Yu. A. Molodtsova

Synthesis and Characterization of Large Stereoregular Organosiloxane Cycles

The large stereoregular phenyltrimethylsiloxysiloxane macrocycles of general formula [PhSi(OSiMe 3 )O] n ( n =6 and 12) have been selectively obtained with high yields by trimethylsilylation of cage-like oligophenylmetallasiloxanes (OPMS) which we described earlier. The compounds 3 ( n =6) and 4 ( n =12) have been characterized by NMR-spectroscopy method and by single crystal X-ray analysis. This investigation showed unambiguously that the siloxane macrocycles keep their size and configuration (the same as in the initial OPMS) during the trimethylsilylation. Thus a synthetic route for obtaining large stereoregular siloxane macrocycles has been developed.

A new approach to the synthesis of cage-like metallasiloxanes

Abstract A new approach to the synthesis of cage-like metallasiloxanes has been proposed. Copper-containing metallasiloxanes {Na4[(RSiO2)12Cu4](R′OH)n} (1a, R=Ph, R′=n-Bu; 1b, R=Ph, R′=Me; 2, R=Vi, R′=Me) were prepared from PhSi(OR)3·(R=n-Bu, Me) and ViSi(OMe)3, respectively. Compound 2 was characterized by X-ray single structure analysis. The structures of compounds 1a,b were deduced by their follow up reactions with Me3SiCl.

Hydrolytic condensation of trialkoxysilanes in the presence of alkali metal and copper(II) ions. Influence of the reaction conditions on the structure of Cu/M organosiloxanes

The formation of polyhedral copper/sodium(potassium) organosiloxanes was examined as a result of hydrolytic condensation of organotrialkoxysilanes in the presence of copper(ii) and sodium or potassium ions. High selectivity of the synthesis of copper/sodium(potassium) organosiloxanes having desired structures can be achieved by choosing the reaction conditions.

Synthesis and mesomorphic properties of cis-penta[(phenyl)(trimethylsiloxy)]cyclopentasiloxane

New stereoregular cis-penta[(phenyl)(trimethylsiloxy)]cyclopentasiloxane cis-[PhSi(O)(OSiMe3)]5 was synthesized. According to the data from DSC, X-ray diffraction, and polarization microscopy, the noncrystallizable cyclopentasiloxane exists in the mesomorphic state throughout the temperature range below the temperature of destruction and is transformed into mesomorphic glass below the glass transition temperature. This compound possesses the polymesomorphic properties and forms two mesomorphic modifications. The type of mesomorphic ordering for these modifications was determined.

Synthesis of dimethylcyclosiloxanes in the active medium

The process of condensation of dimethyldiethoxysilane in the active medium in a presence of acetyl chloride, trifluoroacetic acid, and sulfocationites has been investigated. Their impact on the rate and selectivity of the process has been estimated. The prospects of the application of sulfocationites for the polycondensation of dimethyldiethoxysilane in anhydrous acetic acid with an 99% yield have been demonstrated.

APPLICATION OF SIZE-EXCLUSION CHROMATOGRAPHY TO THE STRUCTURAL STUDY OF POLYORGANOMETALLOSILOXANES

Size exclusion chromatography was employed to elucidate the structure of the organosiloxane moiety in trimethylsiloxy derivatives of organometallosiloxanes containing Na, K, Ni, Mn, Cu, and Fe. An efficient technique of trimethylsilylation of organometallosiloxanes was developed to minimize alterations in their structure. The TMS derivatives of organometallosiloxanes were found to exist mostly as a more or less polydisperse mixture of cyclic poly[phenyltrimethylsiloxy siloxane]s. The preferred size of the cycles depends primarily on the nature of the metal in organometallosiloxane.

Peculiarities of the synthesis of cage-like metallosiloxanes

The synthesis of individual Ni-, Mn-, and Na-containing cage-like organometallosiloxanes has been performed. A possible mechanism of the formation of stable metallosiloxane frameworksvia a transition complex and coordinately bound ion pairs has been proposed. Both monometallic and bimetallic organometallosiloxanes containing only atoms of a transition metal or two different (transition and non-transition) metals, respectively, have been prepared.

Synthesis of macrocyclic tris-cis-tris-trans- dodeca[(phenyl)(hydroxy)]cyclododecasiloxane in carbonic acid solution

ABSTRACT The possibility to synthesize stereoregular tris-cis-tris-trans- dodeca[(phenyl)(hydroxy)]cyclododecasiloxane (tris-cis-tris-trans-[PhSi(O)OH]12) in an inorganic liquid medium – aqueous carbonic acid solution – was shown. The interaction of polyhedral phenylcoppersodiumsiloxane, {[(C6H5Si(O)O−]12(Cu2+)4(Na+)4}*(L)m (L = Bun OH, H2O), with carbonic acid can be considered as a new ‘green’ method to obtain functional organosiloxane macrocycles. In contrast to the known methods, no organic solvents were used during the reaction. The identification of the structure of the end compound was performed by means of NMR and Infrared spectroscopy as well as X-ray crystallography. GRAPHICAL ABSTRACT

Nanodisperse systems as transient state upon the formation of crystalline organometalsiloxanes

Properties of colloidal solutions formed in the course of hydrolytic condensation of phenyltrialkoxysilanes are studied upon the synthesis of organosiloxanolates of alkali metals and cage-like bimetallic organometalsiloxanes containing alkali and transition (Ni, Cu) or rare-earth (Eu) metals. Sizes and shapes of particles are determined by the dynamic and static light scattering methods. The aggregation stability of colloidal solutions is studied as a function of solvent nature and concentration of phenyltrialkoxysilane. Data obtained make it possible to suggest that disclosed aggregates are the nuclei of crystalline phase. Conditions of the existence of stable colloidal aggregates of sodium phenylsiloxanolate and Ni/Na-phenylsiloxane are determined. It is shown that, upon the dissolution of crystalline Ni/Na-phenylsiloxane in butanol, particles whose sizes are comparable with molecules of organometalsiloxanes are formed in the initial solution.

Non-catalytic hydrolytic polycondensation of dialkoxydiorganosilanes under elevated pressure

The process of non-catalytic hydrolytic polycondensation of dialkoxydiorganosilanes under elevated pressure has been investigated. It is shown that non-catalytic hydrolytic polycondensation of diethoxydimethylsilane in an autoclave proceeds with complete monomer conversion for 10 min forming predominantly linear oligomers. Complete conversion of diethoxymethylphenylsilane is achieved by stirring or by increasing of the process temperature. In the hydrolytic polycondensation of dialkoxydimethylsilanes in the autoclave without stirring the reactivity of monomer is regularly decreased with increasing of length of the alkoxy-groups in the series of MeO—EtO—PriO—PrnO—BunO.