- DISILANE-, CARBODISILANE-AND OLIGOSILANE CLEAVAGE WITH CLEAVAGE COMPOUND ACTING AS CATALYST AND HYDROGENATION SOURCE
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The invention relates to a process for the manufacture of monosilanes of formula (I): MexSiHyClz (I), comprising: the step of subjecting a silane substrate (methyldisilanes, methyloligosilanes, or carbodisilanes) to a cleavage reaction of the silicon-silicon bond(s) or the silicon- carbon bonds in silane substrates the reaction involving a cleavage compound selected from a quaternary Group 15 onium compound R4 QX, a heterocyclic amine, a heterocyclic ammonium halide, or a mixture of R3P and RX. The starting material disilanes to be cleaved has the formula (II): MemSi2HnClo (II) The starting material oligosilanes to be cleaved have the general formula (III): MepSiqHrCIs (II I), The starting material carbodisilanes to be cleaved have the general formula (IV): (MeaSiHbCle)-CH2-(MecSiHdClf) (IV)
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Page/Page column 44
(2019/04/16)
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- Synthesis of Functional Monosilanes by Disilane Cleavage with Phosphonium Chlorides
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The Müller–Rochow direct process (DP) for the large-scale production of methylchlorosilanes MenSiCl4?n (n=1–3) generates a disilane residue (MenSi2Cl6?n, n=1–6, DPR) in thousands of tons annually. This report is on methylchlorodisilane cleavage reactions with use of phosphonium chlorides as the cleavage catalysts and reaction partners to preferably obtain bifunctional monosilanes MexSiHyClz (x=2, y=z=1; x,y=1, z=2; x=z=1, y=2). Product formation is controlled by the reaction temperature, the amount of phosphonium chloride employed, the choice of substituents at the phosphorus atom, and optionally by the presence of hydrogen chloride, dissolved in ethers, in the reaction mixture. Replacement of chloro by hydrido substituents at the disilane backbone strongly increases the overall efficiency of disilane cleavage, which allows nearly quantitative silane monomer formation under comparably moderate conditions. This efficient workup of the DPR thus not only increases the economic value of the DP, but also minimizes environmental pollution.
- Santowski, Tobias,Sturm, Alexander G.,Lewis, Kenrick M.,Felder, Thorsten,Holthausen, Max C.,Auner, Norbert
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supporting information
p. 3809 - 3815
(2019/02/13)
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- Conductive molecular silicon
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Bulk silicon, the bedrock of information technology, consists of the deceptively simple electronic structure of just Si-Si σ bonds. Diamond has the same lattice structure as silicon, yet the two materials have dramatically different electronic properties. Here we report the specific synthesis and electrical characterization of a class of molecules, oligosilanes, that contain strongly interacting Si-Si σ bonds, the essential components of the bulk semiconductor. We used the scanning tunneling microscope-based break-junction technique to compare the single-molecule conductance of these oligosilanes to those of alkanes. We found that the molecular conductance decreases exponentially with increasing chain length with a decay constant β = 0.27 ± 0.01 A-1, comparable to that of a conjugated chain of C = C π bonds. This result demonstrates the profound implications of σ conjugation for the conductivity of silicon.
- Klausen, Rebekka S.,Widawsky, Jonathan R.,Steigerwald, Michael L.,Venkataraman, Latha,Nuckolls, Colin
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supporting information; experimental part
p. 4541 - 4544
(2012/04/23)
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- Reactions of dodecamethylcyclohexasilane and polydimethylsilane with metal chlorides
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The reactions of dodecamethylcyclohexasilane and high-molecular-weight polydimethylsilane with chlorides of I, II, IV-VI and VIII Group metals at high temperature in the absence of a solvent were studied. The interaction of (Me2Si)6 with metal chlorides proceeds with the cleavage of Si-Si and Si-C bonds with the formation of chloro derivatives of linear and cyclic permethyloligosilanes. The reactions of polydimethylsilane with metal chlorides afford mixtures of α,ω-dichlorooligosilanes, Cl(Me2Si)nCl (n=2-9). The influence of the reaction conditions (temperature, reaction time and the reagent ratio) on the composition and yields of the reaction products was examined.
- Chernyavskii,Larkin,Chernyavskaya
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- Synthesis of α,ω-dichloropermethyloligosilanes by reactions of polydimethylsilane with metal chlorides
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The reactions of high-molecular-weight polydimethylsilane with metal chlorides in variable oxidation states at high temperature in the absence of a solvent afford mixtures of α,ω-dichloropermethyloligosilanes Cl(Me2Si)mCl (m = 2-9). The influence of the reaction conditions (temperature, reaction time, and the reagent ratio) on the composition and yields of the reaction products was examined.
- Chernyavskii, A. I.,Chernyavskaya, N. A.
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p. 1751 - 1753
(2007/10/03)
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- Synthesis of dichloro derivatives of linear and cyclic permethyloligosilanes and cyclolinear permethylpolysilane-siloxanes and permethylpolyoxysilane based on them
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The reactions of dodecamethylcyclohexasilane with chlorides of I, II, IV-VI, and VIII Group metals were studied as a promising approach to the synthesis of functional oligosilanes. When cyclohexasilane reacts with metal chlorides without a solvent at elevated temperatures, the process is intensified and, in some cases, the selectivity of formation of chloro derivatives of linear and cyclic permethyloligosilanes increases. The cyclolinear permethylpolysilane-siloxanes were prepared by heterofunctional polycondensation of the resulting oligosilanes with bifunctional cyclic and linear permethyloligosiloxanes. Cyclolinear permethylpolyoxysilane was synthesized for the first time by the reaction of 1,3-dihydroxycyclo-hexasilane with 1,3-dichlorohexamethyltrisilane.
- Chernyavskii, A. I.,Larkin, D. Yu.,Chernyavskaya, N. A.
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p. 175 - 180
(2007/10/03)
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- Synthesis of α,ω-dihalopermethyloligosilanes and silane-siloxane copolymers
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α,ω-Dibromopermethyloligosilanes, Br(SiMe2)nBr (n = 2-4, 6), were prepared by the reaction of dodecamethylcyclohexasilane with bromine. The reaction of (Me2Si)6 with MCl4 (M = Sn, Ti) proceeds with the cleavage of Si-Si-and Si-C-bonds with the formation of α,ω-dichloropermethyloligosilanes, Cl(SiMe2)nCI (n = 2-4, 6), and chloro derivatives of cyclohexasilane, ClmSi6Me12-m (m = 1, 2). Silane-siloxane copolymers of regular structure were obtained by heterofunctional copolycondensation of α,ω-dihalopermethyloligosilanes with 1,5-dihydroxyhexamethyltrisiloxane.
- Chernyavskii,Zavin
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p. 1449 - 1453
(2007/10/03)
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- Methylchlorooligosilanes as products of the basecatalysed disproportionation of various methylchlorodisilanes
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The methylchlorodisilanes SiCl2Me-SiCl2Me (1), SiCl2Me-SiClMe2 (2) and SiClMe2-SiClMe2 (3) disproportionate in the presence of a basic catalyst into methylchloromonosilanes and various methylchlorooligosilanes. Oligosilanes involving up to seven silicon atoms were identified by means of 29Si-, 13C-1H-NMR and GC-MS measurements. Formation of methylchlorooligosilanes is thought to take place via silylene intermediates.
- Herzog,Richter,Brendler,Roewer
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p. 221 - 228
(2007/10/03)
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- The behaviour of medium-sized permethylated cyclosilanes towards SOCl2 and SOCl2-HC(OCH3)3
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Treatment of Si6Me12 with SOCl2 in various solvents gives α,ω-dichloropermethylpolysilanes (nSi = 2,3,4,6) at temperatures above 80 deg C.In contrast to an earlier report, treatment of the α,ω-dichloropermethylpolysilanes with HC(OCH3)3 in the presence of SOCl2 does not give Si6Me12.
- Jenkner, P.K.,Spielberger, A.,Hengge, E.
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p. 161 - 164
(2007/10/02)
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- Chlorine Abstraction from Chloromethanes by Dimethylsilanediyls
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Photolysis of dodecamethylcyclohexasilane in carbon tetrachloride gives hexachloroethane; its formation is a result of chlorine abstraction from carbon tetrachloride by dimethylsilanediyl.
- Nakao, Ren,Oka, Kunio,Dohmaru, Takaaki,Nagata, Yoshio,Fukumoto, Tsugio
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p. 766 - 768
(2007/10/02)
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- ?-BOND CONJUGATION IN POLYSILANES, A PES SCALED FREE-ELECTRON APPROACH FOR THE INTERPRETATION OF SKELETAL CLEAVAGE REACTION
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The ?-orbital energies calculated by the simple free-electron model with a parametrization procedure recently by Von Szentpaly correlate very closely with the ?-band positions of the corresponding photoelectron spectra.For the ?-orbitals of three series of molecules: H(CH2)nH (n=2-4); H(SiH2)nH (n=2-5); Me(SiMe2)nMe (n=2-4) the FEMO model yields a standard error (SE) of 0.060 eV.Compared with HMO results (LCGO, LCBO and Sandorfy C) the correlation is significantly improved.The free-electron results are more accurate than those obtained using the PPP, CNDO/2, MINDO/3, SAMO and ab initio methods.The free-electron frontier orbital densities were successfully used to account for features of the skeletal cleavage reactions of polysilanes.
- Herman, Aleksander,Dreczewski, Boguslaw,Wojnowski, Wieslaw
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