A likely pathway of decomposition of haloslianes in the upper atmosphere is 1,2-HX elimination, leading to a species with a formal double bond between a carbon and a silicon atom X2Si=CR2 (X = F, Cl, R = H, F, Cl). While some of these molecules are predicted to be planar using ab initio and DFT methods, geometry optimizations of several of these species leads to a non-classical trans-bent structure using DFT (B3PW91), Hartree-Fock and MP levels of theory. In order to probe the nature of bonding in these trans-bent geometries, we employ the Quantum Theory of Atoms in Molecules (QTAIM) using electron densities generated at the same level of theory as the optimization. The Laplacian of the electron density shows critical points indicative of regions of high electron localization � bonding electron domains and non-bonding electron domains. The presence of two unusual critical points above and below the near plane of the molecule, along with a longer than expected Si-C bond strongly suggest a single bond with singlet-biradical character accounting for the remaining two electrons. Compounds with a planar geometry lack these two unusual critical points and have a shorter Si-C bond length.

QTAIM studies of formal double bonds between silicon and carbon atoms

246th National Meeting (2013)

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