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Science 6 October 2006:
Vol. 314. no. 5796, pp. 113 - 115
DOI: 10.1126/science.1131914
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Reports

Boryllithium: Isolation, Characterization, and Reactivity as a Boryl Anion

Yasutomo Segawa, Makoto Yamashita,* Kyoko Nozaki*

Nucleophilic, anionic boryl compounds are long-sought but elusive species. We report that reductive cleavage of the boron-bromine bond in N,N'-bis(2,6-diisopropylphenyl)-2-bromo-2,3-dihydro-1H-1,3,2-diazaborole by lithium naphthalenide afforded the corresponding boryllithium, which is isoelectronic with an N-heterocyclic carbene. The structure of the boryllithium determined by x-ray crystallography was consistent with sp2 boron hybridization and revealed a boron-lithium bond length of 2.291 ± 0.006 angstroms. The structural similarity between this compound and the calculated free boryl anion suggests that the boron atom has an anionic charge. The 11B nuclear magnetic resonance spectrum also supports the boryl anion character. Moreover, the compound behaves as an efficient base and nucleophile in its reactions with electrophiles such as water, methyl trifluoromethanesulfonate, 1-chlorobutane, and benzaldehyde.

Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656, Japan.

* To whom correspondence should be addressed. E-mail: makotoy{at}chembio.t.u-tokyo.ac.jp (M.Y.); nozaki{at}chembio.t.u-tokyo.ac.jp (K.N.)

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Science. ISSN 0036-8075 (print), 1095-9203 (online)