Tin and iron halogenides as additives in ruthenium-catalyzed olefin metathesis

Different metal halogenides were used as additives in metathesis of 1-octene or in several cross-metathesis reactions catalysed by first and second generation Grubbs catalyst, 1 and 2, as well as by an improved first generation-type Grubbs catalyst 3. Tin(II) chloride and bromide enhance the performance of 1 and 3. The influence on 2 is rather minor under the chosen reaction conditions. The addition of iron(II) chloride and bromide results in an improvement of 1 to a lesser extent as the tin salts. The frequently observed isomerisation of olefins in metathesis reactions catalysed by 1 is suppressed in the presence of the applied tin salts.

The addition of especially tin(II) halogenides to Grubbs catalyst suppresses the common isomerisation and increases catalyst performance in olefin metathesis. The influence depends on the anion of the promoter as well as the used ruthenium carbene catalyst. Crystallographic studies suggest a Ru–SnX3 complex as the active species.Figure optionsDownload as PowerPoint slide