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These elements (rare earths) perplex us in our researches, baffle us in our speculations and haunt us in our dreams. They stretch like an unknown sea before us - mocking, mystifying and murmuring strange revelations and possibilities. Sir William Crookes, Address to the British Association, 1887 Early transition metals, lanthanides, and uranium
Early transition metals, lanthanides, and uranium (d0fn elements) have shown impressive reactivity in transformations ranging from the activation of small, inert molecules such as methane, dinitrogen, and carbon dioxide to reactions with applications in natural product synthesis (e.g. hydroamination) and formation of biodegradable polymers. The high reactivity of d0fn metal centers makes it difficult to tune their behavior without rendering them unreactive. Our solution to this problem involves the design and synthesis of complexes with specific geometric and electronic properties. For example, weak interactions, such as electronic assistance from an electron rich metal center, are used in small molecule activation to generate highly reactive metal species. In a uranium bisferrocene compound, uranium was found to mediate the electronic communication between the two iron centers better than zirconium did in an analogous complex. Monreal, M. J., Carver, C. T., Diaconescu, P. L., Inorganic Chemistry 2007, 46(18), 7226-7228
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Department of Chemistry & Biochemistry UCLA Box 951569 (post) 607 Charles E. Young Drive East (courier) Los Angeles, CA 90095-1569 |
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Reactions with N-heterocycles The activation of C-N bonds in heterocycles is important in the context of hydrodenitrogenation processes. Our group studies the reactions of electrophilic metal-carbon bonds with substrates featuring strong C-N bonds in order to understand the mechanism of intimate reaction steps. Ring-opening of aromatic N-heterocycles can be initiated by d0fn metal-carbon sigma-bonded fragments. These results are different from existing examples, which all involve metal-element multiple bonds. DFT calculations indicate that the ligand system employed by us, 1,1’-ferrocene diamides, may be unique in supporting electrophilic metal centers. Our goal is to understand specific examples of strong bond cleavage in order to develop general transformations. Carver, C. T., Diaconescu, P. L., J. Am. Chem. Soc. 2008, 130(24), 7558-7559
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