The chemistry of cyclopentadienyliron complexes of arenes with sulfur, oxygen and nitrogen bridges

Abstract

This study illustrates the versatility of CpFe+ activated SNAr in the synthesis of oligomeric, polymeric and macrocyclic systems. Initially, the efficiency of this synthetic strategy was demonstrated by the use of chloro- and nitro- (arene)CpFe+ complexes in the design of a variety of species with aliphatic or aromatic oxygen, sulfur or nitrogen bridges. Interest in the chemical behavior of these complexes led to the electrochemical investigation of selected species. Specifically, it was found that the iron centers of etheric complexes behaved as isolated redox centers whereas a small degree of interaction between metal centers was measured with respect to similar thioetheric analogues. An extension of these studies focused on the investigation of the rate of the reaction of the first reduction species of these complexes with the solvent in addition to the determination of several activation parameters. It was found that the nature of the bridging ligand as well as temperature affected the behavior of these species. Cyclopentadienyliron activated nucleophilic aromatic substitution was further investigated with respect to several polymerization techniques. Monomeric design was achieved by the preparation of the complex followed by isolation of the organic counterpart using photolytic demetallation. This two step process allowed for the synthesis of monomeric units which were polymerized using Scholl reaction conditions or ring-opening metathesis polymerization techniques. The synthesis of polyaromatic ether and thioethers with pendent CpFe+ moieties by the reaction of the appropriate complex and dinucleophile, in a one-step process is presented for the first time. Several nitrogen containing macrocyclic complexes were prepared via a two-step process in which the design of a species as desired was achieved by the reaction of a bimetallic complex with a variety of dinucleophiles in the ring closure step.