Related Experiment Video
Updated: Jul 6, 2026

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents
Published on: May 28, 2014
Alkenylsilane structure effects on mononuclear and binuclear organotitanium-mediated ethylene polymerization: scope
1Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Abstract:
Alkenylsilanes of varying chain lengths are investigated as simultaneous chain-transfer agents and comonomers in organotitanium-mediated olefin polymerization processes. Ethylene polymerizations were carried out with activated CGCTiMe2 and EBICGCTi2Me4 (CGC = Me2Si(Me4C5)(NtBu); EBICGC = (mu-CH2CH2-3,3'){(eta5-indenyl)[1-Me2Si(tBuN)]}2) precatalysts in the presence of allylsilane, 3-butenylsilane, 5-hexenylsilane, and 7-octenylsilane. In the presence of these alkenylsilanes, high polymerization activities (up to 107 g of polymer/(mol of Ti.atm ethylene.h)), narrow product copolymer polydispersities, and substantial amounts of long-chain branching are observed. Regardless of Ti nuclearity, alkenylsilane incorporation levels follow the trend C8H15SiH3 < C6H11SiH3 approximately C4H7SiH3 < C3H5SiH3. Alkenylsilane comonomer incorporation levels are consistently higher for CGCTiMe2-mediated copolymerizations (up to 54%) in comparison with EBICGCTi2Me4-mediated copolymerizations (up to 32%). The long-chain branching levels as compared to the total branch content follow the trend C3H5SiH3 < C4H7SiH3 approximately C6H11SiH3 approximately C8H15SiH3, with gel permeation chromatography-multi-angle laser light scattering-derived branching ratios (gM) approaching 1.0 for C8H15SiH3. Time-dependent experiments indicate a linear increase of copolymer Mw with increasing polymerization reaction time. This process for producing long-chain branched polyolefins by coupling of an alpha-olefin with a chain-transfer agent in one comonomer is unprecedented. Under the conditions investigated, alkenylsilanes ranging from C3 to C8 are all efficient chain-transfer agents. Ti nuclearity significantly influences silanolytic chain-transfer processes, with the binuclear system exhibiting a sublinear relationship between Mn and [alkenylsilane](-1) for allylsilane and 3-butenylsilane, and a superlinear relationship between Mn and [alkenylsilane](-1) for 5-hexenylsilane and 7-octenylsilane. For the mononuclear Ti system, alkenylsilanes up to C6 exhibit a linear relationship between Mn and [alkenylsilane](-1), consistent with a simple silanolytic chain termination mechanism.
More Related Videos
09:12Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering
Published on: June 1, 2016
09:34Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly
Published on: February 6, 2020
Related Concept Videos
Hybridization of Atomic Orbitals II
¹H NMR: Complex Splitting
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Polymer Classification: Architecture
Polymer Classification: Stereospecificity
¹H NMR: Long-Range Coupling
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
Pericyclic Reactions: Introduction
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...