cas 541-05-9, Hexamethylcyclotrisiloxane | Articles data

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Electrochemical oxygenation of diorganyldichlorosilanes: A novel route to generation of diorganylsilanones
Interaction of diorganyldichlorosilanes R2SiCl2 (R = Me, Et, Ph) with superoxide or peroxide anions, produced in situ by electroreduction of molecular oxygen, provides short-living diorganylsilanones R2Si=O. The latter undergo cyclization to give lower perorganylcyclosiloxanes (R2SiO)n, n = 3 or 4 and then insert to the molecules of these primary products to form higher cyclic oligomers. When the process is carried out in the presence of a reagent-trap for silanones (hexamethyldisiloxane, hexamethylcyclotrisiloxane), the products of insertion of diorganylsilanones into the molecule-traps (Me3Si(OSiR2)nOSiMe3 with n ≥ 1, and (Me2SiO)3(R2SiO)m with m ≥ 1, respectively) were obtained.
Fattakhova,Jouikov,Voronkov
p. 170 - 176
(2000)
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Silylating Disulfides and Thiols with Hydrosilicones Catalyzed by B(C6F5)3
Hydrosilanes and silicones, catalyzed with B(C6F5)3, may be used to silylate thiols or cleave disulfides giving silyl thio ethers. Alcohols were found to react faster than thiols or disulfides, while alkoxysilanes (the Piers-Rubinsztajn reaction) were slower such that the overall order of reactivity was found to be HO>HS>SS>SiOEt. The resulting silane and silicone-protected thio ethers produced from the sulfur-based functional groups could be cleaved to thiols using alcohols or mild acid with rates that depend on the steric bulk of the siloxane.
Brook, Michael A.,Liao, Mengchen,Zheng, Sijia
supporting information
p. 2694 - 2700
(2021/06/25)

Hydrogenolysis of Polysilanes Catalyzed by Low-Valent Nickel Complexes
The dehydrogenation of organosilanes (RxSiH4?x) under the formation of Si?Si bonds is an intensively investigated process leading to oligo- or polysilanes. The reverse reaction is little studied. To date, the hydrogenolysis of Si?Si bonds requires very harsh conditions and is very unselective, leading to multiple side products. Herein, we describe a new catalytic hydrogenation of oligo- and polysilanes that is highly selective and proceeds under mild conditions. New low-valent nickel hydride complexes are used as catalysts and secondary silanes, RR′SiH2, are obtained as products in high purity.
Comas-Vives, Aleix,Eiler, Frederik,Grützmacher, Hansj?rg,Pribanic, Bruno,Trincado, Monica,Vogt, Matthias
supporting information
p. 15603 - 15609
(2020/04/29)

METHOD FOR PRODUCING SILOXANE OLIGOMER
PROBLEM TO BE SOLVED: To provide a production method capable of simply producing a siloxane oligomer in a high yield when producing a siloxane oligomer by hydrolysis of a silicon halide compound and to provide a production method capable of selectively producing a linear or cyclic siloxane oligomer in particular. SOLUTION: The siloxane oligomer can be efficiently produced without performing any special agitation by providing two electrospray nozzles to oppose to each other in a medium liquid and in the medium liquid, electrostatically spraying in an electric field a first liquid sample containing a silicon halide compound from one nozzle and electrostatically spraying in an electric field a second liquid sample containing water from the other nozzle and allowing the liquid samples to collide and fuse with each other. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPO&INPIT
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Paragraph 0037; 0045

(2017/07/23)

One-Step Synthesis of Siloxanes from the Direct Process Disilane Residue
The well-established Müller–Rochow Direct Process for the chloromethylsilane synthesis produces a disilane residue (DPR) consisting of compounds MenSi2Cl6?n(n=1–6) in thousands of tons annually. Technologically, much effort is made to retransfer the disilanes into monosilanes suitable for introduction into the siloxane production chain for increase in economic value. Here, we report on a single step reaction to directly form cyclic, linear, and cage-like siloxanes upon treatment of the DPR with a 5 m HCl in Et2O solution at about 120 °C for 60 h. For simplification of the Si?Si bond cleavage and aiming on product selectivity the grade of methylation at the silicon backbone is increased to n≥4. Moreover, the HCl/Et2O reagent is also suitable to produce siloxanes from the corresponding monosilanes under comparable conditions.
Neumeyer, Felix,Auner, Norbert
supporting information
p. 17165 - 17168
(2016/11/23)

A dimethyl dichloro silane hydrolysate cracking method
The invention discloses a method for splitting dimethyl dichlorosilane hydrolysate. The method comprises the following steps: carrying out load reaction onto strong-basicity macroporous anion exchange resin, potassium hydroxide, potassium trimethylsilanolate and [bmim]BF4 ionic liquid to obtain a composite catalyst after the reaction is ended; adding dimethyl dichlorosilane hydrolysate into a splitting kettle to obtain a ring-body mixture by splitting and re-arranging solvent oil, the composite catalyst and the hydrolysate; and washing with water to remove high-boiling point residues and low-boiling point residues to obtain products such as octamethylcyclotetrasiloxane D4, hexamethylcyclotrisiloxane and decamethylcyclopentasiloxane.
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Paragraph 0026; 0028

(2017/02/24)

Silanones and silanethiones from the reactions of transient silylenes with oxiranes and thiiranes in solution. The direct detection of diphenylsilanethione
The transient silylenes SiMe2 and SiPh2 react with cyclohexene oxide (CHO), propylene oxide (PrO), and propylene sulfide (PrS) in hydrocarbon solvents to form products consistent with the formation of the corresponding transient silanones and silanethiones, respectively. Laser flash photolysis studies show that these reactions proceed via multistep sequences involving the intermediacy of the corresponding silylene-oxirane or -thiirane complexes, which are formed with rate constants close to the diffusion limit in all cases and exhibit UV absorption spectra similar to those of the corresponding complexes with the nonreactive O- and S-donors, tetrahydrofuran and tetrahydrothiophene. The SiMe2-PrO and SiPh2-PrO complexes both exhibit lifetimes of ca. 300 ns, and are longer-lived than the corresponding complexes with CHO, which are both in the range of 230-240 ns. On the other hand, the silylene-PrS complexes are considerably shorter-lived and vary with silyl substituent; the SiMe2-PrS complex decays with the excitation laser pulse (i.e., τ ≥ 25 ns), while the SiPh2-PrS complex exhibits τ = 48 ± 3 ns. The decay of the SiPh2-PrS complex affords a long-lived transient product exhibiting λ max ≈ 275 nm, which has been assigned to diphenylsilanethione (Ph2Si=S) on the basis of its second order decay kinetics and absolute rate constants for reaction with methanol, tert-butanol, acetic acid, and n-butyl amine, for which values in the range of 1.4 × 108 to 3.2 × 109 M-1 s-1 are reported. The experimental rate constants for decay of the SiMe2-epoxide and -PrS complexes indicate free energy barriers (ΔG?) of ca. 8.5 and ≥7.1 kcal mol-1 for the rate-determining steps leading to dimethylsilanone and -silanethione, respectively, which are compared to the results of DFT (B3LYP/6-311+G(d,p)) calculations of the reactions of SiH 2 and SiMe2 with oxirane and thiirane. The calculations predict a stepwise C-O cleavage mechanism involving singlet biradical intermediates for the silylene-oxirane complexes, and a concerted mechanism for silanethione formation from the silylene-thiirane complexes, in agreement with earlier ab initio studies of the SiH2-oxirane and -thiirane systems.
Kostina, Svetlana S.,Leigh, William J.
supporting information; experimental part
p. 4377 - 4388
(2011/06/11)

Effect of catalyst structure on the reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane
Reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane in the presence of the complexes of platinum(II), palladium(II) and rhodium(I) is explored. It is established that in the presence of platinum catalyst predominantly occurs hydrosilylation of α-methylstyrene leading to formation of β-adduct, on palladium catalysts proceeds reduction of α-methylstyrene, on rhodium catalysts both the processes take place. In the reaction mixture proceeds disproportion and dehydrocondensation of 1,1,3,3-tetramethyldisiloxane that leads to formation of long chain linear and cyclic siloxanes of general formula HMe2Si(OSiMe2) n H and (-OSiMe2-)m (n = 2-6, m = 3-7), respectively. Platinum catalysts promotes formation of linear siloxanes, while both rhodium and palladium catalysts afford linear and cyclic siloxanes as well. Structure of intermediate metallocomplexes is studied.
De Vekki,Skvortsov
body text
p. 762 - 777
(2009/09/26)

A mechanistic study of cyclic siloxane pyrolyses at low pressures
Matrix isolation IR spectroscopy has been used to study the vacuum pyrolysis of hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) and decamethyl cyclopentasiloxane (D5), and the results interpreted in the context of various kinetic models. In particular, it is shown that the significant pyrolysis products - which include CH3, CH4, C2H2, C2H4, C2H 6 and SiO - may be satisfactorily accounted for by radical reactions involving dimethylsiloxane (D1), and estimates are made of the various chain lengths for the proposed reactions based on a range of ambient conditions. the Owner Societies.
Almond, Matthew J.,Becerra, Rosa,Bowes, Sarah J.,Cannady, John P.,Ogden, J. Steven,Walsh, Robin
experimental part
p. 6856 - 6861
(2009/04/18)

METHOD FOR THE PRODUCTION OF CYCLIC POLYSILOXANES
A process for producing cyclic polysiloxanes is disclosed. The first step of the process comprises combining a poiysiloxane, a cafaiyst and a high boiling endblocker, wherein the catalyst is selected from the group consisting of a phosphazene base and a carborane acid. The second step of the process comprises heating said poiysiloxane, catalyst and high boiling endblocker, and the third step of the process comprising recovering the cyclic poiysiloxane,
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Page/Page column 19-21

(2009/01/23)

Phototransformation of perchlorate to chloride in the presence of polysilanes
Perchlorate is a uniquely stable chemical described as an emerging thyroid disrupting agent that is presently detected in several terrestrial and aquatic matrices. The present study was undertaken to deoxygenate perchlorate to the chloride anion photolytically in the presence of dodecamethylcyclohexasilane (Me2Si)6 1. It is found that photolysis of 1 in the presence of dry NaClO4 in tetrahydrofuran (THF) at 254 nm leads to the disappearance of the salt. The removal of ClO4? occurred with the concurrent formation of ClO3? and ClO2?, which disappear to eventually produce the chloride anion quantitatively. The two cyclic silanes (Me2Si)5 3 and (Me2Si)4 4 in addition to several other siloxanes that include (Me2SiO)3, (Me2SiO)4, and (Me2Si)xO2 (x ≤ 4 and 5) were also detected. When the reaction was repeated using uniformly labelled 18O- [ClO4?] it was found that oxygen incorporated in the siloxane products was derived from perchlorate. Mixing 1 with perchlorate in THF in the dark or adding the salt to 1 after the latter being photolyzed in THF did not deoxygenate ClO4?. Based on experimental evidence gathered thus far it is concluded that dimethylsilylene, Me2Si: 2, a reactive intermediate produced by the photolysis of 1, is in part responsible for the deoxygenation of perchlorate. Direct oxygen transfer from ClO 4? to the silanes during photolysis is also suggested as a potential route of deoxygenating ClO4?. CSIRO 2007.
Lazar, Carmen,Halasz, Annamaria,Beaulieu, Chantale,Thiboutot, Sonia,Ampleman, Guy,Hawari, Jalal
p. 857 - 861
(2008/09/19)

Novel direct process
The invention relates to continuous processes for making cyclic dimethylsiloxane oligomers by reacting in situ methyl bromide, dimethyl ether and activated silicon particles in a direct process reaction zone to produce methylsiloxanes, wherein the proportion of dimethylsiloxane produced in said reaction zone is greater than 75 mole % of the methylsiloxanes produced and recovering the dimethylsiloxane from the reactions zone. The invention favors making cyclic dimethylsiloxane oligomers by this in situ direct reaction.
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Page/Page column 19-20

(2008/06/13)

Process for synthesis of diorganosilanes by disproportionation of hydridosiloxanes
The present invention provides a novel method for the preparation of diorganosilanes by disproportionation of a hydridosiloxanes comprising at least one terminal SiH group and at least one siloxane bond in the presence of Lewis acid catalysts. The reaction is both selective and occurs under mild conditions. The triaryl borane, tris(petafluorophenyl)borane, is especially suited for use as a catalyst in the reaction. Organic catalysts such as tris(pentafluorophenyl)borane are typically preferred owing to their greater solubility and stability in the reaction mixture, relative to inorganic Lewis acid catalysts. The product, diorganosilane may be isolated from the product mixture by conventional techniques such as distillation.
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Page/Page column 6

(2008/06/13)

SILICONE CONDENSATION REACTION
A new silicone condensation reaction, the condensation between an alkoxy silane or siloxane or a dihydric phenol and an organo-hydrosilane or siloxane and catalysts therefore is described and claimed.
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Page/Page column 20-21

(2010/10/20)

REACTIVE DISTILLATION OF CHLOROSILANES
Chlorosilanes such as dimethyldichlorosilane are hydrolyzed in a first super-azeotropic hydrochloric acid distillation column A to produce cyclosiloxanes, chlorosiloxanes, and hydrogen chloride gas. The cyclosiloxanes and the chlorosiloxanes are washed and separated according to their volatility in a second sub-azeotropic hydrochloric acid distillation column B, to produce a substantially chloride free volatile cyclosiloxane stream and a substantially chloride free non- volatile siloxane stream. The process is substantially chloride efficient.
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Page/Page column 7-8

(2008/06/13)

A facile and efficient synthesis of organocyclosiloxanes
A new facile preparative method for the synthesis of organocyclosiloxanes is reported. Ring closure of the dichlorosilanes with NaHCO3 and pyridine gave mixture of organocyclosiloxanes with cyclotrisiloxane as a main product.
Zuev, Vjacheslav V.,Kalinin, Alexei V.
p. 1289 - 1294
(2007/10/03)

Electrochemical generation of diorganylsilanones
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Fattakhova,Zhuikov,Voronkov
p. 70 - 72
(2007/10/05)

FTIR study of thermally induced transformations of trimethylsilylmethyl acetate in the temperature range 623-813 K
The chemistry of trimethylsilylmethyl acetate in the gas phase in the temperature range 623-813 K has been investigated under static conditions using Fourier transform IR spectroscopy. Little change occurs at temperatures lower than 623 K, at which temperature a thermally induced isomerization to form ethyldimethylsilyl acetate occurs. Some ethanoic acid is also produced at this temperature. The ethyldimethylsilyl acetate produced undergoes thermolysis at temperatures > 723 K giving methane, ethene, carbon monoxide, carbon dioxide, ethanoic acid, 1,3-diethyl-1,1,3,3-tetramethyldisiloxane, cyclohexamethyltrisiloxane, and cyclooctamethyltetrasiloxane as products. Loss of ethyldimethylsilyl acetate is first order over the whole temperature range, and first-order rate constants vary from 4.87 × 10-5 s-1 at 723 K to 33.5 × 10-5 s-1 at 813 K, respectively, leading to an activation energy, Ea,, of 110(4) kJ mol-1. An intramolecular five-centre process is proposed for the isomerization reaction. The thermolysis is interpreted in terms of principally radical reactions involving initial homolytic dissociation of the EtMe2SiO-C(O)CH3 bond.
Ball, Ian K.,Harrison, Philip G.,Torr, Ashley
p. 185 - 194
(2007/10/03)

New route to permethylcyclosiloxanes
A new method for preparing permethylcyclosiloxanes, based on reaction of 1,1,3,3-tetramethyldisiloxane with iodine (molar ratio 1:1) in inert organic solvents (alkanes, alkyl halides, benzene) is proposed. The products of the reaction react with ethoxytrimethylsilane and tetramethoxysilane in hexamethyldisiloxane to give respectively pentamethyldisiloxane and products of successive substitution of the methoxy groups in Si(OMe)4 by Me2SiHO. A probable scheme of their formation is discussed.
Basenko,Klyba,Voronkov
p. 1368 - 1370
(2007/10/03)

Unusual Transformations of Trimethylphenoxysilane in the Reaction with Gallium Oxide
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Voronkov, M. G.,Tsyrendorzhieva, I. P.,Albanov, A. I.,Shergina, N. I.,Klyba, L. V.,Dubinskaya, E. I.
p. 656 - 657
(2007/10/03)

Reaction of Octamethylcyclotetrasiloxane with Aluminum, Gallium, and Silicon Iodides
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Voronkov, M. G.,Tsyrendorzhieva, I. P.,Albanov, A. I.,Shergina, N. I.,Klyba, L. V.,Dubinskaya, E. I.
p. 654 - 655
(2007/10/03)

Siloxanes as sources of silanones
Pyrolysis of hexamethyldisiloxane (HMDS) and its copyrolysis with chlorotrimethylsilane and tetrachlorosilane were studied. Based on the data of GLC analysis and on the mass spectrum of the condensate obtained after the pyrolysis of HMDS, it was concluded that HMDS acts as a source of dimethylsilanone. The results of the copyrolysis of HMDS with chlorotrimethylsilane used as a trapping reagent indicate that the dimethylsilanone generated from HMDS can be inserted into the Si-Cl and Si-O bonds. In the copyrolysis of HMDS with tetrachlorosilane serving as a trapping reagent for dimethylsilanone, both dimethylsilanone and dichlorosilanone are generated.
Chernyshev,Krasnova,Sergeev,Abramova
p. 1586 - 1589
(2007/10/03)

FT-IR study of the gas phase thermolysis of trimethylsilyl acetate
Thermolysis of neat trimethylsilyl acetate has been investigated in the temperature range 723-818 K under static conditions using Fourier transform infrared spectroscopy. The principal gaseous products formed during the thermal decomposition are methane, hexamethyldisiloxane, cyclohexamethyltrisiloxane, carbon dioxide, and carbon monoxide, the relative amounts of which vary with the temperature. Small amounts of water and ethanoic acid are also formed. Loss of trimethylsilyl acetate is first-order over the whole temperature range; the first-order rate constants vary from 1.66 × 10-5s-1 at 723 K to 15.7 × 10-5s-1 at 818 K, leading to an activation energy Ea of 104(5)kJ mol-1. In the presence of methyl iodide the decomposition is substantially faster and the products are methane, hexamethyldisiloxane and ethanoic acid. Decomposition is also faster in the presence of nitric oxide and oxygen, although complete identification of the product mixtures was not possible in these cases. The mechanisms of the reactions are interpreted in terms of principally radical reactions involving initial homolytic dissociation of the Me3SiO-C(O)CH3 bond.
Harrison, Philip G.,Torr, Ashley
p. 19 - 29
(2007/10/03)

The hydroxyl radical reaction rate constants and atmospheric reaction products of three siloxanes
The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of hexamethyldisiloxane (MM, (CH3)3Si-O-Si(CH3)3), octamethyltrisiloxane (MDM, (CH3)3Si-O-Si(CH3)2-O-Si(CH 3)3), and decamethyltetrasiloxane (MD2M, (CH3)3Si-O-Si(CH3)2-O-Si(CH 3)2-O-Si(CH3)3). Hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane react with OH with bimolecular rate constants of 1.32 ± 0.05 × 10-12 cm3molecule-1s-1, 1.83 ± 0.09 × 10-12 cm3 molecule-1, and 2.66 ±0.13 × 10-12 cm3molecule-1s-1, respectively. Investigation of the OH + siloxane reaction products yielded trimethylsilanol, pentamethyldisiloxanol, heptamethyltetrasiloxanol, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and other compounds. Several of these products have not been reported before because these siloxanes and the proposed reaction mechanisms yielding these products are complicated. Some unusual cyclic siloxane products were observed and their formation pathways are discussed in light of current understanding of siloxane atmospheric chemistry.
Markgraf, Stewart J.,Wells
p. 445 - 451
(2007/10/03)

Dimethylsilanethione - Generation by retro-ene reaction and cycloaddition with ketene
Dimethylsilanethione was cleanly generated, under flash vacuum thermolysis conditions, by retro-ene cleavage of propargylthiodimethylsilane. The cothermolysis of this latter and ketene dimer led in 60% yield to an only [2 + 2] cycloadduct, 2,2-dimethyl-4-methylene-2-sila-3-thiaoxetane, which in turn can be cleaved at higher temperature to give hexamethylcyclotrisiloxane.
Lefevre, Valerie,Dat, Yves,Ripoll, Jean-Louis
p. 7017 - 7018
(2007/10/03)

Reaction of Dimethyl Sulfoxide with Diorganyldichlorosilanes: A New Route of Generation of Diorganylsilanones
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Basenko, S.V.,Voronkov, M.G.
p. 248 - 250
(2007/10/02)

Laser-powered homogeneous pyrolysis of 1,1-dimethyl-1-silacyclobutane in the presence of some common monomers
Laser-induced homogeneous pyrolysis of 1,1-dimethyl-1-silacyclobutane yields 1,1,3,3-tetramethyl-1,3-disilacyclobutane and ethene as major products.In the presence of vinyl acetate, allyl methyl ether, acrolein, methyl vinyl ether, methyl acrylate or meth
Pola, Josef,Cukanova, Dana,Minarik, Milan,Lycka, Antonin,Tlaskal, Jaroslav
p. 23 - 34
(2007/10/02)

FEATURES OF INFLUENCE OF HCl ON HYDROLYTIC COPOLYCONDENSATION OF BIFUNCTIONAL ORGANOCHLOROSILANES WITH TRIMETHYLCHLOROSILANE
The hydrogen chloride that is formed in the hydrolytic copolycondensation of R'RSiCl2 with Me3SiCl affects the composition of the reaction products only at cocentrations above 30-35percent, where it is responsible for splitting out the terminal trimethylsiloxy group.The stability of the terminal groups increases with increasing size of the substituents on the silicon atom in the R'RSiCl2.The total yield of Me3SiO(R'RSiO)mSiMe3 with m = 1-4 also increases with increasing size of the substituents on the silicon atom in the R'RSiCl2.The total yield of p with p = 3-5 increases with decreasing tendency of the R'RSiCl2 to form rings by hydrolytic polycondensation, and with increasing sensitivity of the terminal trimethylsiloxy group in the cocondensation products to the action of HCl and its activity with respect to the siloxane bond.
Kopylov, V. M.,Agashkov, S. P.,Sunkovich, G. V.,Prikhod'ko, P. L.
p. 1257 - 1261
(2007/10/02)

Siloxane basicity toward strong acid in nonpolar solution
The relative basicities of ten siloxanes and an ether were studied in benzene by determining from visible spectroscopic measurements the thermodynamic constants for the competition between the substrate and a reference base (4-chloro-2-nitroaniline) for acid (trifluoromethanesulfonic acid): RB-HA + S ? RB + S·HA. The Keq values were considered as a measure of basicity with the following order established and explained by inductive effects in the protonated species: permethyl linear siloxanes (Me3Si(OSiMe2)nOSiMe3, n = 0-3) > dibutyl ether > HMe2SiOSiMe2H > branched siloxanes ((Me3SiO)3SiMe, (Me3SiO)4Si) > cyclic siloxanes ((Me2SiO)n, n = 3-5). The ΔH and ΔS values were positive and increased with higher basicity; this behavior was attributed to differential solvation of ion pairs.
Shepherd, Brian D.
p. 5581 - 5583
(2007/10/02)

EFFECT OF HYDROCHLORIC ACID ON RING FORMATION IN HYDROLYTIC POLYCONDENSATION OF DIFUNCTIONAL ORGANOCHLOROSILANES
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Kopylov, V. M.,Agashkov, S. P.,Sunkovich, G. V.,Prikhod'ko, P. L.,Ezerets, M. A.,Glukhova, M. A.
p. 1873 - 1878
(2007/10/02)

On the Problem of the Intermediate Formation of Silanone R2Si=O by Reactions of Silenes with Dinitrogen Oxide
The silaethene Me2Si=C(SiMe3)2 (1a; unstable; from 1a * Ph2C=MSiMe3 = 4) forms with N2O an unstable cycloadduct, which decomposes under isomerization or cleavage.It was not possible to decide clearly, whether the last reaction, which leads to (Me3Si)2CN2 and polymers with (Me2SiO)n groups, proceeds with intermediate formation of silanone Me2Si=O or not (no trapping product with Et3SiH, but with Me3SiCl).The silanimines Me2Si=NSitBu3 (2a; unstable; from 2a * tBu3SiN3 = 7) and tBu2Si=NSitBu3 (2b; metastable) form with N2O unstable cycloadducts, which, under participation of the silanimines, react into products (10) being composed of a molecular silanone and a molecule silanimine.As has been shown by trapping experiments with Et3SiH, Me3SiCl, or Me3SiOMe, latter reaction involves unstable free silanones Me2Si=O (3a) or tBuSi=O (3b) as intermediates. 3b, generated in benzene from 2b/NO2 in the presence of equimolar amounts of tetrahydrofuran (THF), obviously forms an adduct 3b*THF, which is trapped by excess 2b.When 3b is produced in THF as solvent, the silanone starts THF polymerization, indicating a high Lewis acidity of silanones.
Wiberg, Nils,Preiner, Gerhard,Schurz, Klaus
p. 1407 - 1412
(2007/10/02)

Direct spectroscopic study of unstable molecules with silicon-oxygen multiple bonds: Low temperature matrix stabilization of (CH3)2Si=O and (CD3)2Si=O in the gas phase
To continue the IR spectroscopic investigations of intermediates with doublebonded silicon, the silanones (CH3)2Si=O and (CD3)2Si=O have been generated by vacuum pyrolysis of the corresponding 6-oxa-3-silabicyclohexanes and of Diels-Alder adducts of silapyranes with maleic anhydride.The above silanones have first been stabilized from the gas phase in argon matrices at 12 K and studied by IR spectroscopy.Using the dependence of the spectra on temperature and pressure in the pyrolysis zone or in warming-up experiments (to 35-40 K) the following vibrational bands of silanones have been revealed: (CH3)2Si=O 1244, 1240, 1210, 822, 798, 770, 657 cm-1; (CD3)2Si=O 1215, 1032, 1007, 995, 712, 685, 674 cm-1.The limits of thermal ( 850 deg C) and kinetic (5 x 10E-4 torr) stability of dimethylsilanone were determined.By comparison of frequencies found with computed values the band 1210 cm-1 in (CH3)2Si=O (1215 cm-1 in (CD3)2Si=O) was assigned to a Si=O streching vibration.This frequency as well as the calculated force constant (8.32 mdyn/Angstroem) and order (1.45) of the Si=O bond are considered as evidence of significant double bonding in dimethylsilanone.
Khabashesku, V. N.,Kerzina, Z. A.,Baskir, E. G.,Maltsev, A. K.,Nefedov, O. M.
p. 277 - 294
(2007/10/02)

BENZYLOXYDIMETHYLSILANE - A GENERATOR OF DIMETHYL- AND METHYLSILANONES
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Chernyshev, E. A.,Mudrova, N. A.,Krasnova, T. L.,Petrunin, A. B.
p. 634 - 635
(2007/10/02)

Silathione (Me2Si=S) Extrusion in the Thermolysis of Silylthioketenes
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Barton, Thomas J.,Paul, Gitendra C.
p. 5292 - 5293
(2007/10/02)

Reaction of 6-Oxa-3-silabicyclohexanes with Phosphinimines. Synthesis of 6-Vinyl-1,3-dioxa-2,4-disilacyclohexanes
Reaction of 3,3-dimethyl-6-oxa-3-silabicyclohexane with N-benzyltriphenylphosphinimine yields 1,3-butadiene and 2,2,4,4-tetramethyl-6-vinyl-1,3-dioxa-2,4-disilacyclohexane (3).A mechanism for the formation of (3) which involves the reaction of dimethylsilanone with 2,2-dimethyl-4-vinylsilaoxetane is proposed.
Baceiredo, Antoine,Juengst, Clifford D.,Manuel, Georges,Weber, William P.
p. 237 - 240
(2007/10/02)

REACTION OF ORGANOCHLOROSILANES WITH OXYGEN HETEROCYCLES AND LITHIUM
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Krasnova, T. L.,Mudrova, N. A.,Bochkarev, V. N.,Kisin, A. V.
p. 1358 - 1362
(2007/10/02)

Thermal Extrusion of Dimethylsilanone from (Hydridosilyl)ketenes. A Retro-Wolff Rearrangement?
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Barton, Thomas J.,Groh, Brian L.
p. 7221 - 7222
(2007/10/02)

SILYL AND SILYLMETHYL RADICALS, SILYLENES, SILA-ALKENES, AND SMALL RING SILACYCLES IN REACTIONS OF ORGANOCHLOROSILANES WITH ALKALI METAL VAPOURS
Dehalogenation of the organochlorosilanes Me3SiCl (I), Me2PrSiCl (II), Me3SiSiMe2Cl (III), Me3SiCH2SiMe2Cl (IV), ClCH2SiMe3 (V), ClCH2SiMe2SiMe3 (VI), ClCH2Me2SiSiMe2CH2Cl (VII), Me2SiCl2 (VIII), MePrSiCl2 (IX), Me3SiCH2SiMeCl2 (X), Me3SiCH2CH2SiMeCl2 (XI), Me3SiCH2CH2CH2SiMeCl2 (XII), ClCH2Si(H)MeCl (XIII), ClCH2SiMe2Cl (XIV), ClMe2SiSiMe2Cl (XV), ClCH2CH2CH2Si(H)MeCl (XVI), ClCH2CH2CH2SiMe2Cl (XVII), ClCH2CH2OSiMe2Cl (XVIII), ClMe2SiCH2SiMe2Cl (XIX), ClMe2SiCH2CH2SiMe2Cl (XX), and ClMe2SiCH2CH2CH2SiMe2Cl (XXI) with K/Na alloy vapours at 0.1-1 Torr and 300-320 deg C yields products derived from the reactions of short-lived intermediates, such as silyl and silylmethyl radicals, silylenes, and sila-alkenes.In addition, small-ring silacycles of low stability are formed as the intermediates in some of the dehalogenation reactions.Combination and H-atom abstraction are the main reactions of silyl and silyl-methyl radicals.These radicals are not prone to decomposition reactions when C-H, C-C, or Si-C bonds are at the β(Si-Si) bond with the formation of Me2Si=CH2 and the trimethylsilyl radical.The generation of alkylmethylsilylenes is accompanied by their decomposition processes, which involves intramolecular β(C-H) insertion of alkylmethylsilylenes and 2+1>-thermocyclodecomposition of intermediate silacyclopropanes.The contribution of δ(C-H) and ε(C-H) insertion reactions is much less pronounced, and in the formation of five- or six-membered silacycles.We did not succeed in obtaining monosilacyclobutanes, as the intramolecular γ(C-H) insertion is not typical for silylenes with alkyl substituents.Dehalogenation of chloromethylchlorosilanes with alkali metal vapours yields sila-alkenes, and that of 1,2-dichlorodisilanes gives disilenes. 1-Methyl-1-silaethylene, obtained by this method, does not rearrange into dimethylsilene, but dimerizes to give 1,3-dimethyl-1,3-disilacyclobutane.The formation of 1,3,5-trisilacyclohexanes takes place due to subsequent radical addition at the silicon-carbon double bond and cyclization of 1,6-biradicals.Dehalogenation of organochlorosilanes XVI, XVII, and XX opens up possibilities for the gas-phase synthesis of small organosilicon heterocycles: monosilecyclobutanes and 1,2-disilacyclobutanes.A new, low-stability heterocycle, i.e. 1,1,2,2-tetramethyl-1,2-disilacyclobutane, has been obtained, which enables a new, high polymer, polyethylenetetramethyldisilene, to be obtained.In the case of organochlorosilanes XVIII and XIX, cyclization is accompanied by secondary reactions of silacycles, rearrangements, dimerization, or decomposition.
Gusel'nikov, L. E.,Polyakov, Yu. P.,Volnina, E. A.,Nametkin, N. S.
p. 189 - 204
(2007/10/02)

PYROLYSIS OF SILICON-CONTAINING CYCLIC POLYSULPHIDES
Thermal decomposition of silicon-containing monocyclic polysulphides (1-methyl-3-trimethylsilyl-2,5-dithiacyclopentane (I), 1,4-bis(trimethylsilyl)-2,3,6,7-tetrathiacyclooctane (II) and 1-trimethylsilyl-2,3,4,5,6-pentathiacycloheptane (III)) has been stud
Chernyshev, E. A.,Kuz'min, O. V.,Lebedev, A. V.,Zaikin, V. G.,Mikaya, A. I.
p. 231 - 238
(2007/10/02)

MISE EN EVIDENCE DE LA FORMATION DE R2M=MR2 A PARTIR DE DISILA-1,2 ET DIGERMA-1,2 CYCLOHEXENES-4
Intermediates with ?-bonded Si or Ge are generated during gas phase pyrolysis of 1,2-disila- or 1,2-digerma-cyclohex-4-enes. Compounds such as R2M=MR2 are successfully trapped by addition or and cycloadditions.These results were proved by mass spectrometry.
Marchand, Annette,Gerval, Pierre,Duboudin, Francoise,Gaufryau, M.-H.,Joanny, Marguerite,Mazerolles, Pierre
p. 93 - 106
(2007/10/02)

Nickel-katalysierte Reduktion von Kohlenmonoxid mit Hexamethyldisilan: eine neuartige Synthese von Siloxanen
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Vollhardt, K. Peter C.,Yang, Zhen-Yu
p. 449 - 450
(2007/10/02)

THERMAL DECOMPOSITION OF 1-TRIMETHYLSILYL-μ3-S,S'-ETHYLENEDITHIOLATOHEXACARBONYLDIIRON
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Chernyshev, E.A.,Kuz'min, O.V.,Lebedev, A.V.,Kabanov, B.K.,Tyurin, V.D.,et al.
p. 2184 - 2187
(2007/10/02)

SELECTIVITY IN THE REACTIONS OF ALKYLLITHIUM REAGENTS WITH α, ω-DICHLOROPERMETHYLSILOXANES
The reactions of 1,3-dichlorotetramethyldisiloxane and 1,5-dichlorohexamethyltrisiloxane with alkyllithium reagents have been studied.At low temperature (-78 deg C) only one of the two silicon-chlorine bonds of 1,3-dichlorotetramethyldisiloxane reacts readily with alkyllithium reagents.This permits the selective preparation of 1-alkyl-3-chlorotetramethyldisiloxanes or by hydrolysis 1-alkyl-3-hydroxytetramethyldisoloxanes.The silicon-chlorine bond of 1-alkyl-3-chlorotetramethyldisiloxanes reacts with alkyllithium reagents at higher temperatures (0 deg C).Both the silicon-chlorine bonds of 1,5-dichlorohexamethyltrisiloxane react competitively with alkyllithium reagents at -78 deg C.No cleavage of siloxane bonds by alkyllithium reagents is observed under these conditions.Spectral properties of a number of 1-alkyl-3-hydroxytetramethyldisiloxane and 1-alkyl-5-hydroxyhexamethyltrisoloxanes are reported.
Kazoura, Samih Amine,Weber, Wolliam P.
p. 149 - 156
(2007/10/02)

Direct Thermal and Photochemical Generation of Silanones
2-Silapyrans (1,2-oxasilins) are synthesized by the pyrolysis of 1-disilanyl-4-methoxy-1,3-butadienes via initial 1,5-silyl migration to afford an intermediate 1-sila-1,3-butadiene.Diels-Alder reaction of the silapyrans and perfluoro-2-butyne does not lead to isolable adducts but rather leads to apparent extrusion of silanone (R2Si=O), which is trapped by a variety of reagents.Reaction of the silapyrans and maleic anhydride provides stable adducts that extrude silanones upon either thermolysis or photolysis.No evidence could not be found for rearrangement of a silylsilanone to a siloxysilylene.
Hussmann, Gregory,Wulff, William D.,Barton, Thomas J.
p. 1263 - 1269
(2007/10/02)

NEW REACTION LEADING TO UNSTABLE 2,2-DIMETHYL-1,2-OXASILETANE
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Gusel'nikov, L. E.,Kerzina, Z. A.,Polyakov, Yu. P.,Nametkin, N. S.
p. 401
(2007/10/02)

THE SILICON-OXYGEN DOUBLE-BONDED INTERMEDIATES. A NEW METHOD FOR THE FORMATION OF ORGANOSILANONES
The kinetics and mechanism of thermal decomposition of R1R2(H)SiOOR3 silylperoxides have been studied.It has been shown that peroxides generated diorganosilanones, R1R2Si=O, with a high yield in the temperature range 130-180 deg C.A mechanism is suggested for the silanone formation.The interaction of silanones with cyclosiloxanes, triethylsilane, α-methylstyrene has been investigated as well as the cyclisation of silanones.
Tomadze, A. V.,Yablokova, N. V.,Yablokov, V. A.,Razuvaev, G. A.
p. 43 - 50
(2007/10/02)

Kinetics of Addition of 2-Methyl-2-silapropene to Hydrogen Chloride, Hydrogen Bromide, and Oxygen
2-Methyl-2-silapropene adds rapidly to hydrogen chloride and hydrogen bromide in the gas phase to form the corresponding trimethylsilyl halide, and to molecular oxygen to form dimethylsilanone; Arrhenius parameters for these reactions have been measured.
Davidson, Iain M. T.,Dean, Christopher E.,Lawrence, F. Timothy
p. 52 - 53
(2007/10/02)

EVIDENCE FOR THE INTERMEDIACY OF 1,1-DIMETHYL-2-PHENYL-1-SILA-1,3-BUTADIENE IN THE PHOTOCHEMISTRY AND PYROLYSIS OF 1,1-DIMETHYL-2-PHENYL-1-SILA-2-CYCLOBUTENE
Photolysis of 1,1-dimethyl-2-phenyl-1-sila-2-cyclobutene (I) in methanol and methanol-O-d1 yields dimethylmethoxy(1-phenyl-2-propenyl)silane and dimethylmethoxy(1-d1-1-phenyl-2-propenyl)silane, respectively, as major products.These products may be formed by reaction of methanol or methanol-O-d1 with 1,1-dimethyl-2-phenyl-1-sila-1,3-butadiene.Gas phase pyrolysis of I and acetone or formaldehyde have also been studied.
Tzeng, Dongjaw,Fong, Raymond H.,Soysa, H. S. Dilanjan,Weber, William P.
p. 153 - 161
(2007/10/02)

METALLA IV-b-PHOSPHOLANNES II-METALLA-2 (OXA-, THIA- ou AZA-)-3 PHOSPHOLANNES
2-sila-, germa- or stanna- 3-(oxa-, thia- or aza-) phospholanes have been synthesized by reactions of dihalometalla-IV-b compounds with dilithiated β-phosphorus alcohols, thiols or amines HYCH2CH2P(H)Ph (Y=O, S, NMe).Germa- and stanna- heterocycles can also be obtained from germyl- or stannyldiamines and the same β-phosphorus alcohols, thiols or amines. 2-sila 3-(oxa- or thia-) phospholanes are of particular interest for their decomposition reaction leading to silanone or silathione and phosphirane.
Andriamizaka, J. D.,Escudie, J.,Couret, C.,Satge, J.
p. 279 - 286
(2007/10/02)

GENERATION AND TRAPPING OF 6,6-DIMETHYL-6-SILAFULVENE
Flow pyrolysis of allylcyclopentadienyldimethylsilane and of 1-dimethylmethoxysilyl-1-trimethylsilylcyclopentadiene afforded 6,6-dimethyl-6-silafulvene which was either trapped or allowed to dimerize.
Barton, Thomas J.,Burns, Gary T.,Arnold, Edward V.,Clardy, Jon
p. 7 - 10
(2007/10/02)