Unusual Nitrile–Nitrile and Nitrile–Alkyne Coupling of Fc-C≡N and Fc-C≡C-C≡N

摘要

The reactions of the Group 4 metallocene alkyne complexes, [Cp_2~*M(η~2-Me_3SiC_2SiMe_3)] (1a: M=Ti, 1b: M=Zr, Cp~*=h~5-pentamethylcyclopentadienyl), with the ferrocenyl nitriles, Fc-C≡N and Fc-C≡C-C≡N (Fc=Fe(η~5-C_5H_5)(η~5-C_5H_4)), is described. In case of Fc-C≡N an unusual nitrile–nitrile C-C homocoupling was observed and 1-metalla-2,5-diaza-cyclopenta- 2,4-dienes (3a, b) were obtained. As the first step of the reaction with 1b, the nitrile was coordinated to give [Cp_2~*Zr(η~2-Me_3SiC_2SiMe_3)(N≡C-Fc)] (2b). The reactions with the 3-ferrocenyl-2-propyne-nitrile Fc-C≡C-C≡N lead to an alkyne–nitrile C-C coupling of two substrates and the formation of 1-metalla-2-aza-cyclopenta-2,4-dienes (4a, b). For M=Zr, the compound is stabilized by dimerization as evidenced by single-crystal X-ray structure analysis. The electrochemical behavior of 3a, b and 4a, b was investigated, showing decomposition after oxidation, leading to different redox-active products.