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

Abstract

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.

Synthesis, structure and properties of trivalent and pentavalent tricarbabismatranes

“…The Mayer bond orders for 4 and 8b are respectively calculated to be 0.07 and 0.20; the latter value is comparable to those of typical silatranes, N(CH 2 CH 2 O) 3 SiX (0.167 for X = F; 0.213 for X = ONO 2 ). 24 Molecular orbitals relating the Bi-N interaction are shown in Fig. S6 (ESI †).…”

3-Aminopropylsilatrane and Its Derivatives: A Variety of Applications

“…Such a skeleton of silatranes with hypervalent (pentacoordinated) silicon predetermines their unusual physical and chemical properties, for example, a strong dipole moment of the molecule, a strong electron-donor effect of the silatrane group, and, hence, a high reactivity [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. In contrast to the starting alkoxysilanes, a striking feature of silatranes is their relative resistance to hydrolysis ( Scheme 2 ) [ 20 , 21 , 22 , 23 ].…”

Structural and Conformational Aspects in the Chemistry of Heterocycles

“…The inversion of the role of steric, hyperconjugation, stereoelectronic, and electrostatic effects, as well as of conformational preferences, was clearly shown. Another type of the 14 group elements containing heterocycles was investigated theoretically in the paper on sila- and germatranes (tricyclic intramolecular complexes), their bi- and monocyclic analogues—sil- or germocanes and hyposilatranes and hypogermatranes [ 2 ]. A pivotal factor determining the properties of all compounds of this type is the intramolecular transannular N→X (X = Si, Ge) bond.…”