Stabilization of Planar Tetracoordinate Carbon

Abstract

The energies of planar vs. tetrahedral geometries of tetracoordinate organic molecules have been surveyed by ab initio molecular orbital calculations. Because of their π acceptor and donor character, electropositive substituents, especially lithium, are particularly effective in stabilizing the planar arrangements selectively. Multiple substitution by such metals and by three-membered rings provides further stabilization, and 1,1-dilithiocyclopropane (XVII) and 3,3-dilithiocyclopropene (XVIII), inter alia, are actually calculated (RHF/STO-3G theory) to be more stable planar than tetrahedral. © 1976, American Chemical Society. All rights reserved.