Hexafluorophosphates

Phosphorus pentafluoride PF will readily accept an electron pair from a fluoride ion F to form the stable hexafluorophosphate(V) anion PF C. This ion is isoelectronic with SF. and neither SF nor PF show any notable tendency to accept further electron pairs, though there is some evidence for the existence of an SF ion. 

Pentamethylbenzene and anthracene react very rapidly with nitronium tetrafluoroborate in sulpholan to give cr-complexes, which decompose slowly (see below), and durene behaves similarly with nitronium hexafluorophosphate in acetonitrile. ... 

A number of salts of the monofluoro- and hexafluorophosphoric acids are known and some are commercially important. The salts of difluorophosphoric acid are typically less stable toward hydrolysis and are less well characterized. Sodium monofluorophosphate [7631-97-2] the most widely used dentifrice additive for the reduction of tooth decay, is best known (see Dentifrices). Several hexafluorophosphates can be prepared by neutralization of the appropriate base using hexafluorophosphoric acid. The monofluorophosphates are usually prepared by other methods (57) because neutralization of the acid usually results in extensive hydrolysis. 

The NH4PO2F2 can be extracted from the soHd reaction product with boiling methanol (80). Alkali metal difluorophosphates are prepared from the hexafluorophosphates by one of the following fusion reactions (81) ... 

Hexafluorophosphates. There is a great deal of interest in the hexafluorophosphate anion [1691-18-8], mostly as organic hexafluorophosphates for catalysis in photopolymerization. A number of the compounds are diazonium compounds (see Photoreactivepolymers). 

The hexafluorophosphates are among the most stable halogen complexes known. The highly symmetrical PF ion is stable to boiling aqueous alkaH and is decomposed only slowly in acidic solutions at ambient temperatures. It does hydrolyze rapidly at elevated temperatures in acid (85). The stabiHty of the PF 3 ion can be compared to the isoelectronic SF. The hexafluorophosphates can be decomposed yielding PF although in many cases only at temperatures where the PF reacts with the metal containers. Benzenediazonium hexafluorophosphate can be decomposed to PF, N2, and fluorobenzene at 120°C (86) and is a convenient source for laboratory amounts of PF as well as a frequently used catalyst. 

Many of the organic and inorganic hexafluorophosphates can be prepared by reaction of hexafluorophosphoric acid and the appropriate base. Another method involves reaction of the appropriate chloride and PCI3 with anhydrous HF (87). 

Anhydrous silver hexafluorophosphate [26042-63-7] AgPF, as well as other silver fluorosalts, is unusual in that it is soluble in ben2ene, toluene, and xylene and forms 1 2 molecular crystalline complexes with these solvents (91). Olefins form complexes with AgPF and this characteristic has been used in the separation of olefins from paraffins (92). AgPF also is used as a catalyst. Lithium hexafluorophosphate [21324-40-3] LiPF, as well as KPF and other PF g salts, is used as electrolytes in lithium anode batteries (qv). 

The silver fluorocomplexes, ie, silver hexafluoroantimonate [26042-64-8], AgSbF silver hexafluorophosphate [26042-63-7], AgPF silver tetrafluoroborate [14104-20-2], AgBF and other salts such as silver trifluoromethane sulfonate [2923-28-6], CF SO Ag, and silver trifluoroacetate [2966-50-9], CF COOAg, play an important role in the synthesis of organic compounds and have gained potential industrial importance. 

These compounds perform a dual function in synthesis procedures. The introduction of a complex anion assists in the stabilization of the desired product and the generation of unique intermediates by chloride displacement, eg, silver hexafluorophosphate, AgPF, forms adducts with neutral diamagnetic organometaHics which can act as controUed sources of highly reactive cations (29). Silver hexafluoroantimonate, AgSbF, is an electrophilic... 

Protonic initiation is also the end result of a large number of other initiating systems. Strong acids are generated in situ by a variety of different chemistries (6). These include initiation by carbenium ions, eg, trityl or diazonium salts (151) by an electric current in the presence of a quartenary ammonium salt (152) by halonium, triaryl sulfonium, and triaryl selenonium salts with uv irradiation (153—155) by mercuric perchlorate, nitrosyl hexafluorophosphate, or nitryl hexafluorophosphate (156) and by interaction of free radicals with certain metal salts (157). Reports of "new" initiating systems are often the result of such secondary reactions. Other reports suggest standard polymerization processes with perhaps novel anions. These latter include (Tf)4Al (158) heteropoly acids, eg, tungstophosphate anion (159,160) transition-metal-based systems, eg, Pt (161) or rare earths (162) and numerous systems based on tri flic acid (158,163—166). Coordination polymerization of THF may be in a different class (167). 

The principal electrophiles to attack ring sulfur are either oxidants or alkylating reagents. Thiophene sulfoxide and sulfone formation is discussed in Section 3.02.2.6. Alkylating agents capable of forming thiophenium salts include trimethyloxonium tetrafluoroborate (MeaO BF ) and alkyl fluorosulfonates (ROSO2F). The salts e.g. 87) are conveniently isolated as hexafluorophosphates (88). 

Tetraselenafulvalene, tetramethyl-, hexafluorophosphate-, TCNQ salt X-ray, 1, 355 <79AX(B)772>... 

S-Methylthiophenium hexafluorophosphate synthesis, 4, 765 Methyprylone as sedative, 1, 165 Methyridine... 

Phosphonium hexafluorophosphate, benzotriazolyl-N-hydroxytris(dimethylamino)-in peptide synthesis, 5, 728 Phosphonium salts chromene synthesis from, 3, 753 reactions, 1, 531 Phosphonium salts, vinyl-in pyrrole synthesis, 4, 343 Phosphonium ylides in heterocyclic synthesis, 5, 165 Phosphoramide, triethylene-as pharmaceutical, 1, 157 Phosphoramide, triethylenethio-as pharmaceutical, 1, 157 Phosphorane, pentaphenyl-synthesis, 1, 532 Phosphoranes, 1, 527-537 Berry pseudorotation, 1, 529 bonding, 1, 528... 

Tetra-n-butylammonium hexafluorophosphate [3109-63-5] M 387.5, m 239-241 . Recrystd from satd EtOH/water and dried for lOh in vac at 70°. It was also recrystd three times from abs EtOH and dried for 2 days in a drying pistol under vac at boiling toluene temperature [Bedard and Dahl J Am Chem Soc 108 5933 1986],... 

Ammonium hexafluorophosphate [16941-11-0] M 163.0, d 2.181, pK j 0.5, pKj 5.12 (for fluorophosphoric acid H2PO3F). Crystallises from H2O in square plates. Decomposes on heating before melting. Soluble in H2O at 20° (74.8% w/v), also very soluble in Mc2CO, MeOH, EtOH and MeOAc and is decomposed by boiling acids. [Chem Ber 63 1063 1930.]... 

Benzotriazol-l-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP reagent)... 

Potassium hexafluorophosphate [ 17084-13-8 j M 184.1, pK 0.5, pK j 5.12 (for fluorophosphoric acid H2PO3F). Crystd from alkaline aqueous solution, using polyethylene vessels, or from 95% EtOH, and dried in a vacuum desiccator over KOH. 

Hexafluorophosphate and tetrafluoroborate dienyl salts react with many nucleophiles. The tetrafluoroborate salts are to be preferred, being more soluble in organic solvents than the hexafluorophosphates. 

New diazotization techniques for the Balz-Schiemann reaction feature alter native mtrosating agents in place of aqueous sodium nitrite or substitution of other salts such as arenediazonium hexafluorophosphates for arenediazoniuin fluoroborates... 

Arenediazonium hexafluorophosphates represent a promising alternative to diazonium fluoroborates because of decreased water solubility and, in some instances, higher yields of fluoroaromatics [27, 28] (equation 6)... 

Depending on structure, photolysis of films of arenediazonium fluoroborates and hexafluorophosphates at room temperature gives aryl fluorides m 10-75% yield [32] In situ photochemical decomposition of arenediazonium fluoroborates... 

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