Hexafluorophosphate: Difference between revisions
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}}</ref> but is generally extremely stable in solution. [[Hydrolysis]] to the [[phosphate]] ion is very slow even in concentrated acid with warming,<ref>{{cite journal |last1= Gebala|first1= A. E.|last2= Jones|first2= M. M.|year= 1969|title= The Acid Catalyzed Hydrolysis of Hexafluorophosphate|journal= [[Polyhedron (journal)|J. Inorg. Nucl. Chem.]]{{ref|Polyhedron|a|noid=noid}}|volume= 31|issue= 3|pages= 771-776|doi= 10.1016/0022-1902(69)80024-2}}</ref> and even slower under basic conditions.<ref>{{cite journal |last1= Ryss|first1= I. G.|last2= Tulchinskii|first2= V. B.|year= 1964|title= Kinetika Gidroliza Iona Geksaftorofosfata PF<sub>6</sub><sup>-</sup>|journal= Zh. Neorg. Khim.{{ref|Russian|b|noid=noid}}|volume= 9|issue= 4|pages= 836-840}}</ref> |
}}</ref> but is generally extremely stable in solution. [[Hydrolysis]] to the [[phosphate]] ion is very slow even in concentrated acid with warming,<ref>{{cite journal |last1= Gebala|first1= A. E.|last2= Jones|first2= M. M.|year= 1969|title= The Acid Catalyzed Hydrolysis of Hexafluorophosphate|journal= [[Polyhedron (journal)|J. Inorg. Nucl. Chem.]]{{ref|Polyhedron|a|noid=noid}}|volume= 31|issue= 3|pages= 771-776|doi= 10.1016/0022-1902(69)80024-2}}</ref> and even slower under basic conditions.<ref>{{cite journal |last1= Ryss|first1= I. G.|last2= Tulchinskii|first2= V. B.|year= 1964|title= Kinetika Gidroliza Iona Geksaftorofosfata PF<sub>6</sub><sup>-</sup>|journal= Zh. Neorg. Khim.{{ref|Russian|b|noid=noid}}|volume= 9|issue= 4|pages= 836-840}}</ref> |
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==Synthesis== |
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[[Halide]] anions are easily replaced with {{chem|PF|6|-}} by reaction with [[silver hexafluorophosphate]] as the precipitation of insoluble silver halide [[salt (chemistry)|salt]] helps drive this reaction to completion. Some room temperature ionic liquids, such as [[1-Butyl-3-methylimidazolium hexafluorophosphate|bmimPF<sub>6</sub>]], use {{chem|PF|6|-}} as a counterion.<ref>{{cite doi|10.1039/a806169f}}</ref> |
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Hexafluorophosphate salts can be prepared by the reaction of [[Phosphorus pentachloride]] and alkali or ammonium halide in a solution of [[hydrogen fluoride]]: <ref>{{cite journal | author = Woyski, M. M. | title = Hexafluorophosphates of Sodium, Ammonium, and Potassium | journal = [[Inorg. Synth.]] | volume = 3 | pages = 111–117 | doi = 10.1002/9780470132340.ch29 | year = 1950 | last2 = Shenk | first2 = W. J. | last3 = Pellon | first3 = E. R.}}</ref> |
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:PCl<sub>5</sub> + MCl + 6 HF → MPF<sub>6</sub> + 6 HCl |
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These reactions require specialized equipment associated with the hazards of the hydrogen fluoride solvent. |
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==Applications== |
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Also, many [[imidazolium]] and [[formamidinium]] hexafluorophosphate salts are insoluble in water. The addition of [[ammonium hexafluorophosphate]] (NH<sub>4</sub>PF<sub>6</sub>) to an aqueous solution of the formamdinium/imidazolium salt results in a precipitate of the formamidinium/imidazolium hexafluorophosphate salt which can be gathered by [[filtration]]. This method can have advantages over the silver hexafluorophosphate method mentioned above in terms of expense and in systems where contamination with metal ions is strongly discouraged. |
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The main commercial use of hexafluorophosphate is as its lithium salt, [[lithium hexafluorophosphate]]. This salt in combination with [[dimethylcarbonate]], is a common electrolyte in commercial secondary batteries. 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.<ref>"Challenges for Rechargeable Li Batteries" J. B. Goodenough, Y. Kim ''Chemistry of Materials'', 2010, volume 22, pp. 587–603. {{DOI|10.1021/cm901452z}}</ref> |
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===Organic and organometallic chemistry=== |
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| ⚫ | Hexafluorophosphate salts are |
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In the research laboratory, {{chem|PF|6|-}} is often used to generate organometallic and organic salts that are soluble in organic solvents. One route to such compounds involves reactions with [[silver hexafluorophosphate]] with the halide salt. Precipitation of insoluble silver halide [[salt (chemistry)|salt]] 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]] (NH<sub>4</sub>PF<sub>6</sub>) to aqueous solutions of many organic and inorganic salts gives solid precipitates of hexafluorophosphate salts. This method can have advantages over the silver hexafluorophosphate method in terms of expense and in systems where contamination with metal ions is strongly discouraged. In this way, some room temperature ionic liquids have been prepared, such as [[1-Butyl-3-methylimidazolium hexafluorophosphate|bmimPF<sub>6</sub>]], use {{chem|PF|6|-}} as a counterion.<ref>{{cite doi|10.1039/a806169f}}</ref> |
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| ⚫ | Hexafluorophosphate salts are in [[organometallic chemistry|organometallic]] [[chemical synthesis|syntheses]] to provide an inert and non-coordinating counterion. [[Tetrafluoroborate]] salts are a common alternative choice. However, [[solvolysis]] reactions of the hexafluorophosphate ion are known - for example, the tris([[solvent]]) [[organorhodium chemistry|rhodium]] complex [(η<sup>5</sup>-C<sub>5</sub>[[methyl|Me]]<sub>5</sub>)Rh(Me<sub>2</sub>CO)<sub>3</sub>](PF<sub>6</sub>)<sub>2</sub> undergoes solvolysis when heated in [[acetone]], forming a difluorophosphate-bridged complex [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)Rh(μ-OPF<sub>2</sub>O)<sub>3</sub>Rh(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)]PF<sub>6</sub>.<ref>{{cite journal |last1= Thompson|first1= S. J.|last2= Bailey|first2= P. M.|last3= White|first3= C.|last4= Maitlis|first4= P. M.|year= 1976|title= Solvolysis of the Hexafluorophosphate Ion and the Structure of [Tris(μ-difluorophosphato)bis(penta-methylcyclopentadienylrhodium)] Hexafluorophosphate|journal= [[Angewandte Chemie|Angew. Chem. Int. Ed.]]|volume= 15|issue= 8|pages= 490-491|doi= 10.1002/anie.197604901}}</ref><ref>{{cite journal |last2= Thompson|first2= S. J.|last1= White|first1= C.|last3= Maitlis|first3= P. M.|year= 1977|title= Pentamethylcyclopentadienyl-rhodium and -iridium Complexes '''''XIV.''''' The Solvolysis of Coordinated Acetone Solvent Species to Tris(μ-difluorophosphato)bis[η<sup>5</sup>-pentamethylcyclopentadienylrhodium(III)] Hexafluorophosphate, to the η<sup>5</sup>-(2,4-dimethyl-1-oxapenta-1,3-dienyl)(pentamethylcyclopentadienyl)iridium Cation, or to the η<sup>5</sup>-(2-hydroxy-4-methylpentadienyl)(η<sup>5</sup>-pentamethylcyclopentadienyl)iridium Cation|journal= [[Journal of Organometallic Chemistry|J. Organomet. Chem.]]|volume= 134|issue= 3|pages= 319-325|doi= 10.1016/S0022-328X(00)93278-9}}</ref> |
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[[Image:Partial solvolysis of hexafluorophospate.PNG|center|Heating [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)Rh(Me<sub>2</sub>CO)<sub>3</sub>](PF<sub>6</sub>)<sub>2</sub> in acetone results in the formation of the complex [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)Rh(μ-OPF<sub>2</sub>O)<sub>3</sub>Rh(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)]PF<sub>6</sub>]] |
[[Image:Partial solvolysis of hexafluorophospate.PNG|center|Heating [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)Rh(Me<sub>2</sub>CO)<sub>3</sub>](PF<sub>6</sub>)<sub>2</sub> in acetone results in the formation of the complex [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)Rh(μ-OPF<sub>2</sub>O)<sub>3</sub>Rh(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)]PF<sub>6</sub>]] |
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Revision as of 17:50, 13 August 2010
Hexafluorophosphate is an anion with chemical formula of PF−
6. As a non-coordinating anion,[1][2][3] it is a poor nucleophile. It is prone to decomposition with the release of hydrogen fluoride in ionic liquids[4] but is generally extremely stable in solution. Hydrolysis to the phosphate ion is very slow even in concentrated acid with warming,[5] and even slower under basic conditions.[6]
Synthesis
Hexafluorophosphate salts can be prepared by the reaction of Phosphorus pentachloride and alkali or ammonium halide in a solution of hydrogen fluoride: [7]
- PCl5 + MCl + 6 HF → MPF6 + 6 HCl
These reactions require specialized equipment associated with the hazards of the hydrogen fluoride solvent.
Applications
The main commercial use of hexafluorophosphate is as its lithium salt, lithium hexafluorophosphate. This salt in combination with dimethylcarbonate, is a common electrolyte in commercial secondary batteries. 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.[8]
Organic and organometallic chemistry
In the research laboratory, PF−
6 is often used to generate organometallic and organic salts that are soluble in organic solvents. One route to such compounds involves reactions with silver hexafluorophosphate with the halide salt. Precipitation of insoluble silver halide salt 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. This method can have advantages over the silver hexafluorophosphate method in terms of expense and in systems where contamination with metal ions is strongly discouraged. In this way, some room temperature ionic liquids have been prepared, such as bmimPF6, use PF−
6 as a counterion.[9]
Hexafluorophosphate salts are often included in organometallic syntheses to provide an inert and non-coordinating counterion. Tetrafluoroborate salts are a common alternative choice. However, solvolysis reactions of the hexafluorophosphate ion are known - for example, the tris(solvent) 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.[10][11]
2 in acetone results in the formation of the complex [(η5-C5Me5)Rh(μ-OPF2O)3Rh(η5-C5Me5)]PF6](https://anichin-myid.netlify.app/host-https-en.wikipedia.org/wiki/File:Partial_solvolysis_of_hexafluorophospate.PNG)
See also
References
- ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/j.inoche.2007.05.008, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1016/j.inoche.2007.05.008instead. - ^ Julian A. Davies (1996). Synthetic coordination chemistry: principles and practice. World Scientific. p. 165. ISBN 9810220847.
- ^ Samuel Constant; Jerome Lacour (2005). Jean-Pierre Majoral (ed.). New trends in hexacoordinated phosphorus chemistry. New aspects in phosphorus chemistry. Vol. 5. Springer. p. 3. ISBN 354022498X.
- ^ Paul J. Dyson (2005). Tilmann J. Geldbach (ed.). Metal catalysed reactions in ionic liquids. Catalysis by metal complexes. Vol. 29. Springer Science & Business. p. 27. ISBN 140203914X.
- ^ Gebala, A. E.; Jones, M. M. (1969). "The Acid Catalyzed Hydrolysis of Hexafluorophosphate". J. Inorg. Nucl. Chem.a. 31 (3): 771–776. doi:10.1016/0022-1902(69)80024-2.
- ^ Ryss, I. G.; Tulchinskii, V. B. (1964). "Kinetika Gidroliza Iona Geksaftorofosfata PF6-". Zh. Neorg. Khim.b. 9 (4): 836–840.
- ^ Woyski, M. M.; Shenk, W. J.; Pellon, E. R. (1950). "Hexafluorophosphates of Sodium, Ammonium, and Potassium". Inorg. Synth. 3: 111–117. doi:10.1002/9780470132340.ch29.
- ^ "Challenges for Rechargeable Li Batteries" J. B. Goodenough, Y. Kim Chemistry of Materials, 2010, volume 22, pp. 587–603. doi:10.1021/cm901452z
- ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1039/a806169f, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1039/a806169finstead. - ^ Thompson, S. J.; Bailey, P. M.; White, C.; Maitlis, P. M. (1976). "Solvolysis of the Hexafluorophosphate Ion and the Structure of [Tris(μ-difluorophosphato)bis(penta-methylcyclopentadienylrhodium)] Hexafluorophosphate". Angew. Chem. Int. Ed. 15 (8): 490–491. doi:10.1002/anie.197604901.
- ^ White, C.; Thompson, S. J.; Maitlis, P. M. (1977). "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". J. Organomet. Chem. 134 (3): 319–325. doi:10.1016/S0022-328X(00)93278-9.
Notes
^a The Journal of Inorganic and Nuclear Chemistry has since been subsumed within the journal Polyhedron
^b The journal Zhurnal Neorganicheskoi Khimii is now the Russian Journal of Inorganic Chemistry
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