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(NII) Novel Catalytic, Synthesis Methods for Main Group
Technical Report,01 Sep 2013,31 Aug 2014
Regents of the University of California, Berkeley Berkeley
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In our efforts to develop reactive group 5 systems, we discovered that the combination of an imido group and the Beta-diketiminate BDI ligand provides a robust platform to support low-valent niobium complexes. We have since discovered that these well-defined niobium III complexes, in which low-valent Nb is stabilized by a labile arene ligand, are capable of activating fluoroaromatic substrates. The C-F activation shows unusual substrate selectivity in comparison with late transition metal compounds that activate C-F bonds. Under appropriate conditions, this hydride fluorination reaction has been rendered catalytic for fluorobenzene, as well as for 1,2- and 1,3-difluorobenzene, releasing benzene and fluorobenzene respectively. We have also been able to use these low-valent niobium systems to access niobium bisimido systems that are reactive across their metal-nitrogen pi-bonds. Recently, we have observed that these niobium bis imido complexes react reversibly with H2 and irreversibly with silanes via 1,2-addition. We have also observed that these bis imido compounds react with aryl isocyanides to exchange nitrene fragments between a tert-buty imido group and the isocyanide. DFT calculations suggest that this reaction proceeds through a 2 2-like transition state.
APPROVED FOR PUBLIC RELEASE