Distinct Catalytic Performance of Dirhodium(II) Complexes with ortho-Metalated DPPP in Dehydrosilylation of Styrene Derivatives with Alkoxysilanes

Herein, we describe dirhodium­(II) complexes for the ortho-metalated 1,3-bis(diphenylphosphino)­propane (DPPP)-catalyzed dehydrosilylation of vinylarenes with tertiary silanes, particularly alkoxysilanes. This catalytic method displays a broad substrate scope. Both electron-donating and electron-withdrawing substituents on the vinylarenes are well tolerated in this protocol. The dehydrosilylation reactions are compatible with a diverse range of tertiary silanes such as (EtO)3SiH, (TMSO)2MeSiH, (HSiMe2)2O, Et3SiH, and Ph3SiH. Mechanistic studies indicated that a mixture of Rh2(OAc)4, DPPP, and P­(OMe)3 provided a stable and rigid dirhodium­(II) complex with ortho-metalated DPPP as the bridging ligand and the phosphonate as the axial ligand in the catalytic system. The structure of the dirhodium­(II) complexes was also supported by X-ray crystal diffraction. Further experiments confirmed that the dirhodium­(II) complexes may be the active species that catalyze the dehydrosilylation reaction. Control experiments showed that norbornene works as the hydrogen acceptor in the reaction and plays a crucial role in the generation of the key catalytic intermediate, a rhodium silicon species.