Multiple Metal-Carbon Bonds, Metallacycles and Catalytic Olefin Metathesis Reactions

The Chemical Catalysis Program of the Division of Chemistry is funding Professor Richard R. Schrock of the Massachusetts Institute of Technology to carry out fundamental studies on olefin metathesis catalysts based on the two earth abundant elements, molybdenum and tungsten. Olefin metathesis is a reaction that consists of breaking and rearranging carbon-carbon double bonds in organic molecules. The olefin metathesis reaction has revolutionized the synthesis of organic molecules relevant to natural and unnatural products for treatment of diseases such as cancers and AIDS, as well as the synthesis of specialty materials. Professor Schrock is studying ways to make the catalysts more reactive, selective, and durable than any previous catalysts. The broader impacts of the research could be wide ranging in terms of furthering the role of olefin metathesis in chemical science, advancing commercial uses of olefin metathesis, and training and educating students.

The Schrock research group is performing synthetic, mechanistic, structural, and reactivity studies of newly designed catalysts for the olefin metathesis reaction. Four new catalyst classes are being investigated with a focus on several specific challenges in olefin metathesis catalysis: synthesizing new oxo alkylidene complexes of tungsten that are activated through binding of a Lewis acid to the oxo ligand; supporting well-defined oxo alkylidene metathesis catalysts on silica; developing imido alkylidene catalysts that contain a sterically demanding 2,6-disubstituted phenylimido ligands in order to limit reactions to ones in which only anti-alkylidene isomers can form; and creating potentially more reactive, coordinatively unsaturated cationic complexes paired with a weakly coordinating anion. Heterogeneous metathesis catalysts are employed for the largest volume metathesis reactions, but the least is known about how to prepare them as single, well-defined species on the surface and to control their reactivity at a molecular level. This research has the potential to generate new classes of metathesis catalysts and advance the general understanding of metathesis chemistry.