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

Abstract

Organometallic hydrazines of general formula [(η 5-Cp)Fe(η 6- p-RC 6H 4NHNH 2)] +PF 6 − (Cp=C 5H 5; R=H, ( 1) +PF 6 −; Me, ( 2) +PF 6 −; MeO, ( 3) +PF 6 −; Cl, ( 4) +PF 6 −) react with equimolar quantities of ( E)-4-(2-ferrocenylvinyl)-benzaldehyde, ( E)-[(η 5-Cp)Fe(η 5-C 5H 4)CHCHC 6H 4CHO], to afford stereoselectively, the new homodimetallic hydrazones formulated as ( E)-[(η 5-Cp)Fe(η 6- p-RC 6H 4)NHNCHC 6H 4CHCH(η 5-C 5H 4)Fe(η 5-Cp)] +PF 6 − (R=H, ( 5) +PF 6 −; Me, ( 6) +PF 6 −; MeO, ( 7) +PF 6 −; Cl, ( 8) +PF 6 −). These compounds were fully characterized by elemental analysis and spectroscopic techniques ( 1H- and 13C-NMR, IR and UV–vis) and, in the case of complex ( 6) +PF 6 −, by single crystal X-ray diffraction methods. The rotations of the ferrocenyl unit by 37.2° out of the NHNCHC 6H 4CHCH spacer and coordinated phenyl ring planes, may generate an unfavorable structure to allow π-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.