期刊
ACS CATALYSIS
卷 6, 期 2, 页码 1274-1284出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.5b02624
关键词
hydrosilylation; platinum catalysis; mechanism; silanes; Karstedt's catalyst; isotopic labeling; kinetic study; deactivation
资金
- Fonds der Chemischen Industrie
- Wacker Chemie AG
- TUM Graduate School
Hydrosilylation of C-C multiple bonds is one of the most important applications of homogeneous catalysis in industry. The reaction is characterized by its atom-efficiency, broad substrate scope, and widespread application. To date, industry still relies on highly active platinum-based systems that were developed over half a century ago. Despite the rapid evolution of vast synthetic applications, the development of a fundamental understanding of the catalytic reaction pathway has been difficult and slow, particularly for the industrially highly relevant Karstedt's catalyst. A detailed mechanistic study unraveling several new aspects of platinum-catalyzed hydrosilylation using Karstedt's catalyst as platinum source is presented in this work. A combination of H-2-labeling experiments, Pt-195 NMR studies, and an in-depth kinetic study provides the basis for a further development of the well-established Chalk-Harrod mechanism. It is concluded that the coordination strength of the olefin exerts a decisive effect on the kinetics of the reaction. In addition, it is demonstrated how distinct structural features of the active catalyst species can be derived from kinetic data. A primary kinetic isotope effect as well as a characteristic product distribution in deuterium-labeling experiments lead to the conclusion that the rate-limiting step of platinum-catalyzed hydrosilylation is in fact the insertion of the olefin into the Pt-H bond rather than reductive elimination of the product in the olefin/silane combinations studied.
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