| abstract |
Catalysts useful for polymerizing olefins are disclosed. The catalysts comprise an activator and a Group 4 transition metal complex which comprises at least one monoanionic R 1 N-XR 2 ligand, where X is O or S, and each of R 1 and R 2 is independently alkyl, aryl, arylalkyl, alkylaryl, or trialkylsilyl. The complexes are readily made from R 1 NH-XR 2 precursors and are often useful as catalyst components without further purification. The catalysts have good activities, incorporate comonomers well, and provide polymers with high molecular weight. |