Controlled design of oligomeric ethers with pendant cyclopentadienyliron moieties

Abstract

Synthetic strategies for the design of oligomeric ethers with pendant cyclopentadienyliron moieties have been developed. A wide range of these materials have been prepared via nucleophilic aromatic substitution reactions of a mono- or di-hydroxyaromatic nucleophiles and a variety of chloroarene complexes under mild experimental conditions. The mono- and bis-(cyclopentadienyliron) arene complexes were used as building blocks for the larger systems. The crystal structures of three bis(cyclopentadienyliron) arene dications, [(η⁵-C₅H₅)Fe(η⁶-C₆H₅)-o-XC₆H₄X-(η⁶-C₆H₅)Fe(η⁵-C₅H₅)]²⁺(X = O or S) and [(η⁵-C₅H₅)Fe(η⁶-C₆H₅)-m-OC₆H₄O-(η⁶-C₆H₅)Fe(η⁵-C₅H₅)]²⁺, have been determined by X-ray crystal structure analysis. A number of routes to the synthesis of the oligomeric species (tri-, tetra- and hexa-iron moieties) have been investigated to determine the flexibility and efficiency of the proposed strategies, and these materials have been fully characterized using spectroscopic and analytical techniques. To prove further the structures of these complexes, some of them have been prepared using different starting materials, giving the same proposed products. A series of polyiron complexes containing terminal hydroxy groups have also been prepared and used as dinucleophiles. The systematic increase in the number of rings and iron moieties allowed full characterization by monitoring the changes in the NMR spectra. Furthermore, the possibility of preparing homo- and mixed-polyaromatic ethers where the number of cyclopentadienyliron moieties varied from two to thirty-five has been demonstrated.