Influence of a Co-immobilized Tertiary Amine on the Structure and Reactivity of a Rh Complex: Accelerating Effect on Heterogeneous Hydrosilylation

• Published in: Journal of physical chemistry. C Vol. 123; no. 23; pp. 14556 - 14563
• Main Authors: Maeda, Kyogo, Uemura, Yohei, Kim, Minjune, Nakajima, Kiyotaka, Tanaka, Shinji, Chun, Wang-Jae, Motokura, Ken
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.06.2019
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.9b03280

Co-immobilization of a Rh complex and a tertiary amine on the same silica surface enhances the hydrosilylation reaction of olefins. In our previous study, the silica-supported Rh complex-tertiary amine catalyst (SiO2/Rh-NEt2) showed higher activity than a silica-supported Rh complex (SiO2/Rh) alone. Herein, the influence of the amine on the local structure of the Rh complex was evaluated by DNP-enhanced solid-state 15N NMR spectroscopy and Rh K-edge XAFS measured at 20 K. The amine distorts the structure of the cyclooctadiene (COD) ligand in the Rh complex immobilized on the silica surface. The reactivity of the COD ligand with hydrosilane was confirmed by the in situ FTIR spectra, and it was found that the presence of an amine facilitates COD dissociation from the Rh center. This phenomenon accelerates the ligand exchange process in Rh-catalyzed hydrosilylation.