Abstract

A series of new conjugated bimetallic ferrocenyl 1,1?-bis- substituted compounds of the type (E)-[CpFe(?6-p-RC 6H4)NHN=CH(?5-C5H 4)Fe(?5-C5H4)-CH=CHC 6H4-p-R?]+PF6- (Cp = ?5-C5H5; R, R? = H, NO 2, 11; Me, NO2, 12; MeO, NO2, 13; Cl, NO 2, 14; Me, CN, 15; Me, Me, 16), with end-capped (E)-ethenylaryl and [CpFe(arylhydrazone)]+ substituents, have been prepared by the condensation reaction of 1,1?-(p-R?-arylethenyl) ferrocenecarboxaldehyde (R? = Me, 4; NO2, 5; CN, 6) with the organometallic hydrazine precursors [CpFe(?6-p-RC 6H4NHNH2)]+PF6- (R = H, 7; Me, 8; MeO, 9; Cl, 10). In the trimetallic series, {[CpFe(?6-p-RC6H4)NHN=CH(? 5-C5H4)]2Fe}2+[PF 6-]2 (R = H, 17; Me, 18; MeO, 19, Cl, 20), which results from the condensation of two equivalents of the same organometallic hydrazine precursor (7-10) with 1,1?- ferrocenedicarboxaldehyde, the ferrocenediyl core symmetrically links two cationic mixed-sandwich units. These ten hydrazones (11-20) were stereoselectively obtained as their trans isomers about the N=C double bond. All the new compounds were thoroughly characterized by a combination of elemental analysis, spectroscopic techniques (1H NMR, IR and UV-Vis) and electrochemical studies in order to prove electronic interaction between the donating and accepting units through the ?-conjugated system. A representative example of each series has also been characterized by single crystal X-ray diffraction analysis. The bimetallic complex 16+ adopts an anti conformation with the two iron atoms on opposite faces of the dinucleating hydrazonato ligand, whereas the trinuclear complex 192+ adopts a syn conformation with an Fe-Fe-Fe angle of 180°. Other salient features of these structures are the long Fe-Cipso bond distances and the slight cyclohexadienyl character at the coordinated C6 ring, with a folding angle of 7.4° and 7.0° for 16+ and 19 2+, respectively.