2.73[3] (pKa of conjugate acid, aqueous scale) Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to PPh3 or Ph3P.

It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry.

The industrial synthesis involves the reaction between phosphorus trichloride, chlorobenzene, and sodium:[5] Triphenylphosphine crystallizes in triclinic[6] and monoclinic modification.

[11] It forms isolable triphenylphosphonium salts with strong acids such as HBr:[12] PPh3 is widely used in organic synthesis.

Aryl halides will quaternize PPh3 to give tetraphenylphosphonium salts: The reaction however requires elevated temperatures and metal catalysts.

In the Mitsunobu reaction, a mixture of triphenylphosphine and diisopropyl azodicarboxylate ("DIAD", or its diethyl analogue, DEAD) converts an alcohol and a carboxylic acid to an ester.

The easy oxygenation of PPh3 is exploited in its use to deoxygenate organic peroxides, which generally occurs with retention of configuration: It is also used for the decomposition of organic ozonides to ketones and aldehydes, although dimethyl sulfide is more popular for the reaction as the side product, dimethyl sulfoxide is more readily separated from the reaction mixture than triphenylphosphine oxide.

Aromatic N-oxides are reduced to the corresponding amine in high yield at room temperature with irradiation:[14] Sulfonation of PPh3 gives tris(3-sulfophenyl)phosphine, P(C6H4-3-SO3−)3 (TPPTS), usually isolated as the trisodium salt.

In an early application in homogeneous catalysis, NiBr2(PPh3)2 was used by Walter Reppe for the synthesis of acrylate esters from alkynes, carbon monoxide, and alcohols.