Boletín de la Sociedad Chilena de Química
Print version ISSN 0366-1644
MANZUR, Carolina et al. ORGANOMETALLIC IRON(II) COMPLEXES CONTAINING P-SUBSTITUTED ACETOPHENONE-ARYLHYDRAZONE LIGANDS. Bol. Soc. Chil. Quím. [online]. 2002, vol.47, n.4, pp.431-440. ISSN 0366-1644. http://dx.doi.org/10.4067/S0366-16442002000400014.
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, +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 [(h 5-Cp)Fe(h 6-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.
Keywords : Mixed sandwiches; organometallic arylhydrazone; acetophenome-arylhydrazone; dipolar chomophores; X-ray structure.