Yu. A. Pozdnyakova

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.

Crystal structure of the La3+ sandwich complex based on 8-membered macrocyclic siloxanolate ligands

The product of the reaction between anhydrous lanthanum trichloride and potassium vinylsiloxanolate, K5[VinSiO2]8La4(μ4-OH)[O2SiVin]8 · 5n-BuOH·2H2O has been studied by X-ray diffraction. The compound is a «sandwich»-type complex where macrocyclic vinyloctasiloxanolate ligands with regularcis-configuration have co-axial and antiparallel orientation. These ligands coordinate a planar «cationic layer» formed by four La3+ ions and stabilized by an additional μ4-OH− bridge ligand. A three-dimensional cage structure of complex lanthansiloxanolate pentaanions linked through the coordinated K+ counter-ions is formed in the crystal studied.

CRYSTAL STRUCTURE OF THE ND, GD, AND DY SANDWICH COMPLEXES INVOLVING 8-MEMBERED MACROCYCLIC PHENYLSILOXANOLATE LIGANDS

An X-ray structural investigation of the interaction products of anhydrous trivalent neodymium, gadolynium, and dysprosium chlorides with sodium phenylsiloxanolate was carried out. The synthesized compounds with the general formula Na6[PhSiO2]8M4(μ4-O)[O2SiPh]8 · 10EtOH · 8H2O (M = Nd, Gd, Dy) were found to be isomorphous isostructural sandwich complexes. The macrocyclic octaphenyloctasiloxanolate ligands in the complexes have anall-cis-configuration and are arranged in co-axial antiparallel pairs and coordinate the square planar groups of the four Nd3+, Gd3+, or Dy3+ ions stabilized by an additional central μ4-bridging O2− ligand. Six Na+ counterions form the outer coordination sphere of the complexes such that four of them coordinate the siloxane macrocycle O atoms in pairs in analogy with crown-ether complexes.

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.

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.

Effect of the method used for crystal structure formation on the rheological behavior of organocyclotetrasiloxane in the plastically crystalline state

The rheological properties of cis-cyclotetrasiloxane, cis-[PhSi(O)(OSiMe3)]4, in the plastically crystalline state were investigated. The yield stress and non-Newtonian character of the flow indicates that cis-[PhSi(O)(OSiMe3)]4 is a viscoplastic material with respect to its rheological behavior. The conditions of crystal structure formation determine the rheological properties of organocyclotetrasiloxane in the mesophase. The temperature and stress during capillary flow were shown to affect the size and orientation of crystallites formed upon cooling of extrudates.

Investigation of the structure of polyphenylironsiloxane

The main features of the polyphenylironsiloxane (PPIS) structure were established by a combination of preparative fractionation, elemental analysis, gel-permeation chromatography,1H NMR and UV spectroscopy, and destructive trimethylsilylation. Specimens of PPIS contain a large amount of oligophenylsiloxane, which is apparently closed polycyclic oligomers. PPIS macromolecules consist of oligomerc siloxane fragments linkedvia iron oxide fragments. PPIS is characterized by the high heterogeneity of macromolecules and their fragments.