Molecular Structure of Silatrane Determined by Gas Electron Diffraction and Quantum-Mechanical Calculations

Shishkov, Igor F.; Khristenko, L. V.; Rudakov, F. M.; Golubinskii, A. B.; Vilkov, L. V.; Karlov, Sergey S.; Зайцева, Г. С.; Samdal, Svein

doi:10.1023/b:stuc.0000010464.93848.bd

Cited by 35 publications

(31 citation statements)

References 7 publications

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“…This is in line with general trend that the length of the equilibrium SiÁ Á ÁN distance in silatranes and silocanes obtained by DFT methods reproduces well the experimental SiÁ Á ÁN bond length in the gas phase, but substantially overestimates interatomic distances defined in X-ray studies of corresponding crystals. The MP2 optimization, probably fortuitously, gives the SiÁ Á ÁN transannular bond length much closer to the solid state experimental value [21][22][23][24]. In our case the same effect is observed.…”

Section: Resultssupporting

confidence: 75%

Molecular and crystal structures of 2-phenyl-2-hydro-6-methyl-1,3-dioxa-6-aza-2-silacyclooctane

Ignatyev

Кочина

Аврорин

et al. 2015

Journal of Molecular Structure

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Section: Resultssupporting

confidence: 75%

Molecular and crystal structures of 2-phenyl-2-hydro-6-methyl-1,3-dioxa-6-aza-2-silacyclooctane

Ignatyev

Кочина

Аврорин

et al. 2015

Journal of Molecular Structure

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“…20 The soft character of the dependence of the total energy on d Si-N established for 1-3 9-11,43 is manifested in a significant medium effect on their geometry and spectral properties. 8,10, [31][32][33]43 For example, for silatranes 1 (X ) H, CH 3 , F) upon going from the gas phase to the solid state a dramatic shortening (by ∼0.3 Å) of the coordination Si‚‚‚N contact is observed. [31][32][33] Therefore, on the basis of the form of the potential function of silacarbatrane 8b (see Figure 3), one would expect a substantial decrease in the C 1 ‚‚‚N distance upon the influence of external factors in polar compounds 8 and 9 as well.…”

Section: Methodsmentioning

confidence: 99%

“…The possible reason is a 1-5 attractive C‚‚‚N interaction. Indeed, the internuclear distances d C1-N in 8 and 9 are ∼0.5 Å shorter than the sum of the van der Waals (vdW) radii of ∼3.35 Å for C and N. Note that in silatranes 1, possessing a relatively strong coordination SirN bond (according to various estimates, 2,8 its energy is higher than 10 kcal/mol), the length of d Si-N is less than the sum of the vdW radii of Si and N by ∼1 Å, as shown by electron diffraction (ED) data, [31][32][33] X-ray experiments, 3,5,8 and ab initio calculations. [9][10][11]20,[34][35][36][37][38] An increase of the electronegativity of substituent X (replacement of H by F) results in the shortening of the C 1 -N distance both in 8 and in 9.…”

Section: Methodsmentioning

confidence: 99%

Hypercoordinated Carbon in 2,8,9-Sila- and Thia-Substituted Carbatranes

et al. 2007

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Ab initio methods demonstrate that internally protonated forms (a) of the molecules of carbatranes XC(SiH2CH2CH2)3N (X = H, F) are significantly more favorable than their externally protonated forms (b). The quantum-topological AIM approach suggests that the main reason for that is the formation of a medium-strength hydrogen C···H+N bond unknown previously in the silacarbanyl cations a. Disciplines Chemistry CommentsReprinted (adapted) with permission from Organometallics 26 (2007) The structures of carbatranes XC(SiH 2 CH 2 CH 2 ) 3 N (8) and XC(SCH 2 CH 2 ) 3 N (9), where X ) H, F, and their in and out protonated forms were studied at the MP2 level of theory using the 6-31G*, 6-311G**, and 6-311++G** basis sets. Compounds 8 and 9 are the first representatives of the derivatives of 5-aza-1-carbabicyclo[3.3.3]undecanes, whose endo-isomer contains a nitrogen lone electron pair directed inside the cage. The geometrical, AIM, and NBO peculiarities of sila-(8) and thiacarbatranes (9) are indicative of the existence of a weak coordination XCrN interaction in these compounds, which is enhanced with the increasing of electronegativity of the axial substituent X. The MP2 and MP4/SDQ(T) (single-point calculations) methods demonstrate that the in protonated forms of compounds 8 are significantly (>6 kcal/mol) more favorable than their out forms. The quantum-topological AIM approach suggests that the main reason for this is the formation of a medium-strength (4-15 kcal/mol) hydrogen C 1 ‚‚‚H + N bond unknown previously in the in silacarbanyl cations. That bond provides a high pentacoordination degree (>60%) of the bridged carbon atom C 1 in the compounds.

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“…6 The electron diffraction and quantum chemistry meth ods allowed the study of the structure of molecule 1 in the gas phase. 7 It was found that a longer bond N→Si in an individual molecule of 1 (2.406 Å) (as compared to that in the structure we determined in the crystal) has an inter mediate value between the corresponding lengths of bonds N→Si in the molecules of 1 methylsilatrane (2) 8 and 1 fluorosilatrane (3) 9 (2.453 and 2.324 Å, respectively). Therefore, on the basis of the length of the bond N→Si molecule 1 is closer to 2 rather than to 3.…”

mentioning

confidence: 92%

Chemical bonding in the crystal structure of 1-hydrosilatrane

et al. 2009

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A study has been made of the crystal and molecular structure of 1 hydrosilatrane HSi(OCH 2 CH 2 ) 3 N. The quantum chemical calculations of its crystal structure have been carried out. According to an estimate of the energy, the coordination bond N→Si is by 5 kcal mol -1 stronger than that in the crystal of 1 methylsilatrane. The charge values calcu lated within the framework of the topological analysis of the electron density demonstrate that the electron density of the coordination bond N→Si is primarily transferred to the region of the equatorial bonds Si-O and, to a lesser extent, to the bond Si-H. On going from the isolated molecule of 1 hydrosilatrane to its crystal, the interatomic distance N-Si decreases, mainly owing to the weak intermolecular interaction C-H…O.Key words: silatranes, 1 hydrosilatrane, X ray diffraction study, quantum chemical calcu lations, N→Si bond energy, density functional theory, basis sets of plane waves.As surprising as it may seem, the molecular and crystal structure of the parent compound of a broad family of silatranes, viz., 1 hydrosilatrane or silatrane, HSi(OCH 2 CH 2 ) 3 N (1), 1-4 has not been studied. This stems from the fact that so far the preparation of single crystals of 1 pos sessing high diffraction quality has failed. At the same time, the molecular structure of this compound, the most straightforward and convenient method of synthesis of which was suggested by one of us as early as 40 years ago, 5 attracted great interest of researchers. It was established by IR spectroscopy that the frequency and integral inten sity of the Si-H bond vibrations in molecule 1 (and, consequently, the distribution of electron density in the axial fragment N→SiH) depends on the polarity (dielec tric constant ε) of the solvent and temperature. 6 The electron diffraction and quantum chemistry meth ods allowed the study of the structure of molecule 1 in the gas phase. 7 It was found that a longer bond N→Si in an individual molecule of 1 (2.406 Å) (as compared to that in the structure we determined in the crystal) has an inter mediate value between the corresponding lengths of bonds N→Si in the molecules of 1 methylsilatrane (2) 8 and 1 fluorosilatrane (3) 9 (2.453 and 2.324 Å, respectively). Therefore, on the basis of the length of the bond N→Si molecule 1 is closer to 2 rather than to 3. This indicates the proximity of the values of the interaction energies of * Dedicated to academician A. I. Konovalov on his 75th birthday. the nitrogen and silicon atoms in the former two mol ecules. The bond length N→Si in molecule 1 calculated with the B3LYP/6 311G(d) and MP2 basis set amounts to 2.335 Å (see Ref. 10) and 2.351 Å (see Ref. 7), respec tively. As to the lengths of the bonds N-C, O-C, Si-O, and C-C, they are approximately the same as in mol ecules 2 and 3. In molecule 1 the silicon atom is shifted from the equatorial plane of three oxygen atoms surround ing it in the direction opposite to the nitrogen atom, the angle N-Si-O is smaller than 90°, while the angle Si-N-C is larger than 90°. ...

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Molecular Structure of Silatrane Determined by Gas Electron Diffraction and Quantum-Mechanical Calculations

Cited by 35 publications

References 7 publications

Molecular and crystal structures of 2-phenyl-2-hydro-6-methyl-1,3-dioxa-6-aza-2-silacyclooctane

Molecular and crystal structures of 2-phenyl-2-hydro-6-methyl-1,3-dioxa-6-aza-2-silacyclooctane

Hypercoordinated Carbon in 2,8,9-Sila- and Thia-Substituted Carbatranes

Chemical bonding in the crystal structure of 1-hydrosilatrane

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