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Cyclic(alkyl)(amino) carbene-promoted ring expansion of a carbodicarbene beryllacycle

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posted on 30.04.2021, 03:36 by Jacob E Walley, Akachukwu D Obi, Grace Breiner, Guocang Wang, Diane A Dickie, Andrew Molino, Jason Dutton, David Wilson, Robert J Gilliard
Recent synthetic efforts have uncovered several bond activation pathways mediated by beryllium. Having the highest charge density and electronegativity, the chemistry of beryllium often diverges from that of its heavier alkaline earth metal congeners. Herein, we report the synthesis of a new carbodicarbene beryllacycle (2). Compound 2 converts to 3 via an unprecedented cyclic(alkyl)(amino) carbene (CAAC)-promoted ring expansion reaction (RER). While CAAC activates a carbon-beryllium bond, N-heterocyclic carbene (NHC) coordinates to beryllium to give the tetracoordinate complex 4, which contains the longest C-Be bond to date at 1.856(4) Å. All of the compounds were fully characterized by X-ray crystallography, Fourier transform infrared spectroscopy, and H, C, and Be NMR spectroscopy. The ring expansion mechanism was modeled with both NHC and CAAC using density functional theory calculations. While the activation energy for the observed beryllium ring expansion with CAAC was found to be 14 kJ mol , the energy barrier for the hypothetical NHC RER is significantly higher (199.1 kJ mol ). carbene.

Funding

The authors acknowledge the Univ. of Virginia (UVA) for support of this work. We also thank X. Jia from the Gunnoe Group at UVA for his assistance with the hydrogenation step of the carbodicarbene ligand synthesis. Generous allocation of computing resources from National Computational Infrastructure, Intersect, and La Trobe Univ. are acknowledged.

History

Publication Date

01/01/2019

Journal

Inorganic Chemistry

Volume

58

Issue

16

Pagination

9p. (p. 11118-11126)

Publisher

American Chemical Society

ISSN

0020-1669

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