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Heterogeneous Removal of Water-Soluble Ruthenium Olefin Metathesis Catalyst from Aqueous Media Via Host-Guest Interaction
Published on: August 23, 2018
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Probing Stereoselectivity in Ring-Opening Metathesis Polymerization Mediated by Cyclometalated Ruthenium-Based
L E Rosebrugh1, T S Ahmed1, V M Marx1
1Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
Journal of the American Chemical Society
|January 5, 2016
Summary
Ring-opening metathesis polymerization (ROMP) using ruthenium catalysts yields polymers with a cis,syndiotactic microstructure. Errors in the polymer structure are also syndiotactic, explained by metal control and isomerization mechanisms.
Area of Science:
- Polymer Chemistry
- Organometallic Chemistry
- Materials Science
Background:
- Ring-opening metathesis polymerization (ROMP) is a versatile method for polymer synthesis.
- Control over polymer microstructure is crucial for tailoring material properties.
- Cyclometalated ruthenium-carbene catalysts offer unique reactivity in ROMP.
Purpose of the Study:
- To investigate the microstructural characteristics of polymers synthesized via ROMP.
- To elucidate the stereochemical control mechanisms governing ROMP with specific ruthenium catalysts.
- To understand the origins of microstructural defects in ROMP polymers.
Main Methods:
- Experimental investigation of polymer microstructures.
- Analysis using computational methods, including reaction intermediates and transition structures.
- Correlation of experimental findings with theoretical predictions.
Main Results:
- Polymers produced exhibit a strong preference for a cis,syndiotactic microstructure.
- Minimal head-to-tail bias was observed in the polymer chains.
- Trans errors, when present, were also found to be syndiotactic.
- Computational analysis supported a mechanism involving stereogenic metal control for cis,syndio-selectivity.
Conclusions:
- The study elucidates the stereoselective mechanism of ROMP using cyclometalated ruthenium catalysts.
- Stereogenic metal control dictates the cis,syndiotactic preference.
- Alkylidene isomerization via rotation around the Ru═C double bond is the primary cause of microstructural errors.
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