Triethyl phosphite
Triethyl phosphite is an organophosphorus compound with the formula P(OCHCH), often abbreviated P(OEt). 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 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 affords diethylphosphite ((EtO)2P(O)H). Of the many related compounds can  be prepared similarly, triisopropyl phosphite is an example (b.p. 43.5 °C/1.0 mm; CAS# 116-17-6). As a ligand. 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(P(OEt)) and Ni(P(OEt)) (m.p. 108 °C).