Synthesis and properties of new stacked metallocene polymers

The substituted cyclopentadienes 5a,b are readily prepared in two steps fro m benzyloxybenzaldehyde and 4-dimethylaminobenzaldehyde by condensation wit h cyclopentadiene followed by lithium aluminum hydride reduction of the ful venes 4a,b. Coupling of the zinc salts of 5a,b with 1,8-diiodonaphthalene i n the presence of a catalytic amount of CuI gives the cyclopentadienylated iodonaphthalenes 6a,b. This new protocol represents a significant improveme nt over earlier procedures for the preparation of such compounds. Conversio n of Ba,b to the ferrocenes 7a,b, followed by a second cyclopentadienylatio n step, affords 8a,b or 9a. These serve as monomers for the synthesis of po lymers 1d,e and copolymers 1f-h. These materials show increased molecular w eights and improved solubility compared with Ib,e and analogues, in which t he cyclopentadienyl-ring substituents are alkyl chains.