Synthesis of (Imido)Vanadium(V) Dichloride Complexes Containing Anionic N-Heterocyclic Carbenes That Contain a Weakly Coordinating Borate Moiety: New MAO-Free Ethylene Polymerization Catalysts

Synthesis and structural analysis of (imido)vanadium(V) complexes containing anionic N-heterocyclic carbenes with a weakly coordinating borate [B(C6F5)3] moiety (WCA-NHC) of the type [V(NR)Cl2(WCA-NHC)] [R = 1-adamantyl, C6H5, 2,6-Me2C6H3; NHC = 1,3-bis(2,6-dimethylphenyl)imidazolin-2-ylidene] have been explored; the WCA-NHC forms a σ-bond with vanadium as alkyl ligand (without strong π-donation) on the basis of crystallographic analysis [V–CNHC = 2.039(3)–2.049(2) A]. [V(N-2,6-Me2C6H3)Cl2(WCA-NHC)] exhibited remarkable catalytic activity (e.g., 11000 kg-PE/mol-V·h) for ethylene polymerization in the presence of AliBu3, and the activity was much higher than those in the presence of MAO and Et2AlCl.