Selective Insertion in Copolymerization of Ethylene and Styrene Catalyzed by Half-Titanocene System Bearing Ketimide Ligand: A Theoretical Study

摘要: The copolymerization of ethylene and styrene can be efficiently carried out by using Cp*TiCl2(N = CtBu2)/MAO (Cp*=η5-C5Me5) system, yielding the poly(ethylene-co-styrene)s with isolated units. In order to investigate reasons for formation structure, mechanism copolymerization, especially selective insertion styrene, is studied in detail density functional theory (DFT) method. At initiation stage, kinetically more favorable than thermodynamically prefers 2,1-insertion. That different from conventional half-titanocene which 1,2-insertion favorable. chain propagation computational results suggest that continuous hard occur at room temperature due high free energy barriers (28.90 35.04 kcal/mol 1,2-insertion, 29.15 34.00 2,1-insertion) unfavorable factors two conditions. mainly attributed steric hindrance between coming chain-end or ketimide ligand. are good agreement experimental data.