Cationic Zirconium and Hafnium Isobutyl Complexes as Models for Intermediates in Metallocene-Catalyzed Propylene Polymerizations. Detection of an .alpha.-Agostic Interaction in (C5Me5)2Hf(CH2CHMe2)(PMe3)+

Guo, Zhaoyu; Swenson, Dale C.; Jordan, Richard F.

doi:10.1021/om00016a050

Cited by 117 publications

(84 citation statements)

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“…␤-Agostic species have been identified as the ground-state structures in several d 0 metal alkyl complexes and are thought in many cases to be the catalyst resting state in olefin polymerizations (63)(64)(65). Species exhibiting ␥-agostic interactions are formed upon insertion of olefins into an ␣-agostic species (Scheme 5) and have also been proposed as possible catalyst resting states (66)(67)(68)(69)(70)(71)(72).…”

Section: Role Of Agostic Interactions In Reaction Intermediates and Tmentioning

confidence: 99%

Agostic interactions in transition metal compounds

Brookhart

Green

Parkin

2007

Proc. Natl. Acad. Sci. U.S.A.

1,025

831

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Section: Role Of Agostic Interactions In Reaction Intermediates and Tmentioning

confidence: 99%

Agostic interactions in transition metal compounds

Brookhart

Green

Parkin

2007

Proc. Natl. Acad. Sci. U.S.A.

1,025

831

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“…[42] On the other side, b-Et elimination has never been observed in 1-butene oligo-or polymerization with the same catalysts. [42,43] By means of 1 H and 13 C NMR analysis of poly(1-butene)s prepared with rac-Me 2 Si(H 4 Ind) 2 ZrCl 2 / MAO at 100 8C, Rossi and Odian [44] assigned the structure of several types of terminal unsaturations, such as vinylidene, trisubstituted double bonds, and vinylene, and listed the possible reactions leading to these unsaturated end groups. The presence of so many olefinic end groups might be in part related to the high temperature and to the low monomer concentration used in the experiment.…”

Section: Analysis Of Unsaturations: Chain Release Reactions and Formamentioning

confidence: 99%

Metallocene Catalysts for 1‐Butene Polymerization

Resconi

Camurati

Malizia

2006

Macro Chemistry & Physics

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Summary: Isotactic polybutenes of variable isotacticity and melting points of form I in the range 100–125 °C have been prepared with both C2‐ and C1‐symmetric zirconocenes. The C1‐symmetric zirconocenes bearing the bilateral symmetric 2,5‐dimethyl‐7H‐cyclopenta[1,2‐b:4,3‐b′]dithiophene ligand connected by a dimethylsilandiyl bridge to a substituted indenyl ligand produce iPB with higher molecular mass, up to 400 000 at polymerization temperature of 70 °C in liquid butene. The degree of isotacticity depends on the substitution pattern of the indenyl ligand. The correlations between microstructure and melting points of the crystalline forms I and II of iPB have been defined. Some relevant differences in catalyst selectivity between propylene and 1‐butene polymerizations have been identified.Linear correlation of melting points of form I and form II in isotactic poly(1‐butene)s of different chain regularities.magnified imageLinear correlation of melting points of form I and form II in isotactic poly(1‐butene)s of different chain regularities.

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“…Ligand exchange with PMe 3 yields [Zr(CH 2 CHMe 2 )(PMe 3 )(T|-C 5 H 4 Me) 2 ] [BPh 4 ] (91b), which adopts an agostic Zr-HP-C structure. 26 In contrast, the more crowded hafnium species [Hf(CH 2 CHMe 2 )(L)Cp* 2 ][BPh 4 ] (L = THF (24) or PMe 3 (25)) adopt a-agostic structures, as determined by x-ray crystallography for (24) ( Figure 7) and NMR spectroscopy (including IPR studies) for (25). 26 In these cases, steric interactions between the p-Me groups and the Cp* ligands apparently disfavor an agostic Zr-HP-C structure.…”

Section: Structures Of [M(ch 2 Chme 2 )(L)cp'j + Complexesmentioning

confidence: 99%