Elektrophile Aktivierung von Silicium‐Wasserstoff‐ Bindungen in katalytischen Hydrosilierungen

Lipke, Mark C.; Liberman‐Martin, Allegra L.; Tilley, T. Don

doi:10.1002/ange.201605198

Cited by 59 publications

(2 citation statements)

References 263 publications

(231 reference statements)

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“…However, it can be seen that the removal of the commercial sizing with piranha solution improves the fiber–matrix interface performance significantly, and the maximum pull-out force F max,pull amounts to 20.5 N (approximately 40%) compared to commercial sized fibers. We assume that this improved adhesion performance is related to the presence of ketone groups from the oxidized sizing residues, which are known to undergo catalyzed hydrosilylation with Si-H bonds [ 75 ]. Thus, a direct coupling of the oxidized residues of the sizing with the PDMS matrix (which is a two-component system containing activated Si–H) is obtained, leading to an enhanced pull-out force.…”

Section: Resultsmentioning

confidence: 99%

Tailored Interfaces in Fiber-Reinforced Elastomers: A Surface Treatment Study on Optimized Load Coupling via the Modified Fiber Bundle Debond Technique

et al. 2020

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The interface between the reinforcement and surrounding matrix in a fibrous composite is decisive and critical for maintaining component performance, durability, and mechanical structure properties for load coupling assessment, especially for highly flexible composite materials. The clear trend towards tailored solutions reveals that an in-depth knowledge on surface treating methods to enhance the fiber–matrix interfacial interaction and adhesion properties for an optimized load transfer needs to be ensured. This research aims to quantify the effect of several surface treatments for glass fibers applied in endless fiber-reinforced elastomers with pronounced high deformations. Due to this, the glass fiber surface is directly modified with selected sizings, using a wet chemical treatment, and characterized according to chemical and mechanical aspects. For this purpose, the interfacial adhesion performance between fibers and the surrounding matrix material is investigated by a modified fiber pull-out device. The results clearly show that an optimized surface treatment improves the interface strength and chemical bonding significantly. The fiber pull-out test confirms that an optimized fiber–matrix interface can be enhanced up to 85% compared to standard surface modifications, which distinctly provides the basis of enhanced performances on the component level. These findings were validated by chemical analysis methods and corresponding optical damage analysis.

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Section: Resultsmentioning

confidence: 99%

Tailored Interfaces in Fiber-Reinforced Elastomers: A Surface Treatment Study on Optimized Load Coupling via the Modified Fiber Bundle Debond Technique

et al. 2020

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“…8−10 For mid-to late-transition metal complexes with formally double bonds to silicon (i.e., silylene complexes, M = SiR 2 ), charge localization at the silicon atom is a critical factor in determining reactivity patterns. 5,11 For example, cationic group 8 silylene complexes of the type [Cp*(R 3 P)(H) 2 MSiHR′] + (Cp* = η 5 -C 5 Me 5 ; M = Ru, Os) possess little M−Si doublebond character and exhibit strong positive charge localization at silicon, leading to rapid insertions of olefins into the Si−H bond. 12−14 In contrast, the neutral analogues Cp*(R 3 P)(H)-MSiHR′ (M = Ru, Os) do not react with olefins, even at elevated temperatures.…”

Section: ■ Introductionmentioning

confidence: 96%

Versatile Fe–Sn Bonding Interactions in a Metallostannylene System: Multiple Bonding and C–H Bond Activation

et al. 2021

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The metallostannylene Cp*( i Pr 2 MeP)(H) 2 Fe-SnDMP (1; Cp* = η 5 -C 5 Me 5 ; DMP = 2,6-dimesitylphenyl), formed by hydrogen migration in a putative Cp*( i Pr 2 MeP)HFe-[Sn(H)DMP] intermediate, serves as a robust platform for exploration of transition-metal main-group element bonding and reactivity. Upon one-electron oxidation, 1 expels H 2 to generate the coordinatively unsaturated [Cp*( i Pr 2 MeP)FeSnDMP][B-(C 6 F 5 ) 4 ] ( 3), which possesses a highly polarized Fe−Sn multiple bond that involves interaction of the tin lone pair with iron. Evidence from EPR and 57 Fe Mossbauer spectroscopy, along with DFT studies, shows that 3 is primarily an iron-based radical with charge localization at tin. Upon reduction of 3, C−H bond activation of the phosphine ligand was observed to produce Cp*HFe(κ 2 -(P,Sn)Sn(DMP)CH 2 CHMePMe i Pr) (5). Complex 5 was also accessed via thermolysis of 1, and kinetics studies of this thermolytic pathway indicate that the reductive elimination of H 2 from 1 to produce a stannylyne intermediate, Cp*( i Pr 2 MeP)Fe[SnDMP] (A), is likely rate-determining. Evidence indicates that the production of 5 proceeds through a concerted C−H bond activation. DFT investigations suggest that the transition state for this transformation involves C−H cleavage across the Fe−Sn bond and that a related transition state where C−H bond activation occurs exclusively at the tin center is disfavored, illustrating an effect of iron−tin cooperativity in this system.

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Mechanism‐Based Enantiodivergence in Manganese Reduction Catalysis: A Chiral Pincer Complex for the Highly Enantioselective Hydroboration of Ketones

et al. 2017

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A manganese alkyl complex containing a chiral bis(oxazolinyl‐methylidene)isoindoline pincer ligand is a precatalyst for a catalytic system of unprecedented activity and selectivity in the enantioselective hydroboration of ketones, thus producing preparatively useful chiral alcohols in excellent yields with up to greater than 99 % ee. It is applicable for both aryl alkyl and dialkyl ketone reduction under mild reaction conditions (TOF >450 h−1 at −40 °C). The earth‐abundant base‐metal catalyst operates at very low catalyst loadings (as low as 0.1 mol %) and with a high level of functional‐group tolerance. There is evidence for the existence of two distinct mechanistic pathways for manganese‐catalyzed hydride transfer and their role for enantiocontrol in the selectivity‐determining step is presented.

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Elektrophile Aktivierung von Silicium‐Wasserstoff‐ Bindungen in katalytischen Hydrosilierungen

Cited by 59 publications

References 263 publications

Tailored Interfaces in Fiber-Reinforced Elastomers: A Surface Treatment Study on Optimized Load Coupling via the Modified Fiber Bundle Debond Technique

Tailored Interfaces in Fiber-Reinforced Elastomers: A Surface Treatment Study on Optimized Load Coupling via the Modified Fiber Bundle Debond Technique

Versatile Fe–Sn Bonding Interactions in a Metallostannylene System: Multiple Bonding and C–H Bond Activation

Mechanism‐Based Enantiodivergence in Manganese Reduction Catalysis: A Chiral Pincer Complex for the Highly Enantioselective Hydroboration of Ketones

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