Elvira A. Volnina

Production of poly(silaisoprene) by laser-induced decomposition of 1-methyl-1-vinyl-1-silacyclobutane

Abstract Continuous CO 2 laser-induced decomposition of 1-methyl-1-vinyl-1-silacyclobutane (MVS) in the presence of energy conveying sulfur hexafluoride provides a highly selective method for production of poly(2-methyl-2-silabuta-1,3-diene) (polysilaisoprene). Trapping with hexafluoroacetone and tetrafluoroethene confirms the intermediacy of 2-methyl-2-silabuta-1,3-diene (silaisoprene), polymerization of which depends on the ratio MVS/SF 6 . The IR spectrum of the polymer deposited from the gas-phase on to the reactor surface reveals that silaisoprene polymerizes by participation of both double bonds.

Efficient gas phase polymer deposition by infrared laser-photosensitized decomposition of 4-silaspiro[3.4]octane

Abstract Laser-induced thermolysis of 4-silaspiro[3.4]octane is an efficient method for the gas phase deposition of organosilicon polymer, which is assumed to arise from 1-methylene-1-silacyclopentane generated upon the elimination of ethene from the parent molecule.

Thermal isomerization and decomposition of 3,3-diethyl-2,4-dimethyl-3-silathietane

Pyrolysis of 3,3-diethyl-2,4-dimethyl-3-silathietane (I) has been studied at temperatures from 300 to 530°C using the pulse pyolytic GC-MS method. Decomposition of I proceeds with the elimination of ethane, ethylene, propylene, butadiene, cis- and trans-but-2-ene, and also with the loss of atomic sulphur. Isomerization into sulphur-containing unsaturated compounds is the main transformation process of I. The intermediacy of 1,1-diethyl-2-methyl-1-silaethylene and diethylsilathione is also discussed.

IR laser photosensitized decomposition of 1-methyl-1-silacyclobutane. Efficient gas-phase polymer deposition

Abstract Laser-induced thermolysis of 1-methyl-1-silacyclobutane is a highly selective method for the gas-phase deposition of organosilicon polymer, which is formed by the elimination of ethene and the major participation of methylsilaethene and dimethylsilylene in the polymerization.

Si/C phases from the IR laser-induced decomposition of 1,4-disilabutane

CO 2 laser-induced decomposition of 1,4-disilabutane (DSB) in the gas phase yields gaseous C 1–2 hydrocarbons and RSiH 3 compounds (R=H, CH 3 , C 2 H 5 and C 2 H 3 ), and it represents a convenient process for chemical vapour deposition of thin films composed of Si/C/H, Si/C and Si components.

Novel 2,4-disilathietane ring system from [2 + 2]cycloaddition of 1,1-dimethyl-1-silaethylene,Me2SiCH2, to dimethylsilanthione, Me2SiS. Perturbation molecular orbital (PMO) study on reactivity of intermediates with a double-bonded silicon atom

Copyrolysis of 1,1-dimethyl-1-silacyclobutane (I) with both hexamethylcyclotrisilthiane (II) and tetramethylcyclodisilthiane (III) at 560°C involves 1,1-dimethyl-1-silaethylene, Me2SiCH2 (IV), and dimethylsilanthione, Me2SiS (V), intermediates and yields the following cycloaddition products: the new 2,2,4,4-tetramethyl-2,4-disilathietane (VI), 1,1,3,3-tetramethyl-1,3-disilacyclobutane (VII), and III. Six-membered cyclocarbosilthianes, 1,1,3,3,5,5-hexamethyl-2-thia-1,3,5-trisilacyclohexane (VIII) and 1,1,3,3,5,5-hexamethyl-2,4-dithia-1,3,5-trisilacyclohexane (IX) have also been derived by inserting IV and V into the SiS bond of VI. Copyrolysis of I with thietane (X) also results in four- and six-membered cyclocarbosilthianes, the major product being VI. This is discussed in terms of dimethylsilanthione formation via [2 + 2]cycloaddition of IV to thioformaldehyde (XI) followed by [4 → 2 + 2]cyclodecomposition of the 2-silathietane intermediate. A perturbation molecular orbital study of [2 + 2]cycloaddition involving intermediates IV, V, and XI has shown that IV reacts more readily with V and XI than it cyclodimerizes. Dimerization of V is the most prominent reaction.

Polymer-stabilized nano-sized tellurium films by laser-induced chemical vapour co-deposition process

UV laser-irradiation of a gaseous mixture of dimethyl tellurium and 1,3-disilacyclobutane induces concurrent photolysis of both compounds. Chemical changes taking place are due to expulsion of elemental tellurium from dimethyl tellurium and formation of short-lived and fast polymerizing silene from 1,3-disilacyclobutane. The co-photolysis process results in chemical vapour co-deposition of a nano-sized tellurium–polycarbosilane composite that contains amorphous nano-structures of tellurium stabilized against oxidation by organosilicon polymer.

Laser-induced decomposition of silacyclobutane: extensive H(Si)/H(C) scrambling via 1,2-H shift in silene and radical reactions

Abstract The mechanism of the silacyclobutane decomposition has been further refined through a study of the laser induced decomposition of 1,1-dideuterio-1-silacyclobutane. It is concluded that the identified volatile and solid products and the hydrogen and deuterium content in them are in accord with 1,2-H(D)-shift in intermediate silene and with radical reactions.

Cycloorganosilyl derivatives for the determination of alcohols and carboxylic acids by gas chromatography/mass spectrometry

New silylating agents—methyl(trimethylene-, tetramethylene-, pentamethylene)silyl chlorides, ethyl(tetramethylene-, pentamethylene)silyl chlorides and chloromethyl(pentamethylene)silyl chlorides—are suggested for the investigation of alcohols and carboxylic acids by gas chromatography/mass spectrometry (GC/MS). It is shown that corresponding derivatives may easily be prepared by solution reactions and by on-column silylation. All the derivatives appeared to be less mobile in GC than trimethylsilyl derivatives. Under electron impact (EI), all the derivatives [except chloromethyl(pentamethylene)silyl derivatives] of primary alcohols form pronounced molecular ions. For all kinds of derivatives obtained from secondary alcohols, the most characteristic fragmentation is due to cleavage of a C–C bond near to the silyloxy group. The mass spectra of trimethylene- and tetramethylenesilyl ethers derived from isomeric straight-chain and branched alcohols differ quantitatively. Main fragmentation reactions of the latter derivatives under EI conditions are elucidated with the aid of D-analogues. The mass spectra of cycloorganosilyl esters of alkanoic acids are less characteristic and are due mainly to the loss of an alkyl radical from the silicon atom or to a cleavage of the silacycloalkane ring in molecular ions.