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Abstract
Homogeneously catalysed reactions can be ‘switched on’ by activating latent catalysts. Usually, activation is brought about by heat or an external chemical agent. However, activation of homogeneous catalysts with a mechanical trigger has not been demonstrated. Here, we introduce a general method to activate latent catalysts by mechanically breaking bonds between a metal and one of its ligands. We have found that silver(i) complexes of polymer-functionalized N-heterocyclic carbenes, which are latent organocatalysts, catalyse a transesterification reaction when exposed to ultrasound in solution. Furthermore, ultrasonic activation of a ruthenium biscarbene complex with appended polymer chains results in catalysis of olefin metathesis reactions. In each case, the catalytic activity results from ligand dissociation, brought about by transfer of mechanical forces from the polymeric substituents to the coordination bond. Mechanochemical catalyst activation has potential applications in transduction and amplification of mechanical signals, and mechanically initiated polymerizations hold promise as a novel repair mechanism in self-healing materials. Latent catalysts are usually activated by heating them or adding an external chemical agent, but now it has been shown that mechanical force is also an option in some instances. Ultrasound can be used to dissociate polymeric ligands from metal-containing complexes to reveal the innate catalytic ability of one of the two fragments. Cite this article
Piermattei, A., Karthikeyan, S. & Sijbesma, R. Activating catalysts with mechanical force. Nature Chem 1, 133–137 (2009). https://doi.org/10.1038/nchem.167 