| dc.description | A series of twelve new organometallic acetophenone-hydrazone complexes of general formula [(h 5-Cp)Fe(h 6-o-RC6H4)-NHN=CMe-C6H4-p-R ]+PF6- (Cp= C5H5; R,R =H,Me, [5]+PF6-; H,MeO, [6]+PF6-; H,NMe2, [7]+PF6-; Me,Me, [8]+PF6-; Me,MeO, [9]+PF6-; Me,NMe2, [10]+PF6-; MeO,Me, [11]+PF6-; MeO,MeO, [12]+PF6-; MeO,NMe2, [13]+PF6-; Cl,Me, [14]+PF6-; Cl,MeO, [15]+PF6-; Cl,NMe2, [16]+PF6-) has been prepared by reaction between their corresponding organometallic hydrazine precursors [(h 5-Cp)Fe(h 6-o-RC6H4)-NHNH2]+PF6- (R=H, [1]+PF6-; Me, [2]+PF6-; MeO, [3]+PF6-; Cl, [4]+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 [11]+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. | |
