Density functional theoretical studies on structures and vibrational spectra of fluorovinyl silanimines

The structural stability of 1-fluorovinylsilanimine CH₂=CF-SiH= NH, 1-difluorovinylsilanimine CF₂=CHSiH= NH, and 1- trifluorovinylsilanimine CF₂=CFSiH= NH were investigated using ab initio calculations. The calculations were carried out at the DFT-B3LYP/6-311++Gz.ast;z.ast; level of theory. From the calculations the molecules were predicted to exist predominantly in the trans conformation. The barrier to internal rotation around the C-Si single bond in 1- fluorovinylsilanimine was calculated at DFT-B3LYP/6-311++Gz.ast;z.ast; level to be of a bout 4.6 kcal/mol, while that in 1-difluorovinylsilanimine to be of about 3.7 kcal/mol. However, in the trifluoro derivative the barrier was increased to a value of 4.9 kcal/mol. The vibrational frequencies were computed at DFT-B3LYP level of theory. Normal coordinate calculations were carried out and potential energy distributions were calculated for the stable conformers of the molecules.