Joint Science Chemistry Seminar


"The Characterization and Dynamics of Substituted Ruthenacyclobutanes Relevant to the Olefin Cross-Metathesis Reaction"
Anna Wenzel, Assistant Professor of Chemistry
Joint Science Department
From: 11:00 AM To: 12:00 PM
Tuesday, Mar 22, 2011
Burns Lecture Hall, Keck Science Center
Olefin metathesis is a powerful method for the clean, reliable, and efficient construction of carbon-carbon bonds, a goal that is ubiquitous to many areas of synthetic, polymer, and materials chemistry. This reaction has also garnered recent interest due to its potential in green chemistry applications. The mechanism of ruthenium-catalyzed olefin metathesis has been extensively studied, with the principal steps corresponding to those in the mechanism initially proposed by Hérisson and Chauvin in 1971. However, several mechanistic questions remain. In particular, the geometry and stereochemical orientation about the short-lived ruthenium metallacyclobutane complex has been of key interest for the rational design of enantioselective and E/Z diastereoselective olefin metathesis catalysts. In this talk, the preparation of ruthenium(IV) metallacycles from various alkenes will be discussed. These metallacycles represent some of the first observed examples of substituted ruthenacyclobutanes, and offer important information regarding the preferred stereochemical orientation about metathesis intermediates in cross-metathesis reaction. In addition, new methods for generating ruthenacyclobutanes from commercially-available catalysts have been achieved. From these studies, a greater understanding of the nature of reaction propagation and the overall mechanism of olefin metathesis has been attained.