Recovered on Tape

Abstract

CHEMISTRY A central challenge in homogeneous catalysis is achieving facile separation and recovery of the catalyst once the reaction is over. An increasingly common solution is to append fluorocarbon chains to the catalyst. Because fluorocarbons are poorly miscible with most organic solvents, this modification makes it possible to remove the catalyst by extraction into a fluorous solvent or, in some cases, simply by cooling the reaction mixture to induce precipitation. However, both of these methods can be inefficient at low catalyst loadings. Dinh and Gladysz show that a rhodium catalyst for hydrosilylation of ketones can be recovered efficiently and easily using Teflon tape. The catalyst, bearing three fluoroalkylphosphine ligands, was dissolved with the reagents in dibutyl ether at 55°C, with a strip of tape added to the flask. Upon cooling, the orange catalyst stuck to the tape (and not to the stir bar!) and could be recycled two more times by heating in a fresh reaction mixture. — JSY Angew.Chem. Int. Ed. 10.1002/anie.200500237 (2005).