- Synthesis of 14C-labeled cyclic and linear siloxanes
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Simple procedures to synthesize a variety of 14C-labeled monomeric and polymeric siloxanes are described. Specifically, the synthesis of the following siloxanes, some of which are of significant commercial importance are provided: 14C-octamethylcyclotetrasiloxane (D4), 14C-decamethylcyclopentasiloxane (D5), 14C-hexamethyldisiloxane (MM), 14C-dimethyldimethoxysilane and 14C-dimethylsilanediol (DMSD) are examples of discrete monomeric species. 14C-350 and 1000 cSt polydimethylsiloxanes (PDMS) are examples of polymeric species. Synthesis of the monomeric species with the exception of dimethylsilanediol involve reactions of Grignard reagents with the appropriate chlorosilanes, while the polymeric materials were synthesized via acid catalyzed equilibration reaction of 14C-D4 with dodecamethylpentasiloxane (MD3M). The compound 14C-DMSD was obtained by the hydrolysis of 14C-dimethyldimethoxysilane. The labeled materials listed here were synthesized for their utility as tracers in several of the ongoing environmental fate and effects studies as well as toxicological investigations.
- Varaprath, Sudarsanan
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- Photolysis of (Me2Si)6 in argon matrices doped with high concentrations (ca. 20%) of N2O or C2H4O: Formation of (Me2SiO)6
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Irradiation using a low pressure mercury lamp (λ=ca. 250 nm) of argon matrices containing ca. 1% (Me2Si)6 and ca. 20% ethylene oxide (C2H4O) or nitrous oxide (N2O) for a period of ca. 20 h leads to the formation of the cyclic compound (Me2SiO)6. This has a 12-membered ring with alternating Si and O atoms. It is identified by comparison of its infrared spectrum with a spectrum of an authentic sample. The reaction appears to proceed by stepwise insertion of O atoms into Si-Si bonds.
- Almond, Matthew J.,Cannady, J. Pat,Darling, Tracey A.,Ogden, J. Steven,Walsh, Robin
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- Hydrogenolysis of Polysilanes Catalyzed by Low-Valent Nickel Complexes
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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
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supporting information
p. 15603 - 15609
(2020/04/29)
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- High-efficiency macrocyclic dimethyl siloxane compound preparation method
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The invention discloses a high-efficiency macrocyclic dimethyl siloxane compound preparation method which comprises the following steps: (1) utilizing tetramethyl disiloxane and octamethyl cyclotetrasiloxane as raw materials, performing ring-openingopen cycle in a sodium hydroxide or potassium hydroxide water solution and then inserting again to obtain dimethyl hydrogen silicone end capped direct-linked siloxane; (2) chlorinating the dimethyl hydrogen silicone end capped direct-linked siloxane with acetyl chloride under a catalytic effect of aluminum trichloride to obtain dimethyl chlorosilane end capped direct-linked siloxane; (3) hydrolyzing the direct-linked siloxane under the alkali condition to obtain varieties of macrocyclic diemthyl silicon ring bodies. The preparation method has simple steps and economical and safe technology and can be used for obtaining varieties of high-purity macrocyclic diemthyl silicon ring body products from simple raw materials; thus, high-difficulty distillation is avoided, and the preparation method is very suitable for industrial production.
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Paragraph 0008; 0015
(2017/10/13)
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- One-Step Synthesis of Siloxanes from the Direct Process Disilane Residue
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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
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supporting information
p. 17165 - 17168
(2016/11/23)
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- Selective Formation of Alkoxychlorosilanes and Organotrialkoxysilane with Four Different Substituents by Intermolecular Exchange Reaction
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Alkoxychlorosilanes are scientifically and industrially important toward preparing silicone and silica as well as preparation of siloxane-based nanomaterials by stepwise reactions of Si?OR (R=alkyl) and Si?Cl groups. Intermolecular exchange of alkoxy and chloro groups between alkoxysilanes and chlorosilanes (functional group exchange reaction) provides an efficient and environmentally benign route to alkoxychlorosilanes. BiCl3 as a Lewis acid catalyst can promote the functional group exchange reactions more efficiently than conventional acid catalysts. Higher reactivity has been observed for chlorosilanes with smaller numbers of Si?CH3 groups and for alkoxysilanes with larger numbers of Si?CH3 groups. The reaction mechanism is proposed and selective syntheses of alkoxychlorosilanes are demonstrated. These findings also enable us to synthesize an organotrialkoxysilane with four different substituents.
- Komata, Yuma,Yoshikawa, Masashi,Tamura, Yasuhiro,Wada, Hiroaki,Shimojima, Atsushi,Kuroda, Kazuyuki
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p. 3225 - 3233
(2016/11/29)
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- Platinum-catalyzed reduction of DMF by 1,1,3,3-tetramethyldisiloxane, HMeSi2OSiMe2H: New intermediates HSiMe 2OSiMe2OCH2NMe2 and HSiMe 2(OSiMe2)3OCH2
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The use of Karstedt's catalyst to study the reduction of Me2NCHO (DMF) by the popular "dual SiH"-containing tetramethyldisiloxane, HMe2SiOSiMe2H (1), has revealed that the first step in the process involves an initial sing
- Martinez, Jorge L.,Sharma, Hemant K.,Arias-Ugarte, Renzo,Pannell, Keith H.
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supporting information
p. 2964 - 2967
(2014/07/08)
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- (Me3N)Mo(CO)5-catalyzed reduction of DMF by disiloxane and disilane moieties: Fate of the silicon-containing fragments
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The use of HSiMe2OSiMe2H (1) and various hydrodisilanes, R3SiSiMe2H (2; R = alkyl, aryl), as reductants for N,N-dimethylformamide (DMF) in the presence of (Me 3N)Mo(CO)5 as a catalyst led to the formation of a series of novel and structurally interesting siloxanes as well as trimethylamine. In the case of 1 the cyclic poly(dimethylsiloxanes) D4 and D6 are obtained, and for 2 the products are bis(disilyl) ethers, (R 3SiSiMe2)2O. Siloxymethylamine intermediates resulting from an initial hydrosilylation of DMF, (Me2NCH 2OSiMe2)2O (3) and R3SiSiMe 2OCH2NMe2 (4; R = Me, Ph), from the reactions of 1 and 2, respectively, can be observed and, in the case of 3, isolated and purified. In the presence of the respective starting silanes and the catalyst the intermediates readily react to form the appropriate siloxane materials and trimethylamine. Compound 3 was functionalized by reaction with R3ECl (E = Si, Ge, R = Me, Ph) to provide group 14 containing products (R 3EOSiMe2)2O (R = Me, E = Si (5a), Ge (6a); R = Ph, E = Si (5b), Ge (6b)). Reactions of Me3SiSiMe2OCH 2NMe2 (4a) with R3ECl produced Me 3SiSiMe2OER3 (R = Me, E = Si (7), R = Ph, E = Ge, 8). The crystal structure of (Ph3SiSiMe2)2O (9c) is reported and exhibits an Si-O-Si angle of 165 and the longest Si-Si bond length (2.376(2) A) for such bis(disilyl) ethers. The new (Ph 3EOSiMe2)2O derivatives 5b and 6b have been structurally characterized and exhibit distinct conformations about the central SiOSi fragment. In the case of the Ph3Si compound 5b the dihedral angle between the two end groups is 180 with completely staggered SiMe groups on the central Si atoms, whereas for the Ge congener it is 55.7 and the structure exhibits eclipsed SiMe groups. The distinction seems to be due to both intra- and intermolecular phenyl group π stacking in 6b stabilizing this formally higher energy conformation.
- Sharma, Hemant K.,Arias-Ugarte, Renzo,Tomlinson, David,Gappa, Rie,Metta-Magana, Alejandro J.,Ito, Haruhiko,Pannell, Keith H.
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p. 3788 - 3794
(2013/08/23)
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- Effect of catalyst structure on the reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane
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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
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body text
p. 762 - 777
(2009/09/26)
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- METHOD FOR THE PRODUCTION OF CYCLIC POLYSILOXANES
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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)
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- Novel direct process
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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)
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- PROCESS FOR STABILIZATION OF SILOXANE COMPOUNDS
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A method for stabilizing silicone dry cleaning solvents containing impurities, comprising contacting the silicone solvent with an adsorbent, neutralizing agent or combination thereof to purify the solvent and prevent reequilibration and polymerization, and separating the silicone solvent.
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- Reaction of the dioxane complex of dichlorogermylene with siloxanes
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The major organogermanium compounds formed by reactions of the dioxane complex of dichlorogermylene with hexamethyldisiloxane, octamethyltrisiloxane, and hexamethyltricyclotrisiloxane are bis(trimethylsiloxy)dichlorogermane, 3,3-dichloro-1,1,1,5,5,7,7,7-o
- Shcherbinin,Pushkina,Krivolapova,Bykovchenko,Khromykh,Komalenkova,Chernyshev
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p. 1907 - 1910
(2007/10/03)
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- New route to permethylcyclosiloxanes
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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
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p. 1368 - 1370
(2007/10/03)
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- Cleavage of poly(diorganosiloxanes) by trimethyialuminum
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The interaction of AlMe3 at elevated temperatures with poly(diorganosiloxanes), (RMeSiO)x (R = Me, n-C18H37, -CH2CH2CF3, Ph), leads to rupture of the silicon-oxygen framework and yields the dimeric aluminum siloxides [Me2Al(OSiMe2R)]2. The molecular structure of [Me2Al(OSiMe2Ph)]2 has been confirmed by X-ray crystallography. The compound [Me2Al(OSiMe2Ph)]2 crystallizes in the monoclinic space group P21/n with unit cell dimensions a = 7.970 (3) ?, b = 24.563 (10) ?, c = 13.322 (4) ?, β= 105 05 (3)° Z = 4, 2754 observed data, R = 0.0478, and Rw = 0.0639. At ambient temperatures the cyclic trisiloxane (Me2SiO)3 forms a highly fluxional 1:1 Lewis acid-base adduct with AlMe3.
- Apblett, Allen W.,Barron, Andrew R.
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p. 2137 - 2141
(2008/10/08)
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