Presentation Title

Attachment of Dissymmetric, Bidentate N-Heterocyclic Carbene (NHC) Ligands for the Formation of Stereo-Selective Olefin Metathesis Catalysts

Location

Room 1909

Session Format

Paper Presentation

Research Area Topic:

Natural & Physical Sciences - Chemistry

Roundtable Presentation Participants

Kayla E Warren

Co-Presenters, Co- Authors, Co-Researchers, Mentors, or Faculty Advisors

Dr. Hans-Jorg Schanz (faculty advisor)

Abstract

Ruthenium-based olefin metathesis has extended the possibilities for organic and polymer research. The rearrangement of carbon double bonds often results in a mixture of cis/trans (E/Z) products, often yielding major quantities of the trans (E) configuration with acyclic products. One of the last areas for improvement in the field of catalytic design is to develop stereo-selective catalysts affording large excess amounts of the thermodynamically less-favored cis-alkene product for a broad variety of metathesis substrates. With our approach we target the desymmetrization of the Cl2RuL swing-through plane for the metallacyclobutane intermediate by generating a library of dissymmetric, bidentate NHC ligands. For this purpose, we have developed a three-step synthesis to NHC ligand precursors starting from three different aniline derivatives successfully. We will present new results on the synthesis of the piccolyl-imidazolinium salt precursors for the ligands as well as the results on the catalyst syntheses so far. We will be commenting on new approaches to the strategic attachment of our ligand to Grubb's 1st Generation catalyst and our new work-up procedures isolating the air-sensitive product and reducing the amount of unwanted byproducts. Approaches so far include forming a silver complex with our ligand then attaching to the Ruthenium complex of our catalyst, courtesy of BASF, through transmetallation, before testing our ligands on the more valuable Grubbs catalyst.

Keywords

Calalyst, Stereoselectivity, NHC ligands, Olefin metathesis, Materials science

Presentation Type and Release Option

Presentation (Open Access)

Start Date

4-24-2015 4:00 PM

End Date

4-24-2015 5:00 PM

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Apr 24th, 4:00 PM Apr 24th, 5:00 PM

Attachment of Dissymmetric, Bidentate N-Heterocyclic Carbene (NHC) Ligands for the Formation of Stereo-Selective Olefin Metathesis Catalysts

Room 1909

Ruthenium-based olefin metathesis has extended the possibilities for organic and polymer research. The rearrangement of carbon double bonds often results in a mixture of cis/trans (E/Z) products, often yielding major quantities of the trans (E) configuration with acyclic products. One of the last areas for improvement in the field of catalytic design is to develop stereo-selective catalysts affording large excess amounts of the thermodynamically less-favored cis-alkene product for a broad variety of metathesis substrates. With our approach we target the desymmetrization of the Cl2RuL swing-through plane for the metallacyclobutane intermediate by generating a library of dissymmetric, bidentate NHC ligands. For this purpose, we have developed a three-step synthesis to NHC ligand precursors starting from three different aniline derivatives successfully. We will present new results on the synthesis of the piccolyl-imidazolinium salt precursors for the ligands as well as the results on the catalyst syntheses so far. We will be commenting on new approaches to the strategic attachment of our ligand to Grubb's 1st Generation catalyst and our new work-up procedures isolating the air-sensitive product and reducing the amount of unwanted byproducts. Approaches so far include forming a silver complex with our ligand then attaching to the Ruthenium complex of our catalyst, courtesy of BASF, through transmetallation, before testing our ligands on the more valuable Grubbs catalyst.