Related Experiment Video
Updated: Jul 11, 2026
09:22
Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
Published on: February 7, 2017
Bimetallic phenylene-bridged Cp/amide titanium complexes and their olefin polymerization
Sang Hoon Lee1, Chun Ji Wu, Ui Gab Joung
1Department of Molecular Science and Technology, Suwon, 443-749, South Korea.
Dalton Transactions (Cambridge, England : 2003)
|October 12, 2007
Summary
New bimetallic titanium complexes show high activity in ethylene/1-hexene copolymerization, producing polymers with higher molecular weights and long-chain branching compared to mononuclear analogues.
Area of Science:
- Organometallic Chemistry
- Polymer Science
- Catalysis
Background:
- Titanium complexes are widely studied as catalysts for olefin polymerization.
- Bimetallic complexes offer potential for unique catalytic properties and polymer architectures.
- Developing efficient catalysts for producing polymers with specific characteristics like high molecular weight and branching is crucial.
Purpose of the Study:
- To synthesize novel bimetallic dichlorotitanium complexes.
- To evaluate the catalytic activity of these bimetallic complexes in ethylene/1-hexene copolymerization.
- To compare their performance against mononuclear analogues and analyze the resulting polymer properties.
Main Methods:
- Synthesis of bimetallic dichlorotitanium complexes utilizing Suzuki-coupling reactions.
- X-ray crystallography for structural determination of one complex.
- Ethylene/1-hexene copolymerization experiments using the synthesized complexes as catalysts.
- Analysis of polymer molecular weights and branching content.
Main Results:
- Bimetallic complexes, specifically {2,6-[eta(5)-2,5-Me2C5H2](2)-4-R-C6H2N-microN}{Ti(IV)Cl2}2 and 4,4'-A[{2-(eta(5)-2,3,5-Me3C5H)C6H3NC6H11-kappaN}Ti(IV)Cl2]2, were successfully synthesized.
- Complexes {2,6-[eta(5)-2,5-Me2C5H2](2)-4-R-C6H2N-microN}{Ti(IV)Cl2}2 were inactive for ethylene/1-hexene copolymerization.
- The other bimetallic complexes exhibited high catalytic activity, surpassing their mononuclear analogue {2-(eta(5)-2,3,5-Me3C5H)C6H3NC6H11-kappaN}Ti(IV)Cl2.
- Polymers produced by bimetallic systems had higher molecular weights and slightly increased long-chain branching.
Conclusions:
- Bimetallic titanium complexes can be effective catalysts for ethylene/1-hexene copolymerization.
- The bimetallic structure enhances catalytic activity and influences polymer properties, leading to higher molecular weights and branching.
- These findings open avenues for designing advanced catalysts for tailored polymer synthesis.
Related Concept Videos
01:13Olefin Metathesis Polymerization: Overview
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
01:16Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
00:53Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
01:17Ziegler–Natta Chain-Growth Polymerization: Overview
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular...
00:57Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...