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

Imidovanadium complexes with cyclopentadienyl (Cp) ligands—(Cp)V(?NC₆H₄Me‐4)Cl₂ (1), (Cp)V(?N^tBu)Cl₂ (2), and (^tBuCp)V(?N^tBu)Cl₂ (3; ^tBuCp = tert‐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)(O ?N)Cl₂ (R = C₆H₃ⁱPr₂‐2,6 (4) or n‐hexyl (5), O ?N = 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. J Appl Polym Sci 97: 1008–1015, 2005