- Effect of ether on regioselectivity in hydrosilylation of 1,5-hexadiene with chlorohydrosilanes catalyzed by homogeneous platinum catalysts
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Hydrosilylation of 1,5-hexadiene with chlorohydrosilanes catalyzed by homogeneous platinum catalyst to produce 5-hexenylchlorosilanes was studied. The presence of ether additives was highly effective in improving the regioselectivity and the yield. The formation of a double-bond rearrangement isomer, cis-, or trans-4-hexenylchlorosilanes, during the hydrosilylation was reduced drastically, as well. Copyright Taylor & Francis Group, LLC.
- Saiki, Takeaki
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experimental part
p. 1556 - 1563
(2009/10/14)
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- Alkenylsilane structure effects on mononuclear and binuclear organotitanium-mediated ethylene polymerization: Scope and mechanism of simultaneous polyolefin branch and functional group introduction
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Alkenylsilanes of varying chain lengths are investigated as simultaneous chain-transfer agents and comonomers in organotitanium-mediated olefin polymerization processes. Ethylene polymerizations were carried out with activated CGCTiMe2 and EBICGCTi2Me4 (CGC = Me2Si(Me4C5)(NtBu); EBICGC = (μ-CH2CH2-3,3′){(η5-indenyl)[1- Me2Si(tBuN)]}2) precatalysts in the presence of allylsilane, 3-butenylsilane, 5-hexenylsilane, and 7-octenylsilane. In the presence of these alkenylsilanes, high polymerization activities (up to 10 7 g of polymer/(mol of Ti-atm ethylene·h)), narrow product copolymer polydispersities, and substantial amounts of long-chain branching are observed. Regardless of Ti nuclearity, alkenylsilane incorporation levels follow the trend C8H15SiH3 6H 11SiH3 ≈ C4H7SiH3 3H5SiH3. Alkenylsilane comonomer incorporation levels are consistently higher for CGCTiMe2-mediated copolymerizations (up to 54%) in comparison with EBICGCTi2Me 4-mediated copolymerizations (up to 32%). The long-chain branching levels as compared to the total branch content follow the trend C 3H5SiH3 4H7SiH 3 ≈ C6H11SiH3 ≈ C 8H15SiH3, with gel permeation chromatography-multi-angle laser light scattering-derived branching ratios (gM) approaching 1.0 for C8H15SiH3. Time-dependent experiments indicate a linear increase of copolymer Mw with increasing polymerization reaction time. This process for producing long-chain branched polyolefins by coupling of an α-olefin with a chain-transfer agent in one comonomer is unprecedented. Under the conditions investigated, alkenylsilanes ranging from C3 to C8 are all efficient chain-transfer agents. Ti nuclearity significantly influences silanolytic chain-transfer processes, with the binuclear system exhibiting a sublinear relationship between Mn and [alkenylsilane]-1 for allylsilane and 3-butenylsilane, and a superlinear relationship between Mn and [alkenylsilane]-1 for 5-hexenylsilane and 7-octenylsilane. For the mononuclear Ti system, alkenylsilanes up to C 6 exhibit a linear relationship between Mn and [alkenylsilane]-1, consistent with a simple silanolytic chain termination mechanism.
- Amin, Smruti B.,Marks, Tobin J.
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p. 2938 - 2953
(2007/10/03)
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- Alkenylsilane effects on organotitanium-catalyzed ethylene polymerization. Toward simultaneous polyolefin branch and functional group introduction
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The comonomer 5-hexenylsilane is introduced into organotitanium-mediated ethylene polymerizations to produce silane-terminated ethylene/5-hexenylsilane copolymers. The resulting polymers were characterized by 1H and 13C NMR, GPC, and DSC. High activities (up to 107 g polymer/(mol Ti·atm ethylene·h)) and narrow polydispersities are observed in the polymerization/chain transfer process. Ethylene/5-hexenylsilane copolymer molecular weights are found to be inversely proportional to 5-hexenylsilane concentration, supporting a silanolytic chain transfer mechanism. Control experiments indicate that chain transfer mechanism by 5-hexenylsilane is significantly more efficient than that of n-hexylsilane for organotitanium-mediated ethylene polymerization. The present study represents the first case in which a functionalized comonomer is efficiently used to effect both propagation and chain transfer chemistry during olefin polymerization. Copyright
- Amin, Smruti B.,Marks, Tobin J.
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p. 4506 - 4507
(2007/10/03)
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- PREPARATION OF A HALOSILYLATED CHAIN HYDROCARBON
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A method for the preparation of a chain hydrocarbon halosilylated at its terminal carbon atom or terminal carbon atoms by subjecting a diene-type compound and a hydrogenhalosilane to a hydrosilylation reaction in the presence of a hydrosilylation catalyst and an ether compound having no aliphatic triple bond.A method of conducting a hydrosilylation reaction between a diene-type compound that has vinyl groups on both terminals and a hydrogenhalosilane in the presence of a hydrosilylation catalyst and an ether compound having no aliphatic triple bond.
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Page/Page column 18-19
(2008/06/13)
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- Method for controlling hydrosilylation in a reaction mixture
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This invention discloses a method of controlling hydrosilylations in a reaction mixture by controlling the solution concentration of oxygen in the reaction mixture, relative to any platinum present in the reaction mixture. This invention further discloses a method for controlling isomerization in linear or branched alkenyl compounds having at least 4 carbon atoms during a hydrosilylation reaction by introducing a controlled amount of oxygen into the alkenyl compounds during the hydrosilylation. This invention further discloses a method for producing dicycloalkylsubstituted silanes by reacting a halo-or alkoxy-silane with a unsaturated cycloalkenyl compound in the presence of oxygen and a hydrosilylation catalyst.
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