Studies on the mechanism of olefin-metathesis with Grubbs-Hoveyda complexes

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The present project is focusing on investigations of the mechanism of olefin-metathesis reactions with Grubbs-Hoveyda type complexes.Based on a model developed by us for the analysis of conversion-time data, it is now possible to determine the rate constants for catalyst activation k(act), the catalytic transformation k(cat) and catalyst decomposition (k(dec) of the catalytically active species. Especially k(cat) and k(dec) provide important information for catalyst optimization, since electronic and steric modifications at the catalytic center can now be analyzed separately for k(dec) and k(cat). It is a related aim of this project to learn, which stereoelectronic conditions determine the catalytic activity of Grubbs-Hoveyda complexes and which conclusions can be drawn based on the understanding of such factors for the preparation of improved catalysts.Furthermore, detailed studies on the mechanism of the dominating uni- and bimolecular catalyst deactivation pathways are planned for the species derived from Grubbs-Hoveyda type precatalysts.The role of ethene, which is formed as one reaction product of various olefin metathesis reactions, in the context of precatalyst activation, catalysis and catalyst decomposition is not clear yet. We thus propose to study the kinetics and the mechanism of ethene-induced reactions with Grubbs-Hoveyda type precatalysts.