Antimony fluorides fluorinating agent

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 ... 

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. 

HF In die presence of fluorinating agents, such. as antimony tri- and penta-fluorides. Used as aerosol propint, refrigerant and fire extinguisher... 

Tetrakis(phenyldifluorophosphine)nickel-(0) could also be obtained, using arsenic trifluoride in the presence of catalytic amounts of antimony pentachloride, or zinc fluoride as fluorinating agents. Yields as high as 50% could be obtained, but sizable decomposition on the process of fluorination of the chlorophosphine nickel-(0) complexes in solution could not be entirely suppressed. The marked instability of zerovalent nickel-phosphine complexes in solution in organic solvents, even under strictly anhydrous and anaerobic conditions, has been noted by several workers (16,20), but is still lacking a detailed explanation. A closer examination of the system carbon tetrachloride-tetrakis(trichlorophosphine)nickel-(0) (23) showed the main pa h of the reaction to consist in the formation of hexachloro-ethane with conversion of zerovalent into bivalent nickel, while the coordinated... 

Reaction of 13C-labeled chloroform with this reagent for 3 hours at O C gives 13CHFC12 as the major product. Under modified conditions, when 13CHC13 is added to the fluorinating agent [4 g of solid antimony(III) fluoride and 4 g of liquid antimony(V) chloride] and is warmed to 40 °C, the volatile product that distills off at — 90°C is 13C-labeled chlorodifluoromethane (80% conversion).73... 

Thus, aryl-substituted antimony fluorides provide replacement of chlorine by fluorine atoms in aromatic compounds containing trichloromethyl and pentachloro- or dichlorotri-fluoroethyl groups. Their activity as fluorinating agents decreases in the order tetrafluoro(phenyl)-A5-stibane > trifluorodi(phenyl)-25-stibane >antimony(lIl) fluoride dill uorotri(phenyl)-/i.5-stibane. 

Antimony(III) halides are chemically reactive, but less so than their phosphorus or arsenic analogues. Antimony(III) chloride forms a clear solution with water, and there is no evidence for Sb3+ ions dilution results in precipitation of insoluble oxychlorides of various compositions, e.g. SbOCl, Sb405a2, SbsOuCl2. Some reactions of SbCl3 are shown in Scheme 3. Antimony(III) fluoride is an important fluorinating agent. 

In the same way as intramolecular displacement leads to particularly stable atomic groupings within a molecule, the disproportionation reactions between several molecules are attributable to the tendency for the more stable compound with the higher fluorine content to form. Reactions of this kind are sometimes used to obtain highly fluorinated compounds from products with lower fluorine contents, for example, the catalytic fluorination of chloroalkanes with hydrogen fluoride or with fluorination agents such as antimony(V) fluoride or antimony(III) fluoride. The chlorine compound formed as the second product of the disproportionation process is reused as the starting material for the preparation of the compound to be dispropor-tionated. 

The desired extent of fluorination of the starting material may dictate the fluorinating agent to be used. For example, fluorine converts silicon tetrachloride to silicon tetra-fluoride, whereas antimony(III) fluoride promotes the reactions which produce the chlorofluorides, SiCl3F, SiCl2F2, and SiCIFs. 

The reaction involves the replacement of the halogen atoms in nonpolar halide molecules by fluorine atoms. The fluorinating agent is usually resublimed antimony (III) fluoride. If necessary, a catalyst, such as antimony(V) chloride, chlorine, or bromine, may be used. 

Methyl difluorophosphite is very readily obtained by the action of antimony(III) fluoride on the dichloro ester. The intermediate, partially fluorinated chlorofluoro ester is produced in appreciable yields only under carefully controlled conditions. Although the conditions outlined below, i.e., low temperature, low pressure, and slow rate of addition of fluorinating agent, favor the formation of the chlorofluoro ester, a mixture results, and the yield of the chlorofluoro ester is low compared to that of the difluoro.1... 

Many metal fluorides beside KF have been tried as nucleophilic fluorinating agents but only a few succeeded in establishing themselves as such. We will briefly survey here fluorides of silver, mercury, cesium and antimony. 

Phenyltetrafluorophosphorane was first obtained by the reaction of phenyldichlorophosphine with antimony(V) fluoride or a mixture of antimony(V) chloride and antimony-(III) fluoride. In another method of preparation, phenyl-tetrachlorophosphorane was fluorinated with antimony(III) fluoride. Sulfur(IV) fluoride was used to fluorinate both phenylphosphonic acid and phenylphosphonic difluoride under autogenous pressure. Finally, it was found that phenyltetrafluorophosphorane is formed upon reaction of phenyldichlorophosphine with antimony(III) fluoride, by a simultaneous redox and fluorination reaction. " The last reaction is described below. It is very general in scope and has been employed in the synthesis of a wide variety of tetrafluorophosphoranes. " It may be noted that arsenic-(III) fluoride can be employed similarly as the fluorinating agent instead of antimony(III) fluoride. ... 

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