http://pubs.acs.org/doi/abs/10.1021/acscatal.5b02624

Platinum Catalysis Revisited—Unraveling Principles of Catalytic Olefin Hydrosilylation

Teresa K. Meister†‡, Korbinian Riener‡§, Peter Gigler^∥, Jürgen Stohrer^∥, Wolfgang A. Herrmann§, and Fritz E. Kühn^*†§

^†Molecular Catalysis, ^‡Institut für Siliciumchemie, ^§Chair of Inorganic Chemistry, Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching b. München, Germany

^∥ Wacker Chemie AG, Consortium für elektrochemische Industrie, Zielstattstraße 20, 81379 München, Germany

ACS Catal., 2016, 6, pp 1274–1284

DOI: 10.1021/acscatal.5b02624

Publication Date (Web): January 7, 2016

Copyright © 2016 American Chemical Society

*E-mail: fritz.kuehn@ch.tum.de.

Abstract

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 ²H-labeling experiments, ¹⁹⁵Pt 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.