Watching the progress of catalysis in ionic liquids

New insight is being offered into the role of ionic liquids in catalysis. Although ionic liquids are known to be good media for transition metal catalysis, relatively little quantitative information is known about the rate constants or reaction mechanisms for these solvents. Now teams led by Andrew McLean and Charles Gordon at the University of Paisley, UK, and Rheinisch-Westfälische Technische Hochschule Aachen in Germany have addressed this by studying a catalytic reaction in both ionic liquids and conventional solvents.

Using laser flash photolysis they observed the organometallic intermediates being generated in a chromium-catalysed organic transformation. After comparison of the solvent displacement kinetics for this model system in a variety of ionic liquids and organic solvents they propose a position for the ionic liquids in a spectrochemical series for all the solvents. They also show that water present in the ionic liquids could be problematic for catalysis.

However, Gordon is encouraged by the findings and comments that ’our experiments address a specific, and hitherto unanswered, mechanistic question in an unambiguous manner and in doing so highlight the broad potential of room temperature ionic liquids’.

Caroline Evans