Iron-based diimine complex was immobilized on calcosilicate (CAS-1) to form heterogeneous precatalyst, which oligomerized ethylene to alpha-olefins even without the use Of aluminum alkyl Compounds as activators. The alpha-olefins, upon the catalysis of another catalyst, i.e., silica-supported rac-Et(lnd)(2)ZrCl2 copolymerized with ethylene to produce linear low-density polyethylene (LLDPE). The copolymerization reactions could be performed with the addition of triethylaluminum alone because of the introduction of methylaluminoxane to CAS-1 and silica during the supporting process. In addition to the formation of more alpha-olefins with lower molar mass, the layered structure of CAS-1 acted well in the controlled release of alpha-olefins in the copolymerization process. The simultaneous employment of the aforementioned two catalysts hence resulted in high catalytic activities, smooth kinetic process, well-regulated branching degree, higher molecular weights (M-n), improved thermal stability, and better morphology of the LLDPE obtained. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 2298-2304, 2009