Presence Of Silane Research Articles

Matrix Reactivity of Zn, Cd, or Hg Atoms (M) in the Presence of Silane: Photogeneration and Characterization of the Insertion Product HMSiH3in a Solid Argon Matrix

Matrix-isolation experiments give evidence that broad-band UV−vis irradiation (200 ≤ λ ≤ 800 nm) of an Ar matrix doped with SiH4 and a group 12 metal atom M (M = Zn, Cd, or Hg) induces metal insertion into an Si−H bond to give the silyl metal hydride molecule HMSiH3 as the primary product. Si2H6 is a second product, irrespective of the identity of M, while the binary hydride MH2 is also formed when M = Zn or Cd. The products have been identified by their IR spectra and experiments with SiD4, together with the results of quantum chemical calculations, have provided the means of authentication. The properties of the HMSiH3 molecules are compared with those of related species, and consideration is given to how the products come to be formed.

Asymmetric Cyclization of ω‐Formyl‐1,3‐dienes Catalyzed by a Zerovalent Nickel Complex in the Presence of Silanes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Asymmetric rhodium carbene insertion into the SiH bond: identification of new dirhodium(II) carboxylate catalysts using parallel synthesis techniques

Decomposition of methyl 2-diazophenylacetate in the presence of silanes and a chiral dirhodium(II) catalyst results in SiH insertion of the intermediate carbenoid with varying degrees of enantioselectivity. New chiral dirhodium(II) carboxylate catalysts were identified using solution phase parallel synthesis techniques.

Influence of the synthesis conditions on the photoluminescence of silica gels

The photoluminescence spectra of silica xerogel samples synthesized with ethanol as solvent and xerogel where the ethanol was exchanged by water before drying are reported. In addition, the photoluminescence spectrum of a silica cryogel synthesized with tert-butanol as solvent was investigated. The samples were modified by formamide. Bands at 2.00, 2.20, 2.32 and 2.46 eV were identified. In the photoluminescence spectra of all samples. The band at 2.00 eV is caused by the presence of silane, and the band at 2.20 eV is connected with the nonstoichiometric composition of silica. The photoluminescence band at 2.32 eV was found to originate from the organic groups of the solvent. The origin of this band are E? defect centers, which is a prominenet paramagnetic defect in conventional a ? SiO2.

Influence of the synthesis conditions on the photoluminescence of silica gels

The photoluminescence spectra of silica xerogel samples synthesized with ethanol as solvent and xerogel where the ethanol was exchanged by water before drying are reported. In addition, the photoluminescence spectrum of a silica cryogel synthesized with tert-butanol as solvent was investigated. The samples were modified by formamide. Bands at 2.00, 2.20, 2.32 and 2.46 eV were identified. In the photoluminescence spectra of all samples. The band at 2.00 eV is caused by the presence of silane, and the band at 2.20 eV is connected with the nonstoichiometric composition of silica. The photoluminescence band at 2.32 eV was found to originate from the organic groups of the solvent. The origin of this band are E’ defect centers, which is a prominenet paramagnetic defect in conventional a – SiO2.

Photoactivated isomerization of linear olefins.

The photocatalyzed (350 nm) isomerization of linear olefins catalyzed by platinum(II) bis(acetylacetonato) [Pt(acac)(2)] in the presence of silanes was studied. Catalytic activity depends on the silane. Triphenylsilane is the most reactive silane studied, with more than 98% isomerization of the alkene occurring after 20-min irradiation. There is no concomitant hydrosilylation. The mechanism has been investigated and a metal hydride addition-elimination mechanism proposed.

Asymmetric cyclization of omega-formyl-1,3-dienes catalyzed by a zerovalent nickel complex in the presence of silanes.

A nickel(0)-catalyzed asymmetric cyclization of omega-formyl-1,3-diene in the presence of silanes in which five- or six-membered carbocycles or pyrrolidine derivatives were afforded up to 86% ee by the use of (2R,5R)-2,5-dimethyl-1-phenylphospholane as a monodentate chiral ligand was investigated. The reaction course of this asymmetric cyclization can be explained for by two possible mechanisms: one in which the cyclization proceeds via a pi-allylnickel intermediate to produce a cyclized product having an internal olefin in the side chain, and one in which the cyclization proceeds via a sigma bond metathesis of silane and the nickel-oxygen bond of oxanickelacycle to produce a cyclized compound having a terminal olefin and/or an internal olefin in the side chain. It was speculated that both of these mechanisms operate in this asymmetric cyclization depending upon the nature of silanes and the reaction conditions.

Ab initio studies of the reactions of Cu(2S, 2D, and 2P) with SiH4 and GeH4

The interactions of Cu(2S:3d104s1, 2D:3d94s2, and 2P:3d104p1) with SiH4 and GeH4 were studied by means of Hartree–Fock–SCF and multiconfigurational-SCF followed by variational and multireference second order Möller–Plesset perturbational configuration interaction (CIPSI) calculations, using relativistic effective core potentials. The Cu atom in its P2(3d104p1) state is inserted in the Si–H and Ge–H bonds. In both interactions their corresponding 5 2A′ potential energy surfaces are initially attractive and become repulsive only after having encountered the avoided crossing region with the initially repulsive 4 2A′ surface adiabatically linked with the Cu(2D:3d94s2)–SiH4(GeH4) fragments. The three A′2 curves derived from the interaction of the Cu(2D:3d94s2) atom with silicon (or germane) molecule are initially repulsive. Each one of them shows two avoided crossings and its lowest lying 2 2A′ curve goes sharply down until it meets the X 2A′ curve adiabatically linked with the Cu(2S:3d104s1)+SiH4(GeH4) asymptotes. The 2 2A′ curve becomes repulsive after the avoided crossing with the X 2A′ curve. The lowest-lying X 2A′ potential leads to the HCuZH3 X 2A1 (Z=Si, Ge) intermediate molecule. This intermediate molecule, diabatically correlated with the Cu(2P:3d104p1)+ZH4 fragments which lie 5.8 and 1.6 kcal/mol, respectively, above the ground state reactants, have been carefully characterized as well as the dissociation channels leading to the CuH+ZH3 and H+CuZH3 products. These products are reached from the HCuZH3 intermediates without activation barriers. This work suggests that the simultaneous photoexcitation of the Cu atom in presence of silane and germane molecules in the gas phase could be used to produce better quality a-SiGe:H thin films.

Role of silane coupling agents for performance improvement of poly(vinyl acetate)/tetraethyl orthosilicate hybrid composites prepared by a sol–gel process

AbstractSilica based poly(vinyl acetate)/inorganic hybrid composites were prepared via a sol–gel process under acidic conditions. Because the phase behaviour of the hybrids is greatly affected by weak interactions such as hydrogen bonding between organic polymer and inorganic network, two types of silane coupling agent (vinyl trimethoxysilane and 3‐(trimethoxysilyl)propyl methacrylate) were used to introduce specific interactions and to control phase behaviour in the interface between polymer and silica. The interfacial interactions between polymer and inorganic segment in the presence of silane have been investigated by Fourier transform infrared spectroscopy. Thermogravimetric analysis shows that the thermal stability of organic components in the hybrids is enhanced by addition of silane coupling agents. Scanning electron micrographs reveal that silica particles are homogeneously dispersed in the organic matrix as a result of the specific interactions.© 2001 Society of Chemical Industry

Propylene Ziegler-Natta Polymerization: Numbers and Propagation Rate Constants for Stereospecific and Non-Stereospecific Centers

The data on the number of active centers (Cp) and values of propagation rate constants (Kp) have been obtained for stereospecific and non-stereospecific centers at propylene polymerization with catalytic systems of various composition: TiCl3-AlEt3 (I), TiCl4/D/MgCl2-AlEt3 (II), TiCl4 /D/MgCl2-AlEt3-TES (III), where D – dibutyl phthalate, TES – tetraethoxysilane. The Cp and Kp values were determined by 14CO quenching method at the polymerization in the absence and the presence of hydrogen. The Cp and Kp values were determined for three PP fractions: boiling pentane soluble fraction (atactic PP), boiling heptane soluble fraction (stereoblock PP) and boiling heptane insoluble fraction (isotactic PP). The following results are obtained. (i) The Kp values increase in the following order: atactic centers < stereoblock centers < isotactic centers (from ≈ 200 to ≈ 3·103 l/mol·s, 70°C) for all catalysts studied. (ii) The respective Kp values do not differ essentially with the change of the catalyst composition (systems I, II, III). (iii) As the external donor is introduced in TMC (system III), the portion of stereospecific active centers increases (from 34 to 62%), but the total number of active centers changes insignificantly. Most likely the non-stereospecific active centers transform into stereospecific ones in the presence of silane.

ChemInform Abstract: Development, Synthetic Scope, and Mechanistic Studies of the Palladium‐Catalyzed Cycloisomerization of Functionalized 1,6‐Dienes in the Presence of Silane.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Reductive Cyclization of Dimethyl Diallylmalonate Catalyzed by Palladium-Bisoxazoline Complexes in the Presence of Silane and Water.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Development, Synthetic Scope, and Mechanistic Studies of the Palladium-Catalyzed Cycloisomerization of Functionalized 1,6-Dienes in the Presence of Silane

A 1:1 mixture of the π-allyl palladium complex (η3-C3H5)Pd(Cl)PCy3 (1a) and NaB[3,5-C6H3(CF3)2]4 in the presence of HSiEt3 catalyzed the cycloisomerization of diethyl diallylmalonate (2b) to form 4,4-dicarbomethoxy-1,2-dimethylcyclopentane (3b) in 98% yield with 98% isomeric purity. The procedure tolerated a range of functionality including esters, ketones, sulfones, protected alcohols, and substitution at the allylic and terminal olefinic carbon atoms. Cycloisomerization of 2b obeyed zero-order kinetics to >3 half-lives with initial formation of 1,1-dicarboethoxy-4-methyl-3-methylenecyclopentane (4b), followed by secondary isomerization to 3b. Deuterium labeling studies revealed that the conversion of 2b to 4b was accompanied by significant H/D exchange, consistent with an addition/elimination pathway coupled with facile H/D exchange of the Pd−H(D) intermediates with free silane.

Reductive Cyclization of Dimethyl Diallylmalonate Catalyzed by Palladium−Bisoxazoline Complexes in the Presence of Silane and Water

Reaction of dimethyl diallylmalonate (1) with a stoichiometric amount of water and HSiEt3 catalyzed by a 1:1 mixture of (N−N)Pd(Me)Cl [N−N = 4,4‘-dibenzyl-4,5,4‘,5‘-tetrahydro-2,2‘-bisoxazoline] (4a) and NaBAr4 [Ar = 3,5-C6H3(CF3)2] at 50 °C in 1,2-dichloroethane led to the isolation of a 4.4:1 mixture of trans-dimethyl-3,4-dimethylcyclopentane-1,1-dicarboxylate (5) (≥ 95% de, 38% ee) and dimethyl dipropylmalonate (6) in 88% combined yield. Reaction of 1 with a stoichiometric mixture of D2O/HSiEt3 or H2O/DSiEt3 catalyzed by 4a/NaBAr4 formed predominantly the 5-d1 isotopomer, which possessed a single deuterium atom at one of the exocyclic methyl groups. Reaction of 1 with a stoichiometric mixture of D2O/DSiEt3 catalyzed by 4a/NaBAr4 formed predominantly the 5-d2 isotopomer with a single deuterium atom at each of the exocyclic methyl groups.

Deposition and Characterization of Undoped and Boron and Phosphorus Doped ( SixGe1 − x O 2 ) Glass Films

Glass films of undoped and boron and phosphorus doped glass films were prepared by plasma enhanced chemical vapor deposition using germane, silane, phosphine, diborane, and oxygen as precursor gas sources with argon as a carrier gas. Film synthesis was carried out at 200°C using a dual‐coil, inductively coupled plasma system. The presence of silane was not necessary to catalyze the decomposition of germane in the plasma environment as required in a strictly thermal environment. The index of refraction of undoped films changes linearly with composition, and deposition rate was nearly constant across all film compositions. Oxide film composition was determined using energy dispersive X‐ray spectroscopy and Auger energy spectroscopy. For undoped films, solid‐phase composition varied linearly with silane gas‐phase composition. For doped compositions, phosphorus mole fraction in the solid phase was up to a factor of two greater than that present in the gas phase. In contrast to this, the quantity of boron incorporated into the solid phase was a factor of five to six less than present in the gas phase. When both dopants were present in the gas phase, the amount of each incorporated into the solid phase was similar to that in the gas phase. © 2000 The Electrochemical Society. All rights reserved.

A Novel Asymmetric Cyclization of ω-Formyl-1,3-dienes Catalyzed by a Zerovalent Nickel Complex in the Presence of Silanes

A Novel Asymmetric Cyclization of ω-Formyl-1,3-dienes Catalyzed by a Zerovalent Nickel Complex in the Presence of Silanes

Ab initio studies of the reactions of M(1S,3P, and 1P) with GeH4 (M=Cd, Hg)

The interaction of Cd(1S:5s2, 3,1P:5s15p1) and Hg(1S:6s2, 1,3P:6s16p1) with GeH4 were studied by means of Hartree–Fock self-consistent field (SCF) and multiconfigurational SCF plus variational and multireference second order Möller–Plesset perturbational configuration interaction (CIPSI) calculations, using relativistic effective core potentials. It was found that both metal atoms in their 3P(ns1np1) state break spontaneously the Ge–H bond of the germane molecule, giving place to the MH+GeH3 (M=Cd, Hg) final products. For both atoms, the 1P(ns1np1) state is also inserted in the Ge–H bond and the corresponding interaction surface shows an avoided crossing with the lowest-lying X 1A′ potential surface adiabatically linked with the M(1S:ns2)+GeH4. This interaction leads eventually to the MH+GeH3 products. The HMGeH3 X 1A1 (M=Cd, Hg) intermediate molecules, diabatically correlated with the M(1P:ns1np1)+GeH4, which lie 13.6 and 21 kcal/mol, respectively, above the ground state reactants, have been carefully characterized as well as the dissociation channels leading to the MH+GeH3 and H+MGeH3 products. These products are reached from the HMGeH3 intermediates without activation barriers. Accurate energy differences for all these species are reported. This work suggests that the simultaneous photoexcitation of Cd and Hg atoms in the presence of silane and germane molecules in the gas phase could be used to produce better quality a-SiGe:H thin films.

A Stereospecific Access to Allylic Systems Using Rhodium(II)−Vinyl Carbenoid Insertion into Si−H, O−H, and N−H Bonds

Rhodium-catalyzed decomposition of α-vinyldiazoesters in the presence of silanes, alcohols, ethers, amines, and thiols have been shown to produce the corresponding α-silyl, α-hydroxy, α-alkoxy, α-amino, and α-thioalkoxy esters in generally good yield with a complete retention of the stereochemistry of the double bond of the diazo precursor. An extension of the process in homochiral series has also been devised using either a chiral auxiliary attached to the ester function or achiral α-vinyldiazoesters and Doyle's chiral catalyst Rh2(MEPY)4. In the former approach, pantolactone as chiral auxiliary gave diastereoselectivities of up to 70%, while the second approach produced the desired allylsilane with ee as high as 72%. On the other hand, Rh2(MEPY)4-catalyzed insertion into the O−H bond of water led to poor or no enantioselectivity in good agreement with recent literature reports.

Laser-stimulated processes in metal carbonyls for metal-based film synthesis

The laser induced decomposition chemistry of metal carbonyls has been the subject of numerous investigations. In the area of metal film deposition, the gas-phase photolysis of carbonyls is an area of current interest, owing to their large absorption cross sections in the UV wavelength range. However, detailed analysis showed that the film composition reflects additional thermal and photochemical surface processes, which need to be further elucidated. Although leading to higher film purities, the thermal decomposition of carbonyls in the presence of a laser heated substrate was less explored. Examples of laser-stimulated deposition processes from metal carbonyls are presented, including the UV photolysis of Mo(CO) 6 at long exposure times and the thermal decomposition of Cr(CO) 6. Some aspects related to Mo(CO) 6 decomposition in presence of silane are discussed, in connection with the synthesis of new metal-modified polymers. A comparative analysis of the properties of films obtained from Fe(CO) 5 by photolytic and thermal laser-induced processes indicates that specific growth mechanisms influence the film structure and chemical composition.

一酸化窒素によるオレフィン類の窒素化反応

Nitrosation of various α, β-unsaturated carbonyl compounds with nitrogen monoxide or butyl nitrite was achieved in the presence of silane and a catalytic amount of N, N' -bis (2-ethoxycarbonyl-3- oxobutylidene) ethylenediaminatocobalt (II) complex catalyst. In the presence of a catalytic amount of tris (1, 3-diketonato) iron (III) complex, various terminal and 1, 2-disubstituted olefins were converted into the corresponding nitroso alkane dimers in fairly good yields on treatment with phenylsilane and butyl nitrite.Nitration of various terminal olefins into corresponding nitro olefins were performed on treatment with nitrogen monoxide. Nitroalcohols, minor coproducts, were dehydrated to yield nitro olefins by the subsequent treatment with acidic activated aluminum. By GC analysis, evolution of an equimolar amount of nitrogen gas was observed during the present nitration. A possible reaction pathway including the formation of nitro nitroso compounds, key intermediates, was proposed.