“…Bis(2-phenylindenyl)zirconium dichloride, 1 , and (cyclopentadienyl)(2-phenylindenyl)zirconium dichloride, 2 , were prepared according to literature procedures. Bis(2-methylindenyl)zirconium dichloride, 7 , was prepared analogous to 1 and characterized by comparison to a literature procedure . Polymerization grade ethylene (supplied by Matheson) and toluene were purified by passage through columns containing Q5 and alumina.…”
The copolymerization of ethylene and 1-hexene with a variety of unbridged indenylmetallocenes was investigated and compared to unbridged bis(indenyl)zirconium dichloride and bis(cyclopentadienyl)zirconium dichloride as well as ansa-bridged rac-ethylenebis(indenyl)zirconium dichloride (EBIZrCl 2). The unbridged bis(2-phenylindenyl)zirconium dichloride showed higher selectivity for the incorporation of 1-hexene than the bridged rac-ethylenebis(indenyl)zirconium dichloride and much higher 1-hexene incoporation than the unbridged bis(indenyl)zirconium dichloride and bis(cyclopentadienyl)zirconium dichloride. Both ligands appear to be important since the 1-hexene incorporation of the mixed ligand compound (cyclopentadienyl)(2-phenylindenyl)zirconium dichloride is much lower than that of bis-(2-phenylindenyl)zirconium dichloride. For unbridged bis(indenyl)metallocenes, the nature of the substituent in the 2-position plays an important role in comonomer selectivity: bis(2-methylindenyl)zirconium dichloride and bis(2-phenylethynylindenyl)zirconium dichloride exhibit much higher 1-hexene incorporation than bis(indenyl)zirconium dichloride but lower than bis(2-phenylindenyl)zirconium dichloride.
“…Bis(2-phenylindenyl)zirconium dichloride, 1 , and (cyclopentadienyl)(2-phenylindenyl)zirconium dichloride, 2 , were prepared according to literature procedures. Bis(2-methylindenyl)zirconium dichloride, 7 , was prepared analogous to 1 and characterized by comparison to a literature procedure . Polymerization grade ethylene (supplied by Matheson) and toluene were purified by passage through columns containing Q5 and alumina.…”
The copolymerization of ethylene and 1-hexene with a variety of unbridged indenylmetallocenes was investigated and compared to unbridged bis(indenyl)zirconium dichloride and bis(cyclopentadienyl)zirconium dichloride as well as ansa-bridged rac-ethylenebis(indenyl)zirconium dichloride (EBIZrCl 2). The unbridged bis(2-phenylindenyl)zirconium dichloride showed higher selectivity for the incorporation of 1-hexene than the bridged rac-ethylenebis(indenyl)zirconium dichloride and much higher 1-hexene incoporation than the unbridged bis(indenyl)zirconium dichloride and bis(cyclopentadienyl)zirconium dichloride. Both ligands appear to be important since the 1-hexene incorporation of the mixed ligand compound (cyclopentadienyl)(2-phenylindenyl)zirconium dichloride is much lower than that of bis-(2-phenylindenyl)zirconium dichloride. For unbridged bis(indenyl)metallocenes, the nature of the substituent in the 2-position plays an important role in comonomer selectivity: bis(2-methylindenyl)zirconium dichloride and bis(2-phenylethynylindenyl)zirconium dichloride exhibit much higher 1-hexene incorporation than bis(indenyl)zirconium dichloride but lower than bis(2-phenylindenyl)zirconium dichloride.
“…Previous investigations of the mechanism of propylene polymerization by unbridged bis(2-arylindenyl)zirconium dichloride ((2-ArInd) 2 ZrCl 2 ) activated with methylaluminoxane (MAO) have led to the proposal of a kinetic model (Figure ) where the rate of monomer enchainment is competitive with isomerization of the catalyst between two states which exhibit different stereoselectivities. − The differences in catalyst productivity and molecular weight (MW) and the microstructure of the polypropylenes (PPs) formed by (2-ArInd) 2 ZrCl 2 with variations in ligand structure, ,,,, metal, and polymerization conditions 19,22 have been investigated but are difficult to predict in the absence of a more complete kinetic model. An understanding of the kinetic behavior of the parent system bis(2-phenylindenyl)zirconium dichloride ((2-PhInd) 2 ZrCl 2 ) would assist in the interpretation of past work and aid in designing new catalysts.…”
The kinetics of propylene polymerization in toluene solution by bis(2-phenylindenyl)zirconium
dichloride/methylaluminoxane at 20 °C were investigated. As the structure and properties of elastomeric
polypropylenes produced by these catalysts depend sensitively on the reaction conditions, a detailed study of
the kinetics was carried out to evaluate the influence of these parameters on the polymerization behavior.
Studies of the solubilities and mass-transfer rates reveal that dissolved atactic polypropylene has little effect
on propylene solubility but influences the mass-transfer rate of propylene into solution. The rates of propylene
polymerization reach a maximum after 10−20 min and then decrease. The decrease in rate over time is faster
at higher monomer concentrations. Catalyst activity was negligible at [Al]/[Zr] = 1000 but constant from
[Al]/[Zr] = 2500 to [Al]/[Zr] = 10 000. Analysis of molecular weights as a function of monomer concentration
reveal β-hydride elimination to be the primary chain-transfer mechanism. Narrow molecular weight distributions
(M
w/M
n = 2.0−2.6) were obtained. The increase of the isotactic dyads and pentads ([m] and [mmmm]) with
increasing monomer concentration reveals an additional kinetic event which competes with the stereodifferentiating olefin insertion step. Modeling studies are more consistent with a mechanism involving interconversion
of the catalyst between isospecific and aspecific states than a mechanism involving epimerization of the
stereogenic centers of the growing polymer chain.
“…Bis(2-phenylindenyl)zirconium dichloride ( M1 ) was synthesized according to a literature procedure. , This method involves nucleophilic attack of phenylmagnesium bromide on 2-indanone. A major drawback of this method is the susceptibility of 2-indanone to enolization . This is particularly troublesome for most organolithium nucleophiles as well as sterically demanding nucleophiles.…”
Section: Resultsmentioning
confidence: 99%
“…The synthesis of elastomeric polypropylene using metallocene catalysts was first reported by Chien and co-workers with a stereorigid chiral ansa -titanocene. − Collins has also developed a family of chiral metallocenes for the production of elastomeric polypropylene. − We have been investigating a class of unbridged bis(2-arylindene)metallocenes for the synthesis of stereoblock elastomeric polypropylenes. − These catalysts were designed to interconvert between chiral and achiral torsional isomers − on the time scale of the polymerization reaction in order to produce an isotactic and atactic stereoblock structure (Figure ). The nature of the substituent in the 2-position of the indenyl ligand is crucial; unbridged bis(indenyl)zirconium dichloride/MAO and a variety of bis(2-alkylindenyl)zirconocenes produce atactic polypropylenes. ,− 1 Proposed mechanism for formation of stereoblock polypropylene.…”
Five new indenyl zirconium metallocenes with 2-alkyl and 2-aryl substituents were
synthesized and characterized. For the synthesis of the ligand the di-Grignard reagent 1,2-bis(magnesiomethyl)benzene dichloride was explored as a synthon to 2-substituted indenes.
This procedure provides access to a variety of functionalized 2-indenylmetallocenes such as
bis(2-ferrocenylindene)zirconium dichloride and bis(2-adamantylindenyl)zirconium dichloride.
Crystallographic characterization of bis[2-(4-(dimethylamino)phenyl)indenyl] zirconium
dichloride revealed an anti conformation with a coplanar orientation of the dimethylamino
substituent to the aryl ring in the solid state. The polymerization behavior of all five
zirconocene dichlorides in liquid propylene was studied in the presence of MAO at various
temperatures, and the results were compared to those for the known catalyst system bis(2-phenylindenyl)zirconium dichloride/MAO (M1/MAO). The productivity of the 2-arylindene
metallocenes in propylene polymerization was on the order of 100−7000 kg of PP/((mol of
Zr) h). In contrast, the (2-adamantylindenyl)metallocenes exhibited very low productivities
of 6 kg PP/((mol of Zr) h) in propylene polymerization.
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