Cyclic(alkyl)(amino) Carbene-Promoted Ring Expansion of a Carbodicarbene Beryllacycle

Jacob E Walley; Akachukwu D Obi; Grace Breiner; Guocang Wang; Diane A Dickie; Andrew Molino; Jason L Dutton; David J D Wilson; Robert J Gilliard Jr

doi:10.1021/acs.inorgchem.9b01643

Cyclic(alkyl)(amino) Carbene-Promoted Ring Expansion of a Carbodicarbene Beryllacycle

Inorg Chem. 2019 Aug 19;58(16):11118-11126. doi: 10.1021/acs.inorgchem.9b01643. Epub 2019 Aug 5.

Authors

Jacob E Walley¹, Akachukwu D Obi¹, Grace Breiner¹, Guocang Wang¹, Diane A Dickie¹, Andrew Molino², Jason L Dutton², David J D Wilson², Robert J Gilliard Jr¹

Affiliations

¹ Department of Chemistry , University of Virginia , 409 McCormick Road , PO Box 400319, Charlottesville , Virginia 22904 , United States.
² Department of Chemistry and Physics, La Trobe Institute for Molecular Science , La Trobe University , Melbourne , Australia.

PMID: 31380626
DOI: 10.1021/acs.inorgchem.9b01643

Abstract

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 ^carbeneC-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 ¹H, ¹³C, and ⁹Be 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^-1, the energy barrier for the hypothetical NHC RER is significantly higher (199.1 kJ mol^-1).