Conformation‐Dependent Sequence Design of HP Copolymers: An Algorithm Based on Sequential Modifications of Monomer Units

We present a new modification of the so‐called conformation‐dependent sequence design scheme for HP copolymers which was proposed several years ago (H and P refer to the hydrophobic and polar monomer units, respectively). New method models the real chemical experiments more realistically. We performed Monte Carlo computer simulations using the bond‐fluctuation model for protein‐like copolymers obtained by means of the new “iterative” method and compared the results with those obtained for originally proposed “instantaneous coloring” procedure. Copolymers designed by the “iterative” method are shown to have better‐optimized functional properties. The investigation of the influence of sequence preparation conditions has revealed that the statistical properties of designed HP sequences depend rather strongly on the density of the parent homopolymer globule but not on the composition of H and P units.     

Some peculiarities of hydrosilylation of α,ω-divinyloligosilanes

The stability of Si-Si bonds in linear and cyclic permethyloligosilanes and in ,-divinyloligosilanes under conditions of hydrosilylation in the presence of the Speier's catalyst was studied. Polycarbosilanes containing silylene fragments in their backbone chains were prepared by the reaction of 1,4-bis(dimethylsilyl)benzene with ,-divinyloligosilanes. It was found that the structure of these polymers is disturbed due to the side reaction involving the cleavage of the Si-Si bond in vinyloligosilanes under the action of H₂PtCl₆.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2547–2549, October, 1996.     

Intermolecular rearrangement of cobalt phenylsiloxanes

Intermolecular rearrangement of cobalt phenylsiloxanes was studied. The rearrangement leads to the formation of compounds with metal oxide moieties in the organosiloxane structure and is accompanied by a change in the spectral characteristics of cobalt(II), determined by the second coordination sphere of the metal. The rate-determining step is the decomposition of an intermediate complex formed upon the coordination of the metal siloxane moieties.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1912–1914, September, 2004.     

Catalytic transformations of oligocarbosilanes induced by AlCl3

Catalytic activation of Si−C bonds in poly(vinyltrimethylsilane) was studied using a model reaction of catalytic transformations of oligocarbosilanes Me₃Si(CH₂) _n SiMe₃ (n=2, 3) in dichlorodimethylsilane in the presence of AlCl₃ as an example. The formation of ClMe₂Si(CH₂) _n SiMe₃ was established by chromato-mass spectrometry and GLC. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2265–2266, December, 1997.     

Kristallisehe Struktur der cyclischen Siloxane. 4. Mitt.: Cis-1,2,3-Trimethyl-1,2,3-triphenylcyclotrisiloxan

Ohne Zusammenfassung     

Ion exchange in bimetallic cage copper organosiloxanes and the synthesis of polynuclear metal complexes containing Li and Cu<Superscript>II</Superscript> atoms

The replacement of sodium (potassium) atoms by lithium in a series of bimetallic (“alkaline”) cage copper organosiloxanes was investigated. The reactions of cage Cu^II(Na) or Cu^II(K) derivatives of organometallosiloxanes (OMS) with LiCl afford the corresponding Cu^II(Li) derivatives. The rate and degree of replacement are mainly determined by the structure of the molecular cage of the starting OMS. In the case of globular-like bimetallic OMS of the general formula [RSiO₂]₁₂[Cu₄M₄] (R = Me, H₂C=CH-(Vin), or Ph; M = Na or K), the ion exchange occurs under mild conditions at a high rate to give the corresponding Cu^II(Li) derivatives [RSiO₂]₁₂Cu₄Li₄ with the same structure (∼80% yield). Sandwich-like bimetallic OMS of the general formula [RSiO₂]₆[Cu₄M₄][RSiO₂]₆ (R = Ph or Vin; M = Na or K) react more slowly, the reaction proceeding stepwise. In the latter case, partial substitution products, viz., heterometallic sandwich complexes, for example, {[VinSiO₂]₆}₂Cu₄K₂Li₂, were isolated. The structures and compositions of the reaction products were studied by X-ray diffraction, gel permeation chromatography, and elemental analysis. The selectivity of the replacement of alkali metal atoms allows the synthesis of the desired globular or sandwich cage Cu(Li) metallosiloxanes, which are difficult to prepare.