Mini-Symposium, Paper M7
Gernot Katzer
Institut für Theoretische Chemie
Karl-Franzens Universität Graz
Strassoldogasse 10, A-8010 Graz
Torsion potentials about the X-XH bond in homosubstituted primary carbenes (X=C) and silylenes (X=Si) have been investigated at the multi-reference averaged coupled pair functional (MR-ACPF) level of theory. While the potentials in the triplet states are flat, rather large barriers of torsion have been observed for the singlets if and only if the carbon or silicon atom adjacent to the divalent atom forms small bond angles with two of its further substituents, as in three-rings. This kind of bond angle deformation encourages the formation of a weak dative p-like bond between the two X atoms, which by its twofold symmetry with respect to torsion about the bond axis is responsible for the observed two-minima torsion potential.