Rhodium hexafluoride

The electronic spectrum of RhF6 has not been reported, but ligand field calculations have been used to predict its spectrum.1279 The IR spectrum of RhF6 has been reported,1280 and it is consistent with the expected Oh symmetry. Like IrF6, the rhodium hexafluoride does not show the Jahn-Teller splittings of the Eg mode observed for the analogous Tc, Re and Os hexafluorides. 

Weinstock, Malm, and Weaver have shown that platinum hexafluoride is thermally unstable and dissociates to a lower fluoride and fluorine. In view of this capacity of the hexapositivc platinum to oxidise combined fluorine to the elemental furm. it is not surprising that it is also capable of oxidising the oxygen molecule. A similar oxidation by ruthenium and rhodium hexafluorides is to be looked for. 

Rhodium hexafluoride forms a deep-red adduct with xenon, the composition of which is close to XeRhFe. Krypton does not react with either platinum hexafluoride or with rhodium hexafluoride at temperatures below 50°. 

Reagents.—Platinum hexafluoride and rhodium hexafluoride were prepared from 0.03-in. diameter pure metal wire supplied by Johnson, Matthey, and Mallory Ltd., Toronto. The reaction with fluorine was initiated by electrical heating of the wire, the metal reactor used being similar to that described by Weinstock, Malm, and Weaver [2]. Airco Reagent Grade xenon was used. 

Reaction of xenon with rhodium hexafluoride.—The hexafluoride was purified by vacuum sublimation from the reactor at room temperature to the storage bottle at —75° and was maintained at this temperature for several hours with the bottle open to the high vacuum line. 

A similar experiment with rhodium hexafluoride established that krypton does not react with that fluoride below 50°. 

The departure from the 1 1 reaction stoichiometry in the xenon-rhodium hexafluoride system is less than for the platinum system. This is surprising in view of the greater instability and chemical reactivity of the rhodium fluoride. Ruthenium hexafluoride, which is less reactive than rhodium hexafluoride, has been reported [7] to react non-stoichiometrically with xenon. Perhaps the use of small quantities of rhodium fluoride favored the 1 1 addition. There is as yet no evidence for the oxidation state of rhodium in the adduct, although the formulation Xe -1- [RhFe] would, as in the corresponding platinum case, appear to be energetically more favorable than Xe +[RhF6] . 

In the first reports of platinum < >, ruthenium and rhodium hexafluorides their spontaneous liberation of fluorine at ordinary temperatures was mentioned. Clearly... 

Table 8. — Xenon — rhodium hexafluoride RhFs (solid + gas) -F Xe (gas) in a nickel weighing can...

Rhodium hexafluoride also reacts with xenon and the reacting ratio was, in the two experiments performed, close to 1 1 (Table 8). Presumably the adduct is Xe+ fRhFJ-but again no X-ray patterns were secured. Since rhodium hexafluoride was considered, because of its small size and low thermal stability to be the most powerful oxidizer of... 

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