A series of twelve new organometallic acetophenone-hydrazone complexes of general formula [(η5-Cp)Fe(η6-o-RC6H4)- NHN=CMe-C6H4-p-R']+PF6- (Cp=C5H5; R,R'=H,Me, + PF6-; H,MeO, + PF6-; H,NMe2, + PF6-; Me, Me, + PF6-; Me,MeO, + PF6-; Me,NMe2, + PF6-; MeO,Me, + PF6-; MeO,MeO, + PF6-; MeO,NMe2, + PF6-; Cl,Me, + PF6-; Cl,MeO, +PF6-; Cl,NMe2, +PF6-) has been prepared by reaction between their corresponding organometallic hydrazine precursors [(η5-Cp)Fe(η6-o-RC6H4)- NHNH2]+PF6- (R=H, +PF6-; Me, +PF6-; MeO, +PF6-; Cl, +PF6-, and aromatic ketones of the type MeC(=O)C6H4-p-R' (R'-Me, MeO, NMe2) in refluxing ethanol containing concentrated acetic acid. These mononuclear hydrazones were stereoselectively obtained as their trans-isomers about the N=C double bond, and were characterized by elemental analysis or high resolution mass spectrometry, I.R., UV-Vis, and 1H NMR spectroscopies and, in the case of complex +PF6- (R,R'=MeO,Me), by single-crystal X-ray diffraction analysis. The more salient features of this structure are: (i) the concomitant lengthening of the Fe-Cipso and the shortening of the Cipso-N bond distances leading to a slight iminium-cyclohexadienyl character of the coordinated C6 ring, (ii) the intramolecular hydrogen bonding between the benzylic N-H group and the oxygen atom of the ortho-methoxo-substituent, with the N(1)⋯O(1) separation of ca. 2.627(4) Å, and (iii) the slight deviation of coplanarity between the coordinated and the free phenyl rings (dihedral angle=15.60(0.25)°). Finally, the cyclic voltammetry studies reveal an irreversible one-electron reduction step for compounds [5-7]+PF6-, and the redox potentials clearly indicate that the reduction occurs at the cationic electron acceptor mixed sandwich unit.
- Dipolar chromophores
- Mixed sandwiches
- Organometallic arylhydrazones
- X-ray structure