Diphenylphosphine, also known as diphenylphosphane, is an

organophosphorus compound 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 hydrocarbo ...

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 Catalysis () is the increase in reaction rate, rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst ...

Synthesis

Diphenylphosphine can be prepared from

triphenylphosphine 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 l ...

by reduction to

lithium diphenylphosphide Lithium diphenylphosphide contains lithium and the organophosphorus anion with the formula . It is a red, air-sensitive solid that is used in the preparation of diphenylphosphino compounds. Synthesis and reactions The lithium, sodium, and potas ...

, which can be protonated to give the title compound: :PPh₃ + 2 Li → LiPPh₂ + LiPh :LiPPh₂ + H₂O → Ph₂PH + LiOH

Uses and reactions

In the laboratory, diphenylphosphine is a common intermediate. It can be deprotonated to give diphenylphosphide derivatives: :Ph₂PH + ⁿBuLi → Ph₂PLi + ⁿBuH The preparation of phosphine

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

s, Wittig-Horner reagents, and

phosphonium salt In chemistry, the term phosphonium (more obscurely: phosphinium) describes polyatomic cations with the chemical formula (where R is a hydrogen or an alkyl, aryl, organyl or halogen group). These cations have tetrahedral structures. The salt ...

s are commonly accomplished by alkylating diphenylphosphine. The hydrogen atom connected to phosphorus undergoes Michael-like addition to activated alkenes, providing products with which to produce phosphine ligands such as

1,2-bis(diphenylphosphino)ethane 1,2-Bis(diphenylphosphino)ethane (dppe) is an organophosphorus compound with the formula (PhPCH) (Ph = phenyl). It is a common symmetrical bidentate ligand in coordination chemistry. It is a white solid that is soluble in organic solvents. Prepa ...

(Ph₂PCH₂CH₂PPh₂) and

BINAP BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) is an organophosphorus compound. This Optical isomerism, chiral diphosphines, diphosphine ligand is widely used in chiral synthesis, asymmetric synthesis. It consists of a pair of 2-diphe ...

via their respective bis

triflate In organic chemistry, triflate (Preferred IUPAC name, systematic name: trifluoromethanesulfonate), is a functional group with the Chemical formula, formula and Chemical structure, structure . The triflate group is often represented by , as opp ...

derivatives. Both the (''R'')- and (''S'')-

enantiomer In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...

s, as well as the racemate, are commercially available. One of the wide applications include chemoselective hydrogenation, where BINAP is conjugated to rhodium. Diphenylphosphine and especially diphenylphosphide derivatives are nucleophiles, so they add to carbon – heteroatom double bonds. For example, in the presence of concentrated hydrochloric acid at 100 °C, diphenylphosphine adds to the carbon atom in

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is among the simplest aromatic aldehydes and one of the most industrially useful. It is a colorless liquid with a characteristic almond-li ...

to give (phenyl-(phenylmethyl)phosphoryl)benzene. :Ph₂PH + PhCHO → Ph₂P(O)CH₂Ph Compared to tertiary phosphines, diphenylphosphine is weakly basic. The pKa of the protonated derivative is 0.03:C. A. Streuli, "Determination of Basicity of Substituted Phosphines by Nonaqueous Titrimetry", Analytical Chemistry 1960, volume 32, pages 985-987. :Ph₂PH₂⁺ Ph₂PH + H⁺

Handling properties

Diphenylphosphine readily oxidizes. :Ph₂PH + O₂ → Ph₂P(O)OH An intermediate in this oxidation is diphenylphosphine oxide. The use of the diphenylphosphine–borane complex, Ph₂PH•BH₃ avoids the problem of phosphine oxidation by protecting the phosphine from oxidation and is available through chemical vendors.

References

{{Reflist Phenyl compounds Phosphines Foul-smelling chemicals