CAREER: SusChEM: Development of Manganese Hydrosilylation Catalysts for Silicone Curing

Project: Research project

Description

Overview
In this proposal, Prof. Ryan J. Trovitch of Arizona State University will investigate the ability of manganese catalysts to cure silicones, so they may be used as replacements for toxic and expensive platinum hydrosilylation catalysts. To achieve this objective, efficient manganese olefin hydrosilylation catalysts will be targeted for use in existing formulations and original carbonyl hydrosilylation and dehydrogenative silylation curing pathways will be evaluated. Relying on physical inorganic methods, this effort will establish patterns that relate manganese complex electronic structure to Si-C and Si-O formation activity. Using model substrates, the scope and functional group tolerance of manganese-catalyzed olefin hydrosilylation, carbonyl hydrosilylation, and dehydrogenative silylation will be determined so that optimized catalysts may be developed. Leading catalysts for each transformation will be employed in silicone forming reactions so that their cross-linking activity can be elucidated along with the chemical robustness, color profile, and physical properties of the resulting silicone products. In harmony with sustainable catalyst development, the outreach and educational components of this proposal aim to raise chemical awareness and inform the public of how sustainable chemistry can address some of societys foremost challenges. This objective will be achieved through the development of a workshop for local high school students, the creation of online video content, and the hosting of public lectures at Phoenix Public Library.
Intellectual Merit
Although manganese is Earth-abundant and non-toxic, it remains underutilized in catalytic applications due to its propensity to participate in one electron reaction pathways. Recent efforts have shown that polydentate redox non-innocent chelates enable manganese-catalyzed carbonyl hydrosilylation by reversibly transferring electrons and partially dissociating throughout catalysis. Building on this discovery and preliminary results, three manganese-catalyzed approaches to environmentally responsible silicones will be explored: 1) the application of manganese olefin hydrosilylation catalysts as drop-in replacements for platinum, 2) the development of a novel carbonyl hydrosilylation pathway to cross-link polyones with polyhydrosilanes or polyhydrosiloxanes, and 3) the preparation of silicones from biorenewable monomers by way of dehydrogenative silylation. Using observational and mechanistic information as a guide, highly active manganese catalysts for each transformation will be developed by rationally modifying the ligand framework. Successful completion of this project will transform current knowledge of manganese catalysis while revealing the importance and advantages of high-denticity redox non-innocent chelates. If excellent silicone curing activities are attained along with broad functional group tolerance, the efforts described herein have the potential to supplant platinum hydrosilylation catalyst use, which would represent a significant accomplishment in sustainable chemistry.
Broader Impacts
To enhance public familiarity with the goals of sustainable chemistry, a workshop on this topic for local high school students will be developed, videos that summarize the program will be posted online, and public discussions will be organized. The workshop for local high school students will be marketed and held in collaboration with Phoenix Public Library and will feature modules on determining the societal value of chemicals, the principles of sustainable chemistry, and potential career paths that are available within STEM disciplines. The information discussed in this workshop will be made available online so that it reaches a wider audience that includes younger students, adults, and educators. Raising awareness among adults in Maricopa County will be achieved by holding public discussions on how chemicals both positively and negatively impact humanity and the environment. Undergraduate and graduate students at Arizona State University will be exposed to advanced topics in sustainable chemistry through updated coursework and laboratory exposure. These efforts will benefit society by increasing interest among students both locally and nationally in the virtues of environmentally-responsible scientific research. Students will also be equipped with a background in the principles of sustainable chemistry, which will remain with them as they develop into the scientists of tomorrow.
StatusActive
Effective start/end date3/13/175/31/22

Funding

  • National Science Foundation (NSF): $650,000.00

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Hydrosilylation
Silicones
Manganese
Curing
Catalysts
Students
Alkenes
Technical presentations
Platinum
Functional groups
Catalysis
Electrons
Poisons
Electronic structure
Physical properties
Monomers
Earth (planet)
Ligands
Color