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.