Triphenylphosphine
Encyclopedia
Triphenylphosphine is a common organophosphorus compound with the formula P(C6H5)3 - often abbreviated to P
Ph3
or Ph3P. It is widely used in the synthesis of organic
and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene
and diethyl ether
.
with phenylmagnesium bromide
or phenyllithium
. The industrial synthesis involves the reaction between phosphorus trichloride
, chlorobenzene
, and sodium. PPh3 is pyramidal with a chiral propeller-like arrangement of the three phenyl rings. The rigidity of PPh3 contributes to the ease with which its derivatives crystallize.
, Ph3PO:
This impurity can be removed by recrystallisation
of PPh3 from either hot ethanol
or hot isopropanol. This method capitalizes on the fact that OPPh3 is more polar and hence more soluble in polar solvents than PPh3.
The easy oxygenation of PPh3 is exploited in its use to deoxygenate organic peroxides, which generally occurs with retention of configuration:
Triphenylphosphine abstracts sulfur
from polysulfide
compounds, episulfides, and elemental sulfur
. Simple organosulfur compounds such as thiol
s and thioether
s 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.
Aryl azides react with PPh3 to give imido analogue of OPPh3 via the Staudinger reaction
:
The product imides can be hydrolyzed to the amine. Typically the intermediate imidophosphorane is not isolated.
Cl2 adds to PPh3 to give triphenylphosphine dichloride
([PPh3Cl]Cl), which exists as the moisture-sensitive phosphonium halide, This reagent is used to convert alcohol
s to alkyl chlorides
in organic synthesis
.
PPh3 is a weak base, but does form stable salts with strong acids such as HBr. The product contains the phosphonium cation [HPPh3]+.
. The properties that guide its usage are its nucleophilicity and its reducing character. 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
.
s. The facility of the reaction follows the usual pattern whereby alkyl iodides and benzylic and allylic halides are particularly efficient reactants:
These salts, which are readily isolated as crystalline solids, react with strong bases to form ylide
s:
Such ylides are key reagents in the Wittig reaction
s, used to convert aldehyde
s and ketone
s into alkene
s. Nickel salts are required to react PPh3 with PhBr to give [PPh4]Br. The tetraphenylphosphonium cation is widely used to prepare crystallizable lipophilic salts.
Mitsunobu reaction
In this reaction, a mixture of PPh3 and diisopropyl azodicarboxylate
(“DIAD”, or its diethyl analogue, DEAD) converts an alcohol and a carboxylic acid to an ester. The DIAD is reduced as it serves as the hydrogen acceptor, and the PPh3 is oxidized to OPPh3
.
Appel reaction
PPh3 is oxidized again to OPPh3
in this application, which converts alcohols to alkyl halides using CX4 (X = Cl, Br):
This reaction commences with nucleophilic attack of PPh3 on CBr4, an extension of the quaternization reaction listed above.
s, especially those in the middle and late transition metals of groups 7-10. In terms of steric bulk, PPh3 has a cone angle of 145°, 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 alkyne
s, carbon monoxide
, and alcohol
s. Wilkinson's further popularized the use of PPh3, including the then revolutionary hydroformylation
catalyst RhH(PPh3)2(CO)2.
It is telling that the corresponding triphenylamine
shows little tendency to bind to metals. The difference between the coordinating power of PPh3 and NPh3 reflects the greater steric crowding around the nitrogen atom, which is smaller and favors a more tetrahedral geometry. Far more similar to PPh3 in terms of its coordinating properties is triphenylarsine
, AsPh3.
An important technique for the characterization of metal-PPh3 compounds is 31P NMR spectroscopy. Substantial shifts occur upon complexation and31P-31P spin-spin coupling can provide insight into the structure of complexes containing multiple phosphine ligands.
Illustrative PPh3 complexes:
in THF
and Na or K in NH3 react with PPh3 to give Ph2PM (M = Li, Na, K). These reactions generate equal amounts of phenyllithium (or sodium, potassium analogs thereof) C6H5M, which can be selectively converted to benzene
by selective protonation. Treatment of the resulting alkali metal diphenylphosphide with an alkylating
agent RX gives PRPh2. This method can be used to prepare such ligand
s as PMePh2, methyldiphenylphosphine. The corresponding reaction with dihaloalkanes gives bis(diphenylphosphino)alkanes. For example, 1,2-dibromoethane
and Ph2PM react to give Ph2PCH2CH2PPh2, known as 1,2-bis(diphenylphosphino)ethane
or dppe. Weak acids such ammonium chloride
, converts Ph2PM (M = Li, Na, K) into Ph2PH, known as diphenylphosphine.
. In contrast to PPh3, TPPTS is water soluble as are its metal derivatives. Rhodium complexes of TPPTS are used in certain industrial hydroformylation
reactions because the water-soluble catalyst is readily separated from the organic products.
(PPh2Cl).
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
Ph3
Phenyl group
In organic chemistry, the phenyl group or phenyl ring is a cyclic group of atoms with the formula C6H5. Phenyl groups are closely related to benzene. Phenyl groups have six carbon atoms bonded together in a hexagonal planar ring, five of which are bonded to individual hydrogen atoms, with the...
or Ph3P. It is widely used in the synthesis of organic
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
and diethyl ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
.
Preparation, structure, handling
Triphenylphosphine is a relatively inexpensive substance. It can be prepared in the laboratory by treatment of phosphorus trichloridePhosphorus trichloride
Phosphorus trichloride is a chemical compound of phosphorus and chlorine, having chemical formula PCl3. Its shape is trigonal pyramidal. It is the most important of the three phosphorus chlorides. It is an important industrial chemical, being used for the manufacture of organophosphorus compounds...
with phenylmagnesium bromide
Phenylmagnesium bromide
Phenylmagnesium bromide, with the simplified formula , is a magnesium-containing organometallic compound. It is so commonly used that it is commercially available as a solution in diethyl ether or tetrahydrofuran . Phenylmagnesium bromide is a Grignard reagent...
or phenyllithium
Phenyllithium
Phenyllithium is an organometallic agent with the empirical formula C6H5Li. It is most commonly used as a metalating agent in organic syntheses and a substitute for Grignard reagents for introducing phenyl groups in organic syntheses...
. The industrial synthesis involves the reaction between phosphorus trichloride
Phosphorus trichloride
Phosphorus trichloride is a chemical compound of phosphorus and chlorine, having chemical formula PCl3. Its shape is trigonal pyramidal. It is the most important of the three phosphorus chlorides. It is an important industrial chemical, being used for the manufacture of organophosphorus compounds...
, chlorobenzene
Chlorobenzene
Chlorobenzene is an aromatic organic compound with the chemical formula C6H5Cl. This colorless, flammable liquid is a common solvent and a widely used intermediate in the manufacture of other chemicals.-Uses:...
, and sodium. PPh3 is pyramidal with a chiral propeller-like arrangement of the three phenyl rings. The rigidity of PPh3 contributes to the ease with which its derivatives crystallize.
Principal reactions with chalcogens, halogens, and acids
Triphenylphosphine undergoes slow oxidation by air to give triphenylphosphine oxideTriphenylphosphine oxide
Triphenylphosphine oxide is the chemical compound with the formula OP3. Often chemists abbreviate the formula by writing Ph3PO or PPh3O . This white crystalline compound is a common side product in reactions involving triphenylphosphine...
, Ph3PO:
- 2 PPh3 + O2 → 2 OPPh3
This impurity can be removed by recrystallisation
Recrystallization (chemistry)
-Chemistry:In chemistry, recrystallization is a procedure for purifying compounds. The most typical situation is that a desired "compound A" is contaminated by a small amount of "impurity B". There are various methods of purification that may be attempted , which includes recrystallization...
of PPh3 from either hot ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
or hot isopropanol. This method capitalizes on the fact that OPPh3 is more polar and hence more soluble in polar solvents than PPh3.
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)
Triphenylphosphine abstracts sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
from polysulfide
Polysulfide
Polysulfides are a class of chemical compounds containing chains of sulfur atoms. There are two main classes of polysulfides: anions and organic polysulfides. Anions have the general formula Sn2−. These anions are the conjugate bases of the hydrogen polysulfides H2nSn...
compounds, episulfides, and elemental sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
. Simple organosulfur compounds such as thiol
Thiol
In organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl group...
s and thioether
Thioether
A thioether is a functional group in organosulfur chemistry with the connectivity C-S-C as shown on right. Like many other sulfur-containing compounds, volatile thioethers have foul odors. A thioether is similar to an ether except that it contains a sulfur atom in place of the oxygen...
s are unreactive, however. The phosphorus-containing product is triphenylphosphine sulfide
Triphenylphosphine sulfide
Triphenylphosphine sulfide is the organophosphorus compound with the formula 3PS, usually written Ph3PS . It is a colourless solid, which is soluble in a variety of organic solvents....
, 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
Sé
Sé may refer to:*sé, the word 'he', or the number six in the Irish language.*Sé , a district of São Paulo, Brazil*Sé, Hungary, a village in Hungary*One of several parishes in Portugal:...
. 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.
Aryl azides react with PPh3 to give imido analogue of OPPh3 via the Staudinger reaction
Staudinger reaction
The Staudinger reaction or Staudinger reduction is a chemical reaction in which the combination of an azide with a phosphine or phosphite produces an iminophosphorane intermediate. Combined with the hydrolysis of the aza-ylide to produce a phosphine oxide and an amine, this reaction is a mild...
:
- PPh3 + PhN3 → PhNPPh3 + N2
The product imides can be hydrolyzed to the amine. Typically the intermediate imidophosphorane is not isolated.
- PPh3 + RN3 + H2O → OPPh3 + N2 + RNH2
Cl2 adds to PPh3 to give triphenylphosphine dichloride
Triphenylphosphine dichloride
Triphenylphosphine dichloride, Ph3PCl2, 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.- Structure :In...
([PPh3Cl]Cl), which exists as the moisture-sensitive phosphonium halide, This reagent is used to convert alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s to alkyl chlorides
Haloalkane
The haloalkanes are a group of chemical compounds derived from alkanes containing one or more halogens. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially and, consequently, are known under many chemical and...
in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
.
PPh3 is a weak base, but does form stable salts with strong acids such as HBr. The product contains the phosphonium cation [HPPh3]+.
Principal organic reactions
PPh3 is widely used in organic synthesisOrganic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
. The properties that guide its usage are its nucleophilicity and its reducing character. 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
Suzuki reaction
The Suzuki reaction is the organic reaction of an aryl- or vinyl-boronic acid with an aryl- or vinyl-halide catalyzed by a palladium complex. It is widely used to synthesize poly-olefins, styrenes, and substituted biphenyls, and has been extended to incorporate alkyl bromides...
.
Quaternization
PPh3 combines with most alkyl halides to give phosphonium saltPhosphonium salt
A phosphonium salt is a salt containing the phosphonium ion such as phosphonium iodide . More commonly, phosphonium refers to a quaternary organic derivative such as tetraphenylphosphonium chloride, 4P+ Cl- and tetramethylphosphonium iodide, [P4]+I−.Alkyltriphenylphosphonium salts are widely...
s. The facility of the reaction follows the usual pattern whereby alkyl iodides and benzylic and allylic halides are particularly efficient reactants:
- PPh3 + CH3I → [CH3PPh3]+I−
These salts, which are readily isolated as crystalline solids, react with strong bases to form ylide
Ylide
An ylide or ylid is a neutral dipolar molecule containing a formally negatively charged atom directly attached to a hetero atom with a formal positive charge , and in which both atoms have full octets of electrons. Ylides are thus 1,2-dipolar compounds...
s:
- CH3PPh3+ + base → [CH2PPh3] + baseH+
Such ylides are key reagents in the Wittig reaction
Wittig reaction
The Wittig reaction is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide to give an alkene and triphenylphosphine oxide....
s, used to convert aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s and ketone
Ketone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
s into alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s. Nickel salts are required to react PPh3 with PhBr to give [PPh4]Br. The tetraphenylphosphonium cation is widely used to prepare crystallizable lipophilic salts.
Mitsunobu reactionMitsunobu reactionThe Mitsunobu reaction is an organic reaction that converts an alcohol into a variety of functional groups, such as an ester, using triphenylphosphine and an azodicarboxylate such as diethyl azodicarboxylate or diisopropyl azodicarboxylate . The alcohol undergoes an inversion of stereochemistry...
In this reaction, a mixture of PPh3 and diisopropyl azodicarboxylateDiisopropyl azodicarboxylate
Diisopropyl azodicarboxylate is the diisopropyl ester of azodicarboxylic acid. It is used as a reagent in the production of many organic compounds. It is often used in the Mitsunobu reaction where it serves as an oxidizer of triphenylphosphine to triphenylphosphine oxide. It has also be used to...
(“DIAD”, or its diethyl analogue, DEAD) converts an alcohol and a carboxylic acid to an ester. The DIAD is reduced as it serves as the hydrogen acceptor, and the PPh3 is oxidized to OPPh3
Triphenylphosphine oxide
Triphenylphosphine oxide is the chemical compound with the formula OP3. Often chemists abbreviate the formula by writing Ph3PO or PPh3O . This white crystalline compound is a common side product in reactions involving triphenylphosphine...
.
Appel reactionAppel reactionThe 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 methyl iodide or iodine gives alkyl iodides...
PPh3 is oxidized again to OPPh3Triphenylphosphine oxide
Triphenylphosphine oxide is the chemical compound with the formula OP3. Often chemists abbreviate the formula by writing Ph3PO or PPh3O . This white crystalline compound is a common side product in reactions involving triphenylphosphine...
in this application, which converts alcohols to alkyl halides using CX4 (X = Cl, Br):
- PPh3 + CBr4 + RCH2OH → OPPh3 + RCH2Br + HCBr3
This reaction commences with nucleophilic attack of PPh3 on CBr4, an extension of the quaternization reaction listed above.
Principal transition metal derivatives
Triphenylphosphine binds well to most transition metalTransition metal
The term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
s, especially those in the middle and late transition metals of groups 7-10. In terms of steric bulk, PPh3 has a cone angle of 145°, which is intermediate between those of P(C6H11)3 (170°) and P(CH3)3 (115°). In an early application in homogeneous catalysis
Homogeneous catalysis
In chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.-Acid catalysis:...
, NiBr2(PPh3)2 was used by Walter Reppe
Walter Reppe
Walter Julius Reppe was a German chemist. He is notable for his contributions to the chemistry of acetylene.-Education and career:...
for the synthesis of acrylate esters from alkyne
Alkyne
Alkynes are hydrocarbons that have a triple bond between two carbon atoms, with the formula CnH2n-2. Alkynes are traditionally known as acetylenes, although the name acetylene also refers specifically to C2H2, known formally as ethyne using IUPAC nomenclature...
s, carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
, and alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s. Wilkinson's further popularized the use of PPh3, including the then revolutionary hydroformylation
Hydroformylation
Hydroformylation, also known as oxo synthesis or oxo process, is an important industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group and a hydrogen atom to a carbon-carbon double bond...
catalyst RhH(PPh3)2(CO)2.
It is telling that the corresponding triphenylamine
Triphenylamine
Triphenylamine is an organic compound with formula 3N. In contrast to most amines, triphenylamine is nonbasic. Its derivatives have useful properties in electrical conductivity and electroluminescence, and they are used in OLEDs as hole-transporters....
shows little tendency to bind to metals. The difference between the coordinating power of PPh3 and NPh3 reflects the greater steric crowding around the nitrogen atom, which is smaller and favors a more tetrahedral geometry. Far more similar to PPh3 in terms of its coordinating properties is triphenylarsine
Triphenylarsine
Triphenylarsine is the chemical compound with the formula As3. This organoarsenic compound, often abbreviated AsPh3, is a colorless crystalline solid that is used as a ligand and a reagent in coordination chemistry and organic synthesis...
, AsPh3.
An important technique for the characterization of metal-PPh3 compounds is 31P NMR spectroscopy. Substantial shifts occur upon complexation and31P-31P spin-spin coupling can provide insight into the structure of complexes containing multiple phosphine ligands.
Illustrative PPh3 complexes:
- tetrakis(triphenylphosphine)palladium(0)Tetrakis(triphenylphosphine)palladium(0)Tetrakispalladium is the chemical compound Pd[P3]4, often abbreviated Pd4, or even PdP4. It is a bright yellow crystalline solid that becomes brown upon decomposition in air.-Structure and properties:...
is widely used to catalyse C-C coupling reactions in organic synthesisOrganic synthesisOrganic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
, see Heck reactionHeck reactionThe Heck reaction is the chemical reaction of an unsaturated halide with an alkene and a base and palladium catalyst to form a substituted alkene. Together with the other palladium-catalyzed cross-coupling reactions, this reaction is of great importance, as it allows one to do substitution...
. - Wilkinson's catalystWilkinson's catalystWilkinson's catalyst is the common name for chlorotrisrhodium, a coordination compound with the formula RhCl3 . It is named after the late organometallic chemist and 1973 Nobel Laureate, Sir Geoffrey Wilkinson who popularized its use.-Structure and basic properties:The compound is a square planar,...
, RhCl(PPh3)3 is a square planar Rh(I) complex of historical significance used to catalyzeHomogeneous catalysisIn chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.-Acid catalysis:...
the hydrogenation of alkenes. - Vaska's complexVaska's complexVaska's complex is the trivial name for the chemical compound trans-chlorocarbonylbisiridium, which has the formula IrCl[P3]2. This square planar diamagnetic organometallic complex consists of a central iridium atom bound to two mutually trans triphenylphosphine ligands, carbon monoxide, and a...
, trans-IrCl(CO)(PPh3)2, is also historically significant; it was used to establish the scope of oxidative additionOxidative additionOxidative addition and reductive elimination are two important and related classes of reactions in organometallic chemistry. Oxidative addition is a process that increases both the oxidation state and coordination number of a metal centre...
reactions. This early work provided the insights that led to the flowering of the area of homogeneous catalysisHomogeneous catalysisIn chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.-Acid catalysis:...
. - NiCl2(PPh3)2 is a four coordinate Ni(II) complex that exists as an equilibrium mixture of paramagnetic tetrahedral and diamagnetic square planar geometries. In contrast PdCl2(PPh3)2 is square planar.
- Stryker's reagentStryker's reagentStryker's reagent Stryker's reagent Stryker's reagent ([(PPh3)CuH]6, also known as the Osborn complex, is a hexameric copper hydride ligated with triphenylphosphine. It is a brick red crystalline solid that is very sensitive to air...
, [(PPh3)CuH]6, ligand stabilized transition metal hydrideTransition metal hydrideTransition metal hydrides are chemical compounds containing a transition metal bonded to hydrogen. Most transition metals form hydride complexes and some are significant in various catalytic and synthetic reactions...
used as a catalystHomogeneous catalysisIn chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.-Acid catalysis:...
for conjugate reductions.
Conversion to PPh2 derivatives
Triphenylphosphine is commonly employed as a precursor to other organophosphines. LithiumLithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
in THF
ThF
Follicular B helper T cells , are antigen-experienced CD4+ T cells found in the B cell follicles of secondary lymphoid organs such as lymph nodes, spleens and Peyer's patches, and are identified by their constitutive expression of the B cell follicle homing receptor CXCR5...
and Na or K in NH3 react with PPh3 to give Ph2PM (M = Li, Na, K). These reactions generate equal amounts of phenyllithium (or sodium, potassium analogs thereof) C6H5M, which can be selectively converted to benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
by selective protonation. Treatment of the resulting alkali metal diphenylphosphide with an alkylating
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
agent RX gives PRPh2. This method can be used to prepare such ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
s as PMePh2, methyldiphenylphosphine. The corresponding reaction with dihaloalkanes gives bis(diphenylphosphino)alkanes. For example, 1,2-dibromoethane
1,2-Dibromoethane
1,2-Dibromoethane, also known as ethylene dibromide , is the chemical compound with the formula BrCH2CH2Br. Although trace amounts occur naturally in the ocean, where it is formed probably by algae and kelp, it is mainly a synthetic...
and Ph2PM react to give Ph2PCH2CH2PPh2, known as 1,2-bis(diphenylphosphino)ethane
1,2-Bis(diphenylphosphino)ethane
1,2-Bisethane is a commonly used bidentate ligand in coordination chemistry. Dppe is almost invariably chelated, although there are examples of unidentate and of bridging behavior.-Preparation:...
or dppe. Weak acids such ammonium chloride
Ammonium chloride
Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...
, converts Ph2PM (M = Li, Na, K) into Ph2PH, known as diphenylphosphine.
Sulfonation - access to water-soluble phosphine ligands
Sulfonation of PPh3 gives tris(3-sulfophenyl)phosphine, P(C6H4-3-SO3-)3. This anionic phosphine is usually isolated as the trisodium salt and is known as TPPTSTppts
3,3′,3′′-Phosphinidynetris trisodium salt , is an organic compound that is also known as sodium triphenylphosphine trisulfonate. The compound has the formula P3. This white microcrystalline solid is an unusual example of a water-soluble phosphine...
. In contrast to PPh3, TPPTS is water soluble as are its metal derivatives. Rhodium complexes of TPPTS are used in certain industrial hydroformylation
Hydroformylation
Hydroformylation, also known as oxo synthesis or oxo process, is an important industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group and a hydrogen atom to a carbon-carbon double bond...
reactions because the water-soluble catalyst is readily separated from the organic products.
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 chlorodiphenylphosphineChlorodiphenylphosphine
Chlorodiphenylphosphine is an organophosphorus compound with the formula 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...
(PPh2Cl).