The discussion covers a 2021 publication by the Chirik group (Nature Chemistry, 2021, DOI: 10.1038/s41557-020-00614-w) which details the discovery of a new way to polymerize butadiene through iron-catalyzed [2+2] cycloaddition. This polymer of cyclobutanes (aka, the “polymer of squares”) can also be reversibly deconstructed back to butadiene using the same iron catalyst used in its synthesis. This represents a new plastic-like material that can be chemically recycled back to its constituent monomer.
Here, students explore the organometallic chemistry enabling the synthesis and unique properties of the polymer of squares, especially geared toward the mechanism of formation. It is recommended that students have experience in predicting and drawing organometallic mechanisms prior to completing this Literature Discussion.
This LO is part of a special VIPEr collection honoring the 2021 ACS National Award recipients in the field of inorganic chemistry. Paul J. Chirik was the recipient of the Gabor A. Somorjai Award for Creative Research in Catalysis for pioneering work in sustainable catalysis with Earth-abundant elements that through control of electronic structure transformed the way chemists approach the periodic table.
After completion of this Literature Discussion, students should be able to:
- understand design principles related to the closed loop chemical recycling of plastics
- distinguish between polymerization mechanisms involving insertion versus oxidative cyclization
- identify L versus X type ligands and understand their relation to polymerization pathways
- understand how thermoneutral reactions relate to reversibility and chemical recycling of plastics
- apply their knowledge of electron counting to complexes with redox active ligands
This Literature Discussion could be a take home assignment or an in-class discussion. Included in the Literature Discussion are challenge questions that may best be done in small groups or as part of a whole-class discussion.
The Literature Discussion can be graded as an in-class assignment or as a homework assignment.
This Literature Discussion has not been used in a class yet.