Nitril‐Nitril‐C‐C‐Kupplungen an Gruppe‐4‐Metallocenen zu 1‐Metalla‐2,5‐diazacyclopenta‐2,4‐dienen und deren Reaktionen

Abstract

Die C‐C‐Kupplung von Arylnitrilen an Gruppe‐4‐Metallocene liefert ungewöhnliche 1‐Metalla‐2,5‐diazacyclopenta‐2,4‐diene, deren strukturelle, energetische und chemische Eigenschaften untersucht wurden. Die Reaktionen dieser Verbindungen mit CH3CN, H2, CO2 und HCl führten in den meisten Fällen zur Freisetzung eines Nitrils und dem Einbau eines zweiten Substrats an dessen Stelle.

Reactions of rac‐(ebthi)M(η2‐Me3SiC2SiMe3) (M=Ti, Zr) with Aryl Nitriles

“…This led to the complete conversion of 2 —through the elimination of one nitrile—to give a new compound, which was predicted to be hydride complex 2 b (Scheme , 2nd path). Clues for this assumption are resonances in the NMR spectra ( 1 H: δ =8.97 ppm (d, 1 H; NCH); 13 C: δ =159.5 (CN), 137.4 ppm ( i C)), which are in good accordance to Cp* 2 Ti(H)(NCHPh) ( 1 H: δ =8.79 ppm (NCH); 13 C: δ =153.0 (CN), 136.9 ppm ( i C)); the product of the reaction of Cp* 2 Ti(NC(Ph)C(Ph)N) with H 2 7a. Unfortunately, complex 2 b could not be characterized in detail, due to its further reaction to form 3 through the elimination of H 2 , which starts at ambient temperature.…”

“…We propose that, in the first step, one nitrile is eliminated from 2 through the formation of 2 a (Scheme , 1st path). For the analogous complex Cp* 2 Ti(NC(Ph)C(Ph)N), the release of one nitrile and its replacement by a cosubstrate was already observed in reactions with CH 3 CN, H 2 , and CO 2 7a. The subsequent dimerization of 2 a results in the formation of complex 3 .…”

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

“…Aditionally, by other reactions the conversion of only one pentafulvene [C 5 H 4 =CR 2 ] 2− to Cp′ ligands [C 5 H 4 −CHR 2 ] 1− was described whereas the other remains as [C 5 H 4 =CR 2 ] 2− ligand. This opens the way to a lot of other synthetically very interesting reactions …”

“…Going from the C≡C to the C≡N triple bonds of substrates, the reactions of the complexes Cp* 2 M(η 2 ‐Me 3 SiC 2 SiMe 3 ) with nitriles including PhC≡N, p ‐tolC≡N, o ‐TolC≡N and FcC≡N (Fc=ferrocenyl) resulted in the formation of 1‐metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes which were isolated in high yields (Scheme ) …”

Reaktionen auf die Vollsperrung der Schiersteiner Brücke auf der A643

“…Weiterhin reagiert sie mit Heterocumulenen wie Alkylisocyanat oder CO2 unter Zr+/P‐Addition und Bildung von fünfgliedrigen Metallacyclen. Rosenthal et al erhielten durch die C‐C‐Kupplung von Nitrilen an Gruppe‐4‐Metallocenen fünfgliedrige Metallacyclen (Abbildung 30) 1_35. Die C‐C‐Bindung zwischen den gekuppelten Nitrilen ist relativ labil und kann wieder gespalten werden.…”