Abstract
A series of chromium complexes having Cp-amine type ligands, (R'2NC2H4C5R4) CrX2, were synthesized, whose catalytic behaviors for olefin polymerization were investigated upon activation with modified methylaluminoxane (MMAO). With increasing steric bulkiness of the complex, the catalytic activity increased for ethylene polymerization. These complexes showed high activity for copolymerizations of ethylene with a -olefins as well as for homopolymerizations. A indenyl type complex tended to produce polymers with higher molecular weights. The molybdenum analogues showed relatively high activities for ethylene polymerization among the reported molybdenum complexes, although their activities were much lower than those of the chromium catalysts and Group 4 metallocene catalysts. The corresponding iron complex, [ (Me2NC2H4C5Me4) FeCl] 2, showed no catalytic activity for ethylene polymerization. Catalyses of variously substituted vanadium tris (acetylacetonate) (V (acac) 3) /MMAO systems were also studied. Introduction of electron-withdrawing groups tended to enhance the catalytic activity, while catalysts having bulky substituents yielded polyethylenes with high molecular weight and narrow molecular weight distribution.
