Ethylene/propylene copolymerization catalyzed by vanadium complexes containing N-heterocyclic carbenes

Various vanadium complexes containing N-heterocyclic carbenes, VOCl3[1,3-R-2(NCHv)(2)C:] (V1, R = 2,6-Me2C6H3; V2, R = 2,6-Et2C6H3; V3, R = 2,6-(Pr2C6H3)-Pr-i; V4, R = 2,4,6-Me3C6H2), have been synthesized and employed as catalyst precursors for ethylene/propylene copolymerization after activation by Et3Al2Cl3. Complex V4 showed higher catalytic activity of ca. 38 kg copolymer per (mol of V) per h and an ethylene/propylene copolymer with random monomer distribution could be prepared. Complex V3 consumed more cocatalyst than its analogues to reach higher catalytic activity. The obtained copolymers exhibit relatively narrow polydispersity and contain more randomly distributed monomer units than that the copolymers prepared by using the traditional vanadium catalytic system.