Diphenylphosphine

From formulasearchengine
Jump to navigation Jump to search

Template:Chembox Diphenylphosphine, also known as diphenylphosphane, is 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+ 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. {{#invoke:Citation/CS1|citation |CitationClass=journal }}
  2. 2.0 2.1 2.2 {{#invoke:citation/CS1|citation |CitationClass=encyclopaedia }}
  3. C. A. Streuli, "Determination of Basicity of Substituted Phosphines by Nonaqueous Titrimetry", Analytical Chemistry 1960, volume 32, pages 985-987.Template:Hide in printTemplate:Only in print
  4. Template:Ullmann