Catalytic Metal-Mediated Small Molecule Fixation

University Of Maryland, College Park, College Park MD

Investigators

Abstract

With this award, the Chemical Catalysis Program in the Chemistry Division is funding Dr. Lawrence Sita from the University of Maryland to develop transition-metal catalysts that can be used for the production of high-value specialty chemicals from readily available, safe, and inexpensive starting materials, such as nitrogen, carbon dioxide, carbon monoxide, and sulfur. Advances in chemical technologies for the commercial production of high-value, industrial chemicals must be made in the near term in order to meet the increasing burdens placed on natural resources, energy, and the environment as the global population is anticipated to expand by 3 to 4 billion people over the next 50 years. In response to these needs, the primary objective of the project is the development of transition-metal catalysts that can be used to produce value-added, specialty chemicals from readily-available, inexpensive and safe starting materials, such as nitrogen, carbon dioxide, carbon monoxide, nitrous oxide and sulfur. The broader impact of this work is the potential development of more atom-economical and energy-efficient, industrial-scale chemical transformations that will be beneficial to the world economy, the environment, and the society and that can reduce the health- and security-risk of current technologies that require the generation, transportation, and on-site storage of hazardous reagents and intermediates. The proposed work will further provide an important vehicle by which future generations of undergraduates, graduate students, and postdoctoral researchers are trained. The focus of the research is the synthesis and characterization of mid-valent, second- and third-row, group 5 (Nb, Ta) and 6 (Mo, W) metal complexes with cyclopentadienyl amidinate (CPAM) and cyclopentadienyl guanidinate (CPGU) ligands. These complexes are suited for the study of the coordination and "fixation" of small molecules possessing X-Y multiple bonds (e.g., N2, O2, N2O, CO and CO2). The interaction between these metal complexes and the small molecules leads to (1) X-Y multiple bond cleavage compensated by the formation of strong M-X and M-Y bonding interactions, and (2) pathways for atom-economical, X- and Y-transfers to a substrate, which complete the catalytic cycle with respect to the starting metal complex. The CPAM and CPGU, molecularly-discrete complexes will be fully characterized both in solution using NMR, EPR, UV, and IR spectroscopies, electrospray mass spectrometry, and electrochemistry, and in the solid state using single-crystal X-ray analysis, elemental analyses, and IR and EPR spectroscopies.