N-( Diferrocenylmethylene) anilines Fc2C= N- 4- C6H4- R [ 3a R = CF 3; 3b R = Cl; 3c R = H; 3d R = CH 3; 3e R = OCH3; Fc = Fe(.5- C5H4)(.5- C5H5)] with different electron- donating or - withdrawing functionalities were synthesized by a Schiff base reaction of substituted anilines H2N- 4- C6H4- R ( 2a- 2e) with diferrocenyl ketone ( 1). Within variable temperature NMR experiments activation enthalpies between 68.1 and 72.3 kJ center dot mol- 1 for an E/ Z exchange reaction of the imines were determined. It could be shown that the inversion barrier depends on the nature of the substituent R. Furthermore, electrochemical measurements were performed, demonstrating that the ferrocenyl units are oxidized separately. The electron density at the nitrogen atom is influenced by the electronic nature of the aniline groups R thus giving rise to varying attractive electrostatic interactions to the ferrocenium units. This results in decreasing redox separations for the ferrocenyl oxidation with a decreasing electron- withdrawing character of the anilines. Spectroelectrochemical measurements confirmed that the redox separations are mainly caused by electrostatic interactions as no electronic metal- metal coupling is observed. For 3a, b, d, e the molecular structure in solid state was determined by single- crystal Xray diffractometry. In all compounds different forms of p- p interactions occur. Compound 3a shows a complex network of parallel- and T- shaped p- p interactions, whereas 3d is forming 5- and 6- membered cycles.
|Number of pages||9|
|Journal||Zeitschrift fur Anorganische und Allgemeine Chemie|
|Publication status||Published - Oct 2015|