(Butadiene)metallocene/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> Pathway to Catalyst Systems
for Stereoselective Methyl Methacrylate Polymerization:
Evidence for an Anion Dependent Metallocene Catalyzed
Polymerization Process
Joachim W. Strauch
Jean-Luc Fauré,
Stéphane Bredeau
Cun Wang
Gerald Kehr
Roland Fröhlich
Heinrich Luftmann
Gerhard Erker
10.1021/ja035739y.s001
https://acs.figshare.com/articles/dataset/_Butadiene_metallocene_B_C_sub_6_sub_F_sub_5_sub_sub_3_sub_Pathway_to_Catalyst_Systems_for_Stereoselective_Methyl_Methacrylate_Polymerization_Evidence_for_an_Anion_Dependent_Metallocene_Catalyzed_Polymerization_Process/3348616
The <i>ansa</i>-zirconocene dichlorides [Me<sub>2</sub>Si(C<sub>5</sub>H<sub>4</sub>)(3-R-C<sub>5</sub>H<sub>3</sub>)]ZrCl<sub>2</sub> <b>7a</b><b>−</b><b>e</b> (R = H, CH<sub>3</sub>, cyclohexyl,
−CHMe<sub>2</sub>, −CMe<sub>3</sub>) were reacted with butadiene−magnesium to yield the respective (η<sup>4</sup>-butadiene)metallocenes <b>17a</b><b>−</b><b>e</b>. The chiral examples give a mixture of two s-cis and two s-trans diastereomers. The
strong Lewis acid B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> adds selectively to a terminal butadiene carbon atom to yield the (butadiene)metallocene/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> betaine complexes <b>18a</b><b>−</b><b>e</b>. Initially, the formation of the <i>Z</i>-<b>18</b> isomers is preferred.
These consecutively rearrange to the thermodynamically favored isomers <i>E</i>-<b>18</b>. The dipolar systems <b>18</b>
are active single component metallocene catalysts for the stereospecific polymerization of methyl
methacrylate. With increasing steric bulk of the attached single alkyl substituent an increasingly isotactic
poly(methyl methacrylate) is obtained. A similar trend is observed in the methyl methacrylate polymerization
at the [Me<sub>2</sub>Si(C<sub>5</sub>H<sub>4</sub>)(3-R-C<sub>5</sub>H<sub>3</sub>)]ZrCH<sub>3</sub><sup>+</sup> catalysts (<b>9a</b><b>−</b><b>e</b>) that were conventionally prepared by methyl
abstraction from the corresponding <i>ansa</i>-zirconocene dimethyl complexes by treatment with B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>. A
comparison of the poly(methyl methacrylates) obtained at these two series of catalysts has revealed
substantial differences in stereoselectivity that probably originate from an influence of the respective
counteranions. An initial reactive intermediate of methyl methacrylate addition to the dipolar single component
metallocene catalyst <i>E</i>-<b>18a</b> was experimentally observed and characterized by NMR spectroscopy at 253
K. The subsequently formed series of [PMMA−C<sub>4</sub>H<sub>6</sub><sub>-</sub>B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>]<sup>-</sup> anion oligomers (at the catalyst <b>18c</b>) was
monitored (after quenching) and characterized by electrospray mass spectrometry.
2004-02-25 00:00:00
stereospecific polymerization
component metallocene catalyst E
chiral examples
18 isomers
terminal butadiene carbon atom
NMR spectroscopy
methyl abstraction
PMMA
series
alkyl substituent
catalyst 18 c
anion oligomers
253 K
CH 3
3 betaine complexes 18
methyl methacrylate
Si
isomers E
zirconocene dimethyl complexes
methyl methacrylate addition
methyl methacrylate polymerization
component metallocene catalysts
Anion Dependent Metallocene Catalyzed Polymerization Process
electrospray mass spectrometry
ansa
dipolar systems 18
3 Pathway
steric bulk
zirconocene dichlorides
Catalyst Systems