Main-Group Fragment Synthesis Using Metal Isocyanide Anions

Dr. Joshua Figueroa of the University of California, San Diego will develop new synthetic methodologies for the stabilization of otherwise reactive main-group atom diatomic molecules that possess unusual electronic and bonding properties. Central to this research is the use of organometallic anions as synthetic tools to construct main-group diatomic molecules in the protective and kinetically-stabilizing environment of transition metal centers. This work will specifically focus on main-group diatomic molecules that feature extremes in bond polarization. Normally, this attribute results in the polymerization of diatomic molecules into materials or films. However, by studying a stabilized diatomic form, novel pathways in chemical reactivity will be uncovered for potential applications in the development of advanced materials and new manufacturing processes. The ability to generate, isolate, and deploy these otherwise unavailable reactive species aligns directly with the NSF Priority Area of Advanced Manufacturing, as the knowledge gained could inform the design of next-generation catalysts, specialty chemicals, and novel functional materials that support U.S. industrial competitiveness, innovation, and workforce development. The project will also support a robust training program in synthetic chemistry for graduate and undergraduate students, with a specific emphasis on safety education and the recruitment and mentorship of junior and community college transfer students, which a population that is often overlooked in early STEM research experiences. Through hands-on and intensive laboratory training this initiative aims to broaden participation in the chemical sciences and help build a highly skilled national workforce. This project will pursue the synthesis, characterization, and reactivity of transition-metal complexes bearing terminal main-group diatomic ligands, with a primary emphasis on boron monofluoride (BF). Boron monofluoride is isoelectronic with carbon monoxide (CO) and dinitrogen (N2) but, owing to severe B-F bond polarization and the absence of significant F-to-B π-backdonation, does not exist as a stable free molecule under ambient conditions. Building on the previous results demonstrating that encumbering m-terphenyl isocyanide ligands can stabilize a terminal BF complex of iron, the proposed research will continue a systematically mapping of the reaction chemistry available to this iron platform. Additional synthetic studies will extend terminal BF coordination to cobalt, ruthenium and tungsten for comparison with the iron platform and to fully assess the electronic influence of BF in varying coordination environments. Other synthetic objectives of this project include the construction of currently-unknown main-group diatomic fragments possessing extreme bond polarization and electronegativity mismatches, including heavier Group 13 element sub-halides and multiply-bonded silicon–nitrogen compounds, all to be constructed within the kinetically protective environment afforded by m-terphenyl isocyanide metal platforms. Mechanistic and structural studies will be conducted using multinuclear NMR spectroscopy, single-crystal X-ray diffraction, IR spectroscopy, and computational methods to elucidate bonding interactions and reaction pathways. The outcomes of this research are expected to establish new paradigms in the coordination chemistry of electron-deficient main-group fragments and to reveal novel chemical transformations that arise from their extreme electronic structures. 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.