Researchers in the US have developed a phosphine-free catalytic system, based on ionic liquids, for use in palladium-catalysed reactions.

Jean'ne Shreeve and colleagues at the University of Idaho made a series of ionic liquids that readily coordinate with palladium. The researchers say the pyrazolyl-functionalised methylimidazolium-based ionic liquids serve as both ligands and solvents in palladium-catalysed cross-coupling reactions. 

According to Shreeve, 'palladium-catalysed coupling and cross-coupling reactions exemplify one of the most important processes in organic chemistry.'  Phosphine ligands are often used in these carbon-carbon bond forming reactions, but 'traditional phosphine ligands are . difficult to prepare, air and moisture sensitive, toxic, low loading, and less efficient,' said Shreeve.

The researchers claim that the palladium-ionic liquid catalyst system offers outstanding stability and activity. 'Since our ionic liquids can serve as both solvents and ligands, the palladium catalysts are part of the ionic liquids in the catalytic system, and the decomposition and leaching of catalysts throughout the reaction and product separations can be markedly reduced.'
 
'This work provides a promising pathway toward design and synthesis of highly stable and recyclable phosphine-free catalytic systems,' said Shreeve.

Joanne Bell