Fluorination hexafluorophosphate

Alkali metal hexafluoroantimonates arc used, like hexafluorophosphate or tetrafluoroborate salts, to effect halogen-exchange fluorination in organosilanes both in the presence and in the absence of solvents. Fluorotriphenylsilane and difluorodiphenylsilane are obtained in 87 and 95 % yield by heating the corresponding chlorides with sodium hexafluoroantimonate in tetra-ethylene glycol dimethyl ether (tetraglyme).102 Tetrafluoroborates react with chlorosilanes faster than hexafluorophosphate or hexafluoroantimonate salts. 

Potassium, sodium and lithium tetrafluoroborate as well as sodium hexafluorophosphate and hexafluoroantimonate can be used to fluorinate organosilicon chlorides.64 65 An overview is reported in Table 10.65... 

Dehydrobromation of halogenated phosphonium salts is currently used in the synthesis of unsaturated compounds, (cf. Section II.C) provided that a labile carbanion is created in a suitable position relative to the halogen atom (reaction 261). Such bases as Et3N (for / - or (5-halogenated phosphonium salts)288 or bromide anion357 may induce this elimination. Fluorine atoms of the cationic part of 3-methyl-1,1-difluorocyclopent-2-ene-1-phosphonium hexafluorophosphate were substituted when the compound was treated with absolute methanol under mild conditions412. 

Although fluorine is known to be a rather poor leaving group in substitution reactions, some examples have been reported for the replacement of fluorine by N-nucleophiles. Here, substitution can proceed with amines,1 -3 amides,4 amidines,5-6 hydrazines3-7 or azides.8-9 Nitriles in the presence of nitrosyl hexafluorophosphate replace fluorine in alkyl fluorides, in a Ritter-like reaction, to form tV-alkylnitrilium species, which are hydrolyzed to amides.10... 

Electrochemical fluorination 168,169> is a commercial process for perfluorina-tion of aliphatic compounds. The reaction is performed in liquid hydrogen fluoride -potassium fluoride at a nickel anode. The mechanism is not known free fluorine cannot be detected during electrolysis, so it seems probable that fluorination is a direct electrochemical reaction. Theoretically, hydrogen fluoride-potassium fluoride should be a very oxidation-resistant SSE, and it might well be that the mechanism is analogous to that proposed for anodic acetamidation of aliphatic compounds in acetonitrile-tetrabutylammonium hexafluorophosphate 44 K... 

The water content of the ionic liquid is another, perhaps more complex, factor for consideration. The presence of small amounts (1-4%) of water may be beneficial to the properties of some polymers [33], but it should be noted that some ionic liquids utilizing fluorinated anions, particularly hexafluorophosphate, can slowly hydrolyse in the presence of water to form HF and other species [34], It is important to note that even if an ionic liquid is immiscible with water, it may still contain a significant quantity of water before drying, which can alter its physical properties, such as viscosity [34-36],... 

Introduction of a fluorine atom is achieved using the Schiemann reaction. Originally, the reaction involved gently heating the solid diazonium fluoroborate (Scheme 8.18), but improved yields result from the thermal decomposition the hexafluorophosphate, ArN2 PF, or hexa-fluoroantimonate, ArN2 SbFg, salts. 

Hydrophobicity or hydrophilicity is also an important property, which can be controlled by selecting an appropriate cation and anion combination. Longer alkyl chains on the cation have been found to result in increased hydrophobicity [80, 81]. Hydrophobicity also depends on the identity of the anion. For example, ionic liquids containing fluorinated anions such as tetrafluoroborate and hexafluorophosphate are considerably more hydrophobic than the halide salts of the same cation. Ionic liquids containing the bis(trifluoromethanesulfonyl)amide anion [NTf2] are extremely hydro-phobic whereas their non-fluorinated analogues are sometimes completely miscible with water [82], The immiscibility of the ionic liquid with water or other solvents may be useful for phase separations, but it also has implications on the greenness of the ionic liquid in the event of accidental release into the environment [80],... 

Fluorophosphates. As with many other oxo anions, fluorine can replace OH in phosphate to give mono- and di-fluorophosphate salts and esters. The dialkyl monofluorophosphate esters have been found to inhibit cholinesterase in the body and to be exceedingly toxic. The hexafluorophosphate ion, PFg, has been discussed (page 376). 

Imidazolium ionic liquids are known to be a remarkable solvent for CO2 solubility ref It has been found that anion play the important role in determining the gas solubility in ionic liquids. It has been reported that the bistriflamide anion has the greatest affinity for CO2 experimentally compared to other anions, such as the halides, triflate ([OTf] ), hexafluorophosphate ([PFe] ), tetrafluoroborate ([BF4] ), dicyanamide ([N(CN)2] ) and ethanoate ([MeC02] ) Although fluorination effect are shown to have greatly enhanced the solubility of CO2, these class of ionic liquids are very expensive and are not environmental friendly, due its high stability and low reactivity... 

The influence of the anion type on the thermal stability of the imidazolium ILs has been studied by Awad et al. [32]. TTiey have demonstrated that for the hexa-fluorophosphate PF, tetrafluoroborate BF , and bis(trifluoromethylsulfonyl)amide [(CF3SOj)JN, increase of 100 C in the degradation temperature was obtained compared to the use of the halide salts (bromide and chloride). For nanoclays modified with imidazolium salts as surfactants, the works reported in the literature demonstrate a large increase of degradation temperature under nitrogen and oxidative atmosphere compared to ammonium-treated MMT. However, despite the intrinsic stability of imidazolium ILs induced by the substitution of halide anions by fluorinated ones, no significant improvement in the thermal stability of the MMT treated by ILs having tetrafluoroborate or hexafluorophosphate anions has been reported. 

The choice of anion has a remarkable influence on the balance of hydrophobicity and hydrophi-licity, respectively, and hence the water miscibility of an IL. But the melting point is also affected by the anion (Wasserscheid and Keim, 2000). Besides the halides, frequently used inorganic anions are tetrafluoroborate and hexafluorophosphate. Fluorination of the anion leads to enhanced... 

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