[l,8-C,0H6(NSi'BuMe2)2]TiBr2 (4) has been prepared from dilithio salts [l,8-CinH6(NR),]Li, (2) and TiBr4 in Et2O. This complex showed significant catalytic activity for ethylene polymerization in the presence of a cocatalyst, and the activity is the same as those obtained by using chloride analogues such as [1,8-C10H6(NR)2] TiCl2 (3: R = SiMe3 Si'BuMe2 Si'Pr,). The effective cocatalyst was, however, different between the chloride and the bromide complexes. [ArNCH2CH2CH2NAr]TiCl2 (5, Ar = 2,6-iPr2C6H3), which has been known as an effective catalyst for polymerization of 1-hexene, showed lower activity under the same conditions. The broad molecular weight distributions (Mw/Mn for the resultant polymer can be attributed to the scission of titanium-nitrogen bond by cocatalyst, because the narrow MJMnvalue (1.8) was observed if the polymerization was stopped at the initial stage (2 min) under the same reaction conditions.
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