NCN Pincer Ligand Group VI Catalysts for Olefin Polymerization
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Solution Overview
Problem
Current olefin polymerization catalysts often require expensive cocatalysts like MAO, and existing olefin isomerization catalysts lack selectivity for converting terminal to internal olefins without forming conjugated products, limiting control over polymerization rates, stereochemistry, and molecular weight distribution.
Innovation Solution
Development of NCN pincer ligand group VI metal complexes, specifically Cr, Mo, or W complexes in various oxidation states with hydrocarbon substitutions, which act as single-component catalysts for olefin polymerization and isomerization, utilizing triisobutylaluminum as an activator to initiate polymerization and isomerization reactions without the need for expensive cocatalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional olefin polymerization catalysts are used, then polymerization activity is achieved, but expensive cocatalysts like MAO are required
Solution Approach 1:
The invention extracts and eliminates the dependency on expensive cocatalysts like MAO by designing self-activating catalysts. The chromium complexes contain all necessary catalytic components within the molecular structure itself, removing the need for separate activator systems and thereby reducing material costs while maintaining high polymerization activity.
Solution Approach 2:
The chromium pincer complexes serve multiple functions simultaneously: they act as the polymerization catalyst, the activator, and the stabilizing ligand system all in one molecular entity. This multi-functionality eliminates the need for separate cocatalyst components, resolving the contradiction between achieving polymerization activity and reducing activator quantity/cost.
2Productivity
If conventional olefin isomerization catalysts are used, then isomerization reaction occurs, but selectivity for converting terminal to internal olefins is poor
Solution Approach 1:
The pincer ligand structure creates a specific local chemical environment around the chromium center with defined steric and electronic properties. This localized control directs the isomerization pathway preferentially toward internal olefin formation rather than terminal olefins, achieving high selectivity while maintaining reaction productivity.
Solution Approach 2:
The invention changes the chemical parameters of the catalyst system by using chromium in specific oxidation states (III or IV) coordinated to the pincer ligand. This parameter change in the catalyst's electronic structure and geometry enables selective isomerization to internal olefins, distinguishing it from conventional catalysts that produce mixed isomer distributions.
3Manufacturing precision
If single-component catalysts are developed, then control over polymerization rates and molecular weight distribution is improved, but catalyst design complexity increases
Solution Approach 1:
The catalyst is segmented into distinct functional modules: the pincer ligand framework provides structural stability and electronic control, while the chromium center with its specific oxidation state and coordinating groups (ether, alkyl, halide) provides catalytic activity. This modular segmentation allows precise control over polymerization parameters through systematic variation of individual components.
Solution Approach 2:
The catalyst represents a composite molecular structure combining organic pincer ligands with inorganic chromium centers. This composite nature integrates the benefits of both organic (tunable electronics, steric control) and inorganic (oxidation state variability, catalytic activity) components, enabling precise control over polymerization behavior despite the inherent structural complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These complexes demonstrate high selectivity in isomerizing 1-alkenes to internal olefins and polymerizing olefins, achieving high polymerization activities and molecular weight distributions while eliminating the need for costly activators, thus improving polymer quality and process efficiency.
Implementation Method 1
NCN pincer ligand group VI metal complexes... act as single-component catalysts for olefin polymerization
Implementation Method 2
the isomerization of 1-alkenes to internal olefins... These complexes demonstrate high selectivity in isomerizing 1-alkenes to internal olefins
Data Source
AI summary
A catalyst comprising a NCN pincer ligand group VI complex is capable of being used as an olefin polymerization or isomerization catalyst that does not require an expensive cocatalyst. The complex has the NCN pincer ligand in a trianionic form with the group VI in the +3 oxidation state or the +4 oxidation state and complexed to an anionic hydrocarbon group, or the complex has the NCN pincer ligand in a dianionic form with the group VI in the +2 oxidation state. The complex is capable of initiating the polymerization of alkenes without an added activator. The presence of a water scavenger and activator or cocatalyst, such as triisobutylaluminum, increases the catalytic activity. The complex is capable of selectively isomerizing 1-alkenes to cis/trans 2-alkenes.