Stir-bar contamination may catalyze reactions

Abstract

It seems that the humble stir bar, a workhorse of the chemistry lab, has been mixing things up in a different way—by smuggling rogue metals into chemists’ reaction flasks (ACS Catal. 2019, DOI: 10.1021/acscatal.9b00294). Valentine P. Ananikov and colleagues at the N. D. Zelinsky Institute of Organic Chemistry examined 60 used stir bars with electron microscopy and X-ray spectroscopy. They found that scratches, dents, and cracks marred the surfaces of the polytetrafluoroethylene-coated bars and trapped nano- and micro-sized metal particles, including palladium, gold, platinum, cobalt, and iron. The team then tested used stir bars in the palladium-catalyzed Suzuki-Miyaura reaction. First, they used a palladium catalyst and a fresh stir bar to carry out a series of these reactions; then they repeated the experiments with no catalyst and a contaminated stir bar. In several cases, the dirty stir bar alone delivered a significant amount of the product, and in one case