Olga I. Shchegolikhina

Novel class of transition metal coordination compounds with macrocyclic organosiloxanolate ligands; their synthesis and crystal structure

Abstract Interaction of sodium organosiloxanolates with transition metal chlorides leads to the formation of a novel class of coordination compounds, polymetallaorganosiloxanolates (PMOS) {SiPh(O)-O} n− n M 1 2 n−x 2+ Na n (M = Mn, Co, Ni, Cu), whose structure is elucidated by an X-ray diffraction study.

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.

Phenylsilanetriol — synthesis, stability, and reactivity

Abstract Crystalline phenylsilanetriol, PhSi(OH)3 (1) was obtained by smooth hydrolysis of phenyltrimethoxysilane and characterised by different analytical methods (wide angle X-ray powder diffraction, NMR, IR, thermogravimetric analysis). The title-compound is surprisingly stable in the solid state but slowly condenses in acetone solution. Reaction of 1 with Me3SiCl and Me2(CH2Cl)SiCl gave the corresponding tris-triorganylsiloxy substituted derivatives in high yields.

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.

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.

Bimetallic cyclooligosiloxanolate complexes of copper and nickel

The bimetallic cyclosiloxanolate cluster complexes Na[PhSiO 2 ) 6 Cu 4 Ni 2 ( μ 6 -Cl)(PhSiO 2 ) 6 ] ( 1 ) and Na[(PhSiO 2 ) 6 Cu 3 Ni 3 ( μ 6-Cl)(PhSiO 2 ) 6 ] ( 2 ) were prepared by Na + and Ni 2+ ion exchange from in situ generated Na 2 {[(PhSiO 2 ) 6 ] 2 Na 4 Ni 4 (OH) 2 }. Complexes 1 and 2 were characterized by analytical, spectroscopic and electrochemical methods as well as complex 2 by single-crystal X-ray diffraction. The X-ray structure shows a sandwich-type array comprising two superimposed cyclosiloxanolate rings and an M 6 Cl unit in between. For the first time the regioselectivity of the metal ion exchange could be deduced from the X-ray structural parameters.

Polyhedral silsesquioxanes as precursors of tailor-made heterogeneous catalyst centres: I. Water oxidation

Fe-, Ni-, Cu- and Mn-polyhedral oligometallasilsesquioxanes containing (PhSiO 1.5 ) 12 (MO) n L-fragments (where L=ROH, H 2 O; n=6 for Fe, Ni, Mn and n=4 for Cu; Ni 2 Fe 2 - and Ni 4 Cu 2 -complexes were also used) have been used for the preparation of heterogeneous catalysts to investigate the influence of structural factors on the catalytic properties of the hydroxides of these metals. SAXS have been used for the characterization of the distribution of complexes associated in the solution and on the supports surface. It was found that the complex distribution on the carbon support (soot) is close to monomolecular. The highest O 2 yields have been obtained when Fe 6 /C were used as catalysts. It has been found that supports have a strong influence on the catalytic properties of supported complexes

New mesomorphic organocyclosiloxanes II. Thermal behaviour and mesophase structure of organocyclohexasiloxanes

Investigations of thermotropic phase transitions performed on organocyclosiloxanes [PhSi(O)OSiR]6, where R is Me3, Me2(CH2Cl) or Me2(CH≃CH2), have revealed that all these hexamers are mesomorphic compounds. The hexamers exhibit uncommon polymesomorphic behaviour forming two quite different mesomorphic structures. The molecular arrangement in the low temperature (LT) modification is characterized by two-dimensional (2D) long-range order with hexagonal packing. The X-ray diffraction pattern and peculiarities of molecular packing in the crystal lead us to suggest that the LT-mesophase is columnar, presumably of the Colhd type. The LT-mesophase is formed by dimeric moieties, which associate with each other in column-like substructures, the ring planes not orthogonal to the stack axis. The high temperature (HT) mesophase is a plastic crystal (3D-order), where molecules take up positions in a face-centred cubic lattice. This is a very uncommon example of thermal behaviour for plastic crystals that provides a unique opportunity to bridge the gap between plastic crystalline and liquid crystalline mesomorphic behaviour. The thermal and structural properties of the mesophases depend upon the type of side groups of the hexamers. The size of the ring also affects the phase behaviour and the mesomorphic structure. This conclusion is consistent with data obtained by us earlier for cyclotetrasiloxanes.

Bimetallic siloxane cluster of higher valent transition metals: Na{[η6-cyclo-(PhSiO2)6]2Co2Ni4(μ6-Cl)}

Abstract The bimetallic siloxane cluster / cage compound Na{[η 6 -cyclo-(PhSiO 2 ) 6 ] 2 Co 2 Ni 4 (μ 6 -Cl)} was preparred and characterized by single crystal X-ray diffraction, spectroscopic, magnetic and electrochemical methods.