Ring closing metathesis by Hoveyda–Grubbs catalysts: A theoretical approach of some aspects of the initiation mechanism and the influence of solvent

Sá, Égil de Brito; Matos, José Milton Elias de

doi:10.1016/j.ica.2014.11.007

Cited by 7 publications

(3 citation statements)

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“…Solvent effects in olefin metathesis have been studied in small molecule reactions such as ringclosing metathesis, [22][23][24] acyclic diene metathesis (ADMET) polymerization, 25 and ROMP, focusing mostly on initiation rates or using catalysts other than G3. [26][27][28][29][30][31] For example, Thompson and coworkers found that when performing ROMP using noble metal halide catalysts, solvents that can complex to the propagating species via hydrogen bonding or via Lewis acid/Lewis base interactions resulted in dramatic changes in the tacticity of the polymer products and in the reactivity ratios in copolymerizations.…”

Section: Introductionmentioning

confidence: 99%

“…Solvent effects in olefin metathesis have been studied in small-molecule reactions such as ring-closing metathesis, − acyclic diene metathesis (ADMET) polymerization, and ROMP, focusing mostly on initiation rates or using catalysts other than G3. − For example, Thompson and co-workers found that when performing ROMP using noble metal halide catalysts, solvents that can complex to the propagating species via hydrogen bonding or via Lewis acid/Lewis base interactions resulted in dramatic changes in the tacticity of the polymer products and in the reactivity ratios in copolymerizations . In ADMET, Schulz and Wagener showed that the solvent choice greatly affected the maximum molecular weight achievable, with molecular weights almost an order of magnitude higher in dichloromethane (CH 2 Cl 2 ) than the same polymerization performed in tetrahydrofuran (THF) .…”

Section: Introductionmentioning

confidence: 99%

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Solvent Effects in Grafting-through Ring-Opening Metathesis Polymerization

et al. 2022

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Ring-opening metathesis polymerization (ROMP) utilizing Grubbs' third-generation catalyst ((H2IMes)(Cl)2(pyr)2RuCHPh) shows characteristics of living polymerizations, including molecular weights increasing with monomer conversion and the ability to make (multi)block copolymers. However, irreversible termination reactions still occur due to catalyst decomposition, leading to terminated chains, especially in the context of sterically demanding monomers such as macromonomers (MM). In this work, we performed identical ROMP reactions on three different MMs in six solvents commonly used in ROMP with varying levels of purity. The solvents included ethyl acetate (EtOAc), dichloromethane (CH2Cl2), chloroform (CHCl3), toluene, tetrahydrofuran (THF), and N,N-dimethylformamide (DMF). All polymerizations were conducted under air targeting a bottlebrush polymer backbone degree of polymerization (Nbb) of 100. All three MMs included a norbornene on the α chain end and had molecular weights (Mn) of ~4 kg/mol. They included one polystyrene MM with a bromine on the ω chain end and two poly(n-butyl acrylate)MMs with either a bromine or a trithiocarbonate group on the ω chain end. Solvent choice, and in some cases level of purity, led to significant differences in the propagation rate in these ROMP grafting-through reactions. Of the solvents tested, propagation rates in EtOAc and CH2Cl2 were approximately 4-fold and 2-fold faster, respectively, than CHCl3, toluene, and THF for all MMs.Propagation was much slower in DMF for the polystyrene MM than all the other solvents, and on par with the slower solvents for the two poly(n-butyl acrylate) MMs tested. The purity of the solvent in some cases had a profound effect on the propagation rate: In the case of EtOAc, purification led to a 2-fold decrease in propagation rate; in contrast, purification of THF was required to observe full conversion of MM to bottlebrush polymer. The functional group on the ω chain end did not influence the rate of ROMP. Utilizing UV-Vis spectroscopy to measure catalyst 3 decomposition, the main polymer termination route in ROMP, we uncovered dramatic solvent effects, where the catalyst decomposed over ten times faster in THF and DMF than in toluene.Finally, studies targeting Nbb = 500 or 1000 revealed that toluene, EtOAc, and CH2Cl2 demonstrated the highest degree of "livingness" in ROMP. These results will enable the synthesis of complex polymer architectures using ROMP with a high degree of living character.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Solvent Effects in Grafting-through Ring-Opening Metathesis Polymerization

et al. 2022

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“…The activation of the Hoveyda-Grubbs-type complexes occurs by breaking the Ru-O bond and simultaneous rotation of the C carbene -C aromatic bond in the benzylidene moiety (Fig. 2) if the dissociative mechanism [8,12,[52][53][54] is assumed. It is known that the activity of this type of catalysts can be significantly modified by changing the steric and/or electronic properties of the Ru-chelating isopropoxy fragment.…”

Section: Activation Of the Hoveyda-grubbs-type Catalystsmentioning

confidence: 99%

Formation of active species from ruthenium alkylidene catalysts—an insight from computational perspective

et al. 2019

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Ruthenium alkylidene complexes are commonly used as olefin metathesis catalysts. Initiation of the catalytic process requires formation of a 14-electron active ruthenium species via dissociation of a respective ligand. In the present work, this initiation step has been computationally studied for the Grubbs-type catalysts 3 ), using density functional theory (DFT). Additionally, the extended-transition-state combined with the natural orbitals for the chemical valence (ETS-NOCV) and the interacting quantum atoms (IQA) energy decomposition methods were applied. The computationally determined activity order within both families of the catalysts and the activation parameters are in agreement with reported experimental data. The significance of solvent simulation and the basis set superposition error (BSSE) correction is discussed. ETS-NOCV demonstrates that the bond between the dissociating ligand and the Ru-based fragment is largely ionic followed by the charge delocalizations: σ(Ru-P) and π(Ru-P) and the secondary CH … Cl, CH … π, and CH … HC interactions. In the case of transition state structures, the majority of stabilization stems from London dispersion forces exerted by the efficient CH … Cl, CH … π, and CH … HC interactions. Interestingly, the height of the electronic dissociation barriers is, however, directly connected with the prevalent (unfavourable) changes in the electrostatic and orbital interaction contributions despite the favourable relief in Pauli repulsion and geometry reorganization terms during the activation process. According to the IQA results, the isopropoxy group in the Hoveyda-Grubbs-type catalysts is an efficient donor of intra-molecular interactions which are important for the activity of these catalysts.

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Olefin Polymerization

Tabba

Abu‐Surrah

2015

Polyolefin Compounds and Materials

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Ring closing metathesis by Hoveyda–Grubbs catalysts: A theoretical approach of some aspects of the initiation mechanism and the influence of solvent

Cited by 7 publications

References 57 publications

Solvent Effects in Grafting-through Ring-Opening Metathesis Polymerization

Solvent Effects in Grafting-through Ring-Opening Metathesis Polymerization

Formation of active species from ruthenium alkylidene catalysts—an insight from computational perspective

Olefin Polymerization

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