Synthesis and Properties of New Stacked Metallocene Polymers

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.