Condensation of primary silanes in the presence of Cp2MCl2/nBuLi (M  Ti, Zr, Hf)

Corey, Joyce Y.; Zhu, Xiaoxia

doi:10.1016/0022-328x(92)80048-3

Cited by 50 publications

(8 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This in turn indicates that the probabilities of m and r coupling are roughly equal ( p m ≈ 0.5); i.e., there is little stereoselection. This is in contrast to the conclusion of Corey and Zhu, who used Cp 2 MCl 2 /BuLi catalysts (M = Ti, Zr Hf) to polymerize BuSiH 3 to low-molecular-weight oligomers. These authors found that one stereoisomer of the tetramer was strongly favored.…”

Section: Resultscontrasting

confidence: 90%

Stereostructures of Linear and Cyclic Polyphenylsilanes Produced by Dehydrocoupling in the Presence of Group 4 Metallocene Catalysts

et al. 1999

View full text Add to dashboard Cite

Phenylsilane was polymerized with a number of group 4 metallocene precatalysts, including (S,S)-[1,2-bis(η 5 -tetrahydroindenyl)ethane]titanium binaphtholate (1)/2BuLi, Cp 2 HfCl 2 (2)/ 2BuLi/B(C 6 F 5 ) 3 , and CpCp*ZrCl 2 (3)/2BuLi/B(C 6 F 5 ) 3 . With 1, polymerization proceeds extremely slowly and it is possible to observe the stepwise oligomerization to Si 2 , Si 3 , Si 4 , and Si 5 species. One-and two-dimensional 1 H and 29 Si NMR experiments permit the assignment of peaks to the stereoisomers of the Si 4 and Si 5 compounds. For the linear oligomers PhSiH 2 SiHPh(SiHPh) n SiHPhSiH 2 Ph (n g 0), the 29 Si NMR resonances group cleanly into the regions δ (ppm) 58-59 (PhSiH 2 ), 59-63 (SiHPhSiHPhSiHPh), and 64-65 (PhSiH 2 SiHPhSiHPh). The chiral catalyst 1 has little influence on the sterochemical outcome of the coupling reaction. Higher molecular weight polymers synthesized with 2 and 3 or obtained by fractionation of lower molecular weight polymers all have nearly identical 29 Si NMR spectra. It is proposed that this spectrum is a reflection of the pentad composition of the polymers and that any deviations from randomness are a result of intrachain interactions at the growing chain end and are unrelated to the structure of the catalyst.

show abstract

Section: Resultscontrasting

confidence: 90%

Stereostructures of Linear and Cyclic Polyphenylsilanes Produced by Dehydrocoupling in the Presence of Group 4 Metallocene Catalysts

et al. 1999

View full text Add to dashboard Cite

show abstract

“…Dehydrocoupling polymerization of 1,3Si 6 was initiated by a series of early transition metal metallocenes (Table ). The highest molecular weight polymer was obtained with zirconocene dichloride in combination with n -butyllithium (Cp 2 ZrCl 2 / n -BuLi, entry 1), a catalytic system first reported by Corey. − Variation of the group 4 metal center did not lead to higher degrees of polymerization (entries 2–3), as observed in 1,4Si 6 polymerization . A several day induction period was observed with dimethylzirconocene (Cp 2 ZrMe 2 ), however, performing the reaction neat resulted in a reasonable degree of polymerization (entry 4).…”

Section: Resultsmentioning

confidence: 95%

“…Primary and secondary monosilanes (e.g., phenylsilane and diphenylsilane) are polymerized by transition metal-catalyzed dehydrocoupling, yielding polysilanes with the general formula [SiR 2 ] n (R = H, alkyl, or aryl) and hydrogen gas. , Group 4 metallocenes are among the best-studied dehydrocoupling polymerization catalysts. − These complexes are known to be sensitive to the degree of monomer substitution, with primary silanes (RSiH 3 ) producing the highest molecular weight polymers. − Secondary silanes (R 2 SiH 2 ) typically yield a mixture of dimers and trimers . This is due to the step-growth polymerization mechanism, in which dimerization of the secondary silane provides a molecule with unreactive tertiary silane end groups.…”

Section: Resultsmentioning

confidence: 99%

Directional Building Blocks Determine Linear and Cyclic Silicon Architectures

et al. 2018

View full text Add to dashboard Cite

Silicon nanomaterials combine earth abundance and biodegradability with exceptional electronic properties. Strategic synthesis promises access to novel architectures with well-defined surface structure, size, and shape. Herein, we describe a five-step synthesis of functional macrocyclic polysilanes. Comparison of the materials isolated from isomeric building blocks provides evidence that building block directionality controls the shape of the resulting nanomaterial. Infrared (IR) and H andSi NMR spectroscopies, coupled to computational data, provide evidence of a well-defined Si-H and Si-Me terminated structure. The intrinsic porosity and the polarization arising from the hydridic character of the Si-H bond suggest applications in lithium-ion batteries, which are supported by quantum chemical calculations.

show abstract

“…The sterically compressed σ-bond metathesis transition state is responsible for divergent results with primary and secondary silanes. , PhSiH 3 yields higher molecular weight polymers − than Ph 2 SiH 2 as a consequence of the step-growth polymerization: after the first Si–Si bond formation event, Ph 2 SiH 2 is converted to a dimer with unreactive tertiary silane end groups and polymer is not isolated (Scheme b).…”

Section: Poly(cyclosilane)s: Complex Silicon Frameworkmentioning

confidence: 99%

Conjugated Polymers Inspired by Crystalline Silicon

Marro

Klausen

2019

Chem. Mater.

View full text Add to dashboard Cite

Modern technologies depend on the semiconductor silicon. Silicon nanostructures evince compelling properties including luminescence and biodegradability. Silicon-based soft matter is less explored, despite the attractive properties of conjugated polymers and small molecules inspired by crystalline silicon. This perspective describes the major synthetic approaches to polysilanes and summarizes innovations in the preparation of structurally complex functional polysilanes that combine unusual conjugation phenomena, solution processability, and morphological control. A connection is drawn between the limitations of current polymerization methodology and fine control of structure−property relationships.

show abstract

Condensation of primary silanes in the presence of Cp2MCl2/nBuLi (M  Ti, Zr, Hf)

Cited by 50 publications

References 21 publications

Stereostructures of Linear and Cyclic Polyphenylsilanes Produced by Dehydrocoupling in the Presence of Group 4 Metallocene Catalysts

Stereostructures of Linear and Cyclic Polyphenylsilanes Produced by Dehydrocoupling in the Presence of Group 4 Metallocene Catalysts

Directional Building Blocks Determine Linear and Cyclic Silicon Architectures

Conjugated Polymers Inspired by Crystalline Silicon

Contact Info

Product

Resources

About