The rotational spectrum of silacyclohexane

Favero, Laura B.; Camináti, Walther; Arnason, Ingvar; Kvaran, Ágúst

doi:10.1016/j.jms.2004.09.008

Cited by 22 publications

(11 citation statements)

References 16 publications

(15 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The molecular structure of 6 has been determined by gas electron diffraction (GED) 13 and microwave spectroscopy (MW). 14 A theoretical study on the potential energy surface (PES) of 6 has been reported 15 and the path for its chair-to-chair inversion has been calculated. 16 Reports on monosubstituted silacyclohexanes are rather limited; yet, interesting results have emerged so far.…”

Section: Introductionmentioning

confidence: 99%

Conformational Properties of 1-Silyl-1-Silacyclohexane, C₅H₁₀SiHSiH₃: Gas Electron Diffraction, Low-Temperature NMR, Temperature-Dependent Raman Spectroscopy, and Quantum Chemical Calculations

et al. 2010

Self Cite

View full text Add to dashboard Cite

The molecular structure of axial and equatorial conformers of 1-silyl-silacyclohexane, C(5)H(10)SiHSiH(3), and the thermodynamic equilibrium between these species were investigated by means of gas electron diffraction (GED), dynamic nuclear magnetic resonance (DNMR), temperature-dependent Raman spectroscopy, and quantum chemical calculations (CCSD(T), MP2 and DFT methods). According to GED, the compound exists as a mixture of two conformers possessing the chair conformation of the six-membered ring and C(s) symmetry and differing in the axial or equatorial position of the SiH(3) group (axial = 57(7) mol %/equatorial = 43(7) mol %) at T = 321 K. This corresponds to an A value (free energy difference = G(axial) - G(equatorial)) of -0.17(15) kcal mol(-1). A low-temperature (13)C NMR experiment using SiD(4) as a solvent resulted in an axial/equatorial ratio of 45(3)/55(3) mol % at 110 K corresponding to an A value of 0.05(3) kcal mol(-1), and a DeltaG(#) value of 5.7(2) kcal mol(-1) was found at 124 K. Temperature-dependent Raman spectroscopy in the temperature range of 210-300 K of the neat liquid, a THF solution, and a heptane solution indicates that the axial conformer is favored over the equatorial one by 0.26(10), 0.23(10), and 0.22(10) kcal mol(-1) (DeltaH values), respectively. CCSD(T)/CBS and MP2/CBS calculations in general predict both conformations to have very similar stability and are, thus, in excellent agreement with the DNMR result but in a slight disagreement with the GED and Raman results. Two DFT functionals, that account for dispersion interactions, M06-2X/pc-3 and B2PLYP-D/QZVPP, deviate from the high-level coupled cluster and MP2 calculations by only 0.1 kcal mol(-1) on average, whereas B3LYP/pc-3 calculations greatly overestimate the stability of the equatorial conformer.

show abstract

Section: Introductionmentioning

confidence: 99%

Conformational Properties of 1-Silyl-1-Silacyclohexane, C₅H₁₀SiHSiH₃: Gas Electron Diffraction, Low-Temperature NMR, Temperature-Dependent Raman Spectroscopy, and Quantum Chemical Calculations

et al. 2010

Self Cite

View full text Add to dashboard Cite

show abstract

“…A number of monosubstituted 1-silacyclohexanes have been studied by experimental and theoretical methods in the last few years in order to explore the effect that silicon substitution has on the axial/equatorial equilibrium of the cyclohexane ring. [8][9][10][11][12][13] Because the synthesis and accurate measurement of these air-sensitive molecules are difficult, an attractive alternative is to explore the conformational properties by theoretical calculations, DFT being a computationally feasible option. The energy difference between axial and equatorial conformers of a monosubstituted cyclohexane or heterocycle can be very small, depending on both the ring system and substituent, and thus the reliability of the QM method used is important.…”

Section: Introductionmentioning

confidence: 99%

“…The method of choice should be reliable for calculating conformational energies in general. We will restrict the calculations to relative energy values, DE (zero-point energy exclusive at 0 K), it should be pointed out that various experimental methods that have been used in studies of the conformational properties of silacyclohexanes, result in different thermodynamic quantities; microwave spectroscopy in DE (zero-point energy inclusive at room temperature), [10][11][12] temperature-dependent Raman spectroscopy in DH 9 , gas electron diffraction 8,9,13 and DNMR in DG values. 8,9,13 A direct comparison with experiment thus involves calculation of the zero-point energy, enthalpic and entropic corrections that can be done independently with a suitable method.…”

Section: Introductionmentioning

confidence: 99%

Conformational properties of six-membered heterocycles: accurate relative energy differences with DFT, the importance of dispersion interactions and silicon substitution effects

Björnsson

Arnason²

2009

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Density functional methods were evaluated in their ability to predict relative conformational energies of a test set of monosubstituted cyclohexanes and six-membered heterocycles. It is shown that while popular density functionals like B3LYP are unreliable for predicting accurate conformational energies for the axial/equatorial equilibrium of monosubstituted cyclohexanes, 1-silacyclohexanes and tetrahydropyrans, density functionals that take into account dispersion interactions like M06-2X and B2PLYP-D result in energy differences close to CCSD(T)/CBS results. Using the M06-2X density functional, we have then investigated the conformational properties of a large number of monosubstituted silacyclohexanes, with the number of silicon atoms ranging from 1 to 6. Our calculations suggest remarkably different conformational properties when compared to cyclohexane. The carbon/silicon exchange in a cyclohexane ring often has systematic, yet counterintuitive effects on the conformational properties. Dispersion interactions are shown to be especially important for accurate relative energy calculations of polysilacyclohexanes.

show abstract

“…The chair conformation was determined to be the most stable by roughly 4 kcal mol −1 or more 9, 10. The rotational spectrum of the chair form of silacyclohexane has recently been reported by Favero et al 11.…”

Section: Introductionmentioning

confidence: 79%

Intrinsic conformational preferences of and an anomeric‐like effect in 1‐substituted silacyclohexanes

Weldon

Tschumper

2007

Int J of Quantum Chemistry

View full text Add to dashboard Cite

A series of ab initio computations have been performed to estimate the CCSD(T) complete basis set limit of the axial/equatorial energy difference for the chair conformation of 1-fluoro, 1-chloro, 1-methyl, 1-hydroxy, and 1-methoxysilacyclohexanes. The equatorial conformation is more stable than the axial by 0.21 kcal mol Ϫ1 for 1-methylsilacyclohexane, while the axial position is more stable for 1-fluoro, 1-chloro, and 1-methoxysilacyclohexane (by 0.09, 0.40, and 0.15 kcal mol Ϫ1 , respectively). The axial and equatorial orientations of 1-hydroxysilacyclohexane are nearly electronically isoenergetic (equatorial favored by 0.03 kcal mol Ϫ1). Zero point vibrational energy corrections have very little effect on the relative energies (less than 0.08 kcal mol Ϫ1 ). These results suggest the presence of an interesting stereoelectronic effect, similar to the anomeric effect, in these silacyclohexanes even without an additional heteroatom, like O, in the ring.

show abstract

The rotational spectrum of silacyclohexane

Cited by 22 publications

References 16 publications

Conformational Properties of 1-Silyl-1-Silacyclohexane, C₅H₁₀SiHSiH₃: Gas Electron Diffraction, Low-Temperature NMR, Temperature-Dependent Raman Spectroscopy, and Quantum Chemical Calculations

Conformational Properties of 1-Silyl-1-Silacyclohexane, C₅H₁₀SiHSiH₃: Gas Electron Diffraction, Low-Temperature NMR, Temperature-Dependent Raman Spectroscopy, and Quantum Chemical Calculations

Conformational properties of six-membered heterocycles: accurate relative energy differences with DFT, the importance of dispersion interactions and silicon substitution effects

Intrinsic conformational preferences of and an anomeric‐like effect in 1‐substituted silacyclohexanes

Contact Info

Product

Resources

About

The rotational spectrum of silacyclohexane

Cited by 22 publications

References 16 publications

Conformational Properties of 1-Silyl-1-Silacyclohexane, C5H10SiHSiH3: Gas Electron Diffraction, Low-Temperature NMR, Temperature-Dependent Raman Spectroscopy, and Quantum Chemical Calculations

Conformational Properties of 1-Silyl-1-Silacyclohexane, C5H10SiHSiH3: Gas Electron Diffraction, Low-Temperature NMR, Temperature-Dependent Raman Spectroscopy, and Quantum Chemical Calculations

Conformational properties of six-membered heterocycles: accurate relative energy differences with DFT, the importance of dispersion interactions and silicon substitution effects

Intrinsic conformational preferences of and an anomeric‐like effect in 1‐substituted silacyclohexanes

Contact Info

Product

Resources

About

Conformational Properties of 1-Silyl-1-Silacyclohexane, C₅H₁₀SiHSiH₃: Gas Electron Diffraction, Low-Temperature NMR, Temperature-Dependent Raman Spectroscopy, and Quantum Chemical Calculations

Conformational Properties of 1-Silyl-1-Silacyclohexane, C₅H₁₀SiHSiH₃: Gas Electron Diffraction, Low-Temperature NMR, Temperature-Dependent Raman Spectroscopy, and Quantum Chemical Calculations