Mechanistic Investigations into the Behavior of a Labeled Zirconocene Polymerization Catalyst

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• 作者：Beth M. Moscato ; Bolin Zhu ; Clark R. Landis
• 刊名：Organometallics
• 出版年：2012
• 出版时间：March 12, 2012
• 年：2012
• 卷：31
• 期：5
• 页码：2097-2107
• 全文大小：503K
• 年卷期：v.31,no.5(March 12, 2012)
• ISSN：1520-6041

文摘

Kinetics associated with the [(SBI)Zr(CH₂SiMe₂(C₆H₄)NMe₂)][MeB(C₆F₅)₃] (1a)-catalyzed polymerization of 1-hexene in a mixed toluene-d₈/chlorobenzene-d₅ solvent at 鈭?3 掳C were investigated via ¹H NMR and compared to the kinetics associated with the (SBI)ZrMe(MeB(C₆F₅)₃) (1c)-catalyzed polymerization of 1-hexene under identical conditions. In the presence of 1-hexene, both catalysts form an identical propagating species, (SBI)Zr(poly-1-hexyl)(MeB(C₆F₅)₃) (1b), but the concentration of 1b during 1a-catalyzed polymerization is only ca. 40% of the anticipated value. Under reaction conditions, 1b reacts reversibly with the model complex p-TMS-C₆H₄-NMe₂ (2) to yield the outer-sphere ion pair tentatively identified as [(SBI)Zr(poly-1-hexyl)(2)][MeB(C₆F₅)₃] (1e), which acts as an essentially dormant site during 1-hexene polymerization. Warming of 1b in the absence of additives generates the well-defined hydridoborate complex (SBI)ZrMe(HB(C₆F₅)₃) (1d), which does not reinitiate in the presence of 1-hexene. 尾-Hydride elimination of 1b in the presence of additives such as 1,2-dichloroethane and 2 results in catalyst decomposition.