Triethyl phosphite (TEP) is an organophosphorus compound, specifically a phosphite ester, with the formula P(OCH<sub>2</sub>CH<sub>3</sub>)<sub>3</sub>, often abbreviated P(OEt)<sub>3</sub>. It is a colorless, malodorous liquid. It is used as a ligand in organometallic chemistry and as a reagent in organic synthesis.
The molecule features a pyramidal phosphorus(III) center bound to three ethoxide groups. Its <sup>31</sup>P NMR spectrum features a signal at around +139 ppm vs phosphoric acid standard.
Triethylphosphite is prepared by treating phosphorus trichloride with ethanol in the presence of a base, typically a tertiary amine:
In the absence of the base, the reaction of ethanol and phosphorus trichloride affords diethylphosphite ((EtO)<sub>2</sub>P(O)H). Of the many related compounds can be prepared similarly, triisopropyl phosphite is an example (b.p. 43.5 ðC/1.0 mm; CAS# 116-17-6).
Triethyl phosphite can react with electrophiles in a MichaelisâÂÂArbuzov reaction to produce organophosphonates. For example, the reaction between triethyl phosphite and ethyl bromoacetate produces a phosphonate suitable for use in the HornerâÂÂWadsworthâÂÂEmmons reaction.
Reduction/deoxygenation of hydroperoxides to the alcohols can also be effected using triethyl phosphite. This approach can be utilized for carbonyl ñ-hydroxylation by reacting the enolate with oxygen, producing an ñ-hydroperoxide which can be reduced by triethyl phosphite to the alcohol. A proposed mechanism is shown below.
Triethyl phosphite can also be used in the CoreyâÂÂWinter olefin synthesis.
In coordination chemistry and homogeneous catalysis, triethylphosphite finds use as a soft ligand. Its complexes are generally lipophilic and feature metals in low oxidation states. Examples include the colorless complexes FeH<sub>2</sub>(P(OEt)<sub>3</sub>)<sub>4</sub> and Ni(P(OEt)<sub>3</sub>)<sub>4</sub> (m.p. 108 ðC). It also forms a stable complex with copper(I) iodide.