Density functional theoretica studies of [2+2] cycloaddition of simple transient silenes and germenes to ethylene, formaldehyde, and thioformaldehyde, and vibrational analysis of spectra of reactants and cyclic products

摘要

The cycloadditions of small unsaturated organic molecules, such as ethylene, formaldehyde, and thioformaldehyde, to simple silenes and their germanium analogues were studied by the density functiona theory B3LYP/6-311G(d,p) method. The optimized geometry parameters, vibrational frequencies, and energies of the ground states of the reactants and products and those of reaction transition states found were discussed. A lower reactivity of germenes than silenes in the reactions studied was predicted and a non-concerted two-step mechanism of [2+2] cycloadditions suggested.