RUI: CHE-DRP (SYN): CAS: Temperature-controlled Mechanosynthesis as a Sustainable Synthetic Platform for Preparation of Transition Metal Complexes

With the support of the Chemical Synthesis program in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), Rachel J. Allenbaugh of Murray State University will study small molecule mechanosynthesis kinetics under temperature-controlled conditions to enhance basic understanding of mechanochemistry. Mechanochemistry has the potential to open up new, more sustainable chemistry methods. Traditional chemical processes involve dissolving starting materials in a solvent and heating. The solvent usually must be removed and often becomes a hazardous waste. Consequently, new methods not involving solvents would be very desirable. Mechanosynthesis is such a technique that does not rely on solvents and replaces thermal energy derived from heating with mechanical impacts. This technique also tends to improve yields while reducing reaction time, thereby increasing the efficiency and lowering the cost of a process. Dr. Allenbaugh and her group will be developing methods for temperature-controlled ball-milling to better understand the kinetics and mechanisms in the production of commercially relevant transition metal complexes. In this project, a diverse group of undergraduate and M.S. students will be trained in sustainable synthesis methods. High school students will be introduced to sustainable chemistry through continuing education activities with local high school teachers. Methods for integrating mechanosynthesis as a part of a cost-effective, sustainable synthetic methodology for primarily undergraduate institutions will be explored. Despite the advantage of mechanosynthesis, widespread adoption is hindered by the absence of systematic reaction optimization methods and the limited kinetic understanding in small molecule mechanosynthesis. Dr. Allenbaugh and her group will analyze mechanosynthesis kinetics for the formation of a wide variety of metal complexes, palladacycle catalysts, and pre-catalysts including the Najera II and 2-aminobiphenyl palladacycles. Through the development of a temperature-controlled ball milling apparatus, mechanosynthetic temperature effects will be explored. Kinetic modelling will allow for a more thorough understanding of the mechanisms of mechanosynthesis, resulting in more rational methods for optimizing yields and reaction times. More broadly, Dr. Allenbaugh’s research seeks to introduce a wider community to alternative methods for imparting energy into chemical reactions, an approach that includes mechanosynthesis and microwave chemistry. These avenues are less explored than methods utilizing direct thermal or light energy to drive chemical reactions and have the potential to widen the palette of reaction modalities available to chemists and chemical engineers. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.