Metal-silicon bonding energetics in organo-Group 4 and organo—f-element complexes. Implications for bonding and reactivity

King, Wayne A.; Marks, Tobin J.

doi:10.1016/0020-1693(94)04265-w

Cited by 49 publications

(27 citation statements)

References 60 publications

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“…Bei dem Beispiel in Schema erfolgt zunächst eine exotherme Olefininsertion in eine Ln‐H‐Bindung, wofür es bereits etliche Literaturbeispiele gibt 18. Anschließend kommt es zu einer umsatzbestimmenden, exothermen19a,b M‐C/Si‐H‐Umlagerung 20. Aus mechanistischen Studien17d geht hervor, dass bei der α‐Olefinhydrosilylierung die Wechselfrequenz und die Regioselektivität für eine 2,1‐Addition höher sind, wenn der Katalysator eine offenere Koordinationsumgebung aufweist.…”

Section: Introductionunclassified

In‐situ‐Funktionalisierung von Polyolefinen mit Heteroatomen: Reaktionswege und katalytische Kettenübertragung

Amin

Marks

2008

Angewandte Chemie

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Kettenübertragungen sind effiziente und selektive chemische Prozesse für die d‐ und f‐Metall‐katalysierte In‐situ‐Funktionalisierung von Polyolefinen. Eine Reihe höchst unterschiedlicher elektronenarmer wie auch elektronenreicher Kettenüberträger eignet sich dafür, bei der Single‐Site‐Polymerisation von Olefinen einen selektiven Kettenabbruch mit gleichzeitiger Kohlenstoff‐Heteroelement‐Verknüpfung herbeizuführen. Als Kettenüberträger finden z. B. Silane, Borane, Alane, Phosphine und Amine Verwendung. Mit ihnen sind hohe Polymerisationsaktivitäten, eine Kontrolle von Molekulargewicht und Mikrostruktur der Polyolefine und eine selektive Kettenfunktionalisierung möglich. Für elektronenarme und elektronenreiche Reagentien findet man deutlich unterschiedliche Mechanismen. Als Katalysatoren für diese selektiven Kettenabbruchs‐/Funktionalisierungsprozesse eignen sich vielfältige Metallzentren (frühe Übergangsmetalle, Lanthanoide, späte Übergangsmetalle) und Single‐Site‐Hilfsliganden (Metallocene, Halbmetallocene, Nichtmetallocene).

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Section: Introductionunclassified

In‐situ‐Funktionalisierung von Polyolefinen mit Heteroatomen: Reaktionswege und katalytische Kettenübertragung

Amin

Marks

2008

Angewandte Chemie

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“…Although it has never been noted in the polymerization process, there are precedents in the stoichiometric reaction with late transition metal complexes . In addition, thermodynamic data derived from calorimetric measurement suggests β‐silyl elimination is endothermic as the β‐H elimination (eqs 5 and 6) …”

Section: Resultsmentioning

confidence: 99%

Silyl‐functionalized polyolefins via co‐polymerization of vinylsilanes with ethylene or propylene catalyzed by group IV metallocene complexes

Yang

2018

J. Polym. Sci. Part A: Polym. Chem.

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Vinylsilanes CH2CHSiR3 (R = Me, NMe2, OMe, OTMS) copolymerize with ethylene rapidly in the presence of catalytic amounts of [Cp′2ZrMe][MeB(C6F5)3] (Cp′ = η5‐C5Me5) (I) to give high molecular weight silyl‐functionalized polyethylene. The molecular weight of the polymer can be controlled by varying the comonomer concentration as well as the reaction temperature. Relatively low molecular weight polymer was produced at a higher silyl monomer concentration and a higher polymerization temperature. The incorporation of silyl monomer in the polymer is in the range of 0.1‐ 6.0%. On the other hands, catalysts [Cp2ZrMe][MeB(C6F5)3] (Cp′ = η5‐C5H5) (II) and [Cp″2ZrMe][MeB(C6F5)3] (Cp″ = η5‐1,2‐C5Me2H3) (III) show much lower activity. With the use of more coordinatively unsaturated constrained geometry catalysts (CGC), Me2Si(η5‐C5Me4)(NtBu)MMe][MeB(C6F5)3] (IV, M = Zr; V, M = Ti), the silyl monomer incorporation in the polymer was increased to 40%. The Ti catalyst is more active and produces polymer with a higher molecular weight with a higher silyl monomer incorporation at 23 °C. The copolymerization of vinyltrimethylsilane with propylene was also investigated with these catalysts, yielding high silyl‐functionalized propylene copolymer/oligmer. The microstructure of the copolymers/oligomers has been thoroughly investigated by 1D and 2D NMR techniques (1H, 13C, NOE, DEPT, HETCOR, and FLOCK). The results show that the backbone of the copolymers/oligomers is essentially random. Several termination pathways have been identified. In particular, two unsaturated silyl terminations, cis and/or trans‐TMSCHCH, were identified with the constrained geometry catalysts. Their formation was rationalized based on transition state models. It was found that occasional 1,2‐insertion of either propylene or vinyltrimethylsilane into the chain propagation process has a high probability serving as the trigger for polymer chain termination via β‐H elimination. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1308–1321

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“…While the relative solubility of the two compounds in aromatic hydrocarbon solvents follows the trend suggested by the Δ(δ paraF − δ metaF ) parameter, and 4-dpe is significantly more soluble in bromobenzene-d 5 than in benzene-d 6 , one might expect that the structure, and thus the 19 F NMR-based parameter, would be affected by solvent polarity. That is not the case, and this parameter for 4-tmeda is apparently unaffected by a solvent change from benzene-d 6 to bromobenzene-d 5 . In that context, it is also worth noting that the 11 3 and MeB(C 6 F 5 ) 3 groups are identical in 4-dpe, but distinct from 4-tmeda.…”

Section: ■ Introductionmentioning

confidence: 91%

“…For comparison, Marks's studies of ion-pair separation and methide transfer in (C 5 H 3 Me 2 ) 2 ZrMe-(μ-Me)B(C 6 F 5 ) 3 indicate that ion-pair separation is 10× faster than borane dissociation in toluene-d 8 3 ion-pairs show that borane dissociation is not facile with more electropositive metal complexes; however, processes involving MeB(C 6 F 5 ) 3 dissociation from the scandium center are sufficiently slow that they can be studied by 1 H NMR spectroscopy. 18 The and 3.9 ppm in bromobenzene-d 5 . Previously, Horton suggested that a Δ(δ paraF − δ metaF ) value greater than 3.5 ppm corresponds to an inner sphere interaction (Zr−Me−B, the socalled contact ion-pair), whereas Δ(δ paraF − δ metaF ) < 3.5 ppm indicates that a solvent-separated ion-pair is formed.…”

Section: ■ Introductionmentioning

confidence: 96%

Nucleophilicity of Neutral versus Cationic Magnesium Silyl Compounds

et al. 2013

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Charge and ancillary ligands affect the reactivity of monomeric tris(trimethylsilyl)silyl magnesium compounds. Diamine-coordinated (tmeda)Mg{Si(SiMe3)3}Me (tmeda = tetramethylethylenediamine; 2-tmeda) and (dpe)Mg{Si(SiMe3)3}Me (dpe =1,2-N,N-dipyrrolidenylethane; 2-dpe) are synthesized by salt elimination reactions of L2MgMeBr and KSi(SiMe3)3. Compounds 2-tmeda or 2-dpe react with MeI or MeOTf to give MeSi(SiMe3)3 as the product of Si-C bond formation. In contrast, 2-tmeda and 2-dpe undergo exclusively reaction at the magnesium methyl group with electrophiles such as Me3SiI, B(C6F5)3, HB(C6F5)2, and [Ph3C][B(C6F5)4]. These reactions provide a series of neutral, zwitterionic, and cationic magnesium silyl compounds, and from this series we have found that silyl group transfer is less effective with cationic magnesium compounds than neutral complexes. KeywordsAncillary ligands, Electrophiles, elimination reaction, neutral complexes, nucleophilicities, Si-C bond formation, Tetramethylethylenediamine, Trimethylsilyl, magnesium Disciplines Chemistry CommentsReprinted (adapted) with permission from Organometallics 32 (2013) ABSTRACT: Charge and ancillary ligands affect the reactivity of monomeric tris(trimethylsilyl)silyl magnesium compounds. Diamine-coordinated (tmeda)-Mg{Si(SiMe 3 ) 3 }Me (tmeda = tetramethylethylenediamine; 2-tmeda) and (dpe)Mg{Si(SiMe 3 ) 3 }Me (dpe =1,2-N,N-dipyrrolidenylethane; 2-dpe) are synthesized by salt elimination reactions of L 2 MgMeBr and KSi(SiMe 3 ) 3 . Compounds 2-tmeda or 2-dpe react with MeI or MeOTf to give MeSi(SiMe 3 ) 3 as the product of Si−C bond formation. In contrast, 2-tmeda and 2-dpe undergo exclusively reaction at the magnesium methyl group with electrophiles such as Me 3 SiI, B(C 6 F 5 ) 3 , HB(C 6 F 5 ) 2 , and [Ph 3 C][B(C 6 F 5 ) 4 ]. These reactions provide a series of neutral, zwitterionic, and cationic magnesium silyl compounds, and from this series we have found that silyl group transfer is less effective with cationic magnesium compounds than neutral complexes.

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Metal-silicon bonding energetics in organo-Group 4 and organo—f-element complexes. Implications for bonding and reactivity

Cited by 49 publications

References 60 publications

In‐situ‐Funktionalisierung von Polyolefinen mit Heteroatomen: Reaktionswege und katalytische Kettenübertragung

In‐situ‐Funktionalisierung von Polyolefinen mit Heteroatomen: Reaktionswege und katalytische Kettenübertragung

Silyl‐functionalized polyolefins via co‐polymerization of vinylsilanes with ethylene or propylene catalyzed by group IV metallocene complexes

Nucleophilicity of Neutral versus Cationic Magnesium Silyl Compounds

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