The oligomerization of ethylene catalyzed by Cp~2ZrL~2(L=Cl, Me, OC~6H~4-p-Me)/EAO (ethylaluminoxane) afforded not only common chain oligomers but also methylenecyclopentane. It is the first example of oligomerization and simultaneous cyclization of ethylene to a cyclic oligomer. The selectivity of methylenecyclopentane, affected by the structure and the concentration of precatalysts, solvents, aging and reaction temperature and some other factors, came up to 37% when a third-component C~5H~5N was added to the Cp~2ZrCl~2/EAO system under optimal conditions.

Key words: ETHYLENE, OLIGOMERIZATION, CYCLIZATION, ZIRCONIUM COMPLEX, METALLOCENES