Diphenylphosphine

Diphenylphosphine

Names
IUPAC name diphenylphosphane
Identifiers
CAS Number	829-85-6
ChemSpider	63209
Jmol interactive 3D	Image
InChI InChI=1S/C12H11P/c1-3-7-11(8-4-1)13-12-9-5-2-6-10-12/h1-10,13H Key: GPAYUJZHTULNBE-UHFFFAOYSA-N InChI=1/C12H11P/c1-3-7-11(8-4-1)13-12-9-5-2-6-10-12/h1-10,13H Key: GPAYUJZHTULNBE-UHFFFAOYAN
SMILES c2c(Pc1ccccc1)cccc2
Properties
Chemical formula	C12H11P
Molar mass	186.19 g/mol
Appearance	colorless liquid
Density	1.07 g/cm^3, liquid
Boiling point	280 °C (536 °F; 553 K)
Solubility in water	Insoluble
Hazards
Safety data sheet	External MSDS
R-phrases	17-36/37/38
S-phrases	26-36
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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.

Synthesis

Diphenylphosphine can be prepared cheaply from triphenylphosphine.^[1]

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:^[2]

Ph₂PH + ⁿBuLi → Ph₂PLi + ⁿBuH

The preparation of phosphine ligands, Wittig-Horner reagents, and phosphonium salts 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 (Ph₂PC₂H₄PPh₂). Diphenylphosphine and especially diphenylphosphide derivatives are nucleophiles, so they add to carbon – heteroatom double bonds.^[2] For example, in the presence of concentrated hydrochloric acid at 100 °C, diphenylphosphine adds to the carbon atom in benzaldehyde 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:^[3]

Ph₂PH₂⁺ $\rightleftharpoons$ Ph₂PH + H⁺

Handling properties

During the handling of diphenylphosphine, care must be taken to avoid oxidation of diphenylphosphine.^[4]

Ph₂PH + O₂ → Ph₂P(O)OH

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.^[2]

References

1. Wittenberg, D.; Gilman, H. (1958). "Lithium Cleavages of Triphenyl Derivatives of Some Group Vb Elements in Tetrahydrofuran". Journal of Organic Chemistry 23 (7): 1063–1065. doi:10.1021/jo01101a613.
2. Piotrowski, D. W. (2001). "Diphenylphosphine". Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.rd427.
3. C. A. Streuli, "Determination of Basicity of Substituted Phosphines by Nonaqueous Titrimetry", Analytical Chemistry 1960, volume 32, pages 985-987.doi:10.1021/ac60164a027
4. Svara, J.; Weferling, N.; Hofmann, T. (2005), "Phosphorus Compounds, Organic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a19_545.pub2