Conformational properties of 1-cyano-1-silacyclohexane, C5H10SiHCN: Gas electron diffraction, low-temperature NMR and quantum chemical calculations

Belyakov, A. V.; Sigolaev, Yrii F.; Shlykov, Sergey A.; Wallevik, Sunna Ó.; Jonsdottir, Nanna R.; Jónsdóttir, Sigríður; Kvaran, Ágúst; Björnsson, Ragnar; Arnason, Ingvar

doi:10.1016/j.molstruc.2016.10.012

Cited by 13 publications

(12 citation statements)

References 60 publications

(32 reference statements)

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“…The results are compiled in Table 4. For comparison, the recently published data for 1-cyano- [74] and 1-methoxy-1-silacyclohexane [75] as well as disubstituted silacyclohexanes with the phenyl group and Hlg = F, Cl [76] or other electronegative groups at silicon are included. Note, that 1-bromo-1-phenylsilacyclohexane has also been synthesized [77] but, because of low stability, its conformational analysis could not be performed.…”

Section: Si-x-silacyclohexanes (X = Hlg Cn Ome)mentioning

confidence: 99%

Silacyclohexanes, Sila(hetero)cyclohexanes and Related Compounds: Structure and Conformational Analysis

Shainyan

2020

Molecules

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Conformational analysis of Si-mono- and Si,Si-disubstituted silacyclohexanes as well as their analogues with a heteroatom(s) in the ring is reviewed with the focus on the recent results. Experimental measurements in the gas phase (gas electron diffraction, GED) and low temperature NMR spectroscopy (LT NMR) on 1H, 13C and 29Si nuclei are described along with theoretical calculations at the DFT and MP2 levels of theory. Structural and conformational specific features are shown to be principally different from those of the carbon predecessors—the corresponding cyclohexanes, oxanes, thianes and piperidines. The role of various effects (steric, hyperconjugation, stereoelectronic, electrostatic) is demonstrated.

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Section: Si-x-silacyclohexanes (X = Hlg Cn Ome)mentioning

confidence: 99%

Silacyclohexanes, Sila(hetero)cyclohexanes and Related Compounds: Structure and Conformational Analysis

Shainyan

2020

Molecules

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“…Auxiliary basis sets (CABS) in the form of cc-pVnZ-F12/OptRI were used in all calculations [24]. Similar CCSD(T)/CBS protocols have been used in studies on silacyclohexanes [7].…”

Section: Computational Detailsmentioning

confidence: 99%

“…For comparison, the free Gibbs energy barrier of ring inversion of 1-cyanosilacylohexane is ∆G # (e→a) =5.6(1) kcal/mol from NMR spectroscopy [7]. Thus, the short N-Cα bond nearly doubles the energy barrier of the ring inversion process as compared with the longer C-Si bond.…”

Section: M062xmentioning

confidence: 99%

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Intramolecular inversions, structure and conformational behavior of gaseous and liquid N-cyanopiperidine. Comparison with other 1-cyanoheterocyclohexanes

Shlykov

Phien

Weber

2017

Journal of Molecular Structure

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The molecular structure and intramolecular inversions of N-cyanopiperidine (CNP) were studied by various quantum chemical methods and using synchronous gas electron diffraction/mass spectrometry (GED/MS) and IR spectroscopy. The contribution of the equatorial conformer was found GED 52(6), IR 60(6), B3LYP 77, B3LYP-GD3 67, M062X 59, MP2 54%. Interpolation using CCSD(T)-F12/CBS predicts E axE eq =0.26 kcal/mol. The NBO analysis shows a strong hyperconjugation of the nitrogen atom lone pair with the triple bond making the r(N-C CN)=1.355(3) Å distance as short as a typical sesquilateral bond. A low energy barrier for the Eq→Ax transition of 1.0-2.3 kcal/mol in CNP leads to difficulties in NMR conformational ratio studies. This leaves the GED method almost as the only experimental method to study both structural and conformational properties. Conformational properties of the related compounds are found to depend on the X-C CN bond distance and hyperconjugation between the CN group and the lone pair on the heteroatom. The contribution of the axial form of 1-cyano-heterocyclohexanes increases in the series of heteroatoms X in the cyclohexane ring: NCSiP.

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“…Closing the circle by low-temperature NMR spectroscopy studied silacyclohexanes, let us consider the conformational equilibria of the mono- ( 2 ) and disubstituted ( 3 , 4 ) silacyclohexanes, as depicted in Scheme . In compounds 2 , the substituent X can be found in both equatorial (Me, SiH 3 , CN) and axial positions (F, CF 3 , Cl, Br, I, OMe, and NMe 2 ), − the latter unlike the case for the corresponding cyclohexanes, where they still remain equatorial. , …”

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At the Experimental Limit of the NMR Conformational Analysis: ²⁹Si and ¹³C NMR Study of the Conformational Equilibrium of 1-Phenyl-1-tert-butylsilacyclohexane

2020

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The low temperature (95 K) NMR study of 1-Ph-1-t-Bu-silacyclohexane (1) showed the conformational equilibrium to be extremely one-sided toward thePhax,t-Bueq conformer. The barrier to interconversion has been measured (4.2–4.6 kcal/mol) and the conformational equilibrium [Δν = 1990.64 ppm (29Si), 618.9 ppm (13C), 1-Phax:1-Pheq = (95.6–96.6%):(3.4–4.4%), K = 25 ± 3, ΔG° = −RT ln K = 0.58–0.63 kcal/mol] analyzed. The assignment and quantification of the NMR signals is supported by MP2 and DFT calculations.

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Conformational properties of 1-cyano-1-silacyclohexane, C5H10SiHCN: Gas electron diffraction, low-temperature NMR and quantum chemical calculations

Cited by 13 publications

References 60 publications

Silacyclohexanes, Sila(hetero)cyclohexanes and Related Compounds: Structure and Conformational Analysis

Silacyclohexanes, Sila(hetero)cyclohexanes and Related Compounds: Structure and Conformational Analysis

Intramolecular inversions, structure and conformational behavior of gaseous and liquid N-cyanopiperidine. Comparison with other 1-cyanoheterocyclohexanes

At the Experimental Limit of the NMR Conformational Analysis: ²⁹Si and ¹³C NMR Study of the Conformational Equilibrium of 1-Phenyl-1-tert-butylsilacyclohexane

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Conformational properties of 1-cyano-1-silacyclohexane, C5H10SiHCN: Gas electron diffraction, low-temperature NMR and quantum chemical calculations

Cited by 13 publications

References 60 publications

Silacyclohexanes, Sila(hetero)cyclohexanes and Related Compounds: Structure and Conformational Analysis

Silacyclohexanes, Sila(hetero)cyclohexanes and Related Compounds: Structure and Conformational Analysis

Intramolecular inversions, structure and conformational behavior of gaseous and liquid N-cyanopiperidine. Comparison with other 1-cyanoheterocyclohexanes

At the Experimental Limit of the NMR Conformational Analysis: 29Si and 13C NMR Study of the Conformational Equilibrium of 1-Phenyl-1-tert-butylsilacyclohexane

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At the Experimental Limit of the NMR Conformational Analysis: ²⁹Si and ¹³C NMR Study of the Conformational Equilibrium of 1-Phenyl-1-tert-butylsilacyclohexane