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

Abstract

Various vanadium complexes containing N-heterocyclic carbenes, VOCl₃[1,3-R₂(NCH)₂C:] (V1, R = 2,6-Me₂C₆H₃; V2, R = 2,6-Et₂C₆H₃; V3, R = 2,6-ⁱPr₂C₆H₃; 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.