Synthesis and Characterization of Cyclopentadienyl and Pentamethylcyclopentadienyl Ruthenium Complexes of Oligothiophenes

David D. Graf, Nancy C. Day, Kent R Mann

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We report the synthesis and characterization of 14 complexes of the general form [CpRu(oligothiophene)]PF6 and [Cp*Ru(oligothiophene)]PF6 (Cp = η5-cyclopentadienyl; Cp* = η5-pentamethylcyclopentadienyl). The complexes were synthesized from [CpRu(CH3CN)3]PF6 or [Cp*Ru(CH3CN)3]PF6 and the appropriate oligothiophene via procedures previously reported for other [Cp/Cp*Ru(η6-arene)]PF6 sandwich complexes. For the oligothiophenes 2,2′-bithiophene (Bth), 2,2′:5′,2″-terthiophene (Tth), 2,2′:5′,2″:5″,2‴-quaterthiophene (Qth), and 5,5″-dimethyl-2,2′:5′,2″-terthiophene (Me2Tth), the Ru is bound η5 to the outermost thiophene ring while the complexes of the oligothiophene 5,5″-diphenyl-2,2′:5′,2″-terthiophene (Ph2Tth) have Ru bound η6 to a pendant phenyl group. The complexes with ruthenium bound to an arene are very stable with respect to decomplexation; complexes with ruthenium bound to a thiophene ring are stable in the solid state and in dichloromethane solutions; in acetone, rearrangement reactions occur to produce equilibrium mixtures of free oligothiophene and mono- and diruthenated species. Detailed analysis of 1H and 13C NMR spectra, 1H-1H decoupling experiments, heteronuclear multiple-bond correlation (HMBC), and heteronuclear multiple-quantum coherence (HMQC) experiments enabled the assignment of all 1H and 13C resonances. These assignments show that binding ruthenium to a thiophene ring of an oligothiophene shifts the bound ring resonances upfield and the unbound thiophene rings downfield. The coordination of ruthenium exerts a larger electronic effect in oligothiophene complexes than in polyaromatic complexes (quaterphenyl). Complexation of a thiophene ring by ruthenium will affect the electronic structure of up to five thiophene rings: The bound ring and the next two unbound thiophene rings on either side.

Original languageEnglish (US)
Pages (from-to)1562-1575
Number of pages14
JournalInorganic Chemistry
Issue number6
StatePublished - Mar 1 1995


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