Synthesis and reactivity of cyclic and acyclic (1-(acyloxy)pentadienyl)Fe(CO)(2)LX and (1-alkoxypentadienyl)Fe(CO)(2)LX salts (L=CO, PPh(3))

A variety of cyclic and acyclic [(pentadienyl)Fe(CO)(2)L]X complexes (L = CO, PPh(3)) containing terminal acyloxy or alkoxy substituents have been prepared. In situ NMR studies indicate that for the acyclic series where L = CO, stability is limited by solvolysis reactions. The position of nucleophilic attack (ipso for alkoxy, internal for acyloxy) in the acyclic series indicates an electron-donating and electron-withdrawing nature for alkoxy and acyloxy substituents, respectively. In the cyclic series, the different regiodirecting powers of alkoxy and acyloxy groups provide access to regioisomeric substituted cyclohexadienyl salts. Crystal structures of the Psi-exo and Psi-endo stereoisomers of [5-(benzoyloxy)-2,4-hexadien-1-ol]Fe-(CO)(2)PPh(3) (34 and 35) and of [(1,3,4,5-eta)-1-(benzoyloxy)-2-methyl-3-pentene-1,5-diyl]Fe-(CO)(2)PPh(3) (57) have been determined.