With this award from the Chemical Synthesis (SYN) Program of the Chemistry Division, Professor Burjor Captain of the Department of Chemistry at the University of Miami will explore the structures and reactivity of transition metal complexes containing bulky tin ligands. The main drive is to indice activation of hydrogen and small molecules as well as to investigate their potential as hydroformylation and hydrogenation catalysts. The work will consist of incorporating sterically encumbered tin ligands to bring about electronic and/or coordinative unsaturation around the metal atoms in transition metal complexes. This work will begin by exploring synthetic, structural, and catalytic chemistry on platinum-tin systems and then be extended to include complexes of non-precious transition metals such as Ni and Fe. The central theme is the use of tin which offers significant advantages and is largely untested. There is precedent for the potential scope and effectiveness of this strategy in the widely investigated use of phosphine ligands to modify both binding sites and catalytic properties. However, bulky tin ligands offer additional incentives for their investigation compared to phosphine ligands. Because the stannyl group is a radical with an odd number of electrons, its utilization at a metal site changes formal oxidation numbers, but more importantly electron densities at the metal center, in ways quite different from that of coordinated phosphines. The long range goal of this work is development of robust, economic, and efficient catalysts of use to chemical industry.
The broader impact of this project is that it calls for synthesis of a new class of materials in a relatively unexplored area of inorganic chemistry. This provides the opportunity to discover new binding patterns of small molecules. Some of these may be predictable, but some may be unanticipated and lead to new insights of broad impact in fundamental chemical science. There has been a renaissance in main group chemistry, and this work combines main group with transition metal chemistry in an exciting and potentially breakthrough area. The proposed small molecule activation studies center on hydrogen- by trying to understand how it behaves in a main group metal-transition group metal setting. Transition metal complexes have and always will play the crucial part in the chemistry of hydrogen, but this may be modified by the presence of the added bulky tin ligand. The question is how and to what extent it will be modified. The long term impact of this work will be in helping to better utilize this important resource in binding and catalytic reactivity. A final area of impact is in student training (undergraduate and graduate) to be scientists and professionals. Students will be trained to prepare and handle air-sensitive compounds, and will learn various methods such as X-Ray crystallography, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry, calorimetry and computational analysis. The results will be broadly disseminated in refereed research journals and through presentations at meetings. Due to the diversity of the proposed research, students trained in this program will have the skill set and creative attitude needed to find viable solutions for the emerging energy crisis and contribute to sustainability.
