Bimetallic Approaches in Olefin Polymerization and Metathesis

Ainooson, Michael K.; Meyer, Franc

doi:10.1016/b978-0-08-097774-4.00818-4

Cited by 4 publications

(9 citation statements)

References 151 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After filtration, product 1 was isolated as a colorless powder (5.5 g, 71%). 1 H NMR (400 MHz, CDCl 3 , 25 • C): δ 7.95-7.86 (m, 1H), 7.80 (d, J = 8.2 Hz, 1H), 7.73 (d, J = 1.7 Hz, 1H), 7.64-7.55 (m, 1H), 7.50 (dd, J = 8.2, 1.8 Hz, 1H), 7.42-7.33 (m, 2H), −0.05 (s, 18H), −0.06 (s, 1H). 13 C NMR (100 MHz, CDCl 3 , 25 (9,9-Bis(trimethylsilyl)-fluoren-2-yl)boronic acid (2).…”

Section: Computational Studiesmentioning

confidence: 99%

“…As described in the literature [23], 2-bromo-9H-fluorene-9,9-diyl)bis(trimethylsilane) (1) (1.95 g, 5.0 mmol) in dry THF (30 mL) was deprotonated using nBuLi (2.6 mL of a 2.50 M solution in hexane, 6.5 mmol, 1.2 equiv) and subsequently reacted with triisopropylborate (2.3 mL, 10.0 mmol, 2.0 equiv) at −78 • C. After workup and recrystallization from refluxing hexane, compound 2 was obtained as a white powder (1.15 g, 65%). 1 H NMR (300 MHz, C 6 D 6 , 25 • C): δ 7.95 (dd, J = 1.7, 0.5 Hz, 1H), 7.72-7.68 (m, 1H), 7.55-7.42 (m, 3H), 7.41 (dd, J = 8.2, 1.7 Hz, 2H), 7.24-7.19 (m, 2H), −0.17 (s, 18H). 13 C NMR (75 MHz, C 6 D 6 , 25…”

Section: Computational Studiesmentioning

confidence: 99%

“…Removal of solvent gave compound 4 as a colorless crystalline powder (2.95 g, 74%). 1 (5). 2-Bromo-7-(tert-butyl)-9H-fluorene (4) (0.82 g, 2.7 mmol), (9,9-bis(trimethylsilyl)-9H-fluoren-2-yl)boronic acid (2) (1.00 g, 2.8 mmol), toluene (30 mL), and aqueous K 2 CO 3 solution (10 mL, 2 M) were combined.…”

Section: -Bromo-7-(tert-butyl)-9h-fluorene (4)mentioning

confidence: 99%

“…In order to discover unique/more efficient catalytic performances in olefin polymerization processes, a variety of dinuclear group 4 metallocene compounds that contain two covalently linked metallocene units have recently been prepared and reported [1][2][3]. In some ideal cases, such dinuclear systems may generate, in a one-step process, bimodal distributions made of two inherently different macromolecule populations, differing either in molecular weight, comonomer incorporation, or microstructure (tacticity, branching, etc.).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

An Asymmetric Dinuclear Bis(ansa-Zirconocene) Complex: Synthesis and Performance in Olefin (co-)Polymerization

et al. 2023

View full text Add to dashboard Cite

A synthetic strategy to access asymmetric dinuclear bis(ansa-metallocene) pre-catalysts is described. As a key step, the Pd-catalyzed Suzuki cross-coupling of 9,9-bis(trimethylsilyl)-fluoren-2-yl-boronic acid with a substituted 2-bromo-9H-fluorene generates an asymmetric 2,2′-bifluorene platform, which can be individually functionalized at the two differentiated 9-positions. Herein, as a first demonstration of this strategy, we report the asymmetric dinuclear bis(ansa-zirconocene) complex 2,2′-[{Me2C(Flu)(Cp)}ZrCl2][{Me2C(7-tBuFlu)(Cp)}ZrCl2], which has been characterized with NMR spectroscopy and high-resolution mass spectrometry. The performance of this bimetallic pre-catalyst when combined with MAO has been evaluated in ethylene, propylene, and ethylene/1-hexene (co-)polymerization. This pre-catalyst is revealed to be less productive than the mononuclear reference pre-catalyst {Me2C(2,7-tBuFlu)(Cp)}ZrCl2, likely because of higher steric hindrance induced by the linkage at the difluorenyl platform. The resulting (co-)polymers featured only slight differences in terms of molecular weights, tacticity, and comonomer incorporation. No bimodal molecular weight distribution was achieved at any produced polymer; this might have originated from the close similarity of the connected Cp/Flu moieties or a rapid chain-transfer phenomenon between the different active sites which were quite close to each other.

show abstract

Section: Computational Studiesmentioning

confidence: 99%

Section: Computational Studiesmentioning

confidence: 99%

Section: -Bromo-7-(tert-butyl)-9h-fluorene (4)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An Asymmetric Dinuclear Bis(ansa-Zirconocene) Complex: Synthesis and Performance in Olefin (co-)Polymerization

et al. 2023

View full text Add to dashboard Cite

show abstract

“…This concept has been well established in C–H activation, metal–halogen exchange, and olefin polymerization , and has shown good promise in ring-opening copolymerization. , However, within the ring-opening polymerization (ROP) of cyclic esters, the vast majority of catalyst development has focused on tailored ligand design. Heterometallic reactivity enhancement is an equally promising yet much less explored method of improving ROP catalyst performance, and many of the overarching design principles are still not well understood. − …”

Section: Introductionmentioning

confidence: 99%

Cooperative Heterometallic Catalysts for Lactide Ring-Opening Polymerization: Combining Aluminum with Divalent Metals

et al. 2021

View full text Add to dashboard Cite

While homometallic (salen)Al catalysts display excellent performance in lactide ring-opening polymerization (ROP), heterometallic (salen)Al complexes have yet to be reported. Herein, we describe four heterobimetallic (salen)Al catalysts and show that the choice of the heterometal is key. Cooperative Al/Mg and Al/Zn combinations improved the catalyst activity by a factor of up to 11 compared to the mono-Al analogue, whereas the mono-Mg and mono-Zn analogues were completely inactive. In contrast, Al/Li and Al/Ca heterocombinations stunted the polymerization rate. Kinetic and computational studies suggest that Al/Mg and Al/Zn cooperativity arises from the close intermetallic proximity facilitating chloride bridging (thus enhancing initiation), which promotes a rigid square pyramidal geometry around the Al center and further increases the available monomer coordination sites. This work also translates the use of ab initio molecular dynamics calculations to ROP, introducing a useful method of investigating catalyst flexibility and revealing that ligand strain and molecular rigidity can enhance heterometallic catalyst performance.

show abstract