Promoting Effect of AlCl_3 on the Fe-catalyzed Dimerization of Bicyclo[2.2.1]hepta-2,5-diene

Abstract

The activity of the catalytic system composed of Fe(acetylacetonate) 3 (Fe(acac) 3 ), triphenylphosphine, and diethylaluminum chloride for the dimerization of bicyclo[2.2.1]hepta-2,5-diene (2,5-norbornadiene, NBD) to produce hexacyclic endo-endo dimer (hexacyclo[7.2.1.0 2,8 .1 3,7 .1 5,13 .0 4,6 ]tetradec-10-ene, H nn ) was significantly enhanced by the presence of AlCl 3 , especially at the molar ratios of NBD/Fe(acac) 3 of 500. XPS analysis of the catalytic systems clearly demonstrates that AlCl 3 facilitates the reduction of Fe(acac) 3 to form active species, Fe(II) and Fe(0) species. The layer separation was observed when [BMIm]Cl was used along with AlCl 3 , but catalyst recycle was not very successful.