- Synthesis of Trifluorosilyl Organometallic Complexes from Trifluorosilyl Radicals and Metal Atoms
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Trifluorosilyl radicals generated in a radio frequency glow discharge of hexafluorodisilane were reacted with metal atoms to give the first homoleptic trifluorosilyl metal compounds.Bis(trifluorosilyl)tellurium, tris(trifluorosilyl)bismuth, tris(trifluorosilyl)antimony, and bis(trifluorosilyl)mercury were formed in moderate yields by cocondensation of tellurium, bismuth, antimony, and mercury with trifluorosilyl radicals (.SiF3) on a cryogenic surface.In a similar manner trifluorosilyl complexes containing additional ligands were also prepared.For example, we have successfully prepared bis(trifluorosilyl)tris(trimethylphosphine)nickel, (η6-toluene)bis(trifluorosilyl)nickel, bis(trifluorosilyl)bis(trimethylphosphine)palladium, bis(trifluorosilyl)cadmium-glyme, and bis(trifluorosilyl)zinc-2-pyridine.
- Bierschenk, T. R.,Guerra, M. A.,Juhlke, T. J.,Larson, S. B.,Lagow, R. J.
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- Reaction of tetrafluorosilane with tris(2-hydroxyethyl)amine, tris(2-trimethylsiloxyethyl)amine and bis(2-trimethylsiloxyethyl)amine and its N-methyl derivative. 1,1-Difluoroquasisilatranes
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Reaction of tetrafluorosilane with tris(2-hydroxyethyl)- and tris(2-trimethylsiloxyethyl)amine results in formation of 1-fluorosilatrane and fluorosilatrane in 75 and 53% yield, respectively. Reaction of tetrafluorosilane with bis(2-trimethylsiloxyethyl)a
- Voronkov,Grebneva,Trofimova,Albanov,Chernov,Chipanina
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- REACTION OF GLASSES WITH HYDROFLUORIC ACID SOLUTION.
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The gravimetric method was used to study the reaction between fused silica and silicate glasses with HF acid solution. The reaction was found to be transport-controlled. Additions of Al//2O//3, CaO, or both to fused silica caused a reduction in corrosion resistance of the resulting glasses.
- Tso,Pask
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p. 360 - 362,360 - 362
(1982)
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- Preparation of high-purity silicon tetrafluoride by thermal dissociation of Na2SiF6
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The possibility of preparing high-purity silicon tetrafluoride by the thermal dissociation of pure grade Na2SiF6 was studied. The impurity composition of the product was studied by IR and atomic emission spectroscopy and by mass spec
- Bulanov,Pryakhin,Balabanov
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- Integrated utilization of silicon tetrafluoride and zirconium dioxide
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The reaction of silicon tetrafluoride with zirconium dioxide was studied. A technological scheme was suggested for utilization of silicon tetrafluoride and reprocessing of spent zirconium dioxide to obtain zircon and zirconium tetrafluoride.
- Guzeev,D'yachenko,Grishkov
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- Mechanism and Parameters Controlling the Decomposition Kinetics of Na2SiF6 Powder to SiF4
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Sodium hexafluorosilicate (Na2SiF6) powder has been used as a silicon source for formation of Si3N4 coatings by the hybrid precursor system-chemical vapor deposition (HYSY-CVD) route. The quantitative effect of processing time, temperature, gas flow rate, and process atmosphere (N2 and N2:5% NH3) upon the fractional weight loss during the decomposition of Na2SiF6 was studied using a standard L9 Taguchi experimental design and analysis of variance. The decomposition kinetics of Na2SiF6(s) was studied theoretically and experimentally in the temperature range of 550-650°C by applying the shrinking core model. It was found that regardless of atmosphere type, the reaction order is n ≈ 0.12 and that a two-stage mixed mechanism consisting of chemical reaction and boundary layer gas transfer controls the decomposition rate. The determined fractional weight loss during Na2SiF6 decomposition in nitrogen atmosphere is about 1.05-1.5 orders of magnitude greater than that in N2:NH3. The gas flow rate affects the dissociation activation energy, being of 121, 109, and 94 kJ/mol in N2 and of 140, 120, and 115 kJ/mol in N2:NH3, for the flow rates of 20, 60, and 100 cm3/min, respectively, in both atmosphere types. A good agreement is observed by comparing experimental weight loss data with model predictions.
- Soltani,Pech-Canul, Martin I.,González,Bahrami
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- Phase diagram for mullite-SiF4
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At 1 atm of SiF4, mullite and SiF4 react below 660° ± 7°C to form AlF3 and SiO2. From 660° to 1056° ± 5°C, the product is fluorotopaz. Mullite is stable in the presence of 1 atm of SiF4 above 1056°C. The transition temperatures at other pressures of SiF4 can be calculated from log p(atm) = 11.587 - 10811/T(K) and log p(atm) = 9.9609 - 13238/T(K). The phase diagram shows only gas-solid equilibria, but there is evidence for a metastable melt from which acicular mullite and fluorotopaz grow.
- Moyer
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- Evaluation of FNO and F3NO as substitute gases for semiconductor CVD chamber cleaning
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Two types of FNO compounds (FNO and F3NO) were evaluated as candidates for new chemical vapor deposition (CVD) chamber cleaning gases. NF3 and C2F6 were measured as the reference. Like NF3, as these gases have no carbon in their molecules, no perfluoro carbon (PFC) is thought to be emitted. FNO is a compound highly susceptible to hydrolysis. F3NO is expected to decompose more easily than NF3 in the atmosphere because its N-F bond has been weakened by introducing an N=O bond into the molecule. Hence, the contribution to global warming of these compounds is expected to be small. Performance of these gases was evaluated by measuring their etch rates and their exhaust gases. The results showed that the etch rate of F3NO is virtually the same as that of NF3, whereas the etch rate of FNO is about 1/2 that of NF3. However, from the results of exhaust gas analysis, it was found that an unexpected side reaction had occurred in the chamber, and therefore, it was confirmed that it is important to take this property into account in designing applications.
- Yonemura,Fukae,Ohira,Mitsui,Takaichi,Sekiya,Beppu
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- IR spectroscopic and ab initio quantum-chemical study of the products of hydrolysis of silicon tetrafluoride at low water concentrations
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According to the results of IR spectroscopic study and quantum-chemical calculations, hydroxo derivatives SiF4-x(OH)x are formed in the course of hydrolysis of silicon tetrafluoride in the presence of small amount of water along with
- Sennikov,Ikrin,Ignatov,Bagatur'yants,Klimov
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- C1-C4 hydrocarbon release in the preparation of SiF4 through Na2SiF6 pyrolysis
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Hydrocarbon impurities in silicon tetrafluoride originate from the sodium hexafluorosilicate used as a precursor for the preparation of SiF4 through the thermal decomposition of Na2SiF6. We have studied the fraction of C1-C4 hydrocarbons released as a function of temperature during the thermal decomposition of sodium hexafluorosilicate. The lighter hydrocarbons-methane, ethane, and ethylene-are shown to be released at lower temperatures. One source of hydrocarbon impurities in sodium hexafluorosilicate is the sodium carbonate used to prepare it.
- Krylov,Sorochkina,Bulanov,Lashkov
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- Comparison of the interactions of XeF2 and F2 with Si(100)(2 ?? 1)
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The interaction of low-energy XeF2 with Si(100)(2 ?? 1) has been studied and compared to that of F2. Helium atom diffraction, beam-surface scattering, and thermal desorption measurements are the major techniques used in this study. It is found that XeF2 dissociatively chemisorbs with high probability solely on the Si dangling bonds up to a coverage of about one monolayer (ML). Molecular fluorine has previously been observed to react similarly, saturating the dangling bonds at 1 ML coverage. The thermal desorption kinetics and products from the fluorinated layer produced by XeF2 exposure are identical to those produced by F2 exposure. The interactions of XeF2 and F2 are also strikingly similar with respect to the long-range order of the fluorinated Si up to about 1 ML coverage. The order is monitored by He diffraction. In both systems, the diffracted He beams exhibit a sharp decrease in intensity because of the disorder produced by the fluorination of random surface-unit cells as the coverage increases from 0 to about 0.3 ML. The intensity then increases until the fluorine overlayer has fully recovered its (2 ?? 1) periodicity at about 1 ML. This recovery corresponds to the decoration of each Si dangling bond with a fluorine atom. A critical observation of this study is that despite the large exothermicity of the dissociative chemisorption of XeF2 or F2 the order of the surface is not destroyed in either system. After saturation of the dangling bonds, F2 ceases to react with the surface whereas XeF2 continues to deposit fluorine by reacting with the Si-Si ?? dimer bonds and the Si-Si lattice bonds. The order is destroyed as a result of the continued fluorine deposition, and ultimately, etching occurs by the formation of volatile SiF4.
- Holt,Hefty,Tate,Ceyer
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- Isotope-Selective Infrared Multiple Photon Decomposition of Hexafluorodisilane
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The infrared multiple photon decomposition of hexafluorodisilane has been studied with a CO2 TEA laser with the intention of silicon isotope separation.The products were SiF4 (55 percent in silicon balance), a trace of Si3F8, and a whitish film.SiF4 was found to be considerably enriched with 30Si in the decomposition at P(6)-P(20) lines of the 10.6-μm CO2 band.Product yields and enrichment factors were examined as funcitons of irradiation wavenumber, laser fluence, and Si2F6 pressure.Decomposition occorred at a fluence as low as 0.15 J cm-2.The isotope content of 30Si in SiF4 was nearly 50 percent for example, in the irradiation of 2 Torr of natural Si2F6 with laser radiation at 951.19 cm-1 and 0.25 J cm-2.On the basis of the observed results, large-scale separation of 30Si was carried out by using a flow system and a high-repetition laser.SiF4 with a 30Si content of 33 percent was produced at a rate of 1.47 g/h.
- Kamioka, Masatsugu,Ishikawa, Yo-ichi,Kaetsu, Hayato,Isomura, Shohei,Arai, Shigeyoshi
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- Distribution coefficients in the systems SiF4-Si 2OF6 and SiF4-SiOF2
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The liquid-vapor distribution coefficients in the SiF4-Si 2OF6and SiF4-SiOF2systems were determined between 183 and 250 K. The results were used to evaluate the enthalpies of Si2OF6/s
- Devyatykh,Pryakhin,Bulanov
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- Silicon Tetrakis(trifluoromethanesulfonate): A Simple Neutral Silane Acting as a Soft and Hard Lewis Superacid
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A facile synthesis and isolation of pristine silicon tetrakis(trifluoromethanesulfonate), Si(OTf)4, is reported, acting as the first neutral silicon-based Lewis superacid suitable towards soft and hard Lewis bases. Its OTf groups have a dual function: they are excellent leaving groups and modulate the degree of reactivity towards soft and hard Lewis bases. Exposed to soft Lewis donors, Si(OTf)4 leads to [L2Si(OTf)4] complexes (L=isocyanide, thioether and carbonyl compounds) with retention of all Si?OTf bonds. In contrast, it can cleave C?X bonds (X=F, Cl) of hard organic Lewis bases with a high tendency to form SiX4 (X=F, Cl) after halide/triflate exchange. Most notable, Si(OTf)4 allows a gentle oxydefluorination of mono- and bis(trifluoromethyl)benzenes, resulting in the formation of the corresponding benzoylium species, which are stabilized by the weakly coordinating [Si(OTf)6] dianion.
- Driess, Matthias,Hermannsdorfer, André
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supporting information
p. 13656 - 13660
(2021/05/03)
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- Novel synthetic route to perfluoroallyl cyanide (PFACN) reacting perfluoroallyl fluorosulfonate with cyanide
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A novel synthetic method for the preparation of perfluoroallyl cyanide CF2[dbnd]CFCF2CN (PFACN) is presented. This includes the addition – elimination reaction of cyanide anion with perfluoroallyl fluorosulfate CF2[dbnd]CF
- Tverdomed, Sergey N.,Hirschberg, Markus E.,Pajkert, Romana,Hintzer, Klaus,R?schenthaler, Gerd-Volker
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- Bis(perchlorocatecholato)silane—A Neutral Silicon Lewis Super Acid
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No neutral silicon Lewis super acids are known to date. We report on the synthesis of bis(perchlorocatecholato)silane and verify its Lewis super acidity by computation (DLPNO-CCSD(T)) and experiment (fluoride abstraction from SbF6?). The exceptional affinity towards donors is further demonstrated by, for example, the characterization of an unprecedented SiO4F2 dianion and applied in the first hydrodefluorination reaction catalyzed by a neutral silicon Lewis acid. Given the strength and convenient access to this new Lewis acid, versatile applications might be foreseen.
- Maskey, Rezisha,Sch?dler, Marcel,Legler, Claudia,Greb, Lutz
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supporting information
p. 1717 - 1720
(2018/01/27)
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- Synthesis of tris- and tetrakis(pentafluoroethyl)silanes
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The synthesis and complete characterization of functional, highly Lewis acidic tris(pentafluoroethyl)silanes as well as tetrakis(perfluoroalkyl)silanes Si(C2F5)4 and Si(C2F 5)3CF3 by direct fluorination is described. The reaction of SiCl4 with LiC2F5 invariably affords (pentafluoroethyl)fluorosilicates. To avoid silicate formation by fluoride transfer from LiC2F5 the Lewis acidity of the silane has to be decreased by electron-donating substituents, such as dialkylamino groups. The easily accessible Si(C2F5) 3NEt2 is a valuable precursor for a series of tris(pentafluoroethyl)silanes. Special eFfects: functional and highly Lewis acidic tris(pentafluoroethyl)silanes as well as the tetrakis(perfluoroalkyl) silanes Si(C2F5)4 and Si(C2F 5)3CF3 are prepared. The two tetrakis species were formed in the direct fluorination of tris-(pentafluoroethyl)ethyl- and methylsilane. Si(C2F5)4 was characterized by X-ray crystallography (see figure).
- Steinhauer, Simon,Bader, Julia,Stammler, Hans-Georg,Ignat'Ev, Nikolai,Hoge, Berthold
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supporting information
p. 5206 - 5209
(2014/05/20)
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- High-yield synthesis of single-crystal silicon nanoparticles as anode materials of lithium ion batteries via photosensitizer-assisted laser pyrolysis
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Single crystal silicon nanoparticles (Si-NPs) of 20 nm were produced via laser pyrolysis with a virtually complete conversion from SiH4 to Si-NPs. SF6 was used as the photosensitizer to transfer laser beam energy to silicon precursor
- Kim, Seongbeom,Hwang, Chihyun,Park, Song Yi,Ko, Seo-Jin,Park, Hyungmin,Choi, Won Chul,Kim, Jong Bok,Kim, Dong Suk,Park, Soojin,Kim, Jin Young,Song, Hyun-Kon
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p. 18070 - 18075
(2015/02/02)
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- A thermogravimetric study of the reactions of molybdenum disilicide with anhydrous hydrogen fluoride and fluorine
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The results of a thermogravimetric study into the dry fluorination of molybdenum disilicide, MoSi2, using hydrogen fluoride and dilute fluorine gas as fluorinating agents are reported. The reaction between molybdenum disilicide and fluorine follows the thermodynamically preferred route, viz. the formation of the volatile molybdenum hexafluoride along with gaseous silicon tetrafluoride, with the reaction starting just below 200 °C. The reaction with hydrogen fluoride yields solid molybdenum metal and gaseous silicon tetrafluoride, similarly thermodynamically predicted, above 250 °C. No reaction is observed at low temperatures where solid molybdenum trifluoride is expected to form. The results of a kinetic analysis of the data for the reaction with hydrogen fluoride are reported. In the range 250-450 °C the kinetics are chemical reaction controlled. Above this, up to 700 °C, the rate is controlled by diffusion through the stagnant gas films surrounding the solid particles. Evidence for a third, un-quantified, high-temperature mechanism is given.
- Gama,Wagener,Crouse
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- Etching silicon with HF-HNO3-H2SO4/H 2O mixtures- unprecedented formation of trifluorosilane, hexafluorodisiloxane, and Si-F surface groups
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The etching behaviour of sulfuric-acid-containing HF-HNO3 solutions towards crystalline silicon surfaces has been studied over a wide range of H2SO4 concentrations. For mixtures with low sulfuric acid concentration, NO2/N2O4, N 2O3, NO and N2O have been detected by means of FTIR spectroscopy. Increasing concentrations of nitric acid lead to high etching rates and to an enhanced formation of NO2/N2O 4. Different products were observed for the etching of silicon with sulfuric-acid-rich mixtures [c(H2SO4) > 13 mol L -1]. Trifluorosilane and hexafluorodisiloxane were identified by FTIR spectroscopy as additional reaction products. In contrast to the commonly accepted wet chemical etching mechanism, the formation of trifluorosilane is not accompanied by the formation of molecular hydrogen (according to Raman spectroscopy). Thermodynamic calculations and direct reactions of F 3SiH with the etching solution support an intermediate oxidation of trifluorosilane and the formation of hexafluorodisiloxane. The etched silicon surfaces were investigated by diffuse reflection FTIR and X-ray photoelectron spectroscopy (XPS). Surprisingly, no SiH terminations were observed after etching in sulfuric-acid-rich mixtures. Instead, a fluorine-terminated surface was found.
- Lippold, Marcus,Boehme, Uwe,Gondek, Christoph,Kronstein, Martin,Patzig-Klein, Sebastian,Weser, Martin,Kroke, Edwin
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p. 5714 - 5721
(2013/02/25)
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- Gas-phase oxidation of vinyltrifluorosilane with nitrogen dioxide under the action of a pulse CO2 laser
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A chemical reaction between C2H3SiF3 and NO2 induced by radiation from a pulse CO2 laser was studied by mass spectrometry and IR spectroscopy. The composition of gaseous products was determined. A macrokinetic approach was developed to study bimolecular reactions initiated by pulsed IR radiation. The procedure developed allowed us to answer the question of whether the test reaction occurs under conditions when the molecules of only one reactant are vibrationally excited or under conditions of equal vibrational temperatures. The use of this approach to the reaction between C2H3SiF3 and NO 2 demonstrated that its acceleration was due to the equilibrium heating of the system.
- Dement'ev,Koshlyakov,Chesnokov
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experimental part
p. 624 - 634
(2011/02/16)
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- Development and implementation of industrial technologies for synthesis of fluorine compound with the application of elemental fluorine
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A survey is given on the application of elemental fluorine in chemical plants and research centers of Russian Federation.
- Pashkevich,Barabanov,Maksimov
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p. 1142 - 1148
(2009/12/01)
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- Hydrocarbon impurities in SiF4 and SiH4 prepared from it
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Using gas chromatography and high-resolution Fourier-transform IR spectroscopy, we have determined the concentrations of C1-C 4 hydrocarbon impurities in isotopically unmodified silicon tetrafluoride before and after fine purificatio
- Bulanov,Sennikov,Krylov,Sorochkina,Chuprov,Chernova,Troshin
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p. 364 - 368
(2008/10/09)
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- Conversion of SiO2 diatom frustules to BaTiO3 and SrTiO3
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Diatom frustules were used as bio-templates to synthesize functional ceramics via solid-gas displacement reactions. Silica-based frustules were exposed to TiF4 at 330°C to form TiOF2, which was later converted to TiO2 (anatase) by he
- Dudley, Shannon,Kalem, Tugba,Akinc, Mufit
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p. 2434 - 2439
(2008/10/09)
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- The possibility of carbonyl fluoride as a new CVD chamber cleaning gas
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Carbonyl fluoride (COF2) has been investigated as an alternative gas for plasma-enhanced chemical vapor deposition (PECVD) chamber cleaning in order to reduce greenhouse gases emitted from the cleaning process in semiconductor manufacturing. The cleaning performance of COF2 and the environmental impact of its exhaust gases were evaluated using an experimental plasma tool. The results indicated that the cleaning performance of COF 2 was equivalent to that of conventional C2F6. Furthermore, it was confirmed that the use of COF2 would enable the reduction of global warming emissions by over 95% relative to the use of C 2F6, and thus COF2 is considered to be a promising alternative cleaning gas.
- Mitsui, Yuki,Ohira, Yutaka,Yonemura, Taisuke,Takaichi, Tsuyoshi,Sekiya, Akira,Beppu, Tatsuro
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p. G297-G301
(2008/10/09)
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- Conversion of alkyltrifluoroborates into alkyldichloroboranes with tetrachlorosilane in coordinating solvents
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Organotrifluoroborate salts are converted rapidly by tetrachlorosilane in nucleophilic solvents such as THF or acetonitrile into organodichloroboranes coordinated with the solvent (see scheme). This reaction completes a sequence from alkylboronic esters via the trifluoroborate salts to reactive alkyldichloroboranes under mild conditions.
- Kim, Byung Ju,Matteson, Donald S.
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p. 3056 - 3058
(2007/10/03)
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- Phase equilibria in the system silicofluoric acid-tris-(oxymethyl) aminomethane-water at 25°C
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The interaction in the silicofluoric acid-tris(oxymethyl)aminomethane (TRIS)-H2O system has been studied at 25°C by the isothermal solubility method. A new compound 2TRIS·H2SiF6 has been found and characterized by elemental analysis, IR and mass spectroscopy, and thermogravimetry. The compound solubility along the crystallization curve varies within 22.28-47.94 wt %.
- Gel'mbol'dt,Gavrilova,Sokhranenko,Ennan
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p. 1431 - 1433
(2008/10/08)
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- Preparation and fine purification of SiF4 and 28SiH4
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Silicon tetrafluoride was obtained by the thermal decomposition of pure-grade sodium hexafluorosilicate and purified by low-temperature distillation. Next, SiF4 was 28Si-enriched by centrifugation and converted to silane by calcium h
- Bulanov,Balabanov,Pryakhin,Troshin
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p. 283 - 287
(2008/10/08)
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- Separation of silicon isotopes by silicon tetrafluoride-silane technology
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Silane enriched in silicon isotopes was obtained in high yield by reacting SiF4 with a solution of NaAlH4 in diethylene glycol dimethyl ether in a purpose-designed apparatus. Chemical analyses are presented for isotopically enriched silicon obtained by the thermal decomposition of silane.
- Korolev,Mashirov,Perepech,Polyakov,Shil'nikov,Godisov,Kaliteevskii,Ber,Kovarskii
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p. 539 - 541
(2008/10/08)
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- Thermal decomposition of 2,2-bis(difluoroamino) propane studied by FTIR spectrometry and quantum chemical calculations: The primary dissociation kinetics and the mechanism for decomposition of the (CH3)2CNF2 radical
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The kinetics of the thermal decomposition of 2,2-bis(difluoroamino) propane (BDFP) has been studied by pyrolysis/FTIR spectrometry at temperatures between 528 and 553 K using toluene as radical scavenger. The disappearance of BDFP was found to follow the first-order kinetics with the rate constant, k1 = 1016.0±0.7 exp[-(24200 ± 840)/T] s-1, which agrees closely with the expression obtained by Fokin et al. [Dokl. Akad. Nauk. 332 (1993) 735], k1 = 1015.60 exp(-23600/T) s-1. The measured large A-factor supports the earlier conclusion that the primary fragmentation process corresponds to the breaking of one of the two NF2 groups. The measured activation energy is also consistent with the predicted first C-N bond dissociation energy, 44-48 kcal/mol, by the hybrid density-functional theory and that evaluated by variational RRKM calculations fitting the observed rate constant, 47.9 kcal/mol. The 2-difluoroamino propyl radical, (CH3)2CNF2, was predicted to be thermally unstable, producing readily F atoms and HF molecules via the (CH3)2CFNF intermediate. The quantum-chemically predicted mechanisms for the fragmentation of (CH3)2C(NF2)2 and (CH3)2CNF2 agree with the product distribution reported by Ross and coworkers.
- Park,Chakraborty,Jamindar,Xia,Lin,Bedford
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p. 101 - 111
(2008/10/08)
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- Reactivity of Tin Difluoride
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A new value of the enthalpy of formation of tin difluoride was used to calculate the thermodynamic parameters of reactions of SnF2 with elemental substances and several metal oxides. SnF2 can act as an oxidizer and is useful for the synthesis of higher fluorides of group III-V transition metals, including those that have previously been prepared only by reactions with elemental fluorine (TiF4, NbF5, TaF5). The fact that such reactions occur was verified experimentally.
- Goryacheva,Rakov,Solov'ev
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p. 949 - 952
(2008/10/08)
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- F3SiSH and (F3Si)2S: Conflicting observations resolved by unambiguous syntheses
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The reaction between liquid F3SiI and red HgS mainly yields the disilylsulfane (F3Si)2S and, in smaller amounts, hitherto unknown (F3SiS)2SiF2. These fluorosilylsulfanes have different thermal stabilities. (F3Si)2S is a versatile precursor for F3Si derivatives, and at ambient temperature it is stable, while (F3SiS)2SiF2 decomposes rapidly. F3SiSH has been obtained, along with F3SiBr, by selective cleavage of one of the Si-S bonds in (F3Si)2S with HBr in the liquid phase and was for the first time unambiguously characterized. Contrary to previous reports, (F3Si)2O rather than (F2SiS)2 is formed when SiF4 is passed over SiS2 at 1298 K in a quartz tube. Raman and infrared spectra of (F3Si)2S, F3SiSH and its deuterated derivative F3SiSD have been measured and assigned to vibrational fundamentals. Multinuclear NMR spectra have been recorded. Wiley-VCH Verlag GmbH, 2001.
- Beckers, Helmut,Buerger, Hans
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p. 1217 - 1224
(2008/10/08)
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- A (19)F nuclear magnetic resonance study of the conjugate Bronsted-Lewis superacid HSO3F-SbF5. Part 1
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The Bronsted-Lewis superacid HSO3F-SbF5 or 'magic acid' is re-investigated by modern (19)F NMR methods over a wide concentration range. The system is found to be considerably more complex than had been assumed previously. A total of 13 different anions are identified of which only five have previously been identified in magic acid. With increasing SbF5 contents the concentration of monomeric anions like [SbF6]-, [SbF5(SO3F)]-, cis- and trans-[SbF4(SO3F)2]-, and mer-[SbF3(SO3F)3]- gradually decreases. Except for [Sb2F11]-, which is present in very small concentrations only, the formation of oligomers involves exclusively μ-fluorosulfato bridges. In addition to donor (SO3F)- and acceptor (SbF5) complex formation to give [SbF5(SO3F)]- and possibly ligand redistribution, the solvolysis of SbF5 or SbF4(SO3F) in HSO3F appears to be the principal formation reaction for polyfluorosulfatofluoroantimonate(V) anions. In glass (NMR tubes) the solvolysis product HF is converted to the oxonium ion [H3O]+, which has previously been identified by 1H NMR and structurally characterized as [H3O][Sb2F11] by us.
- Zhang, Dingliang,Heubes, Markus,Haegele, Gerhard,Aubke, Friedhelm
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p. 1869 - 1886
(2007/10/03)
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- Difluorosilanethione F2Si=S by flash vacuum thermolysis of (F3Si)2S and by reaction of SiS with F2 - Matrix studies and ab initio calculations
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Difluorosilanethione F2Si=S (1) has been synthesized by Flash Vacuum Pyrolysis of (F3Si)2S at ≥ 500 °C and trapped in an Ar matrix. Furthermore, 1 has been obtained by codeposition of SiS and F2/Ar and by pyrolysis of a matrix-isolated SiS2-XeF2 complex under cryogenic conditions. All six vibrational fundamentals of 1 have been observed in the matrix IR spectrum. Ab initio calculations at the MP2 and CCSD(T) levels using large basis sets have been performed. These calculations have guided the detection of 1 and the vibrational assignment. The best estimate of the structure of 1 with C(2v) symmetry is: r(Si=S) 191.1(1) pm, r(SiF) 156.1(1) pm, angle(FSiF) 103.3(2)°.
- Beckers, Helmut,Breidung, Ju?rgen,Bu?rger, Hans,Ko?ppe, Ralf,Ko?tting, Carsten,Sander, Wolfram,Schno?ckel, Hansgeorg,Thiel, Walter
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p. 2013 - 2019
(2007/10/03)
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- Application of thermal analysis to mineral synthesis
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Differential thermal analysis (DTA) and thermogravimetry (TG) are applied to various fields of mineral science. The present work illustrates the importance of the application of thermal analysis to mineral synthesis, to the determination of the mechanism
- Abdel-Rehim
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p. 177 - 202
(2008/10/08)
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- Process for the preparation of nuclear-halogenated benzotrichlorides from the corresponding benzotrifluorides
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Nuclear-halogenated benzotrichlorides are prepared in a particularly advantageous manner from the corresponding nuclear-halogenated benzotrifluorides by reacting nuclear-halogenated benzotrifluorides with silicon tetrachloride in the presence of catalytic amounts of aluminium trichloride.
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- Matrix Reactions of SiH4 and GeH4 with F2. Infrared Spectra of Several HF Product Complexes
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Silane and germane were condensed with F2 at high dilution in argon on a 13 +/- 1 K substrate.Weak product complexes produced on condensation and increased by ultraviolet photolysis are assigned to SiH3F..HF, SiH2..HF or SiH2..(HF)2, and HSiF..HF.Annealing produced new bands due to F atom reactions that are attributed to SiH3..HF.The GeH3F molecule was observed in the similar GeH3F..HF complex.H-F vibrations in these complexes suggest that F is more basic in GeH3F than in SiH3F owing to the more electropositive nature of germanium as compared to silicon.
- McInnis, Thomas C.,Andrews, Lester
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p. 5276 - 5284
(2007/10/02)
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- Low temperature fluorination of some non-metals and non-metal compounds with fluorine
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Low temperature fluorination with elemental fluorine of elemental phosphorus, sulphur, silicon, amorphous carbon and phosphorus trichloride, phosphorus pentoxide, triphenylphosphine, hexafluorodisilane, hexachlorodisilane, hexabromodisilane, tetrasulphur tetranitride, sulphur dioxide, thionyl chloride and sulphuryl chloride has been carried out in freon-11 medium.The corresponding fluoro compounds have been isolated in near quanititative yields, purified by low temperature fractional condensation and characterised by IR spectroscopy and elemental analysis.
- Padma, D K,Kalbandkeri, R G,Suresh, B S,Bhat, V Subrahmanya
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p. 172 - 176
(2007/10/02)
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- Synthesis and Properties of Trimethyl(trifluorosilyl)stannane
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Trimethyltin hydride reacts with SiF3SiF3 or SiF3SiF2H to give the new compound SnMe3(SiF3) in 75-80 percent yield.No reaction was observed between SnMe3H and SiF3SiH3.Hydrogen-deuterium exchange was observed between tin and silicon during the course of deuterium-labelling experiments.Dimethylstannylene (SnMe2) was implicated as an intermediate by trapping experiments in the thermolysis of SnMe3(SiF3).
- D'Errico, John,Sharp, Kenneth G.
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p. 1879 - 1882
(2007/10/02)
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- Gas-Phase Lewis Acid-Base Interactions. An Experimental Determination of Cyanide Binding Energies from Ion Cyclotron Resonance and High-Pressure Mass Spectrometric Equilibrium Measurements
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Both ion cyclotron resonance and high-pressure mass spectrometric equilibrium techniques have been used to investigate the binding energies of anions to a variety of Lewis acids.From an analysis of the enthalpy changes associated with CN- binding it is evident that in cases of relatively weak binding considerable freedom of rotational motion of CN- in the complex may be retained.Ab initio calculations and experiment suggest that binding through both the N and C sites of CN- is nearly equally favorable in some cases.In contrast to results previously obtained for Bronsted acids which showed that CN- and Cl- bind nearly identically, the present data for Lewis acids show many cases where cyanide is much more favorably bound than chloride, a consequence of enhanced covalent binding of the CN- complexes.New Kroeger Drago parameters derived for CN- support the importance of covalent binding in cyanide adducts.Correlations of binding energy of anions to Lewis acids with the anion proton affinity show excellent linear relationships which may be used to predict binding energetics for new anions.
- Larson, J. W.,Szulejko, J. E.,McMahon, T. B.
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p. 7604 - 7609
(2007/10/02)
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- THERMAL REACTIONS OF F2 AND NF3 WITH SILICON(110) STUDIED BY LASER IONIZATION MASS SPECTROMETRY
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The techniques of laser and electron ionization mass spectrometry have been employed to study the thermal etching of Si(110) by F2 and NF3 at substrate temperatures between 300 and 1200 K.By two-photon resonance-enhenced ionization of SiF2 via the B1B2 state, the apparent activation energy for gaseous silicon difluoride production was found to be 8.9+/-0.3 and 22.1+/-1.7 kcal/mol for F2 and NF3, respectively.SiF was not detected.An extensive search for SiF3 during etching by F2 at 1000 K, by means of resonance ionization from 320 to 325 and from 416 to 510 nm, also showed no signs of the species.Both SiF and SiF3 are thermochemically unimportant etch products under the conditions employed.In F2 etching, SiF4 and total silicon fluoride ΣSiFx+ signals as measured by electron ionization rose rapidly at lower temperatures and stabilized between 700 and 900 K before rising again.No such behavior was observed for SiF2 production from F2 or for the products formed in NF3 etching.Apparent activation energies for total silicon fluoride and SiF4 production are similar.For F2, they were found to be abaut 9 kcal/mol in the low-temperature region, and for NF3 both were measured to be abaut 21 kcal/mol.A proposed reaction mechanism explaining these and related results is discussed.
- Squire, D. W.,Dagata, J. A.,Hsu, D. S. Y.,Dulcey, C. S.,Lin, M. C.
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p. 2827 - 2834
(2007/10/02)
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- Thermodynamic properties of silicalite SiO2
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Silicalite, a polymorph of SiO2, is a new and interesting molecular-sieve material.Low-temperature (5 to 350 K) heat-capacity, fluorine-combustion, high-temperature (350 to 1500 K) drop-calorimetric, and reaction-calorimetric with HF(aq) measurements have been performed on this material.At T' = 298.15 K, ΔfHm0(T') = -(905.20+/-0.84) kJ * mol-1; Cp,m0(T') = (46.34+/-0.23) J * K-1 * mol-1; 0T'Sm0(T')> = (46.29+/-0.23) J * K-1 * mol-1; and ΔfGm0(T') = -(852.23+/-0.84) kJ * mol-1.The enthalpies of reaction with 24.4 mass per cent hydrofluoric acid of silicalite at mass concentrations of 0.5, 1, 2, and 4 g * dm-3 were determined to be -(144.91+/-0.23), -(144.80+/-0.10), -(145.07+/-0.12), and -(145.06+/-0.14) kJ * mol-1, respectively.The enthalpies of reaction of silicalite with 20.1 and 15.0 mass per cent hydrofluoric acid at a silicalite mass concentration of 1 g * dm-3 were determined to be -(143.85+/-0.19) and -(142.68+/-0.08) kJ * mol-1, respectively.Because silicalite reacts rapidly with HF(aq) at 298.15 K, it has potential as a reference material for thermochemical measurements on inorganic silicates and silicate minerals.Silicalite is less stable than quartz, cristobalite, or tridymite, but more stable than SiO2(glass) or the high-pressure forms coesite or stishovite.
- Johnson, G. K.,Tasker, I. R.,Howell, D. A.,Smith, J. V.
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p. 617 - 632
(2007/10/02)
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- Organosilicon compounds
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There are prepared silafluoroolefins and silafluoroolefin ethers and polymers thereof by reacting carbon with silicon tetrafluoroide and a source of hydrogen followed by polymerization. The polymers are useful for architectural purposes and as release coatings.
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- Reaction of CF3 radicals on fused silica between 320 and 530 K
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The reaction between CF3 radicals and silicon oxide (fused silica) surface was studied in a VLPΦ flow reactor (ca. 0.1-3 mTorr) as functions of surface temperature (32-530 K) and CF3 concentration.The CF3 radicals were generated from CF3I by CO2 laser photolysis, and the subsequent gas-phase reaction products were followed by mass spectroscopy.The surface reaction was found to yield CO, HF, CO2, COF2, and SiF4.It was found that H2O residing on the silicon oxide surface was largely responsible for the oxygen- and hydrogen-containing products, and that little etching of the SiOz itself occurred under these conditions.The rates for the irreversible surface loss of CF3, and for the formation of CO were both first order with respect to .These were found to be temperature dependent with EQa ca. 4.7 and 7.5 kcal/mol, respectively.The CF3 surface loss rate indicates that the sticking coefficient for this radical on quartz is between 0.0014-0.017 for the temperature range of this study.
- Selamoglu, N.,Rossi, M.J.,Golden, D.M.
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p. 2400 - 2407
(2007/10/02)
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- INTERACTION OF SODIUM HEXAFLUOROSILICATE WITH TITANIUM DIOXIDE.
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In the course of preliminary experiments on sintering of NaFS with titanium dioxide neither Na//2TiF//6 nor oxyfluorotitanates were detected in the reaction products; this necessitated an additional study of the process. This investigation was carried out by the thermogravimetric method in conjunction with high-temperature x-ray and chemical analyses of the reaction products. Sodium hexafluorosilicate of 98% purity and chemically pure titanium dioxide were used in the experiments. Experiments showed that interaction of sodium fluoride with TiO//2 is not possible; it can therefore be concluded that fluorination of titanium dioxide is effected by silicon tetrafluoride followed by interaction of the resultant titanium trifluoride with sodium fluoride.
- Kulikov,Istomin,Yakovenko,Bun'kov,Gul'din,Oleinikova
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p. 2084 - 2088
(2008/10/08)
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- Preparation of Hexafluorodisilane and Reactions of Hexafluorodisilane and Hexachlorodisilane with Sulfur Trioxide
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Hexafluorodisilane has been prepared by the fluorination of hexachlorodisilane or hexabromodisilane by potassium fluoride in boiling acetonitrile, in yields approximating 45 and 60percent respectively.Hexafluorodisilane has been characterised by infrared
- Suresh, Bettadapura Srinivasaiah,Padma, Doddaballapur Krishnamurthy
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p. 1867 - 1868
(2007/10/02)
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- Some investigations of the chemistry of tellurium chloride pentafluoride, its reaction with caesium fluoride, and the preparation of cis and trans methoxytellurium(VI)chloride tetrafluoride, (CH3O)TeClF4
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The reaction of TeClF5 with CH3OH, and CH3OSiMe3, leads to a mixture of cis- and trans-(CH3O)TeClF4 in a ratio of 1:6, as well as some unidentified Te(IV) product.The vibrational spectrum of the 1:6 mixture of cis- and trans-(CH3O)TeClF4 was accounted for on the basis of the predominant pseudo-C4v trans isomer.TeClF5 is unreactive towards anhydrous HF, SbF5, AlCl3, SO2, F2, and ClF at room temperature.Over the temperature range 70-250 deg C it thermally decomposes to TeF6, TeF4, and Cl2.It slowly reacts with CsF to form CsTeF5, TeF6, Cl2, and small amounts of ClF, and with HNMe2 it is also reduced to form TeF4*HNMe2.
- Lawlor, Lawrence J.,Passmore, Jack
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p. 1477 - 1482
(2007/10/02)
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- Organosilicon compounds
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There are prepared silafluoroolefins and polymers thereof by reacting carbon with silicon tetrafluoride and a source of hydrogen followed by polymerization. The polymers are useful for architectural purposes.
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