Volume 28, Issue 5 e202104001
Research Article

Rhodium–Iodide Complex on a Catalytically Active SiO2 Surface for One-Pot Hydrosilylation–CO2 Cycloaddition

Kei Usui

Kei Usui

Department of Chemical Science and Engineering, Tokyo Institute of Technology, Meguro City, 226-8502 Yokohama Japan

Department of Chemistry and Life Science, Yokohama National University, 240-8501 Yokohama, Japan

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Prof. Dr. Yuichi Manaka

Prof. Dr. Yuichi Manaka

Department of Chemical Science and Engineering, Tokyo Institute of Technology, Meguro City, 226-8502 Yokohama Japan

Renewable Energy Research Center, National Institute of Advanced Industrial Science and Technology, 963-0298 Fukushima, Japan

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Prof. Dr. Wang-Jae Chun

Prof. Dr. Wang-Jae Chun

Graduate School of Arts and Sciences, International Christian University, 181-8585 Mitaka, Tokyo, Japan

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Prof. Dr. Ken Motokura

Corresponding Author

Prof. Dr. Ken Motokura

Department of Chemical Science and Engineering, Tokyo Institute of Technology, Meguro City, 226-8502 Yokohama Japan

Department of Chemistry and Life Science, Yokohama National University, 240-8501 Yokohama, Japan

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First published: 08 December 2021

Graphical Abstract

A surface Rh–iodide complex for one-pot catalysis: A one-pot synthetic strategy for the hydrosilylation of olefin is developed. The hydrosilylation reaction is accelerated in the presence of a novel Rh–iodide complex developed on the surface of SiO2. The decrease in steric hindrance and electron donation from iodide to Rh promote the catalytic process.

Abstract

In this study, a novel Rh–iodide complex was synthesized through a surface reaction between an immobilized Rh cyclooctadiene complex and alkylammonium iodide (N+I) on SiO2. In the presence of ammonium cations, the SiO2-supported Rh–iodide complex could be effectively used for the one-pot synthesis of various silylcarbonate derivatives starting from epoxy olefins, hydrosilanes, and CO2. The maximum turnover numbers (TONs) for the hydrosilylation reaction and the CO2 cycloaddition were 7600 (Rh) and 130 (N+I), respectively. The catalyst exhibited much higher performance for hydrosilylation than solely the Rh complex on SiO2. The mechanism of the Rh-catalyzed hydrosilylation reaction and the local structure of Rh, which is affected by the co-immobilized N+I, were investigated by using Rh and I K-edge XAFS and XPS. Analysis of the XAFS profiles indicated the presence of a Rh−I bond. The Rh unit was in its electron-rich state. Curve-fitting analysis of the Rh K-edge EXAFS profiles suggests dissociation of the cycloocta-1,5-diene (COD) ligand from the Rh center. Results from spectroscopic and kinetic analyses revealed that the high activity of the catalyst (during hydrosilylation) could be attributed to a decrease in steric hindrance and the electron-rich state of the Rh. The decrease in the steric hindrance could be attributed to the absence of COD, and the electron-rich state promoted the oxidative addition of Si−H. To the best of our knowledge, this is the first example of a one-pot silylcarbonate synthesis as well as a determination of a novel surface Rh–iodide complex and its catalysis.

Conflict of interest

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.