Deoxygenation[edit]
One common way of synthesizing tertiary phosphine ligands is by deoxygenation of phosphine oxides (OPR3) with trichlorosilane. Deoxygenation proceeds with retention or inversion of configuration, depending on conditions. Inversion is favored by a combination of trichlorosilane and triethylamine. In the absence of the base, the reaction proceeds with retention. The stereochemical course is explained mechanistically by complexation followed by intramolecular hydride transfer. On the other hand, the inversion of configuration in the presence of triethylamine is explained by complexation followed by intermolecular hydride transfer from a 1:1 triethylamine-trichlorosilane complex in an SN2 reaction. Based on these observations, it is thought that complexation of OPR3 by trichlorosilane occurs with retention of configuration.[3]