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Planar and Pyramidal Tetracoordinate Carbon in Organoboron Compounds

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journal contribution
posted on 19.08.2005 by Ruslan M. Minyaev, Tatyana N. Gribanova, Vladimir I. Minkin, Andrey G. Starikov, Roald Hoffmann
Using previously proposed C(BH)2(CH)2 (16, 17) and C(CH)2B2 (22) systems with a central planar tetracoordinate carbon (ptC) atom linking two three-membered rings as building blocks, a series of stable structures containing two and three ptC centers within a molecule have been designed and computationally studied with the DFT (B3LYP/6-311+G**) method. Inclusion of a carbon atom ligated with π-accepting and σ-donating boron centers into at least one aromatic ring is critical for stabilization of a planar structure. A square pyramidal configuration at tetracoordinate carbon may be achieved in appropriately strained molecules such as []tetraborafenestrane 45 and others by surrounding the carbon with boron-centered ligands.