Reaction Of SiCl4 Research Articles

Challenges in the Electrochemical Synthesis of Si2Cl6 Starting from Tetrachlorosilane and Trichlorosilane

AbstractThe strongly increasing demand for nano‐ and microelectronics calls for new and environmentally benign reaction pathways for the preparation of one of the most important substrates in the production of semiconductor materials: Si2Cl6. We present a comprehensive study of the opportunities and challenges for the selective electrochemical formation of higher halo‐functionalized silanes to Si2Cl6 achieved by cyclic voltammetry measurements and electrochemical synthesis. Cathodic dehalo‐dimerization reaction of SiCl4 and the approach to halogen exchange for better substrate reduction are envisioned. An anodic halide‐free dimerization pathway by dehydrogenation of HSiCl3 is investigated, including Lewis acid activation of the Si−H bond. In addition, tertiary amine‐driven, Benkeser‐like in‐situ formation of a SiCl3− anion was tested as well. The target molecule Si2Cl6 is strongly promoted to direct electro‐conversions making the anodic and cathodic electrosynthesis very challenging.

Ionic Dissociation of SiCl4 : Formation of [SiL6 ]Cl4 with L=Dimethylphosphinic Acid.

Reactions of SiCl4 with R2PO(OH) (R=Me, Cl) yield compounds with six‐fold coordinated silicon atoms. Whereas R=Me afforded the hexacoordinated tetra‐cationic silicon complex [Si(Me2PO(OH))6]4+ with chloride counter‐ions, R=Cl caused release of HCl with formation of a cyclic dimeric silicon complex [Si(Cl2PO(OH))(Cl2PO2)3(μ‐Cl2PO2)]2 with bridging bidentate dichlorophosphates.

Analytical Electron Microscopy of Silicon Nitride Nanostructures Synthesized from the Vapor Phase

Silicon nitride, Si3N4 is a covalent compound with excellent physical and chemical properties such as corrosion resistance, low-specific weight and good thermal conductivity at ambient and elevated temperatures. Such properties are very attractive in application as advanced ceramics and in semiconductor devise [1]. Nano sized amorphous silicon nitride powders were synthesized at 300 °C by precipitation from the vapor phase reaction of SiCl4 and NH3 and Ar as carrier gas. Solid ammonium halogenide is formed as by-product, in addition to silicon nitride powder.

Reaction of SiCl2·dipp with K[Ge9{Si(SiMe3)3}3] – Synthesis and Characterization of [K(dipp)2][Ge9{Si(SiMe3)3}3]·tol and [dipp‐H][Ge9{Si(SiMe3)3}3]·2acn [dipp = 1,3‐Bis(2,6‐Diisopropylphenyl)imidazol‐2‐ylidene

From solutions of K[Ge9{Si(SiMe3)3}3] with 1,3‐bis(2,6‐diisopropylphenyl‐)imidazol‐2‐ylidene (dipp) two new compounds were obtained. From toluene, single crystals of [K(dipp)2][Ge9{Si(SiMe3)3}3]·tol (1) (tol = toluene) were isolated and the crystal structure was determined [monoclinic, P21/c, a = 16.8386(3), b = 24.6597(5), c = 30.2988(6) Å, β = 101.813(2)°, V = 12314.7(4) Å3, Z = 4, 24192 independent reflections, R1 = 0.046, wR2 = 0.084]. The investigation of single crystals from acetonitrile solution revealed the formation of [dipp‐H][Ge9{Si(SiMe3)3}3]·2acn (2) (acn = acetonitrile) [orthorhombic, P212121, a = 13.4484(4), b = 25.8775(7), c = 26.4390(9) Å, V = 9201.1(5) Å3, Z = 4, 18065 independent reflections, R1 = 0.031, wR2 = 0.052]. The two [Ge9{Si(SiMe3)3}3]– entities show the minimal and maximal distortion of the central tricapped prism that have been reported to date. All compounds were characterized by ESI‐MS, NMR and Raman spectroscopy, and DFT calculations.

Supercritical Fluid Atomic Layer Deposition: Base-Catalyzed Deposition of SiO2.

An in situ FTIR thin film technique was used to study the sequential atomic layer deposition (ALD) reactions of SiCl4, tetraethyl orthosilicate (TEOS) precursors, and water on nonporous silica powder using supercritical CO2 (sc-CO2) as the solvent. The IR work on nonporous powders was used to identify the reaction sequence for using a sc-CO2-based ALD to tune the pore size of a mesoporous silica. The IR studies showed that only trace adsorption of SiCl4 occurred on the silica, and this was due to the desiccating power of sc-CO2 to remove the adsorbed water from the surface. This was overcome by employing a three-step reaction scheme involving a first step of adsorption of triethylamine (TEA), followed by SiCl4 and then H2O. For TEOS, a three-step reaction sequence using TEA, TEOS, and then water offered no advantage, as the TEOS simply displaced the TEA from the silica surface. A two-step reaction involving the addition of TEOS followed by H2O in a second step did lead to silica film growth. However, higher growth rates were obtained when using a mixture of TEOS/TEA in the first step. The hydrolysis of the adsorbed TEOS was also much slower than that of the adsorbed SiCl4, and this was overcome by using a mixture of water/TEA during the second step. While the three-step process with SiCl4 showed a higher linear growth rate than obtained with two-step process using TEOS/TEA, its use was not practical, as the HCl generated led to corrosion of our sc-CO2 delivery system. However, when applying the two-step ALD reaction using TEOS on an MCM-41 powder, a 0.21 nm decrease in pore diameter was obtained after the first ALD cycle whereas further ALD cycles did not lead to further pore size reduction. This was attributed to the difficulty in removal of the H2O in the pores after the first cycle.

Cleavage of the Silicon-Silicon and Silicon-Chlorine Bond oftBu3Si-SiCl3

The reaction of SiCl4 with Na[SitBu3] in thf at −78 °C yielded tBu3Si-SiCl3 along with tBu3SiCl, tBu3Si-SitBu3, and tBu3SiH. After HPLC separation we isolated crystalline tBu3Si-SiCl3 from the eluate (retention time: τ = 39 min). During the work-up process further derivatives of tBu3Si-SiCl3 namely tBu3Si-Si(OH)3 (triclinic space group P-1), tBu3Si-Si(OMe)(OH)2 (monoclinic space group P21/c), and tBu3Si-Si(OMe)2(OH) (monoclinic space group P21/c) crystallize from the eluate. By the reaction of tBu3Si-SiCl3 with K in benzene we obtained the tetrasilatetrahedrane (tBu3Si)4Si4 (tetrasupersilyl-tetrahedro-tetrasilane) along with tBu3Si-SitBu3 and tBu3SiH. In contrast to the reaction in benzene treatment of tBu3Si-SiCl3 with K in thf yielded K[SitBu3]. We further investigated the cleavage of Si−Si bond by treatment of tBu3Si-SiCl3 with [nBu4N]Cl. Thereby tBu3SiCl and [nBu4N]2[Si6Cl14] were formed.

Poly(vinylpyrrolidone) stabilized aluminum nanoparticles obtained by the reaction of SiCl4 with LiAlH4

Isolation and stabilization of Al nanoparticles has been possible by the reaction between SiCl4 and LiAlH4 in the presence of poly(vinylpyrrolidone).

Cationic aza-macrocyclic complexes of germanium(II) and silicon(IV).

[GeCl2(dioxane)] reacts with the neutral aza-macrocyclic ligands L, L = Me3tacn (1,4,7-trimethyl-1,4,7-triazacyclononane), Me4cyclen (1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) or Me4cyclam (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) and two mol. equiv. of Me3SiO3SCF3 in thf solution to yield the unusual and hydrolytically very sensitive [Ge(L)][O3SCF3]2 as white solids in moderate yield. Using shorter reaction times [Ge(Me3tacn)]Cl2 and [Ge(Me3tacn)]Cl[O3SCF3] were also isolated; the preparation of [Ge(Me4cyclen)][GeCl3]2 is also described. The structures of the Me3tacn complexes show κ(3)-coordination of the macrocycle, with the anions interacting only weakly to produce very distorted five- or six-coordination at germanium. In contrast, the structure of [Ge(Me4cyclen)][O3SCF3]2 shows no anion interactions, and a distorted square planar geometry at germanium from coordination to the tetra-aza macrocycle. Crystal structures of the Si(iv) complexes, [SiCl3(Me3tacn)]Y (Y = O3SCF3, BAr(F); [B{3,5-(CF3)2C6H3}4]) and [SiHCl2(Me3tacn)][BAr(F)], obtained from reaction of SiCl4 or SiHCl3 with Me3tacn, followed by addition of either Me3SiO3SCF3 or Na[BAr(F)], contain distorted octahedral cations, with facialκ(3)-coordinated Me3tacn. The open-chain triamine, Me2NCH2CH2N(Me)CH2CH2NMe2 (pmdta), forms [SiCl3(pmdta)][BAr(F)] and [SiBr3(pmdta)][BAr(F)] under similar conditions, containing mer-octahedral cations.

Zinc-silylene complexes.

Reactions of the chlorosilylene [PhC(N(t)Bu)2]SiCl (SiCl) and the aryl and alkyl zincorganyls Zn(C5Me5)2, ZnPh2 and ZnEt2 resulted in the first Zn-silylene complexes. In all reactions the chlorine atom of the silylene and organic groups of the zinc atom are exchanged. By using Zn(C5Me5)2 and ZnPh2 one of the newly formed silylene coordinates to the zinc atom to give [PhC(N(t)Bu)2(η(1)-C5Me5)Si-Zn(η(2)-C5Me5)Cl] and [PhC(N(t)Bu)2PhSi-ZnPh(μ-Cl)]2, respectively. In contrast, the reaction of SiCl with ZnEt2 resulted due the reduced steric demand of the silylene in the disilylene complex [PhC(N(t)Bu)2SiEt]2ZnCl2, in which both ethyl-moieties are exchanged by chlorides and two newly formed ethyl-silylenes coordinate to the zinc atom.

ChemInform Abstract: Crystal Structure and Dimorphism of Silicon Tetraisocyanate Si(NCO)4.

AbstractLiquid Si(NCO)4 is prepared by reaction of SiCl4 and AgNCO in boiling toluene and characterized by Raman and NMR spectroscopy.

ChromiumSilicon Multiple Bonds: The Chemistry of Terminal N‐Heterocyclic‐Carbene‐Stabilized Halosilylidyne Ligands

An efficient method for the synthesis of the first N-heterocyclic carbene (NHC)-stabilized halosilylidyne complexes is reported that starts from SiBr(4). In the first step, SiBr(4) was treated with one equivalent of the N-heterocyclic carbene 1,3-bis[2,6-bis(isopropyl)phenyl]imidazolidin-2-ylidene (SIdipp) to give the 4,5-dihydroimidazolium salt [SiBr(3)(SIdipp)]Br (1-Br), which then was reduced with potassium graphite to afford the silicon(II) dibromide-NHC adduct SiBr(2)(SIdipp)(2-Br) in good yields. Heating 2-Br with Li[CpCr(CO)(3)] afforded the complex [Cp(CO)(2)Cr=SiBr(SIdipp)] (3-Br) upon elimination of CO. Complex 3-Br features a trigonal-planar-coordinated silicon center and a very short CrSi double bond. Similarly, the reaction of SiCl(2)(SIdipp) (2-Cl) with Li[CpCr(CO)(3)] gave the analogous chloro derivative [Cp(CO)(2)Cr=SiCl(SIdipp)] (3-Cl). Complex 3-Br undergoes an NHC exchange with 1,3-dihydro-4,5-dimethyl-1,3-bis(isopropyl)-2H-imidazol-2-ylidene (IMe(2)iPr(2)) to give the complex [Cp(CO)(2)CrSiBr(IMe(2)iPr(2))(2)] (4-Br). Compound 4-Br features a distorted-tetrahedral four-coordinate silicon center. Bromide abstraction occurs readily from 4-Br with Li[B(C(6)F(5))(4)] to give the putative silylidene complex salt [Cp(CO)(2)Cr=Si(IMe(2)iPr(2))(2)][B(C(6)F(5))(4)], which irreversibly dimerizes by means of an Si-promoted electrophilic activation of one carbonyl oxygen atom to yield the dinuclear siloxycarbyne complex [Cp(CO)Cr{(μ-CO)Si(IMe(2)iPr(2))(2)}(2-)Cr(CO)Cp][B(C(6)F(5))(4)](2) (5). All compounds were fully characterized, and the molecular structures of 2-Br-5-Br were determined by single-crystal X-ray diffraction. DFT calculations of 3-Br and 3-Cl and their carbene dissociation products [Cp(CO)(2)Cr=Si-X] (X=Cl, Br) were carried out, and the electronic structures of 3-Br, 3-Cl and [Cp(CO)(2)Cr=Si-X] were analyzed by the natural bond orbital method in combination with natural resonance theory.

ChemInform Abstract: The [Si(S2O7)3]2‐ Anion: A First Example of Octahedral Silicon Coordination by Three Chelating Inorganic Ligands.

AbstractM2[Si(S2O7)3] (M: Na, Cs) is synthesized by reaction of SiCl4 with oleum (65% SO3) in the presence of M2SO4 (glass tubes, 250 °C).

Novel neutral hexacoordinate benzamidinatosilicon(iv) complexes with SiN3OF2, SiN3OCl2, SiN3OBr2, SiN5O and SiN3O3 skeletons

The neutral pentacoordinate monoamidinatosilicon(IV) complex 1 (SiN(2)Cl(3) skeleton) and the neutral hexacoordinate monoamidinatosilicon(IV) complexes 2-9 (SiN(3)OF(2), SiN(3)OCl(2), SiN(3)OBr(2), SiN(5)O and SiN(3)O(3) skeletons) were synthesised and characterised by elemental analyses, single-crystal X-ray diffraction (except for 1) and NMR spectroscopy in the solid state and in solution. Compounds 2-9 contain one bidentate monoanionic N,N'-diisopropylbenzamidinato ligand, one bidentate monoanionic ligand derived from 8-hydroxyquinoline and (i) two identical monoanionic ligands (F, Cl, Br, N(3), NCO, NCS, OSO(2)CF(3)) or (ii) one bidentate dianionic benzene-1,2-diolato ligand. The dynamic behavior of 2-4 (SiN(3)OX(2) skeleton; X = F, Cl, Br) and 9 (SiN(3)O(3)) in solution was studied by multinuclear variable-temperature NMR experiments. Compound 1 was synthesised by reaction of SiCl(4) with the corresponding lithium amidinate, and compound 2 was obtained by reaction of 1 with 8-hydroxyquinoline and triethylamine. Compound 2 served as the starting material in the syntheses of 3-9, in which the two chloro ligands of 2 were substituted by two identical (pseudo)halogeno ligands, two trifluoromethanesulfonato ligands or one benzene-1,2-diolato ligand. Compounds 3 and 4 contain the novel SiN(3)OBr(2) and SiN(3)OF(2) skeletons, while compounds 5-7 are the first neutral hexacoordinate silicon(IV) complexes with an SiN(5)O skeleton.

A Critical Size of Silicon Nano‐Anodes for Lithium Rechargeable Batteries

Due to the high theoretical capacity (ca. 4200 mAhg ) of Si when Li4.4Si is formed, it has been extensively investigated for use as a high-capacity anode material that can replace graphite, which is currently used (372 mAhg ). However, Si exhibits significant volume changes (> 360%) during Li alloying and dealloying. These changes cause cracking and crumbling of the electrode material and a consequent loss of electrical contact between individual particles and hence severe capacity drop. However, such mechanical strain induced by volume change can be reduced by employing smaller particles. To this end, synthetic methods such as spark ablation, aerogel techniques, and sputtering have been employed. Formation of crystalline Si nanoparticles requires higher temperatures due to the more covalent nature of these particles compared to Ge particles, and at low temperature amorphous phases become more common. The first commonly recognized successful production of Si nanoclusters was reported byHeath et al. They showed that Si nanocrystals capped with alkyl groups can be produced by reduction of SiCl4 and RSiCl3 (R=H, C8H17) according to the reaction SiCl4+RSiCl3+Na!Si+NaCl. This process was carried out at high temperature (385 8C) and high pressure (>100 atm) in a steel bomb fitted into a heating mantle. A process that utilizes SiCl4 reduction at room temperature under an inert atmosphere was initially reported by Kauzlarich et al. However, the drawback of their method was that the product obtained at room temperature was not fully crystallized and was severely capped with alkyl terminators. Moreover, an annealing process above 900 8C is required to obtain the crystalline phase. Similar solution syntheses have been reported at low or high temperature after reducing Si salts with LiAlH4 [13,14] or alkyl silanes. However, all of these methods produce a broad particle size distribution or involve aggregation of the nanoparticles. Furthermore, they all yield amounts of material too small for use in anode production for lithium secondary batteries. We now report a synthetic method using reverse micelles at high pressure and temperature in a bomb that produces Si nanoparticles (n-Si) with various particle sizes without aggregation and thus enables the optimal nanoparticle size for use in anode materials to be chosen. Figure 1 shows the XRD pattern and TEM images of n-Si prepared with trimethyloctadecylammonium bromide (OTAB) surfactant. The XRD pattern clearly shows forma-

Reaction of carboxylic acids with tetrachlorosilane

Tetrachlorosilane reacted with carboxylic acids RCOOH (R = Me, Bu, t-Bu) to give the corresponding acid chlorides RCOCl in 75–95% yield. The reactions of SiCl4 with trichloroacetic and 2-fluorobenzoic acids (R = Cl3C, 2-FC6H4) occurred more difficultly, presumably for steric reasons, and the yields of the corresponding acid chlorides were 11 and 22%, respectively. Tetrachlorosilane failed to react with stearic acid under analogous conditions. Products of the reactions of SiCl4 with chloroacetic and benzoic acids RCOOH (R = ClCH2, Ph) were tetraacyloxysilanes Si(OCOR)4, and tetrakis(chloroacetoxy)silane was formed in almost quantitative yield. The reaction of SiCl4 with glutaric acid led to the formation of a rubber-like polymeric material with the composition C5H6Cl2O4Si. The effect of pKa values of carboxylic acids on the direction and mechanism of the examined reaction is discussed.

Novel neutral hexacoordinate silicon(iv) complexes with two bidentate monoanionic benzamidinato ligands

The novel neutral hexacoordinate bis(benzamidinato)silicon(iv) complexes 1-10 (SiN(4)X(2) skeletons; X = F, Cl, Br, C, N, S, Se) were synthesised and characterised by elemental analyses, single-crystal X-ray diffraction (except for 2) and NMR spectroscopy in the solid state and in solution. The dynamic behavior of 1 (SiN(4)Cl(2) skeleton) and 3 (SiN(4)F(2)) was additionally studied by variable-temperature NMR experiments. Compounds 1 and 2 (SiN(4)Br(2)) were obtained by reaction of SiCl(4) and SiBr(4), respectively, with two molar equivalents of the corresponding lithium amidinate. Compound 1 served as the starting material in the syntheses of 3-10, in which the two chloro ligands of 1 were substituted by two (pseudo)halogeno or one bidentate dianionic S,S, S,Se or Se,Se ligand. Compound 4 contains an SiN(4)C(2) skeleton and 5-7 contain an SiN(6) skeleton. With the preparation of 8 (SiN(4)S(2) skeleton), 9 (SiN(4)SSe) and 10 (SiN(4)Se(2)) it could be demonstrated that syntheses of hexacoordinate silicon(iv) complexes with soft chalcogeno ligand atoms are indeed feasible. Compounds 9 and 10 are the first hexacoordinate silicon(iv) complexes with Si-Se bonds.

Tripod Self-Assembled Monolayer on Au(111) Prepared by Reaction of Hydroxyl-Terminated Alkylthiols with SiCl4

Infrared reflection spectroscopy (IRS), single wavelength ellipsometry, and density functional theory were used to elucidate the structure of a molecular tripod self-assembled monolayer (SAM) on polycrystalline gold{111} substrates. The tripod SAM was formed by the reaction of SiCl4 with a densely packed monolayer of 2-mercaptoethanol, 6-mercaptohexanol, and 16-mercaptohexadecanol under inert atmosphere. After reaction with SiCl4, IRS spectra show an intense absorption at approximately 1112 cm(-1) that is attributed to Si-O-C asymmetric stretching vibration of a molecular tripod structure. Harmonic vibrational frequencies computed at the B3LYP/6-311+g** level of theory for the mercaptoethanol tripod SAM closely match the experimental IRS spectra, giving further support for the tripod structure. When rinsed with methanol or water, the Si-Cl-terminated SAM becomes capped with Si-OMe or Si-OH. The silanol-terminated tripod SAM is expected to find use in the preparation of thin zeolite and silica films on gold substrates.

Large‐Scale Synthesis of Magnenium Silicon Nitride Powders at Low Temperature

Magnesium silicon nitride (MgSiN2) powders have been synthesized by the reaction of SiCl4, N2H4·HCl, and Mg in an autoclave at 450°C for 5 h. The yield of the products is calculated to be about 90% according to the amount of SiCl4. X‐ray powder diffraction patterns indicated that the products are orthorhombic MgSiN2 (cell parameters: a=5.252 Å, b=6.426 Å, and c=4.979 Å) together with little amount of Si. The results of scanning electron microscopy and transmission electron microscopy (TEM) observations indicate that the particles have rough surfaces and have diameters in the range of 0.5–3 μm. The high‐resolution TEM image shows clearly resolved fringes separated by 0.248 nm, which corresponds to the (002) d‐spacing of the orthorhombic MgSiN2. The effects of different synthesis conditions on the final formation of MgSiN2 powder, such as the different ratios of the precursors, reaction temperature, and nitrogen sources were also investigated.

High-yield synthesis of single-crystalline 3C–SiC nanowires by a facile autoclave route

Single-crystalline 3C–SiC nanowires have been synthesized in large scale through a one-step autoclave route by the reaction of SiCl 4, (C 5H 5) 2Fe and metallic Na at 500 °C. Electron microscopy investigations show that the nanowires have typical diameters of 15–50 nm, lengths up to several tens of micrometers and grow along the [111] direction. The possible growth mechanism of the nanowires is discussed.

Preparation, spectroscopic characterization, and deprotonation reactions of Si(NHR)4 (R = i-Pr, t-Bu, p-tolyl) — EPR identification of persistent radicals formed by oxidation of polyimidosilicates

Treatment of Cl2Si(NH-t-Bu)2 (6a) with t-BuNH2 in boiling toluene yields trisamino(chloro)silane ClSi(NH-t-Bu)3 (7); formation of the tetraaminosilane Si(NH-t-Bu)4 is not observed. The reaction of SiCl4 with 4 equiv. of LiNHR produces the corresponding tetraaminosilanes Si(NHR)4 (2a, R = i-Pr; 2b, R = t-Bu; 2c, R = p-tol) in good yields. When the sterically demanding adamantyl derivative LiHNAd is employed, only disubstitution occurs to form Cl2Si(NHAd)2 (6b). Oxidation of the dimeric imidosilicates {Li3[Si(NR)3(NHR)]·THF}2 (3a, R = i-Pr; 3b, R = t-Bu) with 1 mol of iodine produces the persistent radicals {Li2[Si(NR)3(NHR)]·LiI·3THF}·, which, on the basis of EPR spectra, exist as SiN3Li3I cubes in solution. The spirocyclic tetraimidosilicate monoanion radical {[(THF)2Li(µ-Nnaph)2Si(µ-Nnaph)2Li(THF)2]}–· (10) is formed upon oxidation of the tetralithiated species {Li4[Si(Nnaph)4]·4Et2O} (1) and {[Li(12-crown-4)]2[(Et2O)2Li(µ-Nnaph)2Si(µ-Nnaph)2Li(Et2O)2]} (8) with iodine. The spectroscopic characterization of hexa(amino)disiloxane (t-BuNH)3SiOSi(NH-t-Bu)3 (14) formed from the reaction of Cl3SiOSiCl3 with 6 equiv. of LiNH-t-Bu is discussed. Key words: imido ligands, silicate, radicals, EPR spectra, lithium.