We report the synthesis of a new ferrocenophane, 1,1′-(1-tertbutyl-1,3-butadienylene)ferrocene (1), and its successful polymerization to yield the first soluble conjugated polymer that contains repeat units of ferrocenylene in the backbone. Conjugated polymers that contain transition metals in the backbone have been targeted since the late 1950s because of their potential use as conducting, semiconducting, and/or optoelectronic materials. [1][2][3][4][5][6][7][8][9] Previous synthetic efforts have led, however, either to oligomeric materials that have poor electrical properties or to polymeric materials that are insoluble and intractable. [10][11][12] Oligomeric materials are less likely to exhibit the mechanical properties displayed by high molecular weight polymers, 13 and insoluble polymers cannot be readily processed because of difficulties in casting the materials into useful shapes and films. The approach reported here provides convenient solutions to both of these problems.Scheme 1 shows the synthesis of ferrocenophane 1 in two steps from 1,1′-(4-oxo-1-butenylene)ferrocene 14 (2). Alkylation of 2 with tert-butyllithium followed by dehydration afforded 1 in 43% overall yield. 14 Purification by column chromatography followed by recrystallization from hexane gave large red needles of 1 that are stable in air and soluble in common organic solvents such as benzene, hexane, CH 2 Cl 2 , and THF.Ring-opening metathesis polymerization (ROMP) 16 of ferrocenophane 1 by the tungsten-based metathesis catalyst W(dNPh)-(dCHPh(2-OMe))(OC(CF 3 ) 2 (CH 3 )) 2 )(THF) 17 readily generated the conjugated polymer 4 (eq 1). 18 During the polymerizations, the initially red solutions became noticeably darker and more viscous. The resultant deep red polymers are soluble in common organic solvents such as benzene, CH 2 Cl 2 , and THF. These

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The unsaturated aryl-substituted ferrocenophanes 1,1‘-(1-phenylbuta-1,3-diene-1,4-diyl)ferrocene and 1,1‘-(1-mesitylbuta-1,3-diene-1,4-diyl)ferrocene were synthesized and used to prepare high molecular weight conjugated polymers by ring-opening metathesis polymerization. X-ray crystal structures of the phenyl- and mesityl-substituted monomers showed substantial bond angle strain in the butadiene bridge. The monomers were readily polymerized upon exposure to a tungsten-based initiator to give high molecular weight polymers that were soluble in common organic solvents. UV/vis spectral analysis indicated that the aryl moieties gave rise to enhanced conjugation when compared to related alkyl-substituted ferrocene-containing polymers. The enhanced conjugation was further supported by electrochemical analysis. The thermal stability of the new ferrocene-containing polymers was similar to that of oligomeric poly(ferrocenylene), and the conductivities upon doping were on the order of 10-5 S cm-1.

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