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-diazacyclopenta-2,4-dienes of group 4 metallocenes, especially of the pyridyl-substituted examples, towards small molecules is investigated. The addition of H-2, CO2, Ph-C Z 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-2*Zr(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.