This award in the Chemical Synthesis (SYN) program supports work by Professor Larry G. Sneddon at the University of Pennsylvania to carry out fundamental studies on the development of new general methodologies that enable the high-yield syntheses of technologically important polyborane compounds, polymers and materials. The project's unique approach uses the activating effects of ionic-liquids and/or transition metal catalysts to induce selective polyborane transformations. The project emphasizes both the discovery of new reactions and an elucidation of their fundamental mechanisms and controlling factors so that a rational basis for applying these methods to a wide range of polyboranes and polyborane reactions is achieved. The broader impacts of the proposed work include the development of new methods for enabling the systematic syntheses of functionally-substituted polyboranes, polyborane-metal complexes and poly(organoborane) polymers that have potential applications as medical agents, high temperature polymers, burn rate modifiers, extractants for nuclear wastes, ceramic precursors and weakly coordinating anions.
This project strongly impacts the related fields of organometallic chemistry, catalysis, medicinal chemistry, materials science and alternative energy research and thereby provides interdisciplinary training to a diverse group of undergraduate, graduate, and postdoctoral students.
Polyborane compounds have a number of important properties that give rise to applications ranging from uses as medical agents, high temperature polymers, burn rate modifiers, extractants for nuclear wastes, ceramic precursors, weakly coordinating anions and chemical hydrogen-storage systems. However, the exploitation of these and other potential uses, as well as the further scientific development of the field, has been hampered by the lack of the synthetic methods necessary to produce even relatively simple boron cluster compounds efficiently. There is a clear and continuing need for new rational, selective, high-yield reaction pathways. The goal of this project was to fulfill this need by developing new general methodologies that enable the systematic, high-yield syntheses of important polyborane compounds, complexes and polymers that have potentially unique chemical and physical properties and applications. Some of the most important achievements of the project include the development of new: (1) high yield routes to the complete series of halopolyboranes and the demonstration that these compounds are important starting materials for the syntheses of functionalized polyboranes and carboranes; (2) metal catalyzed decaborane alkyne-hydroboration reactions that provide efficient routes to mono- and dialkenyldecaboranes; (3) metal-catalyzed and ionic-liquid promoted alkenylborane transformations to important molecular, polymeric and solid state materials; (4) metal catalyzed growth of boron nitride nanostructured materials from polyborane precursors; (5) general methods for the selective synthesis and functionalization of metallatricarbadecaboranyl complexes that should facilitate their uses in biomedical and materials applications; and (6) systematic NCI screening studies of a diverse library of metallatricarbadecaboranyl complexes with potential anti-cancer properties. This research involved both graduate and undergraduate students and resulted in 17 publications in peer-reviewed publications and 17 PI or student presentations at national/international meetings.
