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 6 H 4 NHNH 2 )] + PF 6 − (Cp=C 5 H 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 5 H 4 )CHCHC 6 H 4 CHO], to afford stereoselectively, the new homodimetallic hydrazones formulated as ( E )-[(η 5 -Cp)Fe(η 6 - p -RC 6 H 4 )NHNCHC 6 H 4 CHCH(η 5 -C 5 H 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 ( 1 H- and 13 C-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 6 H 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.