Organodiiron(II)-complexes containing a long conjugated hydrazonato spacer.: Synthesis, characterization, electrochemical and structural studies

Organometallic hydrazines of general formula [(eta(5)-Cp)Fe(eta(6)-p-RC6H4NHNH2)]+PF6- (Cp = C5H5; R = H, (1) +PF6-; Me, (2)+PF6-; MeO, (3)+PF6-; Cl, (4)+PF6-) react with equimolar quantities of (E)-4-(2-ferrocenylvinyl)-benzaldehyde, (E)-[(eta(5)-Cp)Fe(eta(5)-C5H4)-CH=CH-C6H4CHO], to afford stereoselectively, the new homodimetallic hydrazones formulated as (E)-[(eta(5)- Cp)Fe(eta(6)-p -RC6H4)-NHN=CH-C6H4-CH=CH-(eta(5) -C5H4)Fe(eta(5)-Cp)]+PF6- (R = H, (5) +PF6-; Me, (6) +PF6-; MeO, (7)+PF6-; Cl, (8)+PF6-). These compounds were fully characterized by elemental analysis and spectroscopic techniques (H-1-and C-13-NMR, IR and UV-vis) and, in the case of complex (6)+PF6-, by single crystal X-ray diffraction methods. The rotations of the ferrocenyl unit by 37.2degrees out of the -NHN=CH-C6H4-CH=CH- spacer and coordinated phenyl ring planes, may generate an unfavorable structure to allow pi-electron delocalization along the entire hydrazonato backbone between the two metals separated through bonds by more than 1.8 nm, as confirmed by the electrochemical data. (C) 2002 Elsevier Science B.V. All rights reserved.