This contribution reports on the olefin polymerization behavior of phenoxy-imine ligated Zr, Ti, and V complexes 1-10 with MgCl2/RmAl-(OR)(n) systems. Zr complexes 1-4 combined with MgCl2/RmAl(OR)(n) display strikingly high ethylene polymerization activities; indeed, they are some of the highest reported activities for methylalumoxane (MAO)- and borate-free olefin polymerization catalysts (max. 1819 kg-PE/(mmol-cat h), 0.9 MPa ethylene pressure, 50degreesC). In addition, when Ti complexes 5-7 are combined with MgCl2/RmAl(OR)(n) they exhibit high ethylene polymerization activities (max. 36.3 kg-PE/(mmol-cat h), 0.9 MPa ethylene pressure, 50degreesC) and produce polyethylenes with narrow molecular weight distributions (M-w/M-n) and ethylene-propylene copolymers with homogeneous structures, representing the first examples of MAO- and borate-free, highly active single-site catalyst systems. The activities exhibited by the Zr and Ti complexes with MgCl2/R Al(OR)(n) are superior or comparable to those obtained with MAO cocatalyst systems. Moreover, V complexes 9 and 10 in association with MgCl2/RmAl(OR)(n) demonstrate high activities at elevated temperatures (9: 75 degreesC, 65.1 kg-PE/(mmol-cat h), atmospheric ethylene pressure) and are the first reported examples of highly active, thermally robust single-site V-based olefin polymerization catalysts. All of the polyethylenes formed from the MgCl2/RmAl(OR)(n) systems display good polymer morphology, indicating that complexes 1-10 are heterogenized on the surface of the MgCl2/RmAl(OR)(n). These results suggest that MgCl2/RmAl(OR)(n) not only works as an excellent cocatalyst, but is also a good support for phenoxy-imine ligated Zr, Ti, and V complexes. (C) 2003 Elsevier B.V. All rights reserved.