Synthesis and Characterization of Multiferrocenyl-Substituted Group 4 Metallocene Complexes.

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    • Abstract:
      The reaction of different metallocene fragments [Cp2M] (Cp=η5-cyclopentadienyl, M=Ti, Zr) with diferrocenylacetylene and 1,4-diferrocenylbuta-1,3-diyne is described. The titanocene complexes form the highly strained three- and five-membered ring systems [Cp2Ti(η2-FcC2Fc)] ( 1) and [Cp2Ti(η4-FcC4Fc)] ( 2) (Fc=[Fe(η5-C5H4)(η5-C5H5)]) by addition of the appropriate alkyne or diyne to Cp2Ti. Zirconocene precursors react with diferrocenyl- and ferrocenylphenylacetylene under CC bond coupling to yield the metallacyclopentadienes [Cp2Zr(C4Fc4)] ( 3) and [Cp2Zr(C4Fc2Ph2)] ( 5), respectively. The exchange of the zirconocene unit in 3 by hydrogen atoms opens the route to the super-crowded ferrocenyl-substituted compound tetraferrocenylbutadiene ( 4). On the other hand, the reaction of 1,4-diferrocenylbuta-1,3-diyne with zirconocene complexes afforded a cleavage of the central CC bond, and thus, dinuclear [{Cp2Zr(μ-η1:η2-CCFc)}2] ( 6) that consists of two zirconocene acetylide groups was formed. Most of the complexes were characterized by single-crystal X-ray crystallography, showing attractive multinuclear molecules. The redox properties of 3, 5, and 6 were studied by cyclic voltammetry. Upon oxidation to 3 n+, 5 n+, and 6 n+ ( n=1-3), decomposition occured with in situ formation of new species. The follow-up products from 3 and 5 possess two or four reversible redox events pointing to butadiene-based molecules. However, the dinuclear complex 6 afforded ethynylferrocene under the measurement conditions. [ABSTRACT FROM AUTHOR]
    • Abstract:
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