Synthesis of cationic (arene)ironCp complexes via arene exchange

exchange of pyrene, naphthalenes, and cyclooctatetraene occurs in the temperature range of 90-140 degreesC. The most labile complex in the series studied is [(eta(6)-(1-4,4a,8a)-1,4-dimethoxynaphthalene)FeCp][PF6] having the FeCp coordinated to the substituted ring. Pyrene and other naphthalene complexes come next, followed by the cyclooctatetraene complex. Phenanthrene, veratrol, and dihydronaphthalene do not undergo exchange at temperatures up to 130 degreesC. With Me- and OMe-substituted naphthalenes, exchange is reversible and favors the product having the metal coordinated to the non-substituted ring. The X-ray crystal structures of the two regioisomeric 1,4-dimethoxynaphthalene complexes were determined. Arene exchange in fused arene complexes is shown to be a useful synthetic method and provides new arene complexes cleanly and efficiently. The method is particularly attractive for arenes that contain functionalities that are not compatible with the Lewis acid-mediated routes. The starting materials are readily accessible via the TiCl4-assisted Cp exchange in ferrocene. (C) 2003 Elsevier B.V. All rights reserved.