Dd. Graf et al., SYNTHESIS AND CHARACTERIZATION OF CYCLOPENTADIENYL AND PENTAMETHYLCYCLOPENTADIENYL RUTHENIUM COMPLEXES OF OLIGOTHIOPHENES, Inorganic chemistry, 34(6), 1995, pp. 1562-1575
We report the synthesis and characterization of 14 complexes of the ge
neral form [CpRu(oligothiophene)]PF6 and [CpRu(oligothiophene)]PF6 (C
p = eta(5)-cyclopentadienyl; Cp = eta(5)-pentamethylcyclopentadienyl)
. The complexes were synthesized from [CpRu(CH3CN)(3)]PF6 or [CpRu(CH
3CN)(3)]PF6 and the appropriate oligothiophene via procedures previous
ly reported for other [Cp/CpRu(eta(6)-arene)]PF6 sandwich complexes.
For the oligothiophenes 2,2'-bithiophene (Bth), 2,2':5',2 ''-terthioph
ene (Tth), 2,2':5',2 '':5 '',2'''-quaterthiophene (Qth), and 5,5 ''-di
methyl-2,2':5',2 ''-terthiophene (Me(2)Tth), the Ru is bound eta(5) to
the outermost thiophene ring while the complexes of the oligothiophen
e 5,5 ''-diphenyl-2,2':5',2 ''-terthiophene (Ph(2)Tth) have Ru bound e
ta(6) to a pendant phenyl group. The complexes with ruthenium bound to
an arene are very stable with respect to decomplexation; complexes wi
th ruthenium bound to a thiophene ring art stable in the solid state a
nd in dichloromethane solutions; in acetone, rearrangement reactions o
ccur to produce equilibrium mixtures of free oligothiophene and mono-
and diruthenated species. Detailed analysis of H-1 and C-13 NMR spectr
a, H-1-H-1 decoupling experiments. heteronuclear multiple-bond correla
tion (HMBC), and heteronuclear multiple-quantum coherence (HMQC) exper
iments enabled the assignment of all H-1 and C-13 resonances. These as
signments show that binding ruthenium to a thiophene ring of an oligot
hiophene shifts the bound ring resonances upfield and the unbound thio
phene rings downfield. The coordination of ruthenium exerts a larger e
lectronic effect in oligothiophene complexes than in polyaromatic comp
lexes (quaterphenyl). Complexation of a thiophene ring by ruthenium wi
ll affect the electronic structure of up to five thiophene rings: the
bound ring and the next two unbound thiophene rings on either side.