Density functional theory study of the relative energies and structures of the chair, twist, and boat conformations of stannacyclohexane, 1‐methylstannacyclohexane, and 1,1‐dimethylstannacyclohexane

Abstract

AbstractThe relative energies and structures of the chair, twist, and boat conformations of stannacyclohexane, 1‐methylstannacyclohexane, and 1,1‐dimethylstannacyclohexane have been investigated using density functional theory (DFT) (BLYP, B3LYP, B3P86, B3PW91) and hybrid Hartree–Fock/DFT (BH and HLYP) methods with the SDD basis set. The five levels of theory predicted similar energy differences (Erel) among the respective conformations of the stannacyclohexanes. Similar equilibrium geometries were also predicted at the five theoretical levels, with BLYP giving the longest bonds and BH and HLYP giving the shortest bonds. B3LYP predicted the chair conformer of stannacyclohexane to be 3.09, 3.47, and 4.27 kcal/mol, respectively, more stable than the 1,4‐twist and 2,5‐twist conformers and the 2,5‐boat transition state. The chair conformer of axial 1‐methylstannacyclohexane is 2.85, 3.40, and 4.46 kcal/mol, respectively, more stable than the 1,4‐twist and 2,5‐twist conformers and the 2,5‐boat transition state and the chair conformer of equatorial 1‐methylstannacyclohexane is 3.05, 3.52, and 4.56 kcal/mol, respectively, more stable than the 1,4‐twist and 2,5‐twist conformers and the 2,5‐boat transition state. The chair conformer of axial 1‐methylstannacyclohexane is 0.19 kcal/mol less stable than the equatorial chair conformer, and the chair conformer of 1,1‐dimethylstannacyclohexane is 2.94, 3.49, and 4.21 kcal/mol, respectively, more stable than the 1,4‐twist and 2,5‐twist conformers and the 2,5‐boat transition state. The relative energies (Erel) of the conformers of the stannacyclohexanes are also compared with the available experimental and theoretical relative energies of the corresponding cyclohexanes and silacyclohexanes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005