RING OPENING REACTIONS OF SOME η6-HETEROCYCLE-η5-CYCLOPENTADIENYLIRON HEXAFLUOROPHOSPHATES

Article abstract of DOI:10.1016/S0022-328X(00)99207-6

Ring opening upon reaction with a nucleophile for heterocyclic ligands complexed to cyclopentadienyliron has been studied.The ligands investigated included those related to fluorene with an O, S or NH at C(9) or those related to 9,10-dihydroanthracene again with O, S or NH at the C(9) or C(9) and C(10) positions.Upon treatment with pyrrolidine as the nucleophile, it was found that ring opening occurred only at the site of an O heteroatom.For example, such a reaction with the cyclopentadienyliron complex of dibenzofuran or dibenzodioxin gave, respectively, the cyclopentadienyliron complex of o-N-pyrrolidinyl-o'-hydroxybiphenyl or o-N-pyrrolidinyl-o'-hydroxydiphenyl ether.No ring cleavage was observed at the site of a S or NH as the heteroatom; for example, no reaction took place when the cyclopentadienyliron complex of dibenzothiophene or carbazole was treated with pyrrolidine.A mechanism for the formation of the ring opening products based on the activation of the complexed ring towards nucleophilic aromatic substitution is discussed.