The synthesis, structures, and electrochemistry of 1′-heteroaryl-2,5-dimethylazaferrocenes

Abstract

a b s t r a c tWe report the synthesis of 1 0 -heteroaryl-2,5-dimethylazaferrocenes (heteroaryl = 2-bromothiophen-5-yl and 2-bromopyrid-6-yl) via palladium catalysed cross-coupling reactions along with their crystallographically determined structures. The newly synthesized compounds as well as the parent 2,5-dimethylazaferrocene have been investigated by cyclic voltammetry (CV) and were found to exhibit reversible first oxidations followed by an irreversible oxidation at considerably higher potential.

The synthesis and electrochemistry of 2,5-dimethylazaferrocenes with heteroaryl bridges

“…Based on this methodology, complexes 1, 2, 3, 6, 7 and 9 have been obtained [4][5][6][7]. We have already reported that 2,5-dimethylazaferrocenylzinc chloride undergoes palladium catalyzed cross-coupling reactions with dibromoheteroarenes to yield 1 0 -heteroaryl-2,5-dimethylazaferrocenes [13]. As a logical continuation of this study we applied this type of cross-coupling reactions toward the preparation of symmetrical heteroaryl bridged dinuclear azaferrocenyl complexes.…”

“…In the next step a catalytic amount of PdCl 2 (PPh 3 ) 2 in THF and the appropriate reactive 1 0 -heteroaryl-2,5-dimethylazaferrocenes 16 [13], 17 [13] or 18 were successively added at room temperature to the stirring reaction mixtures.…”

“…Electrochemical studies on the heteroaryl bridged 2,5-dimethylazaferrocene derivatives 12, 13 and 14 and on the azaferrocenyl substituted bithiophene 18 were conducted in CH 2 Cl 2 /NBu 4 PF 6 (0.2 M) at 293 K. The choice of this supporting electrolyte follows our recent observation [13] that the 0/+ couple of parent 2,5-dimethylazaferrocene is considerably more reversible in this electrolyte when compared to CH 2 Cl 2 /NBu 4 ClO 4 [15]. Under these conditions, all heteroaryl bridged 2,5-dimethylazaferrocenes displayed two consecutive closely to moderately spaced one-electron oxidations.…”

“…Potentials are given against the ferrocene/ferrocenium couple. The splittings of half-wave potentials were directly taken from the CVs, square wave and differential pulse voltammograms (12) or by deconvolution of the overlapping peaks in square wave and differential pulse voltammetry (13,14). DE 1/2 values were independently calculated from the CV peak potential separations and forward wave half-widths by the method of Richardson and Taube [11].…”

“…Complexes 12 and 13 are close relatives of compounds 1 and 3. The rationale for introduction of 2,5-dimethylazaferrocene was to investigate the degree of electronic interactions mediated by thiophenyl, bithiophenyl and pyridyl bridges when connected to end-groups with a higher redox potential than that of ferrocene [13].…”