Synthesis and properties of new stacked metallocene polymers

Abstract

The substituted cyclopentadienes 5a,b are readily prepared in two steps from benzyloxybenzaldehyde and 4-dimethylaminobenzaldehyde by condensation with cyclopentadiene followed by lithium aluminum hydride reduction of the fulvenes 4a,b. Coupling of the zinc salts of 5a,b with 1,8-diiodonaphthalene in the presence of a catalytic amount of CuI gives the cyclopentadienylated iodonaphthalenes 6a,b. This new protocol represents a significant improvement over earlier procedures for the preparation of such compounds. Conversion of 6a,b to the ferrocenes 7a,b, followed by a second cyclopentadienylation step, affords 8a,b or 9a. These serve as monomers for the synthesis of polymers 1d,e and copolymers 1f-h. These materials show increased molecular weights and improved solubility compared with 1b,c and analogues, in which the cyclopentadienyl-ring substituents are alkyl chains.