Activating influence of aluminosilicate phases of amorphous aluminasilica gels on supported titanium(IV) complexes in isoprene polymerization

Skupiński, Wincenty; Cieślowska-Glińska, I.; Wasilewski, Arthur

doi:10.1016/0304-5102(85)85024-0

Cited by 9 publications

(14 citation statements)

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“…The results of ethylene and propylene polymerization runs initiated at −78, 0, and 25 °C are reported in Tables −4, although it should be noted that the polymerizations initiated at 25 °C were not thermostated effectively and quickly became quite hot. For PE, catalytic activities (16−46 kg of PE/((mol of Ti h atm)) were somewhat lower than for CpTiCl 3 /MAO (62 kg PE/((mol of Ti h atm)) (Table ), although, of course, conditions were not identical 4s…”

Section: Resultsmentioning

confidence: 91%

“…Nature of the Active Catalytic Species. The compounds Cp*TiMeE(μ-Me)B(C 6 F 5 ) 3 (E = Me, C 6 F 5 , OC 6 F 5 ) are all precursors of the cationic species [Cp*TiMeE] + which, on the basis of a very extensive literature, ,− are reasonably believed to be the initiators of polymer chain growth. However, organotitanium(IV) compounds are susceptible to reduction, and there is now extensive evidence for the formation of titanium(III) species, detected utilizing EPR spectroscopy, in many olefin polymerization systems involving monocyclopentadienyltitanium compounds.…”

Section: Resultsmentioning

confidence: 99%

“…We have proposed that the methyl-bridged bonding mode in Cp*TiMe 2 (μ-Me)B(C 6 F 5 ) 3 ( A , Figure , E = Me; CD 2 Cl 2 , −50 °C) 5 is similar to that found in Cp‘ 2 ZrMe(μ-Me)B(C 6 F 5 ) 3 in solution and in the solid state 3a-c and have demonstrated the versatility of A as an active polymerization initiator for a number of olefins . In addition, polymerization of ethylene and propylene has been achieved using CpTiCl 3 and Cp*TiCl 3 activated with large excesses of MAO, and Pellecchia has reported the polymerization of ethylene using the related MAO-free catalysts Cp*MR 2 (μ-R)B(C 6 F 5 ) 3 (M = Zr, R = CH 2 Ph; M = Ti, R = CH 2 Ph, Me), although propylene was polymerized only with the benzyl complexes 4j 1 Proposed structure of Cp*TiMeE(μ-Me)B(C 6 F 5 ) 3 ( A − D ). …”

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confidence: 80%

“…A growing interest in the related half-sandwich complexes of the type Cp‘ML 3 has led our group and others to the formation of rather similar cationic species by the general method of alkyl ligand abstraction using the strongly Lewis acidic borane B(C 6 F 5 ) 3 and formation of alkyl-bridged complexes of the type Cp*TiR 2 (μ-R)B(C 6 F 5 ) 3 (Cp* = η 5 -C 5 Me 5 ) (eq 1). 4j,r,u,v, …”

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confidence: 99%

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Ethylene and Propylene Polymerization by a Series of Highly Electrophilic, Chiral Monocyclopentadienyltitanium Catalysts

et al. 1998

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The compounds Cp*TiMe2C6F5, Cp*TiMe2OC6F5, and Cp*TiMe2Cl (Cp* = η5-C5Me5) react with the borane B(C6F5)3 to form the thermally unstable, chiral complexes Cp*TiMe(C6F5)(μ-Me)B(C6F5)3, Cp*TiMe(OC6F5)(μ-Me)B(C6F5)3, and Cp*TiMeCl(μ-Me)B(C6F5)3, respectively, which are similar to the known Cp*TiMe2(μ-Me)B(C6F5)3. All four μ-Me compounds behave as sources of the highly electrophilic species [Cp*TiMeE]+ (E = Me, Cl, C6F5, OC6F5) when treated with the borane, the last three being chiral, and all four systems exhibit catalytic activities for the polymerization of ethylene to high-molecular-weight polyethylene. Despite the chirality at titanium of three of the compounds, polymerization of propylene by all of them results in the formation of atactic, elastomeric polypropylene. NMR analyses of the propylene polymers formed show that initiation involves 1,2-insertion into a Ti−Me bond, and while propagation involves primarily head-to-tail 1,2-insertions, an unusually high (by metallocene standards) proportion of the insertions also involves 2,1-misinsertions but essentially no 1,3-enchainment. The major olefinic end groups are vinylidene (CH2CMe−), resulting from β-hydrogen transfer following a 1,2-insertion, and vinyl (CH2CH−), resulting from β-hydrogen transfer from the methyl group following a 2,1-insertion or, more likely, β-methyl transfer following a 1,2-insertion. Small amounts of internal olefins are also formed via β-hydrogen transfer following a 2,1-insertion. An EPR study of the Cp*TiMe3/B(C6F5)3 system in toluene indicates that <0.01% of the titanium is occasionally present during polymerization as a complex of titanium(III), suggesting that a contribution to catalysis by titanium(III) species is unlikely.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

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confidence: 80%

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confidence: 99%

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Ethylene and Propylene Polymerization by a Series of Highly Electrophilic, Chiral Monocyclopentadienyltitanium Catalysts

et al. 1998

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“…The alumina-silica containing 80 wt% of Al 2 O 3 is an example. Supported on it only, π -allylnickel complexes are active in propylene oligomerization [3] and the supported cyclopentadienyl titanium (IV) complexes exhibit the greatest activity in isoprene polymerization [19]. Tungsten oxochloro complexes activated with tetrabutyltin and supported on 50% alumina-silica gel exhibited the highest activity in ROMP of cyclopentene [20].…”

Section: Introductionmentioning

confidence: 98%