Theoretical study of silabenzene and its valence isomers

Abstract

Quantum mechanical calculations at the ab initio (MP2, CCSD(T)) and the hybrid density functional levels with an array of basis sets (6-31G*, 6-31G**, cc-pVDZ, 6-311+G**) were performed on 15 (CH)₅SiH structures. Of the 15 structures considered on the (CH)₅SiH potential energy surface, 12 structures were characterized as local minima. Two new valence isomeric forms of silabenzene, V1a_m and V1b_m, have been identified, which lie only about 20 kcal/mol higher than silabenzene (B1). PY, where Si is hexacoordinated, has been characterized as a stationary point, which lies only around 56 kcal/mol higher in energy than silabenzene. The relative energies are contrasted with those of the valence isomers of benzene. The lower magnitudes of the vibrational frequencies corresponding to the skeletal movements support the facile rearrangements witnessed in these compounds. The chemical hardness values were measured, and no direct correlation was obtained between the relative energy ordering and the chemical hardness values.