Fluorides fluorinating agent

Lead iV) fluoride, Pbp4, strong fluorinating agent (PbFa plus F2). Forms complexes containing the [PbFft] " ion. 

Siher I) fluoride, AgF, is prepared by evaporation of a solution of excess Ag20 in HF after filtration or by heating anhydrous AgBF. The anhydrous salt is yellow hydrates are known, It is very soluble in water and in many organic solvents. Used as a mild fluorinating agent. On treatment of a solution with Ag a sub-fluoride, Ag2F, is formed. 

Black silver(II) fluoride, AgF2 (Ag 4- F2), is a strong fluorinating agent. 

Complex siher III) fluorides containing AgF " orAgF " ions and also Cs2AgF containing Ag(IV) are formed with fluorine. They are also strong fluorinating agents. 

Antimony Ill) fluoride is a readily hydrolysable solid which finds use as a fluorinaling agent. Antimony(lll) chloride is a soft solid, m.p. 347 K. It dissolves in water, but on dilution partial hydrolysis occurs and antimony chloride oxide SbOCl is precipitated ... 

As already noted, the simple salts in this oxidation state are powerful oxidising agents and oxidise water. Since, also, Co(III) would oxidise any halide except fluoride to halogen, the only simple halide salt is C0F3. Cobalt(lll) Jluoride, obtained by reaction of fluorine with cobalt(II) fluoride it is a useful fluorinating agent. 

The only important compound is the paramagnetic silver(II) fluoride, AgFj, prepared by fluorination of the metal it is used as a convenient fluorinating agent. 

We also developed a number of other useful new fluorinating reagents. They ineluded a convenient in situ form of sulfur tetrafluoride in pyridinium polyhydrogen fluoride, selenium tetrafluoride, and ey-anurie fluoride. We introdueed uranium hexafluoride (UFg), depleted from the U-235 isotope, which is an abundant by-product of enrichment plants, as an effective fluorinating agent. 

Halogen exchange with KF is not successful ia acetic acid (10). Hydrogen bonding of the acid hydrogen with the fluoride ion was postulated to cause acetate substitution for the haUde however, the products of dissolved KF ia acetic acid are potassium acetate and potassium bifluoride (11). Thus KF acts as a base rather than as a fluorinating agent ia acetic acid. 

Uses. Silver fluoride has found many laboratory and special industrial appHcations. It is used as a soft (nHld) fluorinating agent for selective fluorination (7—17), as a cathode material in batteries (qv) (18), and as an antimicrobial agent (19). Silver fluoride is commercially available from Advance Research Chemicals, Inc., Aldrich Chemicals, Cerac Corp., Johnson/Matthey, PCR, Atochem, and other sources in the United States. The U.S. price of silver fluoride in 1993 was 1000— 1400/kg and the total U.S. consumption was less than 200 kg/yr. 

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). 

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). 

The standard synthesis method features side-chain chlorination of a methylpyridine (picoline), followed by exchange-fluoriaation with hydrogen fluoride or antimony fluorides (432,433). The fluoriaation of pyridinecarboxyHc acids by sulfur tetrafluoride (434) or molybdenum hexafluoride (435) is of limited value for high volume production operations due to high cost of fluorinating agent. 

Iron(III) fluoride [7783-50-8] prepared from FeCl and anhydrous HF or other fluorinating agents ia a flow system at elevated temperature. 

The perchloryl fluoride [7616-94-6] FCIO, the acyl fluoride of perchloric acid, is a stable compound. Normally a gas having a melting poiat of —147.7° C and a boiling poiat of —46.7°C, it can be prepared by electrolysis of a saturated solution of sodium perchlorate ia anhydrous hydrofluoric acid. Some of its uses are as an effective fluorinating agent, as an oxidant ia rocket fuels, and as a gaseous dielectric for transformers (69). 

The reactions are general for chlorine and bromine. Iodine does not react to form pentavalent phosphoms compounds. Fluorides are best formed with less active fluorinating agents. 

Bismuth pentafluoride is an active fluorinating agent. It reacts explosively with water to form ozone, oxygen difluoride, and a voluminous chocolate-brown precipitate, possibly a hydrated bismuth(V) oxyfluoride. A similar brown precipitate is observed when the white soHd compound bismuth oxytrifluoride [66172-91 -6] BiOF, is hydrolyzed. Upon standing, the chocolate-brown precipitate slowly undergoes reduction to yield a white bismuth(Ill) compound. At room temperature BiF reacts vigorously with iodine or sulfur above 50°C it converts paraffin oil to fluorocarbons at 150°C it fluorinates uranium tetrafluoride to uranium pentafluoride and at 180°C it converts Br2 to bromine trifluoride, BrF, and bromine pentafluoride, BrF, and chlorine to chlorine fluoride, GIF. It apparently does not react with dry oxygen. 

Saturated hydrocarbons such as neopentane, notbomane, and cyclooctane have been converted to the corresponding perfluoro derivatives in 10-20% yield by gas-phase reaction with fluorine gas diluted with helium at —78°C. Simple ethers can be completely fluorinated under similar conditions. Crown polyethers can be fluorinated by passing an Fa/He stream over a solid mixture of sodium fluoride and the crown ether. Liquid-phase fluorination of hydrocarbons has also been observed, but the reaction is believed to be ionic, rather than radical, in character. A variety of milder fluorination agents have been developed for synthetic purposes and will be discussed in Chapter 6 of Part B. 

All fluorinating agents should be considered toxic in different amounts and, therefore, handled accordingly Nonvolatile fluorides, however, are not too dangerous in this respect, because it is unlikely that they will be swallowed or that they will penetrate into the blood stream What is extremely dangerous is inhalation of volatile fluorides, that is, gases, liquids, or solids with considerable vapor pressure Such fluorides are indicated in the tables in this chapter... 

Reeently, new fluorinating agents, tetrabutylphosphonium fluoride and its mono- and dihydrofluoride, were used for preparation of fluorohydrins from epoxides [14] (equation 13). 

Mixtures of anhydrous hydrogen fluoride and tetrahydrofuran are successfully used as fluorinating agents to convert 1,1,2-trifluoro-l-allcen-3-ols, easily prepared from bromotrifluoroethene via lithiation followed by the reaction with aldehydes or ketones, to 1,1,1,2-tetrafluoro-2-alkenes The yields are optimal with a 5 1 ratio of hydrogen fluoride to tetrahydrofuran The fluorination reaction involves a fluonde lon-induced rearrangement (Sf,j2 mechanism) of allylic alcohols [65] (equation 40)... 

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