Synthesis of pentavalent imidovanadium complexes and their catalyses for the polymerization of ethylene and propylene

Imidovanadium complexes with cyclopentadienyl (Cp) ligands-(Cp)V(=NC 6H4Me-4)Cl2 (1), (Cp)V(=NtBu)Cl 2 (2), and (tBuCp)V(=NtBu)Cl2 (3; tBuCp = terf-butylcyclopentadienyl)-were synthesized through the reaction of imidovanadium trichloride with (trimethylsilyl)cyclopentadiene derivatives. The molecular structure of 3 was determined by X-ray crystallography. The monocyclopentadienyl complex 1 exhibited moderate activity in combination with methylaluminoxane [MAO; 10.3 kg of polyethylene (mol of V)-1 h-1 atm-1], whereas similar complexes with bulky tBu groups, 2 and 3, were less active. (2-Methyl-8- quinolinolato)imidovanadium complexes, V(=NR)(ÔN)Cl2 (R = C6H3 tPr2-2,6 (4) or n-hexyl (5), ÔN = 2-methyl-8-quinolinolato), were obtained from the reaction of imidovanadium trichloride with 2-methyl-8-quinolinol. Upon activation with modified MAO, complex 4 showed moderate activities for the polymerization of ethylene at room temperature. The complex 5/MAO system also exhibited moderate activity at 0°C. The polyethylenes obtained by these complexes had considerably high melting points, which indicated the formation of linear polyethylene. Moreover, the 5/dried MAO system showed propylene polymerization activities and produced polymers with considerably high molecular weights and narrow molecular weight distributions. © 2005 Wiley Periodicals, Inc.