CAREER: Olefin Polymerization Catalysts with Ligands Featuring Weakly Coordinating Carborane Anions

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In this project funded by the Chemical Catalysis program of the Chemistry Division, Professor Vincent Lavallo of the University of California at Riverside is developing new catalysts capable of converting olefin feedstocks into polymers with distinct and desirable properties. Polymers are long chain organic molecules and are found in many facets of everyday life that utilize plastics, including food packaging, structural materials for automotive and aerospace transportation, and lightweight electronic devices. The preparation of useful polymers, such as plastics, requires the utilization of a catalyst to facilitate the chain building process and control the physical properties of the ensuing material. Professor Lavallo is developing catalysts that contain a novel collection of boron and carbon atoms called a carborane anion, which is predicted to bestow unique properties upon the catalysts. Undergraduate and graduate students in the Chemistry Department at the University of California Riverside are being mentored in this program and are participating in the research. Professor Lavallo is also developing a mentorship program for high school students from economically disadvantaged backgrounds. In the summer months, these high school students will participate in the proposed research at UCR, and during the academic year, a novel curriculum will be implemented at the high school, allowing a large number of students to directly engage in the project. In this project, Professor Lavallo is synthesizing and studying phosphine and N-heterocyclic carbene ligands containing icosahedral carborane anion substituents. Icosahedral carborane anions are far more weakly coordinating, less basic, and larger than sulfonates (palladium complexes of phosphine-sulfonates are an unusual family of olefin polymerization catalysts that produce mostly linear polyethylene copolymers), and these properties should favor the formation of the trans-pi-complexes necessary for catalysis and also inhibit beta-elimination. The objective is to produce olefin polymerization catalysts that display enhanced activity, functional group tolerance, and produce polymers with greater uniformity and molecular weight compared to state-of-the-art systems. The broader impacts of the project pertain to the potential uses of phosphine and N-heterocyclic carbene ligands containing icosahedral carborane anion substituents and the planned educational activities targeted towards high school students from economically disadvantaged backgrounds.