Isomerization of Silylallene
The isomerization of silylallene to seven of its isomers has been studied using ab initio molecular orbital theory. The energetics were obtained using quadratically convergent configuration interaction (QCISD(T)) with the 6-311G(d,p) basis set, at geometries optimized by second-order perturbation theory (MP2) with the 6-31G(d) basis set. Test calculations using multiconfiguration wave functions show that the configurational mixing is small; therefore, the single-configuration-based methods are reliable. In comparison to the isomerization of the parent allene, the silyl group was found to migrate more easily than the hydrogen. In particular, the 1,3-migration that converts silylallene to silylpropyne has barriers of 55.8 and 52.9 kcal mol-1 for the forward and backward reactions, respectively. These are roughly half of the 1,3-hydrogen migration barrier in allene.
Reprinted (adapted) with permission from Organometallics 14 (1005): 3827, doi:10.1021/om00008a033. Copyright 1995 American Chemical Society.