Unsymmetrical cyrhetrenyl and ferrocenyl azines derived from 5-nitrofurane: Synthesis, structural characterization and electrochemistry

A new series of unsymmetrical cyrhetrenyl and ferrocenyl azines that were monosubstituted [(η5-C5H4)-C(R)=N-N=CH(5-NO2-2-C4H2O)]M {with M=Re(CO)3 and R=H (1a) or R=Me (1b); M=Fe(η5-C5H5) and R=H (2a) or R=Me (2b)} and disubstituted [Fe{(η5-C5H4)-C(Me)=N-N=CH(5-NO2-2-C4H2O)}2] (3a) were prepared by condensation reactions of the corresponding organometallic hydrazone [(η5-C5H4)-C(R)=N-NH2)]M with 5-nitro-2-furaldehyde. The 1H and 13C{1H} NMR spectra indicated that these compounds adopted an (E,E)-configuration about the 〉C=N - bond and an s-trans conformation about the N1-N2 bond, and this result was confirmed by X-ray crystallographic analyses of 1a and 2b. The opposite electronic effects of the organometallic fragments correlate with the co-planarity of the [(η5-C5H4)-C(R)=N-N=CH(5-NO2-2-C4H2O)] system, the reduction potential of the nitro group (E1/2) and the chemical shifts of the iminic carbons.A.H.K. wishes to acknowledge FONDECYT-Chile (Projects 1150601 and 1110669) and D.I. Pontificia Universidad Católica de Valparaíso. J.G. wishes to acknowledge CONICYT and DEA for a Doctoral scholarship and D.I.-PUCV