Polarizable organometallic hydrazone chromophores. X-ray crystal structures of [(η5-C5H5)Fe(η5-C5H4)-C(p-MeC6H4)=NNH-(η6-p-MeC6H4) Fe(η5-C5H5)]+PF6-, and of its toluoylferrocene precursor

The homobimetallic hydrazone complex [CpFe(eta6-p- CH3C6H4)NHN=C(C6H4-p-CH3)(eta5-C5H4)FeCp]+PF6- (2) (Cp=eta5-C5H5) is stereoselectively formed by reaction of the organometallic hydrazine precursor [CpFe(eta6-p-CH3C6H4-NHNH2)]+PF6- with the sterically demanding p-toluoylferrocene CpFe(eta5-C5H4)CO(C6H4-p-CH3) (1) in refluxing ethanol. Compound 2 has been fully characterized by IR, UV-vis, and 1H NMR spectroscopy, cyclic voltammetry and by an X-ray diffraction analysis. The most striking features of the crystal structure are the syn-conformation of the two organometallic units, the long Fe-Cipso bond distances and the slight cyclohexadienyl character at the coordinated C6 ring with a folding angle of 6.1 deg, and that coordinated C6- and C5-rings of the binucleating ligand are almost coplanar with a dihedral angle of 8.1 deg. The crystal structure of the p-toluoylferrocene 1 is also presented.