Structural Investigations of Substituted Silacyclopropylidenoids through Computational Techniques

The "ab initio" (MP2) level of theory using 6-311+G(d,p) basis set has been carried out to explore the isomeric structures, energies, and properties of substitued (-H, -CH3, -SiH3, -OH) LiBr-silacyclopropylidenoids. The resulting isomeric structures of LiBr-silacyclopropylidenes reveal three stationary structures: silylenoidal (S), inverted (I), and tetrahedral (T). The theoretical calculations indicate that all substituted LiBr-silacyclopropylidenoids have silylenoidal (S), inverted (I), and tetrahedral (T) forms except –OH substituted silylenoid. Interestingly we have obtained no tetrahedral structure as a minimum for the –OH substituted structure. The silylenoidal forms energetically more stable than the inverted (I) and tetrahedral (T) forms, whereas stability of the tetrahedral (T) forms for the title structures lower than the inverted (I) and silylenoidal (S) forms.