Rare earth elements (REEs) are used everyday in modern technology from cell phones to laptops all the way up to spaceships. Current methods of mining and recycling REEs through countercurrent solvent extraction are not sustainable because they are not energy efficient and do not follow the principles of green chemistry. Thus, new approaches to REE recycling using chelating ligands is desirable. Ongoing research in the O’Connor lab is focused on preparing different ligand scaffolds with sulfonamide moieties using green synthetic approaches. Herein we describe the direct synthesis of 2,6-pyridine diacyl sulfonamide derivatives (Figure 1) via a microwave assisted pathway. No exogenous base or coupling agents are required deeming the reaction more sustainable and atom economic. Both electron poor and electron rich substituents on the sulfonamide moiety are tolerated in the reaction. Electron poor sulfonamides require longer reaction times and generally result in lower yields. These new pincer-style compounds were utilized in metalation reactions with MCl3, M(C2H3O2)3, and M2(CO3)3, where M = Ce, La, Pr, Dy. In all reactions studied to date, hydrolysis of the sulfonamide bond has been observed upon exposure of the ligand to different REEs regardless of the REE or anion utilized. Attempts to circumvent this by modifying the ligand architecture is ongoing and initial findings are presented herein.

Green microwave synthesis of [NNN]-pincer style pyridine acyl arylsulfonamide compounds and rare earth element metalation

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.