Catalyst Nuclearity Effects on Stereo- and Regioinduction
in Pyridylamidohafnium-Catalyzed Propylene and 1‑Octene Polymerizations
Posted on 2018-03-15 - 19:08
In
comparison to monometallic controls, bimetallic olefin polymerization
catalysts often exhibit superior performance in terms of higher polyolefin Mw, higher comonomer incorporation, and higher
polar comonomer tolerance. However, using cooperating catalyst centers
to modulate stereoselectivity in α-olefin polymerizations is
relatively unexplored. In this contribution, the monometallic Hf(IV)
complex, L1-HfMe2 (catalyst A,
L1 = 2,6-diisopropyl-N-{(2-isopropylphenyl)[6-(naphthalen-1-yl)pyridin-2-yl]methyl}aniline),
and homo-bimetallic Hf(IV) complexes, L2-Hf2Me5 (catalyst B) and L2-Hf2Me4 (catalyst C) (L2 = N,N′-{[naphthalene-1,4-diylbis(pyridine-6,2-diyl)]bis[(2-isopropylphenyl)methylene)]bis(2,6-diisopropylaniline}),
are activated with Ph3C+B(C6F5)4– and investigated in propylene
and 1-octene homopolymerizations. In propylene polymerizations, the
conformationally flexible catalyst B-derived bimetallic
dicationic catalyst produces higher Mw polypropylene (up to 7.8×), higher total stereo- and regiodefect
densities (up to 3.5×), and lower Tm (by as much as ∼14 °C) versus the monometallic catalyst A-derived control. In 1-octene polymerizations, the conformationally
flexible catalyst B-derived bimetallic dicationic catalyst
induces greatly reduced isotacticity (23% reduction in [mmmm]) versus the catalyst A-derived monometallic control
([mmmm] > 99%). Interestingly, conformationally
flexible
catalyst B-derived cationic bimetallic Hf catalysts are
also known to undergo rapid intramolecular/intermetal methyl exchange
and to exhibit strong Hf···Hf cooperative enchainment
effects in ethylene homo- and copolymerizations. Steric effects and
intramolecular intermetal chain transfer likely both contribute to
the increased isotactic polyolefin stereo- and regiodefect content.
CITE THIS COLLECTION
DataCite
3 Biotech
3D Printing in Medicine
3D Research
3D-Printed Materials and Systems
4OR
AAPG Bulletin
AAPS Open
AAPS PharmSciTech
Abhandlungen aus dem Mathematischen Seminar der Universität Hamburg
ABI Technik (German)
Academic Medicine
Academic Pediatrics
Academic Psychiatry
Academic Questions
Academy of Management Discoveries
Academy of Management Journal
Academy of Management Learning and Education
Academy of Management Perspectives
Academy of Management Proceedings
Academy of Management Review
Gao, Yanshan; Chen, Xia; Zhang, Jialong; Chen, Jiazhen; Lohr, Tracy L.; Marks, Tobin J. (2018). Catalyst Nuclearity Effects on Stereo- and Regioinduction
in Pyridylamidohafnium-Catalyzed Propylene and 1‑Octene Polymerizations. ACS Publications. Collection. https://doi.org/10.1021/acs.macromol.8b00181
or
Select your citation style and then place your mouse over the citation text to select it.
SHARE
Usage metrics
Read the peer-reviewed publication
AUTHORS (6)
YG
Yanshan Gao
XC
Xia Chen
JZ
Jialong Zhang
JC
Jiazhen Chen
TL
Tracy L. Lohr
TM
Tobin J. Marks
KEYWORDS
1- octene homopolymerizationsisotactic polyolefin stereocatalyst Nuclearity EffectsPh 3 Ccatalyst BL 2L 11- octene polymerizationsα- olefin polymerizationsintramolecular intermetal chain transferHf 2bimetallic olefin polymerization catalystscationic bimetallic Hf catalystsbimetallic dicationic catalyst