NUCLEOPHILIC-ADDITION TO DI-IRON AND POLY-IRON ARENE COMPLEX CATIONS

Hydride and cyanide addition to a series of di- and polycyclopentadien yliron arene complex cations with etheric bridges is described. Reacti on of the di-iron complexes with sodium borohydride resulted in the fo rmation of a number of adducts. p-Methyl- and o,o-dimethylphenoxybenze ne cyclopentadienyliron complexes were used as models in this study to allow for the characterization of the analagous di-iron complexes. Th e use of HH COSY and CH COSY NMR techniques enabled us to identify the isomeric nature of these adducts. The hydride addition results indica ted that the etheric substituent had the predominant effect over the m ethyl group, leading to a higher addition ratio to the meta-, followed by the ortho-, then the para-positions. It was also clear that in the di-iron system, the hydride addition to each complexed arene ring too k place independently. The addition of the cyanide anion to di- and po ly-iron arene systems was more selective than that of the hydride anio n. Reaction of sodium cyanide with p-methyl- or o-methyl-substituted a rene complexes led to the formation of one adduct, with the cyanide be ing added to the meta position to the etheric bridges. However, cyanid e addition to the di-iron complex, with a methyl substituent attached at the meta position of each complexed arene, led to the formation of a mixture of adducts. Cyanide addition to the poly-iron system with p- substituted arenes proved to be very selective, allowing for the forma tion of one adduct. Oxidative demetallation with 2,3-dichloro-5,6-dicy ano-1,4-benzoquinone (DDQ) produced the uncomplexed polyaromatic ether s with cyano groups in a very good yield.