Z-Selective Olefin Metathesis Catalysts via Chelating Ligands
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Solution Overview
Problem
Current olefin metathesis catalysts, particularly ruthenium-based catalysts, exhibit insufficient Z selectivity in producing Z isomers, which limits their application in stereo-controlled organic syntheses, and existing molybdenum or tungsten-based catalysts require complex synthetic steps and strict reaction conditions.
Innovation Solution
Development of C-H activated olefin metathesis catalyst complexes featuring a Group 8 transition metal complex with a chelating ligand structure, including a neutral electron donor ligand and a 2-electron anionic donor bridging moiety, which forms a chelate structure and enhances Z selectivity while being tolerant to functional groups and impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ruthenium-based catalysts are used for olefin metathesis, then high catalytic efficiency and functional group tolerance are achieved, but Z selectivity is insufficient
Solution Approach 1:
The patent introduces a chelating ligand system with specific local structural features (N-heterocyclic carbene and amidine moieties positioned at defined distances) that creates a localized chiral environment around the ruthenium center. This local structural organization enables Z-selective catalyst-substrate interactions while preserving the overall catalytic activity of the ruthenium complex.
Solution Approach 2:
The catalyst employs chiral amidine ligands with asymmetric structural elements (such as chiral centers in the R1-R6 substituent patterns) that create an asymmetric coordination environment around the ruthenium metal center. This asymmetry directs the stereochemistry of the metathesis reaction to favor Z-isomer formation while maintaining catalytic efficiency.
2Manufacturing precision
If molybdenum or tungsten-based catalysts are used to achieve high Z selectivity, then excellent Z isomer production is obtained, but complex synthetic steps and strict reaction conditions are required
Solution Approach 1:
The patent develops a ruthenium-based catalyst system that combines multiple functions: high Z-selectivity (comparable to Mo/W catalysts), broad functional group tolerance (inherent ruthenium advantage), and operational simplicity (ambient temperature and pressure conditions). The chelating ligand design enables this multi-functionality by simultaneously providing structural rigidity for selectivity and chemical stability for versatility.
Solution Approach 2:
The patent modifies key parameters of the catalyst system by changing the metal center from Mo/W to Ru and adjusting the ligand composition (combination of NHC and amidine ligands with specific steric and electronic properties). These parameter changes result in milder reaction conditions (ambient temperature, no strict inert atmosphere requirements) while maintaining high Z-selectivity, thereby reducing synthetic complexity.
3Manufacturing precision
If existing catalysts are used for stereo-controlled olefin metathesis, then some Z selectivity is achieved, but the reaction conditions are harsh and synthesis steps are numerous
Solution Approach 1:
The catalyst is pre-designed with a specific chelating ligand architecture where the N-heterocyclic carbene and amidine ligands are positioned to create an optimal geometry for Z-selective transitions. This preliminary structural arrangement eliminates the need for stepwise ligand additions or complex in-situ generation procedures, reducing the number of synthetic steps and reaction time.
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
The C-H activated catalysts demonstrate improved Z selectivity in olefin metathesis reactions, offering a more efficient and versatile route for producing Z isomers with simpler synthesis and milder reaction conditions compared to existing catalysts.
Implementation Method 1
C-H activated olefin metathesis catalyst complexes featuring a Group 8 transition metal complex with a chelating ligand structure
Implementation Method 2
a 2-electron anionic donor bridging moiety, wherein L1 and Q1 form a chelate structure
Data Source
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AI summary
The invention relates to C-H activated olefin metathesis catalyst compounds, the preparation of such compounds, and the use of such catalysts in the metathesis of olefins and olefin compounds, more particularly, the use of such catalysts in Z selective olefin metathesis reactions. In general, the catalyst compounds of the invention comprise a Group 8 metal (M), an alkylidene moiety (=CR1R2), or more generally (=(C)mC R1R2), an anionic ligand (X1), two or three neutral ligands (L1, L2, and L3) and a 2-electron anionic donor bridging moiety (Q*) that forms a chelate ring structure in conjunction with L1 and M. Such catalysts generally correspond to the formula X1(L3)kL2L1Q*M=(C)mCR1R2, wherein X1 is any anionic ligand, L1, L2, and L3 are, independently, any neural electron donor ligand, k is 0 or 1, m is 0, 1, or 2, Q* is a 2-electron anionic donor bridging moiety linking L1 and M, M is a Group 8 transition metal, and R1 and R2 are, independently, hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, substituted heteroatom- containing hydrocarbyl, or functional groups. The invention has utility in the fields of catalysis, organic synthesis, polymer chemistry, and industrial and fine chemicals chemistry.