Diphenylphosphine oxide is an organophosphorus compound with the formula (C<sub>6</sub>H<sub>5</sub>)<sub>2</sub>P(O)H. It is a white solid that is soluble in polar organic solvents.
Diphenylphosphine oxide can be prepared by the reaction of phosphonic esters, such as diethylphosphite, with Grignard reagents followed by acid workup:
Alternatively, it may be prepared by the partial hydrolysis of chlorodiphenylphosphine or diphenylphosphine.
Diphenylphosphine oxide exists in equilibrium with its minor tautomer diphenylphosphinous acid, ((C<sub>6</sub>H<sub>5</sub>)<sub>2</sub>POH:
Diphenylphosphine oxide is used in Buchwald-Hartwig coupling reactions to introduce diphenylphosphino substituents.
Thionyl chloride converts diphenylphosphine oxide to chlorodiphenylphosphine.
Organophosphinous acids are deoxygenated with DIBAH. The resulting secondary phosphines are precursors to phosphine ligands.