Distinct Catalytic Performance of Dirhodium(II) Complexes with <i>ortho</i>-Metalated DPPP in Dehydrosilylation of Styrene Derivatives with Alkoxysilanes
Wenkui Lu, Xiaoyu Zhu, Liqun Yang, Xiaoyu Wu, Xiaomin Xie, Zhaoguo Zhang
Abstract
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.