Difluorophosphate

Difluorophosphates. Difluorophosphates have limited appHcations largely because of hydrolytic instabiHty of the P03F 2 ion. The ammonium salt can be prepared from ammonium fluoride and phosphoric anhydride. 

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) ... 

Determination as the tetraphenylarsonium compound Discussion. Any ions forming a precipitate with tetraphenylarsonium chloride (e.g. MnO, ClOj, Br , I-, I03 and SCN-) will interfere. Difluorophosphates give slight interference which can be overcome by boiling the solution for a few minutes to hydrolyse difluorophosphate the hexafluorophosphate ion is not affected by this treatment. 

The unsoluble fluorophosphates can be prepared from the sodium salt by reaction with heavy metal nitrates, whereas the watersoluble salts are appropriately prepared by the reaction of the sligthly soluble AgjPOjF with heavy metal chlorides (24). Acid salts M H[P03F] with = Na, K, NH4 result from fractional precipitation by addition of alcohol and ether to the aqueous solution of the free acid (17). Further methods for the synthesis of fluorophosphates are given by Eqs. (12) and (13), which lead to dimethylin fluorophosphate (32) and to tin (II) difluorophosphate (55) ... 

The volatility of the hydrogen chloride allows the quantitative reaction of the components. In this way the following difluorophosphates were prepared ... 

In some cases the use of ammonium difluorophosphate is suitable. The reaction is then performed in ethereal solution, from which the unsoluble ammonium chloride can be separated by filtration ... 

In this way difluorophosphates with mixed Qrganic substituents R and R are obtained (57) as well as dialkylsilicon(bis)difluorophosphates RR Si[P02F2)2 (55). 

The ammonium difluorophosphate which is better soluble in ethanol is separated by extraction with this solvent 34). The reactions (22) 54) and (23) (55) which are run at higher temperatures do not give purer products ... 

Last, but not least, there is to be mentioned, that in some cases a direct transformation of dichlorophosphates (see section 3.4.) into difluorophosphates by fluorination with elementary fluorine (In(P02p2)3, F (P02F2)3 40)) or with arsenic trifluoride at elevated temperature is possible 41). ... 

Up to know crystal structure analyses have been made with difluorophosphates, monofluorophosphates and dichlorophosphates only. Table 3 gives the bond lengths and bond angles in these three halophosphates. 

In both compounds the hydratemolecules form hydrogen bridges, in which as in the difluorophosphates, only the 0-atoms of the [POgF] ions participate in (NH4)2[P03F] H2O there are additional N—H 0 bridges (26). In the P03F ion the formal bond order po decreases from 1.83 to 1.67 (95) in comparison to... 

Analogous spectroscopic behaviour, as pointed out for the dichlorophosphates for example, can be expected in the case of the difluorophosphates and the dihalophos-phates with two different halogen atoms. 

In the series of the dimethylmetal difluorophosphates from aluminium to thallium, the chemical shift in the P-spectra of [(CH3)2T1(P02F2)]2 is most striking. 

A difluorophosphate can be obtained from a phosphorous diimidazolide as demonstrated by the synthesis of a thymidine 5 -difluorophosphate. The diimidazolide was constructed from 3 -dimethoxytritylthymidine and triimidazolylphosphine.[202],[203]... 

Difluorophosphate hydrolysis gives a rate expression with terms analogous to the second and third terms of equation (1), viz. 

Additional types of phosphorus donors include the glycosyl diphenylphosphinates 221, which were used in TMSOTf-promoted reactions [471,474], whereas reaction of difluorophosphates 222 was assisted by AgC104 [497]. 

Diethyl difluoromethylphosphonate has been reported to react at -78°C with a large variety of aldehydes and ketones in the presence of LDA. On heating, the corresponding difluoroalkenes are obtained in 30-75% yields along with small amounts of difluorophosphates. This report has been questioned in a later publication, where it has been found that difluoromethylphosphates are almost always the major products (48-52% isolated yields) of the reaction, with only traces (less than 3%) of the desired difluoroalkenes being formed (Scheme 3.82). ... 

Phosphorus pentoxide (23.5 g.) is heated with 185 g. of NI jF in a 300-ml. nickel or copper crucible until the reaction starts. It progresses by itself, but the mixture should be well stirred. After cooling, the mass is pulverized and boiled in a glass flask with 600 ml. of absolute alcohol. The mixture is filtered hot through a fluted filter the filtrate is immediately cooled and neutralized with ammoniacal alcohol. Ammonium difluorophosphate(V) (8.3 g.) separates out and is removed filtration. The filtrate is evaporated to dryness in a platinum dish on a water bath. The yield is 11.6 g. (70% of theoretical) of crude salt. This NH4P03Fa is still contaminated with NH F but is suitable for many purposes. 

Matsumoto, K., and R. Hagiwara. 2010. Electrochemical properties of the ionic liquid l-ethyl-3-methylimidazolium difluorophosphate as an electrolyte for electric doublelayer capacitors. Journal of the Electrochemical Society 157 A578-A581. 

R. C. Thompson, W. Reed, Nucl. Chem. Lett. 1969, 5, 581-585. Preparation and infrared spectra of alkali metal difluorophosphates. 

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