Quantum-Chemical Study of the Electron-Donating Ability of Endocyclic Nitrogen and Oxygen Atoms in Silicon-Substituted Silatranes

Belyaeva, V. V.; Frolov, Yu. L.; Abumov, Pavel; Воронков, М. Г.

doi:10.1023/b:dopc.0000035401.29788.a5

Cited by 3 publications

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“…These new results allow the available experimental data to be substantiated. Various aspects of the reactivity of atranes are considered in reviews [ 19 , 44 ], the study of the electron-donating ability of heteroatoms of the silatranyl group by calculation methods is described in [ 45 , 46 , 47 ]. There are a few publications concerned with reaction mechanisms of metallatranes and their bicyclic and tricyclic analogs with nucleophiles.…”

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confidence: 99%

Mechanism of Reactions of 1-Substituted Silatranes and Germatranes, 2,2-Disubstituted Silocanes and Germocanes, 1,1,1-Trisubstituted Hyposilatranes and Hypogermatranes with Alcohols (Methanol, Ethanol): DFT Study

2020

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The mechanism of reactions of silatranes and germatranes, and their bicyclic and monocyclic analogues with one molecule of methanol or ethanol, was studied at the Density Functional Theory (DFT) B3PW91/6-311++G(df,p) level of theory. Reactions of 1-substituted sil(germ)atranes, 2,2-disubstituted sil(germ)ocanes, and 1,1,1-trisubstituted hyposil(germ)atranes with alcohol (methanol, ethanol) proceed in one step through four-center transition states followed by the opening of a silicon or germanium skeleton and the formation of products. According to quantum chemical calculations, the activation energies and Gibbs energies of activation of reactions with methanol and ethanol are close, their values decrease in the series of atranes–ocanes–hypoatranes for interactions with both methanol and ethanol. The reactions of germanium-containing derivatives are characterized by lower activation energies in comparison with the reactions of corresponding silicon-containing compounds. The annular configurations of the product molecules with electronegative substituents are stabilized by the transannular N→X (X = Si, Ge) bond and different intramolecular hydrogen contacts with the participation of heteroatoms of substituents at the silicon or germanium.

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Section: Introductionmentioning

confidence: 99%

Mechanism of Reactions of 1-Substituted Silatranes and Germatranes, 2,2-Disubstituted Silocanes and Germocanes, 1,1,1-Trisubstituted Hyposilatranes and Hypogermatranes with Alcohols (Methanol, Ethanol): DFT Study

2020

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“…With increase of the N→Si bond length in the XSa molecules the HCl interaction with the nitrogen atom becomes competitive. Thus, with an N→Si bond length of 2.71 Å in 1-methylsilatrane complexation of HCl with the nitrogen atom (9.72 kcal/mol) becomes more favorable than with the oxygen atom (7.25 kcal/mol) [51].…”

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confidence: 98%

“…The electron-donating capacity of silatrane group heteroatoms was investigated not only by experimental, but also by computational methods [49][50][51]. In the earliest work the symmetrical ap,ap,ap-rotamers of trimethylsiloxanes were chosen as an adequate three-dimensional model of silatranes.…”

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confidence: 99%

“…To investigate the electron-donating ability of the exocyclic nitrogen and oxygen atoms in 1-substituted silatranes in relation to the length of the N→Si coordination bond calculations (by the DFT(B3LYP) method with 6-311G(2d) basis functions and full optimization of the geometry) were undertaken for the HCl complexes with silatranes XSi(OCH 2 CH 2 ) 3 N (X = F, Me) and also with the model MeSi(OMe) 3 molecule [51].…”

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confidence: 99%

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Basicity of silatranes (Review)

Воронков

Belyaeva

Абзаева

2012

Chem Heterocycl Comp

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The silatranes basicity study results are summarized. A large amount of experimental data obtained 25-40 years ago is critically reviewed. It is shown that the reactivity and physicochemical properties of silatranes are determined by their basicity, which depends on the stereoelectronic structure.Silatranes substituted at the silicon atom XSi(OCH 2 CH 2 ) 3 N (XSa) represent a widely studied class of chelate compounds of pentacoordinated silicon. Investigators of silatranes have been attracted primarily by their unique crystal and stereoelectronic structure and also by their high biological activity. The systematic and comprehensive investigations of silatranes started by M. G. Voronkov and co-workers as far back as 1963 continue to this day [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Of particular practical interest here is the specific biological activity of silatranes [11][12][13][14]. Their unique reactivity is due both to the electron density distribution and the spatial structure.During study of the structure and properties of silatranes by numerous physicochemical methods [1-10] greatest attention has been paid to the axial fragment of their molecule and particularly to the length of the transannular N→Si bond. Insufficient attention has been paid to the equatorial fragment of the molecule. Here account was rarely taken of the fact that there is a redistribution of electron density during the transition of the silicon atom from the tetravalent state to the pentacoordinated state; in the silatrane molecule the positive charge of the central silicon atom and the negative charge of the surrounding three oxygen atoms and also of the axial substituent are increased [15][16][17].During studies of the silatranes basicity the attention of investigators was turned first of all to the basicity of the nitrogen atom, which was always considered a stronger nucleophile than the oxygen atom. Nevertheless, the ability of silatranes to form onium complexes with the participation of the nitrogen or oxygen atoms has been the subject of heated discussions in the literature. By this time in a letter to the editor, which initiated the story of silatranes (described at that time by the systematic name 5-aza-2,8,9-trioxa-1-silabicyclo[3.3.3]undecanes), Frye and co-workers unexpectedly announced that silatranes are not neutralized by perchloric acid in anhydrous acetic acid, but are only slowly titrated by it at 100°C. This led said authors to conclusion that the nitrogen atom does not have basic properties due to the presence of the transannular donoracceptor N→Si bond in the silatranes [18].

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Silatranes: a review on their synthesis, structure, reactivity and applications

2011

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This critical review summarizes progress of the rapidly developing and very active field of silatrane chemistry. The first part of the review deals with general synthetic approaches used to synthesize different silatranes. The most interesting feature of silatranes, i.e., variation of Si-N bond length on the basis of the axial substituent of Si, and other structural features, are described in the second part with special emphasis on crystallographic and theoretical studies. It is followed by a discussion on the reactivity of various silatranes. Silatranes have now gained acceptance for a wide variety of applications which are summarized in the last section of review. Some of them have extensive interest due to their medical use to heal wounds or stimulate hair-growth (pilotropic activity), biological properties, pharmacological properties e.g. antitumor, anticancer, antibacterial, anti-inflammatory, fungicidal activity, stimulating effect in animal production and seed germination effects. The review focuses on the extended potential of silatranes in sol-gel processes, mesoporous zeotypes, atomic force microscopy, commercial products such as adhesion promoters, polymer formation and rubber compositions. This critical review will be helpful for general researchers, experts, advanced undergraduates and newcomers working on silatrane chemistry as this review presents greater emphasis on synthesis and characterization, structural properties, reactivity and applications of silatranes in the field of biology, material science, sol-gel chemistry, pharmaceutics, agriculture and medicine (311 references).

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Quantum-Chemical Study of the Electron-Donating Ability of Endocyclic Nitrogen and Oxygen Atoms in Silicon-Substituted Silatranes

Cited by 3 publications

References 4 publications

Mechanism of Reactions of 1-Substituted Silatranes and Germatranes, 2,2-Disubstituted Silocanes and Germocanes, 1,1,1-Trisubstituted Hyposilatranes and Hypogermatranes with Alcohols (Methanol, Ethanol): DFT Study

Mechanism of Reactions of 1-Substituted Silatranes and Germatranes, 2,2-Disubstituted Silocanes and Germocanes, 1,1,1-Trisubstituted Hyposilatranes and Hypogermatranes with Alcohols (Methanol, Ethanol): DFT Study

Basicity of silatranes (Review)

Silatranes: a review on their synthesis, structure, reactivity and applications

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