T. A. Kochina

Tris(2-hydroxyethyl)ammonium salts: 2,8,9-Trihydroprotatranes

New method of synthesis of tris(2-hydroxyethyl)ammonium salts, 2,8,9-trihydroprotatranes X-[HN(CH2CH2OH)3]+, based on the reaction of tris(2-hydroxyethyl)amine (triethanolamine) with ammonium salts NH4X (X = F, Cl, Br, I, NO3, ClO4) was developed. 1H, 13C, 15N NMR and IR spectra of these protatranes were investigated, as well as those of their analogs with X = RCH2COO (R = H; 2-MeC6H4O; 2-Me-4ClC6H3O; 2-MeC6H4S; 4-ClC6H4S; 4-ClC6H4SO2; 3-IndS; 3-(PhCH2-IndS) prepared from the corresponding acids RCH2COOH and triethanolamine. The parameters of IR and NMR spectra of the studied protatranes were governed by the nature of substituent X, which also determined the character of the intra and intermolecular hydrogen bonds NH⋯O and OH⋯O in the protatrane framework.

Radiochemical study of the reaction between the diethylsilylium cation and benzene in gas and liquid phases: experimental and theoretical evidence for rearrangements of the diethylsilylium cation

The ion–molecule reaction between the nucleogenic diethylsilylium cation generated by the β-decay of the tritiated diethylsilane and benzene was studied by the radiochromatographic method in the gas and liquid phases. Diethylphenylsilane possessing the diethylsilyl group of the nascent cation has the lowest yield in the gas phase, although in the liquid phase the yield increases. Two other silylphenylsilanes are products of rearrangement of the diethylsilylium cation. The stationary points on the potential energy surface of the SiC4H11+ system were located by the ab initio correlated methods and the plausible rearrangements within this system are discussed.

Radiochemical study of the gas phase reaction of nucleogenic diethylsilylium ions with methanol and butanol

Abstract The gas phase ion–molecule reactions between alcohols (methanol and n-butanol) and nucleogenic diethylsilylium ions generated by the β-decay of the tritiated diethylsilane were studied by the radiochromatographic method. Among the labelled neutral products of the silylation of alcohols diethylsilylalkoxysilanes exhibit the major yield. Diethyl-butoxysilane contains not only n-butyl groups as in the substrate (21%), but also small amounts of s-butyl (5%) and t-butyl (7%) groups. In other alkoxysilanes the diethylsilyl group of the nascent nucleogenic cation is rearranged and isomerized. Products with the similar distribution of the silylium group isomers were observed earlier in the reaction of benzene, however the yield of the products with rearranged silylium groups was substantially greater for benzene. This difference in the yield of the products with rearranged silylium groups between benzene and alcohols is rationalized taking into account the more acidic character of the proton in the adduct oxonium ions.

Quantum-chemical study of the stereoelectronic structure of 1-fluorosilatrane, 1,1-difluoroquasisilatrane, 1,1,1-trifluorohyposilatrane, and cations formed thereof

Quantum-chemical study of the electronic structure and the equilibrium geometry of the molecules X4−nM(OCH2CH2)nNH3−n and cations X3−n[M(OCH2CH2)nNH3−n]+ (M = Si, Ge; X = F, H; n = 1–3) is performed by the B3LYP method using the cc-PVDZ basis set. It is shown that for X = F the strength of the coordination bond N→M increases with the number of the cycles (n), while for X = H, on the contrary, decreases, that is, the strength of the N→M bond increases with the total electronegativity of the substituents surrounding atom M. Effect of the number of the coordination cycles on the strength of the N→M bond in the cations is negligible. The obtained results agree with the experimental data on the structure and spectral properties of the studied compounds.

Structures and mutual transformations of isomers of germylium ions (CH3)H2Ge+ and (CH3)2HGe+ and their silicon analogs

The potential energy surfaces of the (CH3)nH3−nM+ ions, where n = 1, 2; M = Si, Ge, were scanned using the B3LYP method with 6–31G* and aug-cc-pVDZ basis sets. The major attention was given to isomeric species having the form of complexes of the HM+ and CH3M+ ions with hydrogen, methane, and ethane molecules. These species were characterized previously neither by experimental nor by theoretical methods. It was found that these species become more stable in going from Si to Ge; the complex [CH3Ge+CH4] is the second isomer in the energy after (CH3)2HGe+. However, the heights of the activation barriers to formation of these complexes from the most stable isomer, though decreasing in going from Si to Ge, remain relatively high and, what is particularly important, somewhat exceed the activation barrier to formation of the complex [H3Ge+·C2H4].

A new unprecedented method for the synthesis of 1-fluorosilatrane

We developed the simplest and the most convenient original procedure for the synthesis of fluorosilatrane. The method is shown in the following scheme: parent very viscous liquid (in contrast to other crystalline triethanolammonium halides). To this product was added an equimolar amount of tetraethoxysilane, and stirring while heating was continued with distilling off the evolved ethanol. White powder of the formed fluorosilatrane was heated in a vacuum to remove residual (EtO)4Si and EtOH (yield of the latter was 90%). The FSa formed has sublimation temperature ~300°С at the atmospheric pressure in agreement with the published data [1, 4]. Noteworthy that at the temperature above 220°С the FSa powder is transformed into threadlike crystals. IR spectrum of FSa formed (KBr pellet) contains strong adsorption bands corresponding to vibrations of Si–F (748– 785 cm ), Si–O (790–810 cm), and С–O (1075– 1150 cm) bonds. H and С NMR spectra of solution of FSa in DMSO-d6 are characterized by the following parameters: δH 2.92 and 3.69 ppm, δС 50.5 and 56.8 ppm. The IR and NMR spectra of the fluorosilatrane obtained are consistent with the published data [3, 7– 10].

Germatranes and their quasi and hypo analogs with highly electronegative substituent at the Ge atom

Synthesis of germatranes XGe(OCH2CH2)3N (1), quasigermatranes X2Ge(OCH2CH2)2NR (R = H, Me) (2), and hypogermatranes X3Ge(OCH2CH2)NH2 (3) containing highly electronegative substituents at the Ge atom was described. An exchange reaction of the corresponding hydroxygermatranes with ammonium salts was used for their preparation. The synthesized compounds 1–3 were studied by IR spectroscopy.

Radiochemical Study of Gas-Phase Reactions of Nucleogenic Diethylgermyl Cations with Dibutyl Ether and 1-Butanol

Reactions of tritium-labeled free diethylgermyl cations with dibutyl ether and 1-butanol in a gas phase were studied by the radiochemical method. Mechanisms of the corresponding ion-molecular reactions were suggested, and the most probable paths of the cation (C2H5)2TGe+ conversion into other isomeric forms were shown.

New method of synthesis 1-halogermatranes, germatranyl esters of H-O acids, and their stereoelectronic structure

A fundamentally new method for the synthesis of 1-halogermatranes and germatranyl esters of oxygen-containing acids has been developed. Using this method germatranes XGe(OCH2CH2)3N (X = Hal, ClO4)were synthesized, their elemental analysis was determined, and their stereoelectronic structure was studied by the methods of multinuclear NMR, mass spectrometry, and IR spectroscopy. The obtained data correlate with the results of quantum chemical calculations.

Reactions of silylium ions with nucleophiles

Transformation of the diethylsilylium cation Et2Si+H into ethyl-and dimethylsilylium ions EtSi+H2 and Me2Si+H in reactions with nucleophiles is induced by electron-donor compounds. Their activity increases in the order Bu2O < BuOH < (Me3Si)2O < C6H6 and is determined by the structure of the intermediate adduct and electron density distribution in it. Qualitative estimation shows that the affinity of the tritiated diethylsilylium cation Et2Si+T for a nucleophile increases in the order C6H6 < BuOH < Bu2O < (Me3Si)2O. The higher affinity of the Et2Si+H cation for hexamethyldisiloxane compared to dibutyl ether, at similar basicity of the nucleophiles, is attributable to the higher charge of the oxygen atom in (Me2Si)2O.