Xenon-platinum hexafluoride

THE XENON-PLATINUM HEXAFLUORIDE REACTION AND RELATED REACTIONS... 

In the preliminary communication [1] reporting the interaction of xenon with platinum hexafluoride, the adduct was given the empirical formula XePtF and was assumed to be a derivative of pentapositive platinum. Subsequent work has shown that although the gases may interact in a 1 1 ratio, the product usually contains more platinum and can have the composition Xe(PtFe)2. That the platinum in the xenon-platinum hexafluoride adduct Xe(PtFe) is in the +5 oxidation state has now been established. 

Xenon-platinum hexafluoride in silica apparatus.—In other experiments the reactants were condensed in succession in a silica bulb. On warming, the platinum hexafluoride reacted both as a solid and as a vapor with the gaseous xenon. 

Properties of the adduct Samples prepared in silica and of uncertain composition were deep red. X-ray powder photographs of this material showed only a faint, sharp pattern, perhaps belonging to a minor phase. A similar faint pattern appeared on photographs of some xenon-platinum hexafluoride specimens. 

N. Bartlett and N. K. Jha, The Xenon-Platinum Hexafluoride Reaction and Related Reactions, Noble Gas Compounds, ed. H. H. Hyman, University of Chicago Press (1963) 23-30. 

Binary Compounds. Three fluorides, PtF [13455-15-7], PtF [37782-184-8], and platinum hexafluoride [13693-05-5], PtF, are well documented. The last is a powerful oxidi2ing agent and can oxidi2e dioxygen and xenon (235). Two chlorides exist, platiaum dichloride [10025-65-7],... 

Platinum hexafluoride does not have many commercial apphcations. It is used as a strong oxidizing agent and can oxidize oxygen from the air. It is used in research. Platinum hexafluoride forms compounds with molecular oxygen and xenon, [02" ][PtF6 ] and XePtFe, respectively. 

Although xenon has the stable octet configuration and is thought to be as inert as other noble gases, several xenon compounds have been prepared. The first xenon compound synthesized by N. Bartlett in 1962 was a red sohd, XePtFe, made by the reaction of xenon with platinum hexafluoride undergoing the following oxidation sequence (Cotton, F. A., Wilkinson G., Murillo, C. A. and M. Bochmann. 1999. Advanced Inorganic Chemistry, ed., pp. 588. New York John Wiley Sons) ... 

Should xenon react with platinum hexafluoride ... 

A RECENT Communication described the compound dioxygenyl hcxafluoroplatinatc(v), Oj+PtF, , which is formed when molecular oxygen is oxidised by platinum hexafluoride vapour. Since the first ionisa tion potential of molecular oxygen, 12-2 ev, is comparable with that of xenon, 12-13 ev, it appeared that xenon might also be oxidised by the hexafluoride. 

Although inert-gas clathrates have been described, this compound is believed to be the first xenon charge-transfer compound which is stable at room temperatures. Lattice-energy calculations for the xenon compound, by means of Kapustinskii s equation, give a value 110 kcal. mole", which is only 10 kcal. mole" smaller than that calculated for the dioxygenyl compound. These values indicate that if the compounds are ionic the electron affinity of the platinum hexafluoride must have a minimum value of 170 kcal. mole". ... 

Xenon and platinum hexafluoride interact at room temperature to form a red solid of composition Xe(PtF6)a where x lies between 1 and 2. That the platinum is present in the -f-S oxidation state, no matter what the composition of the adduct, is indicated by the preparation of alkali metal hexafluoroplatinates(V) from material of composition XePtFe and Xe(PtF6)2. Material containing more than one mole of platinum hexafluoride per gram atom of xenon combines with more xenon at 130° to approach the composition XePtFe. 

Xenon tetrafluoride is liberated in the pyrolysis of platinum hexafluoride-rich adduct, e.g., Xe(PtF6)i,8. The residual, brick-red, diamagnetic, xenon-containing platinum compound has a composition close to XePt2Fio. 

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. 

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 their early studies of the oxidation of xenon by platinum hexafluoride Bartlett and Jha found [1] that the stoichiometry of the product of that spontaneous reaction varied between XePtF and Xe(PtFg)2. Chemical and physical evidence Indicated that the oxidation state of the platinum in Xe(PtFg)jj was +5. Pyrolysis of XeCPtFg), at 165°, yielded xenon tetra-fluorlde as the only identified volatile product, (xenon itself was not... 

These investigations have greatly clarified the nature of the products of the interaction of xenon with platinum hexafluoride. Presumably [XeF]+[PtFj] is produced as follows ... 

The reaction of xenon with platinum hexafluoride yields at least two distinct quinquevalent platinum products, XePtF, and Xe(PtFj)j. A third compound XePtjFij which is diamagnetic, is produced by heating the former. During continuing investigations of the reaction between xenon, fluorine, and platinum pentafluoride, at least two different compounds have been detected. The better characterized compound is produced when 1 1 molar ratios of xenon and platinum pentafluoride are employed in admixture with 80 p.s.i. 

Table 6. — Some results for the xenon -F platinum hexafluoride REACTION...

The spontaneous oxidation of molecular oxygen and of atomic xenon, each of which has a first ionization potential of 281 kcal. mole , by platinum hexafluoride, has estabhshed the remarkable oxidizing power of the hexafluoride. None of the other third-transition-series hexafluorides will oxidize these species. Since it is well established - that the platinum hexafluoride-oxygen adduct is the salt Oj+[PtFe] , the lattice energy of which is estimated, employing Kapustinskii s second equation to be 125 kcal. moIe, the electron affinity of the PtF, molecule is required to be >156 kcal. mole, to ar count for the observed exothermic reaction [Pg.244]

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