Elena G. Kononova

Cyclotetrasiloxanetetrols with methyl groups at silicon: isomers all-cis- and cis-trans-cis-[MeSi(O)OH](4).

1,3,5,7-Tetramethyl-1,3,5,7-tetrahydroxycyclotetrasiloxane has been synthesized in good yield from tetrapotassium tetramethylcyclotetrasiloxanolate. Methods for isolation of all-cis-isomer I and cis-trans-cis-isomer II as the only crystalline product have been developed. Both isomers have been characterized by single-crystal X-ray diffraction analysis (XRD), elemental analysis, NMR ((1)H, (13)C, (29)Si), and IR. The stability of these compounds in solutions and the solid state has been investigated.

Vibrational spectra and structure of cesium salts of icosahedral monocarba-closo-dodecarborate anion, [CB11H12]–, and its nido-derivative, [CB100H13]–

The Raman and IR spectra of the cesium salts of monocarbon carboranes, [closo-CB11H12]– and [nido-CB10H13]–, are reported and the assignment of the normal modes is given. Quantum-chemical calculations of the geometry of undistorted closo-anions B12H122– and CB11H12– were carried out and normal coordinate analysis for the latter was performed. Structural parameters and spectral characteristics of isoelectronic closo-polyhedra [B12H12]2–, [CB11H12]–, and p-C2B10H12 and those of the closo- and nido-structures were compared.

Synthesis and study of properties of linear permethylpoly(silane-siloxanes)

Heterofunctional polycondensation of α,ω-dichloropermethyloligosilanes Cl(Me2Si)mCl (m = 2—6) with 1,5-dihydroxyhexamethyltrisiloxane was used to synthesize linear permethylpoly(silane-siloxanes) with the regular structure —[(SiMe2)mO(SiMe2O)3]n—, which are soluble, unlike polydimethylsilane, in common organic solvents. The use of Py instead of Et3N as an acceptor of HNl results in an increase in the yield, molecular weight, and characteristic viscosity of the copolymers. The molecular weight and viscosity characteristics, oxidative and thermal stabilities, and spectral properties of the synthesized copolymers were studied. The dependence of the oxidative and thermal stabilities of the synthesized copolymers on the number of the SiMe2 units in the oligosilane fragment of the main chain was established.