Summary
The solution polycondensation of TMEDA-chelated 1,1′-dilithioferrocene in the presence of Cu+ ion, leading to polyferrocenylenes, is explored, the cupration stoichiometry (Cu∶Li=ca. 0.5) being such as to favor the intermediacy of ferrocenylenecuprates, R2CuLi (R=0.5 ferrocenylene unit). In the first series of experiments, the cuprate intermediates are allowed to undergo thermal or oxidative poly-coupling; in subsequent experiments, they are copolymerized with 1,1′-diiodoferrocene. Both reaction sequences result in the formation of linear oligomeric and polymeric coupling products essentially identical in composition and spectroscopic properties with the poly-1,1′-ferrocenylenes of previous investigations. Best results are obtained in the copolymerizations with the diiodo derivative, which give higher overall yields (70–75%) and molecular masses (typically 4000 for the first fraction) than attained in earlier work. In addition, whereas previous syntheses involving either the oxidative coupling of the dilithioferrocene with Cu2+ ion or the oxidative-thermal coupling of ferroceny-lenecopper(I) intermediates gave large quantities of the dinuclear [0.0]-ferrocenophane at the expense of linear polyferrocenylenes, the copolymerizations with diiodoferrocene distinctly favor linear propagation, and yields of the ferrocenophane are less than one percent. The organocuprate/organoiodide coupling reaction thus constitutes a preparative approach to polyferrocenylenes superior to previous syntheses described.
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References
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Neuse, E.W., Bednarik, L. Synthesis of poly-1,1′-ferrocenylenesvia ferrocenylenecuprates(1) . Transition Met Chem 4, 104–108 (1979). https://doi.org/10.1007/BF00618834
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DOI: https://doi.org/10.1007/BF00618834