The barrier to internal rotation in silabutenes: A density functional theory study

The potential energy surfaces (PESs) for internal were systematically investigated by using DFT with the B3LYP function. QTAIM, NBO, NEDA and BLW-ED were employed to study the origin of rotational barriers. The silabutenes with M¹ = C–M²–M³ skeleton preferred the ac conformer and the M¹ = Si–M²–M³ skeletons have the sp conformer. Silabutenes including SiSi double bond have three stable conformers, two different ac conformer and one gauche conformer. Internal rotation barriers (0.38–2.47 kcal/mol) vary with bond lengths (SiC, SiSi, CC), decomposed into steric, electrostatic, and hyperconjugation terms using NSA, NEDA, and NBO. A linear correlation (R² = 0.78) links barrier heights to energetic differences between stable and metastable conformers. Understanding these factors aids in predicting and rationalizing rotational barriers in silabutenes, crucial for their chemical behavior and applications.