Metallocene derivatives of early transition metals. Part 4. Chemistry of the complexes [M(η-C5H5)2RR′][M = Ti, Zr, or Hf; R = CH2M′Me3(M′= C, Si, Ge, or Sn) or CH(SiMe3)2; R′= Cl or alkyl] and the X-ray structures of [Zr(η-C5H5)2(CH2M′Me3)2](M′= C or Si)

Jeffery, John C.; Läppert, Michael F.; Luong-Thi, Ngoc-Tuyet; Webb, M. J.; Atwood, Jerry L.; Hunter, William E.

doi:10.1039/dt9810001593

Cited by 49 publications

(18 citation statements)

References 2 publications

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“…The CH 2 CMe 3 groups in 7 are more sterically demanding than the CH 2 SiMe 3 groups in 8 [the C−Si bond (ca.1.85 Å) is longer than the C−C bond (ca. 1.54 Å)] and thus contribute significantly to the steric congestion in 7 …”

Section: Resultssupporting

confidence: 71%

Reactions of (Me₃ECH₂)₃ZrSi(SiMe₃)₃(E = C, Si) with 2,6-Dimethylphenyl Isocyanide. Preferential Isocyanide Insertion into Zr−Silyl Bonds

McAlexander

Diminnie

et al. 1998

Organometallics

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The reactions of alkyl silyl complexes (Me3ECH2)3ZrSi(SiMe3)3 [E = C (1), Si (2)] with 2,6-dimethylphenyl isocyanide (ArNC) have been investigated. The first ArNC was found to insert exclusively into the Zr − Si bond, and the second and third ArNC into the Zr−C bonds in 1 and 2. 1 and 2 react with up to 3 equiv of ArNC to give (Me3ECH2)3Zr{η2-C[Si(SiMe3)3]NAr} [E = C (3), Si (4)], (Me3ECH2)2Zr[η2-C(CH2EMe3)NAr]{η2-C[Si(SiMe3)3]NAr} [E = C (5), Si (6)], and (Me3ECH2)Zr[η2-C(CH2EMe3)NAr]2{η2-C[Si(SiMe3)3]NAr} [E = C (7), Si (8)]. The tri-insertion complexes 7 and 8 are inert to excess ArNC. The structures of 3 and 7 have been determined by X-ray crystallography. In the structure of 3, the α-hydrogen atoms on one neopentyl ligand lie in close contact (av 2.41 Å) with the metal center giving rise to Zr−C−Hα bond angles of 90 and 92°. The crystal structure of the precursor 1 has also been determined.

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Section: Resultssupporting

confidence: 71%

Reactions of (Me₃ECH₂)₃ZrSi(SiMe₃)₃(E = C, Si) with 2,6-Dimethylphenyl Isocyanide. Preferential Isocyanide Insertion into Zr−Silyl Bonds

McAlexander

Diminnie

et al. 1998

Organometallics

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“…Unlike their carbon analogues, Pt(CH 2 CMe 2 CHCH 2 ) 2 (COD) and Pt(CH 2 CMe 2 CH 2 CHCH 2 ) 2 (COD), which readily release COD in solution and form the COD-free PtR 2 compounds, 1-COD and 2-COD are stable in solution and very little (<5%) of the bound COD ligands are dissociated at room temperature. The higher binding strength of COD to 1 and 2 relative to their carbon analogues may be ascribed in part to the reduced steric size of unidentate CH 2 SiR 3 vs CH 2 CR 3 groups, although electronic factors such as the lower trans influence ,, of unidentate CH 2 SiR 3 vs CH 2 CR 3 groups may also play a role.…”

Section: Resultsmentioning

confidence: 99%

Platinum(II) Di-ω-alkenyl Complexes as “Slow-Release” Precatalysts for Heat-Triggered Olefin Hydrosilylation

Liu

Girolami

2021

J. Am. Chem. Soc.

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We describe the synthesis, characterization, and catalytic hydrosilylation activity of platinum(II) di-ω-alkenyl compounds of stoichiometry PtR2, where R = CH2SiMe2(vinyl) (1) or CH2SiMe2(allyl) (2), and their adducts with 1,5-cyclooctadiene (COD), dibenzo[a,e]cyclooctatetraene (DBCOT), and norbornadiene (NBD), which can be considered as slow-release sources of the reactive compounds 1 and 2. At loadings of 0.5 × 10–6–5 × 10–6 mol %, 1-COD is an active hydrosilylation catalyst that exhibits heat-triggered latency: no hydrosilylation activity occurs toward many olefin substrates even after several hours at 20 °C, but turnover numbers as high as 200000 are seen after 4 h at 50 °C, with excellent selectivity for formation of the anti-Markovnikov product. Activation of the PtII precatalyst occurs via three steps: slow dissociation of COD from 1-COD to form 1, rapid reaction of 1 with silane, and elimination of both ω-alkenyl ligands to form Pt0 species. The latent catalytic behavior, the high turnover number, and the high anti-Markovnikov selectivity are a result of the slow release of 1 from 1-COD at room temperature, so that the concentration of Pt0 during the initial stages of the catalysis is negligible. As a result, formation of colloidal Pt, which is known to cause side reactions, is minimized, and the amounts of side products are very small and comparable to those seen for platinum(0) carbene catalysts. The latent reaction kinetics and high turnover numbers seen for 1-COD after thermal triggering make this compound a potentially useful precatalyst for injection molding or solvent-free hydrosilylation applications.

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“…Chlorobis^5-2,4-cyclopentadien-l-yl)trimethylsilylmethyltitanium, Cp2Ti(Cl)-CH2Si(CH3)3, was prepared by a modification of a published procedure (16). Trimethylsilylmethylmagnesium chloride in Et20 (25 mL, 0.90 M, 22 mmol, 1.1 equiv; Aldrich) was added with stirring over a 20-min period to a solution of Cp2TiCl2 (4.98 g, 20.0 mmol) in CH2C12 at ambient temperature.…”

Section: Methodsmentioning

confidence: 99%

Active Sites in Soluble Ziegler Polymerization Catalysts Generated from Titanocene Halides and Organoaluminum Lewis Acids

Eisch

1992

Advances in Chemistry

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By means of X-ray single-crystal data the Ti-C and Ti-Cl bond lengths in trimethylsilylmethyltitanocene chloride (11) have been de termined. The operation of σ-hyperconjugation in this compound leads to an unusual shortening of the Ti-C bond. In solution the observed shifts in the 1 H NMR signals of the CH2 or the cyclopentadienyl (Cp) groups of 11 are attributed to varying degrees of coordinative solvation of the titanium center or hydrogen bonding at the chlorine center. Such inherent polarity of the Ti-Cl bond in 11 has been found to be sharply accentuated hy the introduction of a Lewis acid, AlCl2R. By monitoring such reaction mixtures by 1 H, 13 C, and 27 Al NMR spectroscopy, direct evidence is obtained for the gen eration of the alkyltitanocenium ion, Cp2RTi + , andAlCl4-. Such com binations of 11 and Lewis acid are effective catalysts for the polym erization of ethylene, and Me3Si fragments from 11 are found in the resulting polyethylene. These findings support the thesis that Cp2RTi + ions are the active polymerization sites in such Ziegler catalyst sys tems. THENATURE OF OLEFIN POLYMERIZATION CATALYSTS formed from com binations of titanium halides and alkylaluminum halides has remained the subject of controversy (I) since the epoch-making discoveries of Ziegler et al. (2) and of Natta et al. (3) some 35 years ago. Much of the difficulty in 0065-2393/92/0230-0575$06.00/0

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Metallocene derivatives of early transition metals. Part 4. Chemistry of the complexes [M(η-C₅H₅)₂RR′][M = Ti, Zr, or Hf; R = CH₂M′Me₃(M′= C, Si, Ge, or Sn) or CH(SiMe₃)₂; R′= Cl or alkyl] and the X-ray structures of [Zr(η-C₅H₅)₂(CH₂M′Me₃)₂](M′= C or Si)

Abstract: Nuclear magnetic resonance spectroscopic data on metallocene(1v) halogeno-alkyls and dialkyls Chemical shift (T) a

Cited by 49 publications

References 2 publications

Reactions of (Me₃ECH₂)₃ZrSi(SiMe₃)₃(E = C, Si) with 2,6-Dimethylphenyl Isocyanide. Preferential Isocyanide Insertion into Zr−Silyl Bonds

Reactions of (Me₃ECH₂)₃ZrSi(SiMe₃)₃(E = C, Si) with 2,6-Dimethylphenyl Isocyanide. Preferential Isocyanide Insertion into Zr−Silyl Bonds

Platinum(II) Di-ω-alkenyl Complexes as “Slow-Release” Precatalysts for Heat-Triggered Olefin Hydrosilylation

Active Sites in Soluble Ziegler Polymerization Catalysts Generated from Titanocene Halides and Organoaluminum Lewis Acids

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Metallocene derivatives of early transition metals. Part 4. Chemistry of the complexes [M(η-C5H5)2RR′][M = Ti, Zr, or Hf; R = CH2M′Me3(M′= C, Si, Ge, or Sn) or CH(SiMe3)2; R′= Cl or alkyl] and the X-ray structures of [Zr(η-C5H5)2(CH2M′Me3)2](M′= C or Si)

Abstract: Nuclear magnetic resonance spectroscopic data on metallocene(1v) halogeno-alkyls and dialkyls Chemical shift (T) a

Cited by 49 publications

References 2 publications

Reactions of (Me3ECH2)3ZrSi(SiMe3)3(E = C, Si) with 2,6-Dimethylphenyl Isocyanide. Preferential Isocyanide Insertion into Zr−Silyl Bonds

Reactions of (Me3ECH2)3ZrSi(SiMe3)3(E = C, Si) with 2,6-Dimethylphenyl Isocyanide. Preferential Isocyanide Insertion into Zr−Silyl Bonds

Platinum(II) Di-ω-alkenyl Complexes as “Slow-Release” Precatalysts for Heat-Triggered Olefin Hydrosilylation

Active Sites in Soluble Ziegler Polymerization Catalysts Generated from Titanocene Halides and Organoaluminum Lewis Acids

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Metallocene derivatives of early transition metals. Part 4. Chemistry of the complexes [M(η-C₅H₅)₂RR′][M = Ti, Zr, or Hf; R = CH₂M′Me₃(M′= C, Si, Ge, or Sn) or CH(SiMe₃)₂; R′= Cl or alkyl] and the X-ray structures of [Zr(η-C₅H₅)₂(CH₂M′Me₃)₂](M′= C or Si)

Reactions of (Me₃ECH₂)₃ZrSi(SiMe₃)₃(E = C, Si) with 2,6-Dimethylphenyl Isocyanide. Preferential Isocyanide Insertion into Zr−Silyl Bonds

Reactions of (Me₃ECH₂)₃ZrSi(SiMe₃)₃(E = C, Si) with 2,6-Dimethylphenyl Isocyanide. Preferential Isocyanide Insertion into Zr−Silyl Bonds