Synthesis and Characterization of Multiferrocenyl‐Substituted Group 4 Metallocene Complexes |
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Authors: | Dr Katharina Kaleta Frank Strehler Dr Alexander Hildebrandt Dr Torsten Beweries Dr Perdita Arndt Dr Tobias Rüffer Dr Anke Spannenberg Prof?Dr Heinrich Lang Prof?Dr Uwe Rosenthal |
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Institution: | 1. Leibniz‐Institut für Katalyse e.V. an der Universit?t Rostock, Albert‐Einstein‐Strasse 29a, 18059 Rostock (Germany), Fax: (+49)?381‐1281‐51176;2. Technische Universit?t Chemnitz, Lehrstuhl für Anorganische Chemie, Strasse der Nationen 62, 09111 Chemnitz (Germany), Fax: (+49)?371‐531‐21219 |
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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. |
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Keywords: | electrochemistry ferrocenes heterometallic complexes titanocenes zirconocenes |
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