Abstract:The electrochemical investigation of a number of polyarene-iron complexes ([3]"-[915+) containing etheric, sulphide, and sulphone bridges indicated that there were various degrees of interaction based on the nature of the bridging heteroatoms. While the electrochemical investigation of all etheric complexes showed that the metallic moieties behaved as isolated redox centers, it was found that there was electronic communication (ca. 70-80 mV) for the isomeric sulphide complexes [412+ and [612+. The rate constant of the following chemical reaction (k,) was calculated for some of these complexes and it was found that these rates were affected by the nature of the solvent, the bridging ligand, and the temperature. At various temperatures, kfindicated a higher degree of stability for complexes containing sulphide bridges than for those containing etheric bridges, especially at room temperature. The effect of a strong coordinating solvent, such as acetonitrile, on the k, of complex [3]'+ indicated that the substitution of the arene ligand with acetonitrile molecules proceeded as a dissociative mechanism. Controlled potential coulometry was also used to verify the transfer of two electrons in the first reduction process of the di-iron complexes.Key words: cyclopentadienyliron, cyclic voltammetry, arene complexes, isolated and interacting redox centers.
A series of functionalized polynorbornenes containing pendent ether- or ester-bridged poly(aromatic ether) chains were prepared. The ether-bridged norbornene complex was synthesized via cyclopentadienyliron-mediated nucleophilic aromatic substitution reactions. This methodology, combined with that of dicyclohexylcarbodiimide-mediated coupling, allowed for the formation of novel oligomeric aryl ether and ester substituted norbornene complexes. Photolytic demetallation gave the monomers in good yields. Structural identification of the exo and endo isomers of both the metallated and demetallated norbornene derivatives was accomplished using HH and CH COSY NMR techniques. Ring-opening metathesis polymerization (ROMP) of these monomers using RuCl3(hydrate) and (Cy3P)2Cl2Ru=CHPh allowed for the preparation of the functionalized polynorbornenes. Thermal analysis of the resulting polymeric materials demonstrated greater thermal stability as the number of aryl ether groups increased.Key words: aromatic ethers, cyclopentadienyliron, polynorbornene, ROMP, ruthenium catalysts.
Reactions of 5-norbornene-2-methanol with arene cyclopentadienyliron complexes led to the synthesis of two new classes of norbornene monomers with ether or ester bridges ; ring-opening metathesis polymerization of these monomers using ruthenium-based catalysts gave rise to high molecular weight polymers displaying exceptional thermal stability.
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