Reactions of a Four-Membered Borete with Carbon, Silicon, and Gallium Donor Ligands: Fused and Spiro-Type Boracycles

Zeynep Güven; Lars Denker; Hadi Dolati; Daniela Wullschläger; Bartosz Trzaskowski; René Frank

doi:10.1002/chem.202200673

Reactions of a Four-Membered Borete with Carbon, Silicon, and Gallium Donor Ligands: Fused and Spiro-Type Boracycles

Chemistry. 2022 Jun 7;28(32):e202200673. doi: 10.1002/chem.202200673. Epub 2022 Apr 21.

Authors

Zeynep Güven¹, Lars Denker¹, Hadi Dolati¹, Daniela Wullschläger¹, Bartosz Trzaskowski², René Frank¹

Affiliations

¹ Department of Inorganic and Analytical Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106, Braunschweig, Germany.
² Centre of New Technologies, University of Warsaw, Banacha 2 C, 02-097, Warszawa, Poland.

Abstract

Donor-acceptor cyclopropanes or cyclobutanes are dipolar reagents, which are widely used in the synthesis of complex organic (hetero)cycles in ring expansion reactions. Applying this concept to boron containing heterocycles, the four-membered borete cyclo-iPr₂ N-BC₁₀ H₆ reacted with the carbon donor ligands 2,6-xylylisonitrile and the carbene IMes :C(NMesCH)₂ with ring expansion and ring fusion, respectively. In particular, the tetracyclic structure formed with IMes displays zwitterionic character and absorption in the visible region. In contrast to the carbene IMes, the heavier carbenoids :Si(NDippCH)₂ and :Ga(AmIm) with a two-coordinate donor atom afford spiro-type bicyclic compounds, which display four-coordinate geometry at silicon or gallium. (TD-)DFT calculations provide deeper insight into the mechanism of formation and the absorption properties of these new compounds.

Keywords: N-heterocyclic carbenes; donor-acceptor cyclobutanes; gallium carbenoids; inorganic polycycles; inorganic spirocycles; ring expansion reactions; silicon carbenoids.