SiCl4 Research Articles

Mechanism of thermal decomposition of allyltrichlorosilane with formation of three labile intermediates: dichlorosilylene, allyl radical, and atomic chlorine

It is experimentally found that allyltrichlorosilane dissociates under vacuum pyrolysis (~10–2 Torr) at temperatures above 1100 K to form three labile intermediates: allyl radical, dichlorosilylene, and monoatomic chlorine. On the basis of experimental and theoretical data obtained, it is shown that the decomposition reaction proceeds in two steps. The first step is a typical reaction of homolytic decomposition to two radicals (C3H5 and SiCl3) at the weakest Si—C bond. Due to weakness of the Si—Cl bond in the SiCl3 radical, the energy of which is even somewhat lower than the dissociation energy of the Si—C bond in starting AllSiCl3, this radical undergoes further dissociation to SiCl2 and Cl, thus resulting in three intermediates of different classes of highly reactive species formed from AllSiCl3.

Structure Formation of Metallopolymer-Grafted Block Copolymers

Microphase separation drives the structure formation in block copolymers. Here, functional metallopolymer-grafted diblock copolymers consisting of polystyrene-block-polyisoprene (PS-b-PI) as polymer backbone featuring low molar mass polyferrocenyldimethylsilane (PFS) and polyvinylferrocene (PVFc) are synthesized via an iterative anionic grafting-to polymerization strategy. PS-b-PI block copolymers having about 30 mol % 1,2-polyisoprene moieties are subjected to platinum-catalyzed hydrosilylation reaction for the introduction of chlorosilane groups. The Si–Cl moieties are shown to efficiently react with the active metallopolymers yielding block-selective metallopolymer-grafted copolymers with 34 vol % PVFc and 43 vol % PFS as evidenced by 1H NMR spectroscopy as well as size exclusion chromatography. The microphase separation of the functional metallopolymer-grafted block copolymers is evidenced via TEM measurements revealing fascinating morphologies. The structure formation of the PVFc-grafted block copoly...

Effect of SiO2 nanoparticles sizes on the optical properties and radiation resistance of powder mixtures ZrO2 with micron sizes

One way to improve photo- and radiation resistance of materials is by the modification of their nanoparticles. The purpose of work is to study the optical properties and radiation resistance of ZrO2 powder mixtures with SiO2 nanoparticles without high-temperature heating. The ZrO2 powders with micron sizes were mixed in a ratio of 100:7 mas.% with SiO2 nanopowders. The nanopowders were obtained by combustion of silicon tetrachloride in air plasma. Samples were characterized using X-ray diffraction (XRD), high resolution scanning electron microscopy (SEM), and a simulator of the environment of outer space “Spectrum”. The radiation resistance increase of zirconia dioxide powders with micron-sized grains by the addition of silica nanoparticles without heating at a high temperature was found. For these purposes only water evaporation at 150 °C was used. The effectiveness of the modification reaches values of 2.1 times. This value is close to or even more in comparison to its values in the modification by using high-temperature heating. This result is significant for the practical use of this method of incensement of the radiation resistance of oxide reflecting powders.

Basicity and catalytic activity of porous materials based on a (Si,Al)-N framework

Porous materials based on a framework containing T-N linkages, where T represents silicon or silicon and aluminium atoms, have been prepared by the ammonolysis at low temperature of the corresponding silicon and aluminium chlorides in an ionic liquid, both in the presence and in the absence of mineralizing agents such as pyrrolidine, ammonia and sodium amide. IR spectroscopy and XPS data are consistent with these materials having a framework based on T-NH-T groups (T=Si or Al), that contain also a large fraction of T-NH2 terminal groups. Moreover, XPS evidences the presence of Si-NH-Al groups whenever aluminium is present in the solid. The basic strength of the materials has been determined by pyrrole adsorption, and it has been found that the average basic strength increases with the population of T-NH-T groups and with the aluminium content of the framework. However, this strength is lower than that of a calcined hydrotalcite (Al/(Al+Mg)=0.33) taken as a reference. These materials are active and very selective catalysts in the Michael addition reaction between chalcone [and malononitrile (pKa 11), but turned to be inactive when diethylmalonate having a weaker acidity (pKa 13.3) is used as donor.

Hydroalumination and hydrogallation of an aryl-chloro-dialkynylsilane: Si–Cl bond activation by intramolecular Al–Cl and Ga–Cl interactions

Abstract The chlorine functionalized dialkynylsilane (4- t Bu-C6H4)(Cl)Si(C≡C- t Bu)2 (3) reacted with equimolar quantities of H–Al t Bu2 or H–Ga t Bu2 by hydrometallation of a C≡C triple bond and formation of mixed alkenyl-alkynylsilanes (4 and 5) in which the Si and Lewis acidic metal atoms adopt geminal positions at the α-C atoms of the alkenyl groups. Intramolecular M···Cl interactions (M=Al, Ga) afforded four-membered SiCMCl heterocycles which in comparison with 3 had significantly lengthened Si–Cl bonds. Dual hydrometallation of 3 was only observed for H–Ga t Bu2. One Ga atom of the product (6) was coordinated by the silicon-bound Cl atom, while the second one showed an interaction with the aromatic ring of the tert-butyl-phenyl group. Treatment of the aluminium compound 4 with two equivalents of H–Ga t Bu2 afforded a Si–H bond by Cl-H exchange and release of Cl–Al t Bu2. The resulting silane (7) has the Si atom and two Ga atoms bridged by the α-C atoms of two vinyl groups. The specific functionality of 4 caused a remarkable reactivity. Phenyl isocyanate reacted by the formal insertion into the Al–C(vinyl) and the activated Si–Cl bonds and resulted in the formation of a C–C bond. The product (8) has a SiC2N heterocycle with an Si–N bond and exocyclic C=C and C=O double bonds. The keto group is coordinated to a Cl–Al t Bu2 molecule, which was formed by the shift of the Cl atom from silicon to aluminium.

Insertion reactions of bis(silyl)methyl-lithium Li{CH[SiN(Me2)Me2]2} with RCN (R = But, Ph) and their transmetalation products

Four new azaallylamino metallic complexes have been prepared. The insertion reactions of Li{CH[SiN(Me2)Me2]2}(1) with ButCN or PhCN generated azaallyla-mino-lithium Li{[N(Me2)Si(Me2)C(H)C(But)]N[Si(Me2)N(Me2)]·ButCN} (2) or 1,3- diazaallylamino-lithium Li{[N(Me2)Si(Me2)C(H)C(Ph))]N[C(Ph)NSi(Me2)N(Me2)]} (3), respectively. Further transmetalation reaction of 2 with ZrCl4 afforded complex Cl3Zr{[N(Me2)Si(Me2)C(H)C(But)]N[Si(Me2)N(Me2)]}(4), and 3 with SnCl4 yielded Cl3Sn{[N(Me2)Si(Me2)C(H)C(Ph)]N[C(Ph)N(Si(Cl)(Me2))]} (5). The crystal structures of 2, 4 and 5 were reported. Their formation involved 1,3- and 1,5-shift of the bulky silyl group [-Si(NMe2)Me2]. A mechanism of the halogenation reaction is proposed based on the structural parameters of 5.

Synthesis and sintering of silicon nitride nano-powders via sodium reduction in liquid ammonia

Nano-sized silicon nitride powders were synthesized through the reduction of silicon tetrachloride (SiCl4) by sodium in liquid ammonia at around −40°C.The product was in uniform particles of several nanometers, and in the amorphous form. The amorphous structure was stable up to 1200°C and turned to the crystal structure of α-Si3N4 at 1300°C, and then to β-Si3N4 structure when heated at temperatures higher than 1450°C.Via spark plasma sintering (SPS) dense bulks with 97.9% relative density of theoretic value and the grain size of 100–300nm was successfully fabricated at 1500°C without any sintering additives.

Effect of SiCl4 on the preparation of functionalized mixed-structure silica from monodisperse sol–gel silica nanoparticles

Mesoporous functionalized nanoparticles (nanosilica) and functionalized mixed-structure silica with surface Si–Cl groups were prepared via a SiCl4 hydrolysis base-catalyzed sol–gel process. This study presents hierarchically structured systems formed via growth and self-assembly of functionalized silica nanospheres on the surface of Sylopol-948, generating functionalized mixed-structure silica. The fabricated materials were characterized by nitrogen adsorption, small angle X-ray (SAXS), dynamic light scattering (DLS), zeta potential (ZP), infrared spectroscopy (FT-IR), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX). The incorporation of Si–Cl groups (0.02–0.43 Cl/Si) on the surface—to functionalize the nanoparticles and modify their properties—was confirmed by SEM–EDX and cyclic voltammetry. In functionalized mixed-structure silica, the SBET value (567m2/g) increases, particle size (13.6–17.2nm) decreases and surface charge (−9.0mV) diminishes as SiCl4 concentration increases. In functionalized nanosilica, a lower SiCl4 concentration results in a higher SBET value (730.6m2/g), smaller nanoparticle size (6.0–12.4nm) and higher surface charge (−22.9mV). These materials were experimentally compared and found to demonstrate improved characteristics compared to Stöber nanosilica, non-functionalized mixed-structure silica, and Sylopol-948.

Hydrodechlorination of Silicon Tetrachloride to Trichlorosilane Over Ordered Mesoporous Carbon Catalysts: Effect of Pretreatment of Oxygen and Hydrochloric Acid.

This paper reports on the catalytic reaction for the conversion of silicon tetrachloride (STC) to trichlorosilane (TCS) over pretreated ordered mesoporous carbon (OMC) catalysts by oxygen (denoted as OMC-O2) and hydrochloric acid (denoted as OMC-HCl) at 300 degrees C under N2 atmosphere. The OMC-O2 shows significantly improved the surface area (1341.2 m2/g) and pore volume (1.65 cm3/g), which results in the highest conversion rate of 7.3% as compared to bare OMC (4.3%) and OMC-HCI (5.7%). It is found that the conversion rate of STC to TCS is proportional to the number of Si-O bond over OMC catalysts, which suggests that Si-O-C bond formation is crucial to the reaction as active sites. The O2 pretreatment seems to promote the generation of oxygenated species for the formation of Si-O-C.

Dendrimers with 1, 3, 5‐Trisilacyclohexane as Core Unit

Abstract1, 1, 3, 3, 5, 5‐Hexavinyl‐1, 3, 5‐trisilacylohexane [Si(CH=CH2)2CH2]3 was synthesized and hydrosilylated with trichlorosilane to afford the first generation of a dendrimer. Conversion of this molecule with 18 Si–Cl functions on its surface with an excess of vinylmagnesium bromide yielded the 18‐fold vinylated dendrimer. The new compounds were identified by elemental analyses, multi‐nuclear NMR spectroscopy, and mass spectrometry. Crystal structures were obtained for [Si(CH=CH2)2CH2]3 and [Si(CH2–CH2SiCl3)2CH2]3.

Modeling the hydrochlorination reaction in a laboratory-scale fluidized bed reactor

In the manufacturing process of high purity, electronics-grade silicon, the hydrochlorination reaction step for converting silicon tetrachloride (STC) to trichlorosilane (TCS) is usually carried out in a fluidized bed reactor. However, the design and operation of industrial-scale fluidized bed reactors for the conversion of STC to TCS is currently based on ad hoc rules of thumb and operator experience rather than on reaction engineering principles. In this paper, a fluidized bed model was developed by using the Kunii–Levenspiel fluidization framework. The predictive capabilities of this model were tested on laboratory-scale experimental data from the literature. It is shown that the modified Kunii–Levenspiel model accurately predicts the no catalyst addition and copper catalyst addition experiments of the hydrochlorination fluidized bed with an average percent difference of less than 6%. By making a suitable adjustment to catalytically active iron content, the model prediction is in excellent agreement with experimental data with hydrochloric acid in the feed stream. The modified Kunii–Levenspiel model is well suited for use in scale-up calculations for an industrial reactor as all the parameters are physically reasonable and can be predicted for larger reactors.

Experimental and theoretical studies of Si-Cl and Ge-Cl σ-bond activation reactions by iridium-hydride.

We report the iridium hydride-mediated Si-Cl and Ge-Cl σ-bond activation in a low-polarity toluene solution owing to diphosphine-chelation, in which the Si-Cl and Ge-Cl σ-bonds are readily cleaved through an SN2-type pathway via the formation of a free chloride anion.

K- and L-edge X-ray absorption spectrum calculations of closed-shell carbon, silicon, germanium, and sulfur compounds using damped four-component density functional response theory.

X-ray absorption spectra of carbon, silicon, germanium, and sulfur compounds have been investigated by means of damped four-component density functional response theory. It is demonstrated that a reliable description of relativistic effects is obtained at both K- and L-edges. Notably, an excellent agreement with experimental results is obtained for L2,3-spectra-with spin-orbit effects well accounted for-also in cases when the experimental intensity ratio deviates from the statistical one of 2 : 1. The theoretical results are consistent with calculations using standard response theory as well as recently reported real-time propagation methods in time-dependent density functional theory, and the virtues of different approaches are discussed. As compared to silane and silicon tetrachloride, an anomalous error in the absolute energy is reported for the L2,3-spectrum of silicon tetrafluoride, amounting to an additional spectral shift of ∼1 eV. This anomaly is also observed for other exchange-correlation functionals, but it is seen neither at other silicon edges nor at the carbon K-edge of fluorine derivatives of ethene. Considering the series of molecules SiH4-XFX with X = 1, 2, 3, 4, a gradual divergence from interpolated experimental ionization potentials is observed at the level of Kohn-Sham density functional theory (DFT), and to a smaller extent with the use of Hartree-Fock. This anomalous error is thus attributed partly to difficulties in correctly emulating the electronic structure effects imposed by the very electronegative fluorines, and partly due to inconsistencies in the spurious electron self-repulsion in DFT. Substitution with one, or possibly two, fluorine atoms is estimated to yield small enough errors to allow for reliable interpretations and predictions of L2,3-spectra of more complex and extended silicon-based systems.

Catalytic effects of electrode material on the silicon tetrachloride hydrogenation in RF-arc-discharge

A silicon tetrachloride reduction in RF-arc-discharge (40.86 MHz) has been experimentally studied.

ChemInform Abstract: Enantioselective Ring Opening of meso‐Epoxides with Silicon Tetrachloride Catalyzed by Pyridine N‐Oxides Fused with the Bicyclo[3.3.1]nonane Framework.

The synthesis of new chiral Lewis basic organocatalysts that contain pyridine N-oxide moieties fused with the bicyclo[3.3.1]nonane framework is reported. The obtained pyridine N-oxides were employed as catalysts in the enantioselective ring opening of meso-epoxides with silicon tetrachloride. Derivative 1b endowed with two 2,4-diaryl-substituted pyridine N-oxide moieties proved to be a particularly effective catalyst for desymmetrization of norbornene oxide 16i to furnish Wagner–Meerwein rearrangement product 20i in unprecedented 96 % ee. Difunctional congener 3, which is striped of the 4-aryl substituents, exhibited moderate to high levels of asymmetric induction (47–88 % ee) with alicyclic epoxide substrates.

Electrodeposition of crystalline silicon directly from silicon tetrachloride in ionic liquid at low temperature

Crystalline silicon was fabricated directly from silicon tetrachloride in ionic liquid at low temperature of 100 °C. SEM, TEM and SEAD revealed that as-deposited crystalline Si with diamond cubic crystal structure.

Reactivity of different surface sites with silicon chlorides during atomic layer deposition of silicon nitride

The reactivity of surface sites plays a very important role to determine the thermodynamics and kinetics of ALD processes.

Assessment on the antibacterial activity of nanosized silica derived from hypercoordinated silicon(iv) precursors

Silica nanoparticles were synthesized through a versatile sol–gel combustion method from hydrazide based hypercoordinated silicon complexes derived from the reaction of silicon tetrachloride with O-silylated hydrazide derivatives.

Stereoselective Synthesis of Highly Functionalized 2,3-Dihydro-4-pyranones Using Phosphine Oxide as Catalyst.

2,3-Dihydro-4-pyranones were synthesized stereoselectively using a chiral phosphine oxide as the catalyst. The phosphine oxide sequentially activated silicon tetrachloride and promoted the double aldol reaction of 4-methoxy-3-buten-2-one with aldehydes. Subsequent stereoselective cyclization afforded the corresponding highly functionalized 2,3-dihydro-4-pyranones bearing three contiguous chiral centers in good yields and with high diastereo- and enantioselectivities.

Synthesis of SiOx Nano-Powders Using a Microwave Plasma Torch at Atmospheric Pressure

The silicon oxide nano-powders (SiOx-NPs) were obtained in an atmospheric microwave plasma torch using a gas-phase silicon tetrachloride (SiCl4) with N2 and H2. The gas-phase SiCl4 was injected with H2 gas into the microwave plasma torch generated by N2 and air swirl gas, and then the dark brown powders were deposited on the inner wall of a quartz tube. The sample was analyzed by an X-ray photoelectron spectroscopy (XPS), a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and an X-ray diffraction (XRD). The average size and oxidation x values of synthesized SiOx-NPs were approximately 230 nm and 0.91, respectively. Furthermore, the volumetric charge capacity is 1127 mAh/g and has 89.2% retention after 100 cycles.