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Phosphonium

April 26, 2024

In chemistry, the term phosphonium (more obscurely: phosphinium) describes polyatomic cations with the chemical formula PR+
4 (where R is a hydrogen or an alkyl, aryl, or halide group). These cations have tetrahedral structures. The salts are generally colorless or take the color of the anions.[1]

Phosphonium ion
Structure of PH+
4, the parent phosphonium cation.

Types of phosphonium cations edit

Protonated phosphines edit

The parent phosphonium is PH+
4 as found in the iodide salt, phosphonium iodide. Salts of the parent PH+
4 are rarely encountered, but this ion is an intermediate in the preparation of the industrially useful tetrakis(hydroxymethyl)phosphonium chloride:

PH3 + HCl + 4 CH2O → P(CH
2OH)+
4Cl−

Many organophosphonium salts are produced by protonation of primary, secondary, and tertiary phosphines:

PR3 + H+ → HPR+
3

The basicity of phosphines follows the usual trends, with R = alkyl being more basic than R = aryl.[2]

Tetraorganophosphonium cations edit

The most common phosphonium compounds have four organic substituents attached to phosphorus. The quaternary phosphonium cations include tetraphenylphosphonium, (C6H5)4P+ and tetramethylphosphonium P(CH
3)+
4.

 
Tetramethylphosphonium bromide[3]
 
Structure of solid "phosphorus pentachloride", illustrating its autoionization to tetrachlorophosphonium.[4]

Quaternary phosphonium cations (PR+
4) are produced by alkylation of organophosphines.[3] For example, the reaction of triphenylphosphine with methyl bromide gives methyltriphenylphosphonium bromide:

PPh3 + CH3Br → [CH3PPh3]+Br−

The methyl group in such phosphonium salts is mildly acidic, with a pKa estimated to be near 15:[5]

[CH3PPh3]+ + base → CH2=PPh3 + [Hbase]+

This deprotonation reaction gives Wittig reagents.[6]

Phosphorus pentachloride and related compounds edit

Solid phosphorus pentachloride is an ionic compound, formulated PCl+
4PCl−
6, that is, a salt containing the tetrachlorophosphonium cation.[7][8] Dilute solutions dissociate according to the following equilibrium:

PCl5 ⇌ PCl+
4 + Cl−

Triphenylphosphine dichloride (Ph3PCl2) exists both as the pentacoordinate phosphorane and as the chlorotriphenylphosphonium chloride, depending on the medium.[9] The situation is similar to that of PCl5. It is an ionic compound (PPh3Cl)+Cl− in polar solutions and a molecular species with trigonal bipyramidal molecular geometry in apolar solution.[10]

Alkoxyphosphonium salts: Arbuzov reaction edit

The Michaelis–Arbuzov reaction is the chemical reaction of a trivalent phosphorus ester with an alkyl halide to form a pentavalent phosphorus species and another alkyl halide. Commonly, the phosphorus substrate is a phosphite ester (P(OR)3) and the alkylating agent is an alkyl iodide.[11]

 
The mechanism of the Michaelis–Arbuzov reaction

Uses edit

Textile finishes edit

 
Tetrakis(hydroxymethyl)phosphonium chloride is used in production of textiles.

Tetrakis(hydroxymethyl)phosphonium chloride has industrial importance in the production of crease-resistant and flame-retardant finishes on cotton textiles and other cellulosic fabrics.[12][13] A flame-retardant finish can be prepared from THPC by the Proban Process,[14] in which THPC is treated with urea. The urea condenses with the hydroxymethyl groups on THPC. The phosphonium structure is converted to phosphine oxide as the result of this reaction.[15]

Phase-transfer catalysts and precipitating agents edit

Organic phosphonium cations are lipophilic and can be useful in phase transfer catalysis, much like quaternary ammonium salts. Salts or inorganic anions and tetraphenylphosphonium (PPh+
4) are soluble in polar organic solvents. One example is the perrhenate (PPh4[ReO4]).[16]

Reagents for organic synthesis edit

Wittig reagents are used in organic synthesis. They are derived from phosphonium salts. A strong base such as butyllithium or sodium amide is required for the deprotonation:

[Ph3P+CH2R]X− + C4H9Li → Ph3P=CHR + LiX + C4H10

One of the simplest ylides is methylenetriphenylphosphorane (Ph3P=CH2).[6]

The compounds Ph3PX2 (X = Cl, Br) are used in the Kirsanov reaction.[17] The Kinnear–Perren reaction is used to prepare alkylphosphonyl dichlorides (RP(O)Cl2) and esters (RP(O)(OR′)2). A key intermediate are alkyltrichlorophosphonium salts, obtained by the alkylation of phosphorus trichloride:[18]

RCl + PCl3 + AlCl3 → [RPCl3]+AlCl−
4

Ammonia production for "green hydrogen" edit

The main industrial procedure for the production of ammonia today is the thermal Haber-Bosch process, which generally uses fossil gas as a source of hydrogen, which is then combined with nitrogen to produce ammonia. In 2021, Professor Doug MacFarlane and collaborators Alexandr Simonov and Bryan Suryanto of Monash University devised a method of producing green ammonia that has the potential to make Haber-Bosch plants obsolete.[19] Their process is similar to the electrolysis approach for producing hydrogen. While working with local company Verdant, which wanted to make bleach from saltwater by electrolysis, Suryanto discovered that a tetraalkyl phosphonium salt allowed the efficient production of ammonia at room temperature.[20]

See also edit

References edit

  1. ^ Corbridge, D. E. C. (1995). Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology (5th ed.). Amsterdam: Elsevier. ISBN 978-0-444-89307-9.
  2. ^ Li, T.; Lough, A. J.; Morris, R. H. (2007). "An Acidity Scale of Tetrafluoroborate Salts of Phosphonium and Iron Hydride Compounds in [D2]Dichloromethane". Chem. Eur. J. 13 (13): 3796–3803. doi:10.1002/chem.200601484. PMID 17245785.
  3. ^ a b H.-F. Klein (1978). "Trimethylphosphonium Methylide (Trimethyl Methylenephosphorane)". Inorganic Syntheses. Inorganic Syntheses. Vol. 18. pp. 138–140. doi:10.1002/9780470132494.ch23. ISBN 9780470132494.
  4. ^ Finch, A.; Fitch, A.N.; Gates, P.N. (1993). "Crystal and Molecular structure of a metastable modification of phosphorus pentachloride". Journal of the Chemical Society, Chemical Communications (11): 957–958. doi:10.1039/c39930000957.
  5. ^ Ling-Chung, Sim; Sales, Keith D.; Utley, James H. P. (1990). "Measurement of pKa Values for Phosphonium Salts via the Kinetics of Proton Transfer to an Electrogenerated Base". Journal of the Chemical Society, Chemical Communications (9): 662. doi:10.1039/C39900000662.
  6. ^ a b Wittig; Schoellkopf, U. (1960). "Methylenecyclohexane". Organic Syntheses. 40: 66. doi:10.15227/orgsyn.040.0066.. Describes Ph3P=CH2.
  7. ^ Holleman, A. F.; Wiber, E.; Wiberg, N. (2001). Inorganic Chemistry. Academic Press. ISBN 978-0-12-352651-9.
  8. ^ Suter, R. W.; Knachel, H. C.; Petro, V. P.; Howatson, J. H. & Shore, S. G. (1978). "Nature of Phosphorus(V) Chloride in Ionizing and Nonionizing Solvents". Journal of the American Chemical Society. 95 (5): 1474–1479. doi:10.1021/ja00786a021.
  9. ^ S. M. Godfrey; C. A. McAuliffe; R. G. Pritchard; J. M. Sheffield (1996). "An X-ray crystallorgraphic study of the reagent Ph3PCl2; not charge-transfer, R3P–Cl–Cl, trigonal bipyramidal or [R3PCl]Cl but an unusual dinuclear ionic species, [Ph3PCl+⋯Cl–⋯+CIPPh3]Cl containing long Cl–Cl contacts". Chemical Communications (22): 2521–2522. doi:10.1039/CC9960002521.
  10. ^ Jennings, EV; Nikitin, K; Ortin, Y; Gilheany, DG (2014). "Degenerate Nucleophilic Substitution in Phosphonium Salts". J. Am. Chem. Soc. 136 (46): 16217–16226. doi:10.1021/ja507433g. PMID 25384344.
  11. ^ Bhattacharya, A. K.; Thyagarajan, G. (1981). "Michaelis–Arbuzov rearrangement". Chem. Rev. 81 (4): 415–430. doi:10.1021/cr00044a004.
  12. ^ Weil, Edward D.; Levchik, Sergei V. (2008). "Flame Retardants in Commercial Use or Development for Textiles". J. Fire Sci. 26 (3): 243–281. doi:10.1177/0734904108089485. S2CID 98355305.
  13. ^ Svara, Jürgen; Weferling, Norbert ; Hofmann, Thomas. Phosphorus Compounds, Organic. Ullmann's Encyclopedia of Industrial Chemistry. John Wiley & Sons, Inc., 2008 doi:10.1002/14356007.a19_545.pub2
  14. ^ . Rhodia Proban. Archived from the original on December 7, 2012. Retrieved February 25, 2013.
  15. ^ Reeves, Wilson A.; Guthrie, John D. (1956). "Intermediate for Flame-Resistant Polymers-Reactions of Tetrakis(hydroxymethyl)phosphonium Chloride". Industrial and Engineering Chemistry. 48 (1): 64–67. doi:10.1021/ie50553a021.
  16. ^ Dilworth, J. R.; Hussain, W.; Hutson, A. J.; Jones, C. J.; McQuillan, F. S. (1996). "Tetrahalo Oxorhenate Anions". Inorganic Syntheses. Inorganic Syntheses. Vol. XXXI. pp. 257–262. doi:10.1002/9780470132623.ch42. ISBN 9780470132623.
  17. ^ Studies in Organophosphorus Chemistry. I. Conversion of Alcohols and Phenols to Halides by Tertiary Phosphine Dihalides G. A. Wiley, R. L. Hershkowitz, B. M. Rein, B. C. Chung J. Am. Chem. Soc., 1964, 86 (5), pp 964–965 doi:10.1021/ja01059a073
  18. ^ Svara, J.; Weferling, N.; Hofmann, T. "Phosphorus Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_545.pub2. ISBN 978-3527306732.
  19. ^ Breakthrough brings green ammonia production closer to reality
  20. ^ Nitrogen reduction to ammonia at high efficiency and rates based on a phosphonium proton shuttle

April 26, 2024
phosphonium, chemistry, term, phosphonium, more, obscurely, phosphinium, describes, polyatomic, cations, with, chemical, formula, where, hydrogen, alkyl, aryl, halide, group, these, cations, have, tetrahedral, structures, salts, generally, colorless, take, col. In chemistry the term phosphonium more obscurely phosphinium describes polyatomic cations with the chemical formula PR 4 where R is a hydrogen or an alkyl aryl or halide group These cations have tetrahedral structures The salts are generally colorless or take the color of the anions 1 Phosphonium ion Structure of PH 4 the parent phosphonium cation Contents 1 Types of phosphonium cations 1 1 Protonated phosphines 1 2 Tetraorganophosphonium cations 1 3 Phosphorus pentachloride and related compounds 1 4 Alkoxyphosphonium salts Arbuzov reaction 2 Uses 2 1 Textile finishes 2 2 Phase transfer catalysts and precipitating agents 2 3 Reagents for organic synthesis 2 4 Ammonia production for green hydrogen 3 See also 4 ReferencesTypes of phosphonium cations editProtonated phosphines edit The parent phosphonium is PH 4 as found in the iodide salt phosphonium iodide Salts of the parent PH 4 are rarely encountered but this ion is an intermediate in the preparation of the industrially useful tetrakis hydroxymethyl phosphonium chloride PH3 HCl 4 CH2O P CH2 OH 4 Cl Many organophosphonium salts are produced by protonation of primary secondary and tertiary phosphines PR3 H HPR 3 The basicity of phosphines follows the usual trends with R alkyl being more basic than R aryl 2 Tetraorganophosphonium cations edit The most common phosphonium compounds have four organic substituents attached to phosphorus The quaternary phosphonium cations include tetraphenylphosphonium C6H5 4P and tetramethylphosphonium P CH3 4 nbsp Tetramethylphosphonium bromide 3 nbsp Structure of solid phosphorus pentachloride illustrating its autoionization to tetrachlorophosphonium 4 Quaternary phosphonium cations PR 4 are produced by alkylation of organophosphines 3 For example the reaction of triphenylphosphine with methyl bromide gives methyltriphenylphosphonium bromide PPh3 CH3Br CH3PPh3 Br The methyl group in such phosphonium salts is mildly acidic with a pKa estimated to be near 15 5 CH3PPh3 base CH2 PPh3 Hbase This deprotonation reaction gives Wittig reagents 6 Phosphorus pentachloride and related compounds edit Solid phosphorus pentachloride is an ionic compound formulated PCl 4 PCl 6 that is a salt containing the tetrachlorophosphonium cation 7 8 Dilute solutions dissociate according to the following equilibrium PCl5 PCl 4 Cl Triphenylphosphine dichloride Ph3PCl2 exists both as the pentacoordinate phosphorane and as the chlorotriphenylphosphonium chloride depending on the medium 9 The situation is similar to that of PCl5 It is an ionic compound PPh3Cl Cl in polar solutions and a molecular species with trigonal bipyramidal molecular geometry in apolar solution 10 Alkoxyphosphonium salts Arbuzov reaction edit The Michaelis Arbuzov reaction is the chemical reaction of a trivalent phosphorus ester with an alkyl halide to form a pentavalent phosphorus species and another alkyl halide Commonly the phosphorus substrate is a phosphite ester P OR 3 and the alkylating agent is an alkyl iodide 11 nbsp The mechanism of the Michaelis Arbuzov reactionUses editTextile finishes edit nbsp Tetrakis hydroxymethyl phosphonium chloride is used in production of textiles Tetrakis hydroxymethyl phosphonium chloride has industrial importance in the production of crease resistant and flame retardant finishes on cotton textiles and other cellulosic fabrics 12 13 A flame retardant finish can be prepared from THPC by the Proban Process 14 in which THPC is treated with urea The urea condenses with the hydroxymethyl groups on THPC The phosphonium structure is converted to phosphine oxide as the result of this reaction 15 Phase transfer catalysts and precipitating agents edit Organic phosphonium cations are lipophilic and can be useful in phase transfer catalysis much like quaternary ammonium salts Salts or inorganic anions and tetraphenylphosphonium PPh 4 are soluble in polar organic solvents One example is the perrhenate PPh4 ReO4 16 Reagents for organic synthesis edit Wittig reagents are used in organic synthesis They are derived from phosphonium salts A strong base such as butyllithium or sodium amide is required for the deprotonation Ph3P CH2R X C4H9Li Ph3P CHR LiX C4H10 One of the simplest ylides is methylenetriphenylphosphorane Ph3P CH2 6 The compounds Ph3PX2 X Cl Br are used in the Kirsanov reaction 17 The Kinnear Perren reaction is used to prepare alkylphosphonyl dichlorides RP O Cl2 and esters RP O OR 2 A key intermediate are alkyltrichlorophosphonium salts obtained by the alkylation of phosphorus trichloride 18 RCl PCl3 AlCl3 RPCl3 AlCl 4 Ammonia production for green hydrogen edit The main industrial procedure for the production of ammonia today is the thermal Haber Bosch process which generally uses fossil gas as a source of hydrogen which is then combined with nitrogen to produce ammonia In 2021 Professor Doug MacFarlane and collaborators Alexandr Simonov and Bryan Suryanto of Monash University devised a method of producing green ammonia that has the potential to make Haber Bosch plants obsolete 19 Their process is similar to the electrolysis approach for producing hydrogen While working with local company Verdant which wanted to make bleach from saltwater by electrolysis Suryanto discovered that a tetraalkyl phosphonium salt allowed the efficient production of ammonia at room temperature 20 See also editAmmonium NH 4 Arsonium AsH 4 Hydronium H3O Onium compounds Organophosphorus chemistryReferences edit Corbridge D E C 1995 Phosphorus An Outline of its Chemistry Biochemistry and Technology 5th ed Amsterdam Elsevier ISBN 978 0 444 89307 9 Li T Lough A J Morris R H 2007 An Acidity Scale of Tetrafluoroborate Salts of Phosphonium and Iron Hydride Compounds in D2 Dichloromethane Chem Eur J 13 13 3796 3803 doi 10 1002 chem 200601484 PMID 17245785 a b H F Klein 1978 Trimethylphosphonium Methylide Trimethyl Methylenephosphorane Inorganic Syntheses Inorganic Syntheses Vol 18 pp 138 140 doi 10 1002 9780470132494 ch23 ISBN 9780470132494 Finch A Fitch A N Gates P N 1993 Crystal and Molecular structure of a metastable modification of phosphorus pentachloride Journal of the Chemical Society Chemical Communications 11 957 958 doi 10 1039 c39930000957 Ling Chung Sim Sales Keith D Utley James H P 1990 Measurement of pKa Values for Phosphonium Salts via the Kinetics of Proton Transfer to an Electrogenerated Base Journal of the Chemical Society Chemical Communications 9 662 doi 10 1039 C39900000662 a b Wittig Schoellkopf U 1960 Methylenecyclohexane Organic Syntheses 40 66 doi 10 15227 orgsyn 040 0066 Describes Ph3P CH2 Holleman A F Wiber E Wiberg N 2001 Inorganic Chemistry Academic Press ISBN 978 0 12 352651 9 Suter R W Knachel H C Petro V P Howatson J H amp Shore S G 1978 Nature of Phosphorus V Chloride in Ionizing and Nonionizing Solvents Journal of the American Chemical Society 95 5 1474 1479 doi 10 1021 ja00786a021 S M Godfrey C A McAuliffe R G Pritchard J M Sheffield 1996 An X ray crystallorgraphic study of the reagent Ph3PCl2 not charge transfer R3P Cl Cl trigonal bipyramidal or R3PCl Cl but an unusual dinuclear ionic species Ph3PCl Cl CIPPh3 Cl containing long Cl Cl contacts Chemical Communications 22 2521 2522 doi 10 1039 CC9960002521 Jennings EV Nikitin K Ortin Y Gilheany DG 2014 Degenerate Nucleophilic Substitution in Phosphonium Salts J Am Chem Soc 136 46 16217 16226 doi 10 1021 ja507433g PMID 25384344 Bhattacharya A K Thyagarajan G 1981 Michaelis Arbuzov rearrangement Chem Rev 81 4 415 430 doi 10 1021 cr00044a004 Weil Edward D Levchik Sergei V 2008 Flame Retardants in Commercial Use or Development for Textiles J Fire Sci 26 3 243 281 doi 10 1177 0734904108089485 S2CID 98355305 Svara Jurgen Weferling Norbert Hofmann Thomas Phosphorus Compounds Organic Ullmann s Encyclopedia of Industrial Chemistry John Wiley amp Sons Inc 2008 doi 10 1002 14356007 a19 545 pub2 Frequently asked questions What is the PROBAN process Rhodia Proban Archived from the original on December 7 2012 Retrieved February 25 2013 Reeves Wilson A Guthrie John D 1956 Intermediate for Flame Resistant Polymers Reactions of Tetrakis hydroxymethyl phosphonium Chloride Industrial and Engineering Chemistry 48 1 64 67 doi 10 1021 ie50553a021 Dilworth J R Hussain W Hutson A J Jones C J McQuillan F S 1996 Tetrahalo Oxorhenate Anions Inorganic Syntheses Inorganic Syntheses Vol XXXI pp 257 262 doi 10 1002 9780470132623 ch42 ISBN 9780470132623 Studies in Organophosphorus Chemistry I Conversion of Alcohols and Phenols to Halides by Tertiary Phosphine Dihalides G A Wiley R L Hershkowitz B M Rein B C Chung J Am Chem Soc 1964 86 5 pp 964 965 doi 10 1021 ja01059a073 Svara J Weferling N Hofmann T Phosphorus Compounds Organic Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a19 545 pub2 ISBN 978 3527306732 Breakthrough brings green ammonia production closer to reality Nitrogen reduction to ammonia at high efficiency and rates based on a phosphonium proton shuttle Retrieved from https en wikipedia org w index php title Phosphonium amp oldid 1158095919, wikipedia, wiki, book, books, library,

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