and suggest a reason for any discrepancies with experiment. 

As previously noted, spin cross-over behaviour is well established in iron(II) complexes and there are also examples involving iron(III) species. For example, a variety of iron(III) dithiocarbamate complexes of the type [Fe(S2CNR2)3j having a trigonally distorted octahedral geometry display high-spin/low-spin cross-over behviour 49,50 Little is known about the spin forbidden d-d transitions of iron(III) complexes due to near-UV charge transfer bands that tail into the visible part of the spectrum. Even simple iron(III) salts in aqueous media are yellow. 

The europium emission spectrum at 77 K suggests an Oh — C4v symmetry and an octahedral geometry.7 A single crystal X-ray study of the compound indicates a crystallographic octahedral symmetry with a = 20.28(1) A, space group F23. The Ln-O distance is 2.27(1) A.8... 

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