Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

In this work the reactivity of 1‐metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of group 4 metallocenes, especially of the pyridyl‐substituted examples, towards small molecules is investigated. The addition of H₂, CO₂, Ph?C≡N, 2‐py?C≡N, 1,3‐dicyanobenzene or 2,6‐dicyanopyridine results in exchange reactions, which are accompanied by the elimination of a nitrile. For CO₂, a coordination to the five‐membered cycle occurs in case of Cp*₂Zr(N=C(2‐py)?C(2‐py)=N). A 1,4‐diaza‐buta‐1,3‐diene complex is formed by H‐transfer in the conversion of the analogous titanocene compound with CH₃?C≡N, PhCH₂?C≡N or acetone. For CH₃?C≡N a coupling product of three acetonitrile molecules is established additionally. In order to split off the metallocene from the coupled nitriles, we examined reactions with HCl, PhPCl₂, PhPSCl₂ and SOCl₂. In the last case, the respective thiadiazole oxides and the metallocene dichlorides were obtained. A subsequent reaction produced thiadiazoles.