Conformations of silicon-containing rings

Infrared and Raman spectra, DFT-calculations and spectral assignments of 1,1,3,3,5,5-hexafluoro-1,3,5-trisilacyclohexane

“…The calculated energy difference between the two low energy forms chair and twist were 27.2 kJ mol À1 for cyclohexane [20], 9.2 kJ mol À1 for 1,3,5 trisilacyclohexane [11] and 8.0 kJ mol À1 for cyclohexasilane [21,22]. In HFTSC, however, B3LYP/cc-pVTZ calculations gave twist only 2.4 kJ mol À1 higher than chair and showed the boat conformation to be a saddle point between twist forms.…”

“…They can be compared to the antisymmetric (712 cm À1 ) and symmetric (862 cm À1 ) SiF 2 stretches in the solid state spectra of 1,1-difluoro-1-silacyclohexane [14]. In the IR spectrum of 1-fluoro-1-silacyclohexane [22] the single SieF stretch was situated at 845 cm À1 in the equatorial and at 808 cm À1 in the axial conformer. Moreover, the 6 fluorine atoms will lead to 12 SiF 2 bending modes (2 A 1 , 4 E, 2 A 2 ).…”

Stereoelectronic interaction effects on the conformational properties of 5-methyl-5-aza-1,3-dithiacyclohexane and its analogous containing N, P, O, and Se atoms — A hybrid density functional theory (DFT), ab initio study, and natural bond orbital (NBO) analysis

“…Although, due to the nature of the various approximations involved in these theoretical calculations, it is not expected, in principal, to obtain exactly the experimental values; 35 however, it is possible to carry out theoretical calculations, from which many properties and structures can be obtained with an accuracy that is competitive with experiments. [35][36][37][38] Importantly, considering the structures of compounds 1-9 (optimized by B3LYP/6-311+G** method) gave evidence that in the axial stereoisomers of these compounds the s X5-C6 bond lengths are significantly contracted compared to those in the equatorial stereoisomers. Based on the B3LYP/6-311+G** results, the s X5-C6 bond lengths in the equatorial and axial stereoisomers of compound 1 are 1.456 and 1.445 Å , respectively (see Table 6).…”

Stereoelectronic interaction effects (associated with the anomeric effects) on the conformational properties of 2-methylaminotetrahydropyran, 2-methylaminotetrahydrothiopyran, 2-methylaminotetrahydroselenopyran and their analogous containing P and As atoms: An Ab initio study and NBO analysis

“…Although, due to the nature of the various approximations involved in theoretical calculations, it is not expected, in principal, to obtain exactly the experimental values [33]. However, it is possible to carry out theoretical calculations, from which many properties and structures can be obtained with an accuracy that is competitive with experiments [33][34][35][36][37].…”