ORGANOMETALLIC POLYMERS BASED ON S-S AND SE-SE LINKED N-BUTYLFERROCENES

Polyferrocenylene persulfides, [(BUC5H3)(C5H4)FeS2](n), have been prep ared by desulfurization of butyltrithiaferrocenophane (BUC5H3)(C5H4)Fe S3. The molecular precursor was prepared by dilithiation of butylferro cene followed by treatment with elemental sulfur and isolated as a 7:1 mixture of the 1,3,1' and 1,2,1' isomers. The trisulfide was converte d to polymer by treatment with the desulfurization agent PBu(3). The r ate of this desulfurization and the nature of the polymer depends crit ically on the reaction solvent. Desulfurization in DMF and THF afforde d insoluble but swellable rubbers. Desulfurization of BufcS(3) in mixe d CH2Cl2-THF solutions gave soluble polymers with M(n) ranging from 12 000 to 359000, with lower molecular weight products being favored at h igh [CH2Cl2]. The effect of high [CH2Cl2] was modeled by the reaction of [fcS(2)](n) with a CH2Cl2 solution of PBu(3) to give fcS(2)CH(2). M olecular weights for [BufcS(2)](n) were confirmed by light scattering measurements. Soluble [BufcS(2)](n) undergoes reversible electrochemic al oxidation in two steps, centered at 780 V (vs Ag/AgCl) and separate d by similar to 300 mV. The first oxidation potential is similar to th at for the trisulfide monomer and is thought to correspond to oxidatio n of alternating Fe centers, followed by conversion of the remaining F e-II sites. The polymers photodegrade upon exposure to UV light in air . Deselenization of BufcSe(3) gave red soluble [BufcSe(2)](n) with onl y moderate molecular weights and with high polydispersities. The micro structure of this polymer was established by Se-77 NMR studies which s upport the presence of head-to-head, head-to-tail, and tail-to-tail dy ads.