Migratory Insertion into a Hafnium–Phenyl Bond and a Ligand-Assisted Mechanism for Reversible Chain Transfer in the Living Coordinative Polymerization of Olefins

Kuzminski, Brendan R. S.; Fischbach, Danyon M.; Yap, Glenn P. A.; Sita, Lawrence R.

doi:10.1021/acs.organomet.2c00364

Cited by 5 publications

(1 citation statement)

References 49 publications

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“…Furthermore, only reversible chain transfer can generate block-polyolefin architectures. − Very few catalysts that can rapidly and reversibly transfer the polymer chain to a CTA have been reported. Among them, Sita’s Hf-based half metallocene (Scheme a), − the Symyx/Dow Hf-pyridyl-amido post-metallocene (Scheme b), and Gibson’s Fe-based complex − (Scheme c) are notable catalyst precursors.…”

Section: Introductionmentioning

confidence: 99%

Solution Structure and Dynamics of Hf–Al and Hf–Zn Heterobimetallic Adducts Mimicking Relevant Intermediates in Chain Transfer Reactions

Tensi,

Moretti,

Amendola

et al. 2024

Inorg. Chem.

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H f ] [ B ( C 6 F 5 ) 4 ] ( 4 P r ) a n d [Cp iBu Cp CH2CH(Me)CH2 Hf][B(C 6 F 5 ) 4 ] (4a iBu and 4b iBu ) were synthesized from the corresponding [(Cp Pr ) 2 HfMe][B(C 6 F 5 ) 4 ] (1 Pr ) and [(Cp iBu ) 2 HfMe][B(C 6 F 5 ) 4 ] (1 iBu ) complexes via C−H activation.4a iBu , 4b iBu , and 4 Pr , mimicking a propagating M-polymeryl species (M = transition metal) with or without a β-methyl branch on the metalated chains, serve to investigate whether and how the nature of the last inserted olefin molecules changes the structure, stability, and reactivity of the corresponding heterobimetallic complexes, formed in the presence of aluminum-or zinc-alkyl chain transfer agents (CTAs), which are considered relevant intermediates in coordinative chain transfer polymerization (CCTP) and chain shuttling polymerization (CSP) technologies. NMR and DFT data indicate no major structural difference between the resulting heterobridged complexes, all characterized by the presence of multiple α-agostic interactions. On the contrary, thermodynamic and kinetic investigations, concerning the reversible formation and breaking of heterobimetallic adducts, demonstrate that isomer 4a iBu , in which the β-Me is oriented away from the reactive coordination site on Hf, but not 4b iBu , having the β-Me pointing in the opposite direction, is capable of reacting with CTAs. Quantification of kinetic rate constants highlights that the formation process is rate limiting and that the nature of the last inserted α-olefin unit modulates transalkylation kinetics. The reaction of 4a iBu , 4b iBu , and 4 Pr with diisobutylaluminum hydride (DiBAlH) allows the interception and characterization of new heterobinuclear and heterotrinuclear species, featuring both hydride and alkyl bridging moieties, which represent structural models of elusive intermediates in CCTP and CSP processes, capturing the instant when an alkyl chain has just transferred from a transition metal to a main group metal, while the two metals remain engaged in a single heterobimetallic intermediate.

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Section: Introductionmentioning

confidence: 99%

Solution Structure and Dynamics of Hf–Al and Hf–Zn Heterobimetallic Adducts Mimicking Relevant Intermediates in Chain Transfer Reactions

Tensi,

Moretti,

Amendola

et al. 2024

Inorg. Chem.

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The Highly Controlled and Efficient Polymerization of Ethylene

et al. 2023

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The highly controlled and efficient polymerization of ethylene is a very attractive but challenging target. Herein we report on a Coordinative Chain Transfer Polymerization catalyst, which combines a high degree of control and very high activity in ethylene oligo-or polymerization with extremely high chain transfer agent (triethylaluminum) to catalyst ratios (catalyst economy). Our Zr catalyst is long living and temperature stable. The chain length of the polyethylene products increases over time under constant ethylene feed or until a certain volume of ethylene is completely consumed to reach the expected molecular weight. Very high activities are observed if the catalyst elongates 60 000 or more alkyl chains and the polydispersity of the strictly linear polyethylene materials obtained are very low. The key for the combination of high control and efficiency seems to be a catalyst stabilized by only one strongly bound monoanionic N-ligand.

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Versatile Production of Multivariate, Hyperdimensional End Group and Main Chain Functionalized Polyolefins

Fischbach,

Krstic,

Sita

2023

Angewandte Chemie

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The (stereoselective) living coordinative copolymerization of 1‐alkenes with 4‐aryl‐1,6‐heptadienes, in both the absence and presence of multiple equivalents of a reversible chain transfer agent, is established as a highly versatile strategy for production of multivariate hyperdimensional functionalized semi‐crystalline or amorphous polyolefins that optionally possess either mono‐ or difunctionalized (telechelic) end‐groups in combination with a programmable level of incorporation of orthogonal functional groups within the main‐chain. The non‐conjugated diene comonomers are readily obtained from a diverse range of aryl carboxaldehyde precursors through a one‐step bis‐allylation process. These results serve to provide a new platform for exploring the science and technology of a vast new landscape of functionalized classes of polyolefins that are now accessible in practical and scalable quantities.

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Migratory Insertion into a Hafnium–Phenyl Bond and a Ligand-Assisted Mechanism for Reversible Chain Transfer in the Living Coordinative Polymerization of Olefins

Cited by 5 publications

References 49 publications

Solution Structure and Dynamics of Hf–Al and Hf–Zn Heterobimetallic Adducts Mimicking Relevant Intermediates in Chain Transfer Reactions

Solution Structure and Dynamics of Hf–Al and Hf–Zn Heterobimetallic Adducts Mimicking Relevant Intermediates in Chain Transfer Reactions

The Highly Controlled and Efficient Polymerization of Ethylene

Versatile Production of Multivariate, Hyperdimensional End Group and Main Chain Functionalized Polyolefins

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