Abstract:With the self-metathesis of 1-octene to 7-tetradecene catalyzed by Grubbs 1 st generation [benzylidene-bis(tricyclohexylphosphine)dichlororuthenium, (1)] precursor at low concentrations (0.02 mol %) as basis, the effects of the solubility of the substrate in ionic liquids, the solvent polarity, as well as the influence of various impurities stemming from the preparation of ionic liquids have been investigated. The solubility of the substrate in the ionic liquid has little effect on the conversion, and the reaction is not mass-transfer limited. While a higher polarity of an organic solvent increases the rate, it is independent of the polarity excerted by the cation of an ionic liquid. Of paramount importance for reproducible results is the purity of ionic liquids. An extensive study shows that catalyst deactivation by impurities increases in the order of water < halide < 1-methylimidazole. In the presence of water or 1-methylimidazole impurities, the Grubbs-Hoveyda precursor (3) is superior to both the 1 st (1) and 2 nd (2) generation Grubbs complexes. Under impurity-free conditions or in the presence of chloride, the performance of 2 is equivalent to that of 3.

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