Fluorinating agents xenon fluorides

Eused-ring polycycHc fluoroaromatics can be made from the corresponding amino fused-ring polycycHc or from preformed fluoroaromatics, eg, 4-fluorophenyl-acetonitrile [459-22-3] (275). Direct fluorination techniques have been successfully appHed to polycycHc ring systems such as naphthalene, anthracene, benzanthracenes, phenanthrene, pyrene, fluorene, and quinoHnes with a variety of fluorinating agents xenon fluorides (10), acetyl hypofluorite (276), cesium fluoroxysulfate (277), and electrochemical fluorination (278,279). 

Among the noble gas fluorides, the binary fluorides of xenon have received the most attention as fluorinating agents. Krypton fluorides seem to be more exotic novelties than real reagents. 

Silver difluoride [7783-95-1], AgF2, is a black crystalline powder. It has been classified as a hard fluorinating agent (3) which Hberates iodine from KI solutions and o2one from dilute aqueous acid solutions on heating. It spontaneously oxidizes xenon gas to Xe(II) in anhydrous hydrogen fluoride solutions (20). 

The xenon fluorides are used as powerful fluorinating agents (reagents for attaching fluorine atoms to other substances). The tetrafluoride will even fluori-nate platinum metal ... 

Various fluorine compounds, such as xenon(II) fluoride, act under certain conditions (irradiation, gas-phase reaction) as radical fluorinating agents. Electrochemical fluorinations (see Section 7.) carried out in hydrogen fluoride containing systems (ref 7, pp73-76) are further examples of radical-type reactions. 

Electropositive fluorinating agents are categorized in distinct classes as (1) fluoroxy reagents, in which the fluorine is bound to an oxygen atom (for reviews, see references 1,2, 3, 4, 5, and 6) (2) fluoraza reagents, in which the fluorine atom is bound to the nitrogen atom of either an amide or ammonium ion structure (for a partial review, see reference 6), (3) xenon difluoride, in which the fluorine atoms are bound to xenon (for reviews, see references 5, 7, 8, and 114) and (4) perchloryl fluoride, in which the fluorine atom is bound to the chlorine atom of the perchloryl function (for a review, see reference 9). 

Fluorination with elemental fluorine diluted 1 20 with nitrogen was used to prepare pentafluorophenyl tellurium trifluoride from bis[pentafluorophenyl] ditellurium at — 60° with fluorotrichloromethane as the reaction medium. The yield in this reaction was 80% 4-Methoxyphenyl tellurium trifluoride was obtained by electrochemical oxidation of the diaryl ditellurium in 0.5 M hydrofluoric acid at platinum electrodes2. Bisfpentafluoroethyl] ditellurium and chlorine fluoride (1 6) reacted at — 78° to give pentafluoroethyl tellurium trifluoride, a white solid melting at 95°3. The same compound was obtained with xenon difluoride as the fluorinating agent and melted at 143°4. 

In chemical behavior similar to that of interhalogens, the xenon fluorides act as fluorinating agents in a wide variety of reactions. Xenon difluoride is a milder reagent than is the tetrafluoride or the hexafluoride. It readily reacts with olefins to add fluorine ... 

The role of the silver salt is not completely understood. No evidence for a single electron transfer mechanism has been found. Although extremely reactive electrophilic fluorinating agents, such as xenon fluoride triflate (FXeOTf) or trifluoromcthanesulfonyloxy fluoride (TfOF), may be generated from the combination of xenon difluoride and silver(l) triflate, the reaction appears to proceed following initial interaction of the alkcnc with the silver ion. ... 

Xenon hexafluoride hydrolyzes in excess dilute acid or water to produce XeOa [Xe(VI)] in solution. Hydrolysis with strong base results in the precipitation of a perxenate salt [Xe(VIlI)]. Xenon hexafluoride is a fairly strong fluorinating agent, and it forms addition compounds w ith other fluorides such as BF3, AsFs, SbFs, and alkali metal fluorides. 

These reactions can be carried out in glass vessels. The glass will become only slightly frosted. Bis[trifluoromethyl] tellurium difluoride was also obtained using chlorine fluoride, bromine trifluoride, or xenon difluoride as fluorinating agents Diphenyl tellurium dfluoride was produced when diphenyl tellurium in acetonitrile was treated at 20° with methyliodine(III) difluoride or 2,2,2-trifluoroethyliodine(IIl) difluoride. ... 

Xenon fluorides are powerful Jluorinating agents, reagents that attach fluorine to other substances. Xenon trioxide is synthesized by the hydrolysis of xenon tetrafluoride. 

Xenon hexafluoride is a better fluorinating agent than the xenon difluoride described in the previous problem, but it must be carefully isolated from any moisture. This is because xenon hexafluoride reacts with water to form hydrogen fluoride (hydrogen monofluoride) and the dangerously explosive xenon trioxide. 

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