1ST DELOCALIZATION OF A MONO-FULVALENE-BRIDGED MIXED-VALENCE DIIRON COMPLEX ON THE INFRARED TIME SCALE

Measurement of the infrared nu(CH(Cp)) stretch around 800 cm-1 of the Fe(II)Fe(II) (q = 2), Fe(II)Fe(I) (q = 1) and Fe(I)Fe(I) (q = 0) states of [Fe2Fv(C6Me6)2]q+ (Fv = fulvalene) and Fe(II)Fe(II) (q = 0), Fe(II)Fe(III) (q = 1) and Fe(III)Fe(III) (q = 2) states of [Fe2Fv(C5Me5)2]q+ shows that Fe(II)Fe(I) is delocalized whereas Fe(II)Fe(III) is localized; the electrochemical E-degrees values indicate that the cyclopentadienyl permethylation increases the delocalization in the arene series whereas it decreases it in the C5Me5 one.