Phenyl-bridged bis-salicylaldiminato binuclear titanium complexes for ethylene (co)polymerization

P-Phenyl-bridged bis-salicylaldiminato binuclear titanium complexes (TiL1)-L-2, (TiL2)-L-2 and the corresponding momonuclear counterpart TiL4 were synthesized and characterized by H-1 NMR, C-13 NMR, FT-IR, and elemental analysis. The binuclear titanium complex (TiL1)-L-2 showed good catalytic performances for ethylene polymerization and copolymerization with norbornene or 1,5-hexadiene. For ethylene polymerization, the binuclear titanium complex (TiL1)-L-2 exhibited highest activity of 8.70 x 10(5) g/mol(Ti)(.)h(.)atm at 70 & DEG;C and retained an activity of 3.00 x 10(5) g/mol(Ti)(.)h(.)atm at 90 ?, which showed much higher thermal stability compared with its bi- and mono-nuclear derivatives (TiL3)-L-2 and TiL4, due probably to the rigid phenyl-bridged structure offering more stable state of active metal centers. The binuclear complex (TiL1)-L-2 could catalyze ethylene copolymerization with norbornene (NB) or 1,5-hexadiene (1,5-HD) to produce copolymer bearing cyclic groups. Compared with mononuclear complex TiL4, the binuclear (TiL1)-L-2 showed higher catalytic activity and incorporation rate of comonomer for ethylene/NB copolymerization. The mononuclear complex TiL4 could barely catalyze the copolymerization of ethylene and 1,5-HD, however, the binuclear analogue (TiL1)-L-2 exhibited an activity of 1.67 x 10(5) g/mol(Ti)center dot h center dot atm with 4.74% of incorporation rate of 1,5-HD for ethylene/1,5-HD copolymerization, implying that the bimetallic synergistic effect could greatly improve the catalytic performance of the bis-salicylaldiminato binuclear titanium complexes.