SusChEM: New Reactivity Promoted by Group 5 Metal Systems

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In this project funded by the Chemical Synthesis program of the Chemistry Division, the research groups of Professors John Arnold and Robert Bergman of University of California, Berkeley are working toward developing new reagents containing inexpensive and earth-abundant early transition metals that are capable of cleaving strong bonds. Ideally, this research will lead to development of catalysts for removal of fluorine and chlorine from environmentally dangerous halogenated organic wastes, such as CFCs, selective functionalization of chemical feedstocks to produce high-valued organic products, and synthesis of new inorganic polymers and materials. The most immediate broader impacts of the work described in this proposal relate to the training of skilled synthetic chemists and the fact that a more complete understanding of fundamental reaction steps that occur at transition metal sites is important in a wide range of industrially important chemical conversions.This project focuses on the development of new niobium systems supported by imido and β-diketiminate and related ligands. This project is split into two major parts. The first involves reactivity and mechanistic studies of low-valent niobium systems toward developing reagents for activation and functionalization of C-F, C-Cl, and C-O bonds. The second involves synthesis of a series of bis(imido) complexes that are reactive across a niobium-nitrogen multiple bond, and investigation of their reactivity toward cycloaddition of unsaturated substrates and 1,2-addition of C-H and E-H (E = H, B, Al, Si, N, P, O, S) bonds. Target compounds will be characterized using 1D and 2D 1H, 13C, and other heteronuclear NMR techniques, X-ray crystallography, FT-IR (Fourier transform infra-red) spectroscopy, mass spectrometry, and other characterization techniques. Additionally, DFT (Density Functional Theory) calculations will be used to gain electronic structure and mechanistic insights.