Planar and Pyramidal Tetracoordinate Carbon in Organoboron Compounds Ruslan M. Minyaev Tatyana N. Gribanova Vladimir I. Minkin Andrey G. Starikov Roald Hoffmann 10.1021/jo050651j.s001 https://acs.figshare.com/articles/journal_contribution/Planar_and_Pyramidal_Tetracoordinate_Carbon_in_Organoboron_Compounds/3271948 Using previously proposed C(BH)<sub>2</sub>(CH)<sub>2</sub> (<b>16</b>, <b>17</b>) and C(CH)<sub>2</sub>B<sub>2</sub> (<b>22</b>) 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 [3.3.3.3]tetraborafenestrane <b>45</b> and others by surrounding the carbon with boron-centered ligands. 2005-08-19 00:00:00 CH Pyramidal Tetracoordinate Carbon tetracoordinate carbon ptC carbon atom ligated DFT B 3LYP method molecule center