RUI: CAS: Diphosphite Scaffolds for the Synthesis of Bimetallic Complexes Containing Earth Abundant Metals and Strained Rings

Bucknell University, Lewisburg PA

Investigators

Abstract

In this project, with support from the Chemical Synthesis (SYN) Program in the Division of Chemistry of the National Science Foundation, Professor Robert Stockland of Bucknell University is testing new approaches for the preparation of chemical compounds containing iron, cobalt, and nickel. Ultimately, these compounds may be developed into catalysts that are used to speed up chemical reactions and often to selectively produce specifically desired products over others. The project aims to use these abundant metals to ultimately replace rare and precious metals. The main challenge is to enhance the properties of abundant metal-based compounds to match those of the rarer metals. To this end, Professor Stockland is examining the hypothesis that pairs of abundant metals will exhibit enhanced properties. He is designing organic compounds that stabilize such pairs of metals. The research provides undergraduate researchers with hands-on training. Their laboratory training entails experience the handling many different kinds of chemical compounds, the apparatus used for chemical synthesis, and the tools used to characterize the new materials. This research is expected to improve the retention and success rates of the participating students and prepare them for technical careers. The development of chemical transformations that employ earth abundant metals (EAMs) such as iron, cobalt, or nickel as reagents or catalysts is an area of current interest in the synthetic community. While a number of ligand frameworks bind multiple metal centers and promote cooperative interactions, few ligands are known to minimize cooperative activity and promote synergistic interactions. In this project, with support from the Chemical Synthesis (SYN) Program in the Division of Chemistry, Professor Robert Stockland of Bucknell University and his students are using rigid spirocyclic diphosphites to prepare bimetallic compounds through protodemetalation, transmetalation, and base assisted phosphonylation. Furthermore, the selective substitution of one metal for another affords heterobimetallic compounds. Building on these results, the incorporation of oxygen, phosphorus, and sulfur donors into the parent diphosphite core is accomplished through cross-coupling chemistry. These functionalized diphosphites provide unique architectures for binding EAMs. Additionally, the diphosphites are entry points for the construction of a series of cyclic phosphonates containing conjugated fragments. Alkynes and functionalized aryl groups comprise the unsaturated components of the cyclic phosphonates. Undergraduate research is often a pivotal experience that stimulates student curiosity and promoted careers in science, technology, math and engineering. Students in the Stockland group at Bucknell University are gaining hands-on experience and are well prepared to enter the chemical profession or graduate programs. 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.