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Francisco J. Rodriguez - One of the best experts on this subject based on the ideXlab platform.
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further studies on styrene styrene derivative copolymerizations using combined diphenylzinc additive initiator systems
Polymer International, 2005Co-Authors: F M Rabagliati, Carlos J Caro, Francisco J. Rodriguez, Monica A Perez, Nicolas CrispelAbstract:A combination of diphenylzinc, a metallocene and methylaluminoxane (Ph2Zn-metallocene-MAO) is a suitable initiator system for the polymerization of styrene and for its copolymerization with para-alkyl substituted styrenes. This paper reports new experimental results which reinforce our previous findings indicating that polymerization processes are initiated by monomer coordination to active species resulting from these particular combined systems. Polymerization propagates by a cationic pathway. Further to our previous observation that the I+ inductive effect of para-substituents in styrene improves conversion to polymer, we now find that methyl substitution on the vinyl double bond of styrene, in spite of the I+ inductive effect and as a result of increased steric hindrance, makes the polymerization process difficult. On the other hand, the replacement of titanocenes by Zirconocenes or hafnocenes generates Ph2Zn-metallocene-MAO initiator systems which are also able to induce homo- and copolymerization, but with lower yields and producing practically amorphous polymers. The efficiency of our Ph2Zn-metallocene-MAO initiator systems follows the order titanocene > Zirconocene > hafnocene, at least for the studied metallocenes. Copyright © 2004 Society of Chemical Industry
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Further studies on styrene/styrene derivative copolymerizations using combined diphenylzinc-additive initiator systems †
Polymer International, 2004Co-Authors: F M Rabagliati, Carlos J Caro, Francisco J. Rodriguez, Monica A Perez, Nicolas CrispelAbstract:A combination of diphenylzinc, a metallocene and methylaluminoxane (Ph2Zn-metallocene-MAO) is a suitable initiator system for the polymerization of styrene and for its copolymerization with para-alkyl substituted styrenes. This paper reports new experimental results which reinforce our previous findings indicating that polymerization processes are initiated by monomer coordination to active species resulting from these particular combined systems. Polymerization propagates by a cationic pathway. Further to our previous observation that the I+ inductive effect of para-substituents in styrene improves conversion to polymer, we now find that methyl substitution on the vinyl double bond of styrene, in spite of the I+ inductive effect and as a result of increased steric hindrance, makes the polymerization process difficult. On the other hand, the replacement of titanocenes by Zirconocenes or hafnocenes generates Ph2Zn-metallocene-MAO initiator systems which are also able to induce homo- and copolymerization, but with lower yields and producing practically amorphous polymers. The efficiency of our Ph2Zn-metallocene-MAO initiator systems follows the order titanocene > Zirconocene > hafnocene, at least for the studied metallocenes. Copyright © 2004 Society of Chemical Industry
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styrene styrene derivative and styrene 1 alkene copolymerization using ph2zn additive initiator systems
Macromolecular Symposia, 2004Co-Authors: Rodrigo A. Cancino, Monica A Perez, Francisco J. RodriguezAbstract:Diphenylzinc-metallocene-MAO initiator systems have proven to be effective initiator systems for styrene and for substituted styrenes as well as for their styrene/(styrene-derivative) copolymerization. Titanocene produced almost pure syndiotactic polymers while Zirconocenes gave atactic polystyrene together with a low content, less than 20%, of syndiotactic polystyrene. Systems including a Zirconocene, particularly ethenyl(bisindenyl)zirconium dichloride were effective initiators of 1-alkene polymerization and of styrene/1-alkene copolymerization. Conversion to polymer increases with the molecular size of 1-alkene. Styrene derivative and styrene/(styrene derivative) polymerization was greatly influenced by the inductive effect of substituent and by steric hindrance due to the monomer.
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Styrene/(Styrene Derivative) and Styrene/(1‐Alkene) Copolymerization using Ph2Zn‐Additive Initiator Systems
Macromolecular Symposia, 2004Co-Authors: Rodrigo A. Cancino, Monica A Perez, Francisco J. RodriguezAbstract:Diphenylzinc-metallocene-MAO initiator systems have proven to be effective initiator systems for styrene and for substituted styrenes as well as for their styrene/(styrene-derivative) copolymerization. Titanocene produced almost pure syndiotactic polymers while Zirconocenes gave atactic polystyrene together with a low content, less than 20%, of syndiotactic polystyrene. Systems including a Zirconocene, particularly ethenyl(bisindenyl)zirconium dichloride were effective initiators of 1-alkene polymerization and of styrene/1-alkene copolymerization. Conversion to polymer increases with the molecular size of 1-alkene. Styrene derivative and styrene/(styrene derivative) polymerization was greatly influenced by the inductive effect of substituent and by steric hindrance due to the monomer.
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styrene copolymerization using diphenylzinc additive initiator systems styrene p substituted styrenes
Macromolecular Symposia, 2003Co-Authors: Monica A Perez, Rodrigo A. Cancino, Francisco J. Rodriguez, Marcelo A Soto, Carlos J CaroAbstract:Combined systems including diphenylzinc (Ph 2 Zn), a metallocene, and methylaluminoxane (MAO), have been employed to initiate the copolymerization of styrene (S) with p-alkylsubstituted styrenes and with α-olefins. The copolymerization processes depend largely on the comonomer, the nature of the metallocene included in the initiator system, the presence of Ph 2 Zn, the polymerization temperature and the solvent used. Titanocenes produced true copolymers for S/p-substituted styrene, but not in S/α-olefin copolymerization. On the other hand Zirconocenes either did not copolymerize S/p-substituted styrene or produced very low conversions, while they succeeded in copolymerizing S/α-olefin, depending on the particular Zirconocene employed. A low p-methylstyrene (p-MeS) content in the S/p-MeS copolymer and a low p-tertbutylstyrene (p-Bu t S) content in the S/p-Bu t S copolymer decreased Tm, making them easier to process material than s-PS.
Monica A Perez - One of the best experts on this subject based on the ideXlab platform.
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further studies on styrene styrene derivative copolymerizations using combined diphenylzinc additive initiator systems
Polymer International, 2005Co-Authors: F M Rabagliati, Carlos J Caro, Francisco J. Rodriguez, Monica A Perez, Nicolas CrispelAbstract:A combination of diphenylzinc, a metallocene and methylaluminoxane (Ph2Zn-metallocene-MAO) is a suitable initiator system for the polymerization of styrene and for its copolymerization with para-alkyl substituted styrenes. This paper reports new experimental results which reinforce our previous findings indicating that polymerization processes are initiated by monomer coordination to active species resulting from these particular combined systems. Polymerization propagates by a cationic pathway. Further to our previous observation that the I+ inductive effect of para-substituents in styrene improves conversion to polymer, we now find that methyl substitution on the vinyl double bond of styrene, in spite of the I+ inductive effect and as a result of increased steric hindrance, makes the polymerization process difficult. On the other hand, the replacement of titanocenes by Zirconocenes or hafnocenes generates Ph2Zn-metallocene-MAO initiator systems which are also able to induce homo- and copolymerization, but with lower yields and producing practically amorphous polymers. The efficiency of our Ph2Zn-metallocene-MAO initiator systems follows the order titanocene > Zirconocene > hafnocene, at least for the studied metallocenes. Copyright © 2004 Society of Chemical Industry
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Further studies on styrene/styrene derivative copolymerizations using combined diphenylzinc-additive initiator systems †
Polymer International, 2004Co-Authors: F M Rabagliati, Carlos J Caro, Francisco J. Rodriguez, Monica A Perez, Nicolas CrispelAbstract:A combination of diphenylzinc, a metallocene and methylaluminoxane (Ph2Zn-metallocene-MAO) is a suitable initiator system for the polymerization of styrene and for its copolymerization with para-alkyl substituted styrenes. This paper reports new experimental results which reinforce our previous findings indicating that polymerization processes are initiated by monomer coordination to active species resulting from these particular combined systems. Polymerization propagates by a cationic pathway. Further to our previous observation that the I+ inductive effect of para-substituents in styrene improves conversion to polymer, we now find that methyl substitution on the vinyl double bond of styrene, in spite of the I+ inductive effect and as a result of increased steric hindrance, makes the polymerization process difficult. On the other hand, the replacement of titanocenes by Zirconocenes or hafnocenes generates Ph2Zn-metallocene-MAO initiator systems which are also able to induce homo- and copolymerization, but with lower yields and producing practically amorphous polymers. The efficiency of our Ph2Zn-metallocene-MAO initiator systems follows the order titanocene > Zirconocene > hafnocene, at least for the studied metallocenes. Copyright © 2004 Society of Chemical Industry
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styrene styrene derivative and styrene 1 alkene copolymerization using ph2zn additive initiator systems
Macromolecular Symposia, 2004Co-Authors: Rodrigo A. Cancino, Monica A Perez, Francisco J. RodriguezAbstract:Diphenylzinc-metallocene-MAO initiator systems have proven to be effective initiator systems for styrene and for substituted styrenes as well as for their styrene/(styrene-derivative) copolymerization. Titanocene produced almost pure syndiotactic polymers while Zirconocenes gave atactic polystyrene together with a low content, less than 20%, of syndiotactic polystyrene. Systems including a Zirconocene, particularly ethenyl(bisindenyl)zirconium dichloride were effective initiators of 1-alkene polymerization and of styrene/1-alkene copolymerization. Conversion to polymer increases with the molecular size of 1-alkene. Styrene derivative and styrene/(styrene derivative) polymerization was greatly influenced by the inductive effect of substituent and by steric hindrance due to the monomer.
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Styrene/(Styrene Derivative) and Styrene/(1‐Alkene) Copolymerization using Ph2Zn‐Additive Initiator Systems
Macromolecular Symposia, 2004Co-Authors: Rodrigo A. Cancino, Monica A Perez, Francisco J. RodriguezAbstract:Diphenylzinc-metallocene-MAO initiator systems have proven to be effective initiator systems for styrene and for substituted styrenes as well as for their styrene/(styrene-derivative) copolymerization. Titanocene produced almost pure syndiotactic polymers while Zirconocenes gave atactic polystyrene together with a low content, less than 20%, of syndiotactic polystyrene. Systems including a Zirconocene, particularly ethenyl(bisindenyl)zirconium dichloride were effective initiators of 1-alkene polymerization and of styrene/1-alkene copolymerization. Conversion to polymer increases with the molecular size of 1-alkene. Styrene derivative and styrene/(styrene derivative) polymerization was greatly influenced by the inductive effect of substituent and by steric hindrance due to the monomer.
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styrene copolymerization using diphenylzinc additive initiator systems styrene p substituted styrenes
Macromolecular Symposia, 2003Co-Authors: Monica A Perez, Rodrigo A. Cancino, Francisco J. Rodriguez, Marcelo A Soto, Carlos J CaroAbstract:Combined systems including diphenylzinc (Ph 2 Zn), a metallocene, and methylaluminoxane (MAO), have been employed to initiate the copolymerization of styrene (S) with p-alkylsubstituted styrenes and with α-olefins. The copolymerization processes depend largely on the comonomer, the nature of the metallocene included in the initiator system, the presence of Ph 2 Zn, the polymerization temperature and the solvent used. Titanocenes produced true copolymers for S/p-substituted styrene, but not in S/α-olefin copolymerization. On the other hand Zirconocenes either did not copolymerize S/p-substituted styrene or produced very low conversions, while they succeeded in copolymerizing S/α-olefin, depending on the particular Zirconocene employed. A low p-methylstyrene (p-MeS) content in the S/p-MeS copolymer and a low p-tertbutylstyrene (p-Bu t S) content in the S/p-Bu t S copolymer decreased Tm, making them easier to process material than s-PS.
Takeo Taguchi - One of the best experts on this subject based on the ideXlab platform.
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Regioselective Bond Cleavage of Vinylcyclopropane Derivatives with the “Zirconocene-Butene” Complex.
ChemInform, 2010Co-Authors: Yuji Hanzawa, Shinji Harada, Ryoko Nishio, Takeo TaguchiAbstract:Abstract The regioselective bond cleavage of vinylcyclopropanes with Zirconocene-butene complex gave η 3 - and/or η 1 -allylic Zirconocene derivatives depending on the substitutional pattern of the cyclopropylring. The reactions and characterization of the complexes were carried out.
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Stereoselective Zirconocene-mediated Ring Transformation of 2-Vinylhetero- cycles to Vinylcarbocycles
HETEROCYCLES, 2004Co-Authors: Yuji Hanzawa, Hiromichi Kiyono, Takeo TaguchiAbstract:Stereoselective ring transformation of 2-vinylheterocycles to vinylcarbocycles was efficiently carried out by the use of a Zirconocene equivalent ("Cp 2 Zr"). The transformation proceeded through an intramolecular allylation of Z-allylic Zirconocene species to the epoxide or aziridine ring.
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Unprecedented reactions of substituted styrene derivatives with Zirconocene-(1-butene) complex
Tetrahedron Letters, 1995Co-Authors: Yuji Hanzawa, Yutaka Ikeuchi, Takanori Nakamura, Takeo TaguchiAbstract:Abstract Reactions of alkoxymethyl substituted styrene derivatives with a stoichiometric and/or catalytic amount of Zirconocene-(1-butene) complex (“Cp 2 Zr“) causes an unexpected Zirconocene insertion into benzylic position and/or homolytic coupling reaction of the styrene derivatives.
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Regioselective bond cleavage of vinylcyclopropane derivatives with the“Zirconocene-butene” complex
Tetrahedron Letters, 1994Co-Authors: Yuji Hanzawa, Shinji Harada, Ryoko Nishio, Takeo TaguchiAbstract:Abstract The regioselective bond cleavage of vinylcyclopropanes with Zirconocene-butene complex gave η 3 - and/or η 1 -allylic Zirconocene derivatives depending on the substitutional pattern of the cyclopropylring. The reactions and characterization of the complexes were carried out.
Zuowei Xie - One of the best experts on this subject based on the ideXlab platform.
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Facile Synthesis of ansa-Zirconocenes Incorporating a Linked Dicarbollyl Ligand via Direct Deboration of Zirconocene Carboranyl Complexes
Organometallics, 2011Co-Authors: Mei-mei Sit, Hoi-shan Chan, Zuowei XieAbstract:ansa-Zirconocene amides incorporating a Me2C-linked cyclopentadienyl–dicarbollyl or indenyl–dicarbollyl ligand were conveniently prepared from direct deboration of the corresponding carboranyl meta...
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Synthesis, Structure, and Reactivity of a Zirconocene−Carboryne Precursor
Journal of the American Chemical Society, 2005Co-Authors: Liang Deng, Hoi-shan Chan, Zuowei XieAbstract:Transition metal-benzyne complexes have found many applications in organic synthesis, mechanistic studies, and the synthesis of functional materials. In sharp contrast, the reaction chemistry of transition metal-carboryne complexes is virtually unknown although the theoretical calculations indicated that the formation of carboryne (1,2-C2B10H10) and benzyne is very energetically comparable. This communication reports a novel Zirconocene-carboranyl complex Cp2Zr(mu-Cl)(mu-C2B10H10)Li(OEt2)2 (1), an efficient precursor of the Zirconocene-carboryne species, prepared from the reaction of Cp2ZrCl2 with 1 equiv of Li2C2B10H10 in Et2O. The reactivity studies indicated that 1 resembles Zirconocene-benzyne in reactions with polar unsaturated organic molecules. On the other hand, it shows no reactivity toward alkynes and alkenes, a reactivity pattern which is quite different from that of Zirconocene-benzyne. This work also furnishes a novel method for the preparation of functional o-carboranes and their metal complexes which cannot be synthesized by other methods presently known.
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synthesis structure and reactivity of a Zirconocene carboryne precursor
Journal of the American Chemical Society, 2005Co-Authors: Liang Deng, Hoi-shan Chan, Zuowei XieAbstract:Transition metal-benzyne complexes have found many applications in organic synthesis, mechanistic studies, and the synthesis of functional materials. In sharp contrast, the reaction chemistry of transition metal-carboryne complexes is virtually unknown although the theoretical calculations indicated that the formation of carboryne (1,2-C2B10H10) and benzyne is very energetically comparable. This communication reports a novel Zirconocene-carboranyl complex Cp2Zr(mu-Cl)(mu-C2B10H10)Li(OEt2)2 (1), an efficient precursor of the Zirconocene-carboryne species, prepared from the reaction of Cp2ZrCl2 with 1 equiv of Li2C2B10H10 in Et2O. The reactivity studies indicated that 1 resembles Zirconocene-benzyne in reactions with polar unsaturated organic molecules. On the other hand, it shows no reactivity toward alkynes and alkenes, a reactivity pattern which is quite different from that of Zirconocene-benzyne. This work also furnishes a novel method for the preparation of functional o-carboranes and their metal complexes which cannot be synthesized by other methods presently known.
Nicolas Crispel - One of the best experts on this subject based on the ideXlab platform.
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further studies on styrene styrene derivative copolymerizations using combined diphenylzinc additive initiator systems
Polymer International, 2005Co-Authors: F M Rabagliati, Carlos J Caro, Francisco J. Rodriguez, Monica A Perez, Nicolas CrispelAbstract:A combination of diphenylzinc, a metallocene and methylaluminoxane (Ph2Zn-metallocene-MAO) is a suitable initiator system for the polymerization of styrene and for its copolymerization with para-alkyl substituted styrenes. This paper reports new experimental results which reinforce our previous findings indicating that polymerization processes are initiated by monomer coordination to active species resulting from these particular combined systems. Polymerization propagates by a cationic pathway. Further to our previous observation that the I+ inductive effect of para-substituents in styrene improves conversion to polymer, we now find that methyl substitution on the vinyl double bond of styrene, in spite of the I+ inductive effect and as a result of increased steric hindrance, makes the polymerization process difficult. On the other hand, the replacement of titanocenes by Zirconocenes or hafnocenes generates Ph2Zn-metallocene-MAO initiator systems which are also able to induce homo- and copolymerization, but with lower yields and producing practically amorphous polymers. The efficiency of our Ph2Zn-metallocene-MAO initiator systems follows the order titanocene > Zirconocene > hafnocene, at least for the studied metallocenes. Copyright © 2004 Society of Chemical Industry
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Further studies on styrene/styrene derivative copolymerizations using combined diphenylzinc-additive initiator systems †
Polymer International, 2004Co-Authors: F M Rabagliati, Carlos J Caro, Francisco J. Rodriguez, Monica A Perez, Nicolas CrispelAbstract:A combination of diphenylzinc, a metallocene and methylaluminoxane (Ph2Zn-metallocene-MAO) is a suitable initiator system for the polymerization of styrene and for its copolymerization with para-alkyl substituted styrenes. This paper reports new experimental results which reinforce our previous findings indicating that polymerization processes are initiated by monomer coordination to active species resulting from these particular combined systems. Polymerization propagates by a cationic pathway. Further to our previous observation that the I+ inductive effect of para-substituents in styrene improves conversion to polymer, we now find that methyl substitution on the vinyl double bond of styrene, in spite of the I+ inductive effect and as a result of increased steric hindrance, makes the polymerization process difficult. On the other hand, the replacement of titanocenes by Zirconocenes or hafnocenes generates Ph2Zn-metallocene-MAO initiator systems which are also able to induce homo- and copolymerization, but with lower yields and producing practically amorphous polymers. The efficiency of our Ph2Zn-metallocene-MAO initiator systems follows the order titanocene > Zirconocene > hafnocene, at least for the studied metallocenes. Copyright © 2004 Society of Chemical Industry
