“Hexafluorophosphate”的意思、由来-开放百科全书

Hexafluorophosphate salts can be prepared by the reaction of phosphorus pentachloride and alkali or ammonium halide in a solution of hydrofluoric acid:^[4]

Hexafluorophosphoric acid can be prepared by direct reaction of hydrogen fluoride with phosphorus pentafluoride.^[5] It is a strong Brønsted acid that is typically generated in situ immediately prior to its use.

These reactions require specialized equipment to safely handle the hazards associated with hydrofluoric acid and hydrogen fluoride.

Quantitative analysis

Several methods of Quantitative analysis for the hexafluorophosphate ion have been developed. Tetraphenylarsonium chloride, [(C₆H₅)₄As]Cl, has been used both for titrimetric^[6] and gravimetric^[7] quantifications of hexafluorophosphate. Both of these determinations depend on the formation of tetraphenylarsonium hexafluorophosphate:

Hexafluorophosphate can also be determined spectrophotometrically with ferroin.^[8]

Reactions

Hydrolysis is extremely slower under basic conditions.^[9] Acid-catalyzed hydrolysis to the phosphate ion is also slow.^[10] Nonetheless, hexafluorophosphate is prone to decomposition with the release of hydrogen fluoride in ionic liquids.^[11]

Organometallic and inorganic synthesis

Hexafluorophosphate is a common counteranion for cationic metal complexes. It is one of three widely used non-coordinating anions are hexafluorophosphate, tetrafluoroborate {{chem|BF|4|−}}, and perchlorate {{chem|ClO|4|−}}. Of these, the hexafluorophosphate ion has the least coordinating tendency.^[12]

Hexafluorophosphate salts can be prepared by reactions of silver hexafluorophosphate with halide salts. Precipitation of insoluble silver halide helps drive this reaction to completion. Since hexafluorophosphate salts are often insoluble in water but soluble in polar organic solvents, even the addition of ammonium hexafluorophosphate (NH₄PF₆) to aqueous solutions of many organic and inorganic salts gives solid precipitates of hexafluorophosphate salts. One example is the synthesis of rhodocenium salts:^[13] The overall conversion equation is

Hydrolysis of hexafluorophosphate complexes

While the hexafluorophosphate ion is generally inert and hence a suitable counterion, its solvolysis can be induced by highly electrophilic metal centers. For example, the tris(solvento) rhodium complex [(η⁵-C₅Me₅)Rh(Me₂CO)₃](PF₆)₂ undergoes solvolysis when heated in acetone, forming a difluorophosphate-bridged complex [(η⁵-C₅Me₅)Rh(μ-OPF₂O)₃Rh(η⁵-C₅Me₅)]PF₆.^[15]^[16]

Applications

Practical uses of the hexafluorophosphate ion typically exploit one or more of the following properties: that it is a non-coordinating anion; that hexafluorophosphate compounds are typically soluble in organic solvents, particularly polar ones, but have low solubility in aqueous solution; or, that it has a high degree of stability, including resistance to both acidic and basic hydrolysis.

Secondary batteries

The main commercial use of hexafluorophosphate is as its lithium salt, lithium hexafluorophosphate. This salt, in combination with dimethyl carbonate, is a common electrolyte in commercial secondary batteries such as lithium-ion cells. This application exploits the high solubility of hexafluorophosphate salts in organic solvents and the resistance of these salts to reduction by the alkali metal cathode.^[17] Since the lithium ions in these batteries are generally present as coordination complexes within the electrolyte,^[18] the non-coordinating nature of the hexafluorophosphate ion is also a useful property for these applications.

Ionic liquids

Room temperature ionic liquids such as 1-butyl-3-methylimidazolium hexafluorophosphate (typically abbreviated as bmimPF₆) have been prepared.^[19] The advantage of the anion exchange in favour of a non-coordinating anion is that the resulting ionic liquid has much greater thermal stability. 1-Butyl-3-methylimidazolium chloride decomposes to N-methylimidazole and 1-chlorobutane or to N-butylimidazole and chloromethane. Such decompositions are not possible for bmimPF₆ However, thermal decompositions of hexafluorophosphate ionic liquids to generate hydrogen fluoride gas are known.^[11]

References

1. ^¹{{Cite web|title = Hexafluorophosphate(1-) (CHEBI:30201)|url = https://www.ebi.ac.uk/chebi/searchId.do?chebiId=30201|work = Chemical Entities of Biological Interest (ChEBI)|location = UK|publisher = European Bioinformatics Institute}}
2. ^{{cite book| title = Synthetic Coordination Chemistry: Principles and Practice| last1 = Davies| first1 = J. A.| publisher = World Scientific| year = 1996| isbn = 981-02-2084-7| page = 165}}
3. ^{{cite book| series = New Aspects in Phosphorus Chemistry| title = New Trends in Hexacoordinated Phosphorus Chemistry| volume = 5| last1 = Constant| first1 = S.| last2 = Lacour| first2 = J.| editor = Majoral, J.-P.| publisher = Springer| year = 2005| isbn = 3-540-22498-X| page = 3}}
4. ^{{cite journal | last1 = Woyski | first1 = M. M. | title = Hexafluorophosphates of Sodium, Ammonium, and Potassium | journal = Inorg. Synth. | volume = 3 | pages = 111–117 | doi = 10.1002/9780470132340.ch29 | year = 1950}}
5. ^{{cite book|title = Superacid Chemistry|last1 = Molnar|first1 = A.|last2 = Surya Prakash|first2 = G. K.|last3 = Sommer|first3 = J.|edition = 2nd|publisher = Wiley-Interscience|year = 2009|isbn = 0-471-59668-X|page = 44}}
6. ^{{cite journal |last1= Affsprung|first1= H. E.|last2= Archer|first2= V. S.|year= 1963|title= Determination of Hexafluorophosphate by Amperometric Titration with Tetraphenylarsonium Chloride|journal= Anal. Chem.|volume= 35|issue= 8|pages= 976–978|doi= 10.1021/ac60201a017}}
7. ^{{cite journal |last1= Affsprung|first1= H. E.|last2= Archer|first2= V. S.|year= 1963|title= Gravimetric Determination of Hexafluorophosphate as Tetraphenylarsonium Hexafluorophosphate|journal= Anal. Chem.|volume= 35|issue= 12|pages= 1912–1913|doi= 10.1021/ac60205a036}}
8. ^{{cite journal |last2= Doolittle|first2= F. G.|last1= Archer|first1= V. S.|year= 1967|title= Spectrophotometric Determination of Hexafluorophosphate with Ferroin|journal= Anal. Chem.|volume= 39|issue= 3|pages= 371–373|doi= 10.1021/ac60247a035}}
9. ^{{cite journal |last1= Ryss|first1= I. G.|last2= Tulchinskii|first2= V. B.|year= 1964|title= Kinetika Gidroliza Iona Geksaftorofosfata {{chem|PF|6|−}}|journal= Zh. Neorg. Khim. |volume= 9|issue= 4|pages= 836–840}}
10. ^{{cite journal |last1= Gebala|first1= A. E.|last2= Jones|first2= M. M.|year= 1969|title= The Acid Catalyzed Hydrolysis of Hexafluorophosphate|journal= J. Inorg. Nucl. Chem. |volume= 31|issue= 3|pages= 771–776|doi= 10.1016/0022-1902(69)80024-2}}
11. ^¹{{cite book| title = Metal Catalysed Reactions in Ionic Liquids| volume = 29| series = Catalysis by Metal Complexes| last1 = Dyson| first1 = P. J.| editor = Geldbach, T. J.| publisher = Springer Science & Business| year = 2005| isbn = 1-4020-3914-X| page = 27}}
12. ^{{cite journal | last1 = Mayfield | first1 = H. G. | last2 = Bull | first2 = W. E. | title = Co-ordinating Tendencies of the Hexafluorophosphate Ion | year = 1971 | journal = J. Chem. Soc. A | issue = 14 | pages = 2279–2281 | doi = 10.1039/J19710002279}}
13. ^{{cite journal|title = Application of Microwave Dielectric Loss Heating Effects for the Rapid and Convenient Synthesis of Organometallic Compounds|year = 1989|last1 = Baghurst|first1 = D. R.|last2 = Mingos|first2 = D. M. P.|last3 = Watson|first3 = M. J.|journal = J. Organomet. Chem.|volume = 368|issue = 3|pages = C43–C45|url = |doi = 10.1016/0022-328X(89)85418-X|last4 = Watson|first4 = Michael J.}}
14. ^{{cite journal | last1 = Kubas | first1 = G. J. | year = 1979 | title = Tetrakis(acetonitirile)copper(I) Hexaflurorophosphate | journal = Inorg. Synth. | volume = 19 | pages = 90–91 | doi = 10.1002/9780470132593.ch15 }}
15. ^{{cite journal |last1= Thompson|first1= S. J.|last2= Bailey|first2= P. M.|last3= White|first3= C.|last4= Maitlis|first4= P. M.|authorlink4=Peter Maitlis|year= 1976|title= Solvolysis of the Hexafluorophosphate Ion and the Structure of [Tris(μ-difluorophosphato)bis(penta-methylcyclopentadienylrhodium)] Hexafluorophosphate|journal= Angew. Chem. Int. Ed.|volume= 15|issue= 8|pages= 490–491|doi= 10.1002/anie.197604901}}
16. ^{{cite journal |last2= Thompson|first2= S. J.|last1= White|first1= C.|last3= Maitlis|first3= P. M.|authorlink3= Peter Maitlis|year= 1977|title= Pentamethylcyclopentadienyl-rhodium and -iridium Complexes XIV. The Solvolysis of Coordinated Acetone Solvent Species to Tris(μ-difluorophosphato)bis[η⁵-pentamethylcyclopentadienylrhodium(III)] Hexafluorophosphate, to the η⁵-(2,4-dimethyl-1-oxapenta-1,3-dienyl)(pentamethylcyclopentadienyl)iridium Cation, or to the η⁵-(2-hydroxy-4-methylpentadienyl)(η⁵-pentamethylcyclopentadienyl)iridium Cation|journal= J. Organomet. Chem.|volume= 134|issue= 3|pages= 319–325|doi= 10.1016/S0022-328X(00)93278-9}}
17. ^{{cite journal|title = Challenges for Rechargeable Li Batteries|first1 = J. B.|last1 = Goodenough|first2 = Y.|last2 = Kim|journal = Chem. Mater.|year = 2010|volume = 22|issue = 3|pages = 587–603|doi = 10.1021/cm901452z}}
18. ^{{cite web|url = http://www.tek.com/Measurement/Service/msds/01914600.pdf|title = MSDS: National Power Corp Lithium Ion Batteries|work = tek.com|publisher = Tektronix Inc.|date = 7 May 2004|accessdate = 11 June 2010}}
19. ^{{Cite journal| author3 = Alan R. Kennedy| author2 = John D. Holbrey| last1 = Gordon| author4 = Kenneth R. Seddon| issue = 12 | first1 = C. M.| title = Ionic liquid crystals: hexafluorophosphate salts| pages = 2627–2636| year = 1998 | doi = 10.1039/a806169f| journal = Journal of Materials Chemistry| volume = 8}}