A newly synthesized catalyst, a pentamethylene bridged dinuclear zirconocene ([(CH2)(5)(C5H4)(2)][(C9H7)ZrCl2](2)), and its in situ supported catalyst were tested in a ethylene/1-hexene copolymerization and their performance was compared with those Of Cp2ZrCl2 and rac-Et(Ind)(2)ZrCl2. When homogeneous [(CH2)(5)(C5H4)][(C9H7)ZrCl2](2) catalyst was used in the copolymerization, its activity decreased with comonomer incorporation (a negative comonomer effect) and it produced copolymer with a lower comonomer content than other catalysts, both of which were ascribed to the steric effect of the [(CH2)(5)(C5H4)(2)][(C9H7)ZrCl2](2) catalyst. With in situ supported catalysts, the activity did not change much with the increase of I-hexene content in contrast to the homogeneous catalysts. In situ supported catalysts produced copolymers with higher content of 1-hexene and lower melting point and crystallinity. The changes in the molecular weight and its distribution of the copolymer with in situ supporting were significant and dependant on the nature of the catalyst. (C) 2002 Elsevier Science B.V. All rights reserved.