Nucleophilic addition to di- and poly-iron arene complex cations

Hydride and cyanide addn. to di- and polycyclopentadienyliron arene complex cations with etheric bridges is described. Reaction of the di-Fe complexes with NaBH4 gave a no. of adducts. P-Methyl- and o,o-dimethylphenoxybenzene cyclopentadienyliron complexes were used as models in this study to allow for the characterization of the analogous di-Fe complexes. The use of HH COSY and CH COSY NMR techniques enabled the authors to identify the isomeric nature of these adducts. The hydride addn. results indicated that the etheric substituent had the predominant effect over the Me group, leading to a higher addn. ratio to the meta-, followed by the ortho-, then the para-positions. Also in the di-Fe system, the hydride addn. to each complexed arene ring took place independently. The addn. of the cyanide anion to di- and poly-Fe arene systems was more selective than that of the hydride anion. Reaction of NaCN with p-methyl- or o-methyl-substituted arene complexes gave one adduct, with the cyanide being added to the meta position to the etheric bridges. However, cyanide addn. to the di-Fe complex, with a Me substituent attached at the meta position of each complexed arene, gave a mixt. of adducts. Cyanide addn. to the poly-Fe system with p-substituted arenes proved to be very selective, allowing for the formation of one adduct. Oxidative demetalation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) produced the uncomplexed polyarom. ethers with cyano groups in a very good yield