THEORETICAL INVESTIGATIONS ON SOME C2SIH4 ISOMERS

A part of the C2SiH4 potential energy surface has been explored using a nonempirical pseudopotential method. The computed relative stabilities of the five isomers, silylacetylene (0 kcal/mol) < silacyclopropene (3) and silacyclopropylidene (2) (both 17 kcal/mol) < 2-silaallene (46 kcal/mol) < 2-silapropyne (61 kcal/mol), differ significantly from those of the analogous carbon compounds: propyne < allene < cyclopropene « cyclopropylidene. Silacyclopropylidene (2) has a singlet while the carbene analogue a triplet ground state. The relative stabilities of the two cyclic structures 2 and 3 have been analyzed further using extensive Cl calculations. The results do not suggest an aromatic character for 3. © 1979, American Chemical Society. All rights reserved.