METALLOCENE POLYMERS .37. ORGANOLITHIUM ORGANO-HALIDE COUPLING REACTION AS A SYNTHETIC ROUTE TO POLY(1,1'-FERROCENYLENES)

Poly(ferrocenylenes) are synthesized by a step-growth polycoupling reaction involving 1, 1'-dilithioferrocene (chelated with N, N, N', N'-tetramethylethylenediamine) and 1, l'-diiodoferrocene as monomers. The reactions are performed at temperatures ranging from -20 to 80 ºC in ether solvents. Best results with regard to overall polycoupling efficiency (i.e., yield and molecular mass of coupling products) and product purity are obtained in a dimethoxyethane/tetrahydrofuran medium at temperatures not exceeding 25 ºC. Under these conditions, the total yield of the light tan to light orange-brown, soluble poly(ferrocenylenes) amounts to more than 85%, and the number-average molecular mass of the highest molecular fraction constituting some 16% of total product approaches 4000. The addition, at early stages, of catalytic amounts of Cu(II) or Pd(II) salts to the reaction mixture with a view toward utilizing the intermediacy of reactive organocopper or organopalladium species does not lead to further substantial increases in the overall degree of polymerization. Subfractionation from benzene solution under anaerobic conditions gives subfractions with Mn in the 1000-10000 range. Preliminary magnetic susceptibility measurements indicate the polymers to be less contaminated by paramagnetic impurities than the poly(ferrocenylenes) synthesized in previous investigations, an observation of critical importance for future electrophysical studies. Spectroscopic data, supported by the results of nonpolymeric model reactions providing evidence for the absence of a ferrocyne mechanism indicate that propagation proceeds without loss of the heteroannular substituent disposition on the reactants and so are in agreement with a structural representation (3) implying a 1, 1' type of unit interconnection along the polymer chain. © 1979, American Chemical Society. All rights reserved.