Triethylphosphine is the organophosphorus compound with the formula P(CH<sub>2</sub>CH<sub>3</sub>)<sub>3</sub>, commonly abbreviated as PEt<sub>3</sub>. It is a colorless liquid with an unpleasant odor characteristic of alkylphosphines. The compound is a common ligand in organometallic chemistry, such as in auranofin.
It is a pyramidal molecule with approximate C<sub>3v</sub> symmetry.
PEt<sub>3</sub> is usually prepared using Grignard reagents:
PEt<sub>3</sub> reacts with strong acids to give salts [HPEt<sub>3</sub>]X. This reaction is reversible. Similarly, it is also easily alkylated to give phosphonium derivatives. PEt<sub>3</sub> is easily oxidised to the phosphine oxide with oxygen.
Triethylphosphine is a highly basic ligand that forms coordination complexes with many metals. As a ligand, triethylphosphine's Tolman cone angle is 132ð. Being a relatively compact phosphine, several can bind to a single transition metal, as illustrated by the existence of Pt(PEt<sub>3</sub>)<sub>4</sub>. As a phosphine ligand, triethylphosphine gained acceptance earlier than did the simpler trimethylphosphine, as illustrated by the preparation of the hydride complex trans-PtHCl(PEt<sub>3</sub>)<sub>2</sub>.
PEt<sub>3</sub> is toxic. It converts to a low toxicity phosphine oxide upon treatment with sodium hypochlorite or hydrogen peroxide.