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

本课题主要研究GRubbs-Hoveyda络合物催化烯烃歧化反应的反应机理。根据我们建立的用于分析转化时间数据的模型，现在可以确定催化活性物种的催化剂活化k(Act)、催化转化k(Cat)和催化剂分解(k(Dec))的速率常数。特别是k(CAT)和k(DEC)为催化剂优化提供了重要信息，因为现在可以分别分析k(DEC)和k(CAT)在催化中心的电子和空间修饰。本项目的一个相关目标是了解哪些立体电子条件决定了GRubbs-Hoveyda络合物的催化活性，以及在了解这些因素的基础上可以得出哪些结论来制备改进的催化剂。此外，针对GRubbs-Hoveyda类催化剂物种，计划详细研究占主导地位的单分子和双分子催化剂失活途径的机理。作为各种烯烃歧化反应的一种反应产物，乙烯在催化剂预活化、催化和催化剂分解中的作用尚不清楚。因此，我们建议研究乙烯诱导的GRubbs-Hoveyda预催化剂反应的动力学和机理。

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.