Triphenylphosphine

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Triphenylphosphine
Triphenylphosphine-2D-skeletal Smokefoot-style.svg
Triphenylphosphine-ray-3D-balls.png
Triphenylphosphine-3D-vdW.png
Sample of triphenylphosphine.jpg
Names
Preferred IUPAC name
Triphenylphosphane [1]
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.009.124 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 210-036-0
PubChem CID
RTECS number
  • SZ3500000
UNII
UN number 3077
  • InChI=1S/C18H15P/c1-4-10-16(11-5-1)19(17-12-6-2-7-13-17)18-14-8-3-9-15-18/h1-15H Yes check.svgY
    Key: RIOQSEWOXXDEQQ-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C18H15P/c1-4-10-16(11-5-1)19(17-12-6-2-7-13-17)18-14-8-3-9-15-18/h1-15H
    Key: RIOQSEWOXXDEQQ-UHFFFAOYAH
  • c1ccccc1P(c2ccccc2)c3ccccc3
Properties
C18H15P
Molar mass 262.292 g·mol−1
AppearanceWhite Solid
Density 1.1 g cm−3, solid
Melting point 80 °C (176 °F; 353 K)
Boiling point 377 °C (711 °F; 650 K)
Insoluble
Solubility organic solvents
Acidity (pKa)7.64 [2] (pKa of conjugate acid in acetonitrile)

2.73 [3] (pKa of conjugate acid, aqueous scale)

-166.8·10−6 cm3/mol
1.59; εr, etc.
Structure
Pyramidal
1.4 - 1.44 D [4]
Hazards
GHS labelling:
GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg
Danger
H302, H317, H350, H412
P201, P202, P261, P264, P270, P272, P273, P280, P281, P301+P312, P302+P352, P308+P313, P321, P330, P333+P313, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
2
1
2
Flash point 180 °C (356 °F; 453 K)
Safety data sheet (SDS) Fisher Scientific
Related compounds
Trimethylphosphine
Phosphine
Related compounds
Triphenylamine
Triphenylarsine
Triphenylstibine
Triphenylphosphine oxide
Triphenylphosphine sulfide
Triphenylphosphine dichloride
Triphenylphosphine selenide
Pd(PPh3)4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to P Ph3 or Ph3P. It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

Contents

Preparation and structure

Triphenylphosphine can be prepared in the laboratory by treatment of phosphorus trichloride with phenylmagnesium bromide or phenyllithium. The industrial synthesis involves the reaction between phosphorus trichloride, chlorobenzene, and sodium: [5]

PCl3 + 3 PhCl + 6 Na → PPh3 + 6 NaCl

Triphenylphosphine crystallizes in triclinic [6] and monoclinic modification. [7] In both cases, the molecule adopts a pyramidal structure with propeller-like arrangement of the three phenyl groups.

Principal reactions with chalcogens, halogens, and acids

Oxidation

Triphenylphosphine undergoes slow oxidation by air to give triphenylphosphine oxide, Ph3PO:

2 PPh3 + O2 → 2 OPPh3

This impurity can be removed by recrystallisation of PPh3 from either hot ethanol or isopropanol. [8] This method capitalizes on the fact that OPPh3 is more polar and hence more soluble in polar solvents than PPh3.

Triphenylphosphine abstracts sulfur from polysulfide compounds, episulfides, and elemental sulfur. Simple organosulfur compounds such as thiols and thioethers are unreactive, however. The phosphorus-containing product is triphenylphosphine sulfide, Ph3PS. This reaction can be employed to assay the "labile" S0 content of a sample, say vulcanized rubber. Triphenylphosphine selenide, Ph3PSe, may be easily prepared via treatment of PPh3 with red (alpha-monoclinic) Se. Salts of selenocyanate, SeCN, are used as the Se0 source. PPh3 can also form an adduct with Te, although this adduct primarily exists as (Ph3P)2Te rather than PPh3Te. [9]

Aryl azides react with PPh3 to give phosphanimines, analogues of OPPh3, via the Staudinger reaction. Illustrative is the preparation of triphenylphosphine phenylimide:

PPh3 + PhN3 → PhNPPh3 + N2

The phosphanimine can be hydrolyzed to the amine. Typically the intermediate phosphanimine is not isolated.

PPh3 + RN3 + H2O → OPPh3 + N2 + RNH2

Chlorination

Cl2 adds to PPh3 to give triphenylphosphine dichloride ([PPh3Cl]Cl), which exists as the moisture-sensitive phosphonium halide. This reagent is used to convert alcohols to alkyl chlorides in organic synthesis. Bis(triphenylphosphine)iminium chloride (PPN+Cl, formula [(C6H5)3P)2N]Cl is prepared from triphenylphosphine dichloride: [10]

2 Ph3PCl2 + NH2OH·HCl + Ph3P → {[Ph3P]2N}Cl + 4HCl + Ph3PO

Protonation

PPh3 is a weak base (aqueous pKaH = 2.73, determined electrochemically), although it is a considerably stronger base than NPh3 (estimated aqueous pKaH < –3). [11] It forms isolable triphenylphosphonium salts with strong acids such as HBr: [12]

P(C6H5)3 + HBr → [HP(C6H5)3]+Br

Organic reactions

PPh3 is widely used in organic synthesis. The properties that guide its usage are its nucleophilicity and its reducing character. [13] The nucleophilicity of PPh3 is indicated by its reactivity toward electrophilic alkenes, such as Michael-acceptors, and alkyl halides. It is also used in the synthesis of biaryl compounds, such as the Suzuki reaction.

Quaternization

PPh3 combines with alkyl halides to give phosphonium salts. This quaternization reaction is particularly fast for benzylic and allylic halides:

PPh3 + CH3I → [CH3PPh3]+I

These salts, which can often be isolated as crystalline solids, react with strong bases to form ylides, which are reagents in the Wittig reactions.

Aryl halides will quaternize PPh3 to give tetraphenylphosphonium salts:

PPh3 + PhBr → [PPh4]Br

The reaction however requires elevated temperatures and metal catalysts.

Mitsunobu reaction

In the Mitsunobu reaction, a mixture of triphenylphosphine and diisopropyl azodicarboxylate ("DIAD", or its diethyl analogue, DEAD) converts an alcohol and a carboxylic acid to an ester. DIAD is reduced as it serves as the hydrogen acceptor, and the PPh3 is oxidized to OPPh3.

Appel reaction

In the Appel reaction, a mixture of PPh3 and CX4 (X = Cl, Br) is used to convert alcohols to alkyl halides. Triphenylphosphine oxide (OPPh3) is a byproduct.

PPh3 + CBr4 + RCH2OH → OPPh3 + RCH2Br + HCBr3

This reaction commences with nucleophilic attack of PPh3 on CBr4, an extension of the quaternization reaction listed above.

Deoxygenation

The easy oxygenation of PPh3 is exploited in its use to deoxygenate organic peroxides, which generally occurs with retention of configuration:

PPh3 + RO2H → OPPh3 + ROH (R = alkyl)

It is also used for the decomposition of organic ozonides to ketones and aldehydes, although dimethyl sulfide is more popular for the reaction as the side product, dimethyl sulfoxide is more readily separated from the reaction mixture than triphenylphosphine oxide. Aromatic N-oxides are reduced to the corresponding amine in high yield at room temperature with irradiation: [14]

Deoxygenation of an aromatic amine oxide using triphenylphosphine.png

Sulfonation

Sulfonation of PPh3 gives tris(3-sulfophenyl)phosphine, P(C6H4-3-SO3)3 (TPPTS), usually isolated as the trisodium salt. In contrast to PPh3, TPPTS is water-soluble, as are its metal derivatives. Rhodium complexes of TPPTS are used in certain industrial hydroformylation reactions. [15]

3,3',3''-Phosphanetriyltris(benzenesulfonic acid) trisodium salt is a water-soluble derivative of triphenylphosphine. TPPTS.png
3,3,3-Phosphanetriyltris(benzenesulfonic acid) trisodium salt is a water-soluble derivative of triphenylphosphine.

Reduction to diphenylphosphide

Lithium in THF as well as Na or K react with PPh3 to give Ph2PM (M = Li, Na, K). These salts are versatile precursors to tertiary phosphines. [16] [17] For example, 1,2-dibromoethane and Ph2PM react to give Ph2PCH2CH2PPh2. Weak acids such ammonium chloride, convert Ph2PM (M = Li, Na, K) into diphenylphosphine: [17]

(C6H5)2PM + H2O → (C6H5)2PH + MOH

Transition metal complexes

Triphenylphosphine binds well to most transition metals, especially those in the middle and late transition metals of groups 7–10. [18] In terms of steric bulk, PPh3 has a Tolman cone angle of 145°, [19] which is intermediate between those of P(C6H11)3 (170°) and P(CH3)3 (115°). In an early application in homogeneous catalysis, NiBr2(PPh3)2 was used by Walter Reppe for the synthesis of acrylate esters from alkynes, carbon monoxide, and alcohols. [20] The use of PPh3 was popularized by its use in the hydroformylation catalyst RhH(PPh3)3(CO).

Polymer-anchored PPh3 derivatives

Polymeric analogues of PPh3 are known whereby polystyrene is modified with PPh2 groups at the para position. Such polymers can be employed in many of the applications used for PPh3 with the advantage that the polymer, being insoluble, can be separated from products by simple filtration of reaction slurries. Such polymers are prepared via treatment of 4-lithiophenyl-substituted polystyrene with chlorodiphenylphosphine (PPh2Cl).

See also

Related Research Articles

An ylide or ylid is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both atoms have full octets of electrons. The result can be viewed as a structure in which two adjacent atoms are connected by both a covalent and an ionic bond; normally written X+–Y. Ylides are thus 1,2-dipolar compounds, and a subclass of zwitterions. They appear in organic chemistry as reagents or reactive intermediates.

<span class="mw-page-title-main">Appel reaction</span>

The Appel reaction is an organic reaction that converts an alcohol into an alkyl chloride using triphenylphosphine and carbon tetrachloride. The use of carbon tetrabromide or bromine as a halide source will yield alkyl bromides, whereas using carbon tetraiodide, methyl iodide or iodine gives alkyl iodides. The reaction is credited to and named after Rolf Appel, it had however been described earlier. The use of this reaction is becoming less common, due to carbon tetrachloride being restricted under the Montreal protocol.

<span class="mw-page-title-main">Phosphonium</span> Family of polyatomic cations containing phosphorus

In chemistry, the term phosphonium describes polyatomic cations with the chemical formula PR+
4
. These cations have tetrahedral structures. The salts are generally colorless or take the color of the anions.

<span class="mw-page-title-main">Phosphorus trichloride</span> Chemical compound

Phosphorus trichloride is an inorganic compound with the chemical formula PCl3. A colorless liquid when pure, it is an important industrial chemical, being used for the manufacture of phosphites and other organophosphorus compounds. It is toxic and reacts readily with water to release hydrogen chloride.

<span class="mw-page-title-main">Michaelis–Arbuzov reaction</span>

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. The picture below shows the most common types of substrates undergoing the Arbuzov reaction; phosphite esters (1) react to form phosphonates (2), phosphonites (3) react to form phosphinates (4) and phosphinites (5) react to form phosphine oxides (6).

<span class="mw-page-title-main">Rhodium(III) chloride</span> Chemical compound

Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)n, where n varies from 0 to 3. These are diamagnetic solids featuring octahedral Rh(III) centres. Depending on the value of n, the material is either a dense brown solid or a soluble reddish salt. The soluble trihydrated (n = 3) salt is widely used to prepare compounds used in homogeneous catalysis, notably for the industrial production of acetic acid and hydroformylation.

Organophosphorus chemistry is the scientific study of the synthesis and properties of organophosphorus compounds, which are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective insecticides, although some are extremely toxic to humans, including sarin and VX nerve agents.

<span class="mw-page-title-main">Chloro(triphenylphosphine)gold(I)</span> Chemical compound

Chloro(triphenylphosphine)gold(I) or triphenylphosphinegold(I) chloride is a coordination complex with the formula (Ph3P)AuCl. This colorless solid is a common reagent for research on gold compounds.

<span class="mw-page-title-main">Triphenylphosphine oxide</span> Chemical compound

Triphenylphosphine oxide (often abbreviated TPPO) is the organophosphorus compound with the formula OP(C6H5)3, also written as Ph3PO or PPh3O (Ph = C6H5). It is one of the more common phosphine oxides. This colourless crystalline compound is a common but potentially useful waste product in reactions involving triphenylphosphine. It is a popular reagent to induce the crystallizing of chemical compounds.

Organophosphines are organophosphorus compounds with the formula PRnH3−n, where R is an organic substituent. These compounds can be classified according to the value of n: primary phosphines (n = 1), secondary phosphines (n = 2), tertiary phosphines (n = 3). All adopt pyramidal structures. Organophosphines are generally colorless, lipophilic liquids or solids. The parent of the organophosphines is phosphine (PH3).

<span class="mw-page-title-main">Bis(triphenylphosphine)iminium chloride</span> Chemical compound

Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula [( 3P)2N]Cl, often abbreviated [(Ph3P)2N]Cl, where Ph is phenyl C6H5, or even abbreviated [PPN]Cl or [PNP]Cl or PPNCl or PNPCl, where PPN or PNP stands for (Ph3P)2N. This colorless salt is a source of the [(Ph3P)2N]+ cation, which is used as an unreactive and weakly coordinating cation to isolate reactive anions. [(Ph3P)2N]+ is a phosphazene.

<span class="mw-page-title-main">Tetraphenylphosphonium chloride</span> Chemical compound

Tetraphenylphosphonium chloride is the chemical compound with the formula [(C6H5)4P]Cl, abbreviated Ph4PCl or PPh4Cl or [PPh4]Cl, where Ph stands for phenyl. Tetraphenylphosphonium and especially tetraphenylarsonium salts were formerly of interest in gravimetric analysis of perchlorate and related oxyanions. This colourless salt is used to generate lipophilic salts from inorganic and organometallic anions. Thus, [Ph4P]+ is useful as a phase-transfer catalyst, again because it allows inorganic anions to dissolve in organic solvents.

Martin Arthur Bennett FRS is an Australian inorganic chemist. He gained recognition for studies on the co-ordination chemistry of tertiary phosphines, olefins, and acetylenes, and the relationship of their behaviour to homogeneous catalysis.

<span class="mw-page-title-main">Diphenylphosphine</span> Chemical compound

Diphenylphosphine, also known as diphenylphosphane, is an organophosphorus compound with the formula (C6H5)2PH. This foul-smelling, colorless liquid is easily oxidized in air. It is a precursor to organophosphorus ligands for use as catalysts.

<span class="mw-page-title-main">Chlorodiphenylphosphine</span> Chemical compound

Chlorodiphenylphosphine is an organophosphorus compound with the formula (C6H5)2PCl, abbreviated Ph2PCl. It is a colourless oily liquid with a pungent odor that is often described as being garlic-like and detectable even in the ppb range. It is useful reagent for introducing the Ph2P group into molecules, which includes many ligands. Like other halophosphines, Ph2PCl is reactive with many nucleophiles such as water and easily oxidized even by air.

<span class="mw-page-title-main">Triphenylphosphine dichloride</span> Chemical compound

Triphenylphosphine dichloride, (C6H5)3PCl2, is a chlorinating agent widely used in organic chemistry. Applications include the conversion of alcohols and ethers to alkyl chlorides, the cleavage of epoxides to vicinal dichlorides and the chlorination of carboxylic acids to acyl chlorides.

Oxophilicity is the tendency of certain chemical compounds to form oxides by hydrolysis or abstraction of an oxygen atom from another molecule, often from organic compounds. The term is often used to describe metal centers, commonly the early transition metals such as titanium, niobium, and tungsten. Oxophilicity is often stated to be related to the hardness of the element, within the HSAB theory, but it has been shown that oxophilicity depends more on the electronegativity and effective nuclear charge of the element than on its hardness. This explains why the early transition metals, whose electronegativities and effective nuclear charges are low, are very oxophilic. Many main group compounds are also oxophilic, such as derivatives of aluminium, silicon, and phosphorus(III). The handling of oxophilic compounds often requires air-free techniques.

<span class="mw-page-title-main">Dimethylphenylphosphine</span> Chemical compound

Dimethylphenylphosphine is an organophosphorus compound with a formula P(C6H5)(CH3)2. The phosphorus is connected to a phenyl group and two methyl groups, making it the simplest aromatic alkylphosphine. It is colorless air sensitive liquid. It is a member of series (CH3)3-n(C6H5)2P that also includes n = 0, n = 2, and n = 3 that are often employed as ligands in metal phosphine complexes.

<span class="mw-page-title-main">Metal-phosphine complex</span>

A metal-phosphine complex is a coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R3P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. Prominent examples of metal phosphine complexes include Wilkinson's catalyst (Rh(PPh3)3Cl), Grubbs' catalyst, and tetrakis(triphenylphosphine)palladium(0).

In organic chemistry, Wittig reagents are organophosphorus compounds of the formula R3P=CHR', where R is usually phenyl. They are used to convert ketones and aldehydes to alkenes:

References

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  2. Haav, Kristjan; Saame, Jaan; Kütt, Agnes; Leito, Ivo (2012). "Basicity of Phosphanes and Diphosphanes in Acetonitrile". European Journal of Organic Chemistry. 2012 (11): 2167–2172. doi: 10.1002/ejoc.201200009 . ISSN   1434-193X.
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  6. Kooijman, H.; Spek, A. L.; van Bommel, K. J. C.; Verboom, W.; Reinhoudt, D. N. (1998). "A Triclinic Modification of Triphenylphosphine" (PDF). Acta Crystallographica. C54 (11): 1695–1698. Bibcode:1998AcCrC..54.1695K. doi:10.1107/S0108270198009305.
  7. Dunne, B. J.; Orpen, A. G. (1991). "Triphenylphosphine: a Redetermination" (PDF). Acta Crystallographica. C47 (2): 345–347. Bibcode:1991AcCrC..47..345D. doi:10.1107/S010827019000508X.
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  11. Allman, Tim; Goel, Ram G. (1982-03-15). "The basicity of phosphines". Canadian Journal of Chemistry. 60 (6): 716–722. doi: 10.1139/v82-106 . ISSN   0008-4042.
  12. Hercouet, A.; LeCorre, M. (1988) Triphenylphosphonium bromide: A convenient and quantitative source of gaseous hydrogen bromide. Synthesis, 157–158
  13. Cobb, J. E.; Cribbs, C. M.; Henke, B. R.; Uehling, D. E.; Hernan, A. G.; Martin, C.; Rayner, C. M. (2004). "Triphenylphosphine". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rt366.pub2. ISBN   0-471-93623-5.
  14. Burke, S. D.; Danheiser, R. L. (1999). "Triphenylphosphine". Handbook of Reagents for Organic Synthesis, Oxidizing and Reducing Agents. Wiley. p. 495. ISBN   978-0-471-97926-5.
  15. Herrmann, W. A.; Kohlpaintner, C. W. (2007). "Syntheses of Water-Soluble Phosphines and their Transition Metal Complexes". Inorganic Syntheses. Vol. 32. pp. 8–25. doi:10.1002/9780470132630.ch2. ISBN   978-0-470-13263-0.{{cite book}}: |journal= ignored (help)
  16. George W. Luther III; Gordon Beyerle (1977). "Lithium Diphenylphosphide and Diphenyl(Trimethylsilyl)Phosphine". Inorganic Syntheses. Vol. 17. pp. 186–188. doi:10.1002/9780470132487.ch51. ISBN   978-0-470-13248-7.
  17. 1 2 V. D. Bianco S. Doronzo (1976). "Diphenylphosphine". Inorganic Syntheses. Vol. 16. pp. 161–188. doi:10.1002/9780470132470.ch43. ISBN   978-0-470-13247-0.
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    • Reppe, W.; Schweckendiek, W. J. (1948). "Cyclisierende Polymerisation von Acetylen. III Benzol, Benzolderivate und hydroaromatische Verbindungen". Justus Liebigs Annalen der Chemie. 560 (1): 104–116. doi:10.1002/jlac.19485600104.