Comparison of the epoxidation of cyclohexene, dicyclopentadiene and 1,5-cyclooctadiene over LDH hosted Fe and Mn sulfonato-salen complexes

Sulfonato-salen metal complexes containing Fe or Mn metal centres have been synthesised and intercalated into Zn/Al layered double hydroxide hosts and used as catalyst for the epoxidation of cyclohexene, dicyclopentadiene and 1,5-cyclooctadiene. Using a combination of pivalaldehyde and molecular oxygen at atmospheric or higher pressures to produce the corresponding peracid as oxidant, cyclohexene gave two oxidation products, cyclohexene oxide and 2-cyclohexen-1-one, whereas, dicyclopentadiene was transformed exclusively into the corresponding mono-epoxide. The relative order of olefin activity correlates with the C-C=C bond angle for both metal centres. The product selectivity was found to be largely independent of the central metal ion suggesting that the local environment around the central metal ion was of greater importance. A possible mechanism-based on the product distribution is suggested. (c) 2006 Elsevier B.V. All rights reserved.